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Improved membrane flux recovery by Fenton-type reactions
Abstract
Fenton reactions were applied to the degradation of dissolved organic matter (OM) and fouling removal of iron oxide membranes. Humic acid (HA), bovine serum albumin (BSA) and sodium alginate (SA), were used as models of humic substances, proteins and polysaccharides respectively. The degradation reaction was performed with H2O2 1mM at pH of 2.5 and the reactant concentration was measured over time by total organic carbon (TOC) and HPLC. Dissolved and particulate iron were efficient catalyst, achieving mineralization rates of 80%, 40% and 85% for HA, BSA and SA respectively. The H2O2 solution was applied as a cleaning agent on membranes previously fouled by the compounds individually, as well as their mixtures. Hydraulic cleaning of the membrane surfaces did not show significant improvement; Fenton treatment produced a flow recovery of 97% for HA, 86% for BSA and 88% for SA. Flux recovery was slightly lower for mixtures, where chemical interactions between foulants yielded a more compact, recalcitrant layer. Membrane surfaces were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), showing residual foulants after treatment, regardless of the flux recovery achieved. The results showed the cleaning ability of this reagent with a very good recovery of the initial flux.
... Catalytic ceramic membranes, functionalizing the membrane surface with oxidative reactivity, provide a potential oxidation route for fouling removal. Over the past decade, several advanced oxidation processes, including Fenton reactions [16,17], catalytic ozonation [18,19], peroxymonosulfate activation [20,21] and photo-catalysis [22], have tentatively been incorporated in catalyst-tailored ceramic membranes to produce reactive oxygen species (e.g. • OH, O 2 ...
... •− and SO 4 •− radicals) on the membrane surface and/or within the inner pores, potentially removing fouling. Angelis et al. observed that the flux recovery of iron-oxide coated ceramic membranes (fouled with humic acids) by Fenton cleaning, was much higher (97%) than those by forward flush (41%) or acidic/caustic cleaning (39− 42%) [17]. Zhang et al. demonstrated that the flux of MnO 2 -Co 3 O 4 coated ceramic membranes was recovered by 97% with peroxymonosulfate-based oxidative cleaning, while it was only restored by 70-75% using backwash or acidic/caustic cleaning [23]. ...
... A concentrated alginate solution (0.8 g L − 1 ) in the presence of calcium ions was adopted to promote the formation of a thick and compact cake layer on the FeOCl pre-coated membrane, for examining the concept of direct water reclamation from high organic loaded wastewater. Angelis et al. have compared the morphology of organic fouling on an iron oxide coated ceramic membrane by alginate, bovine serum albumin and humic acid, respectively, demonstrating that only the alginate foulant could form thick cake layer fouling on the pre-coat layer while the other two foulants partially blocked its pores without any cake build-up [17,32]. Additionally, as suggested by Katsoufidou et al. [33] and Kim et al. [34], alginate solutions in the presence of calcium consist of both soluble organic matter and large-sized colloids, which are thus assumed to cause adsorptive fouling (or pore blocking) and cake layer fouling, respectively. ...
... Generally, Fenton cleaning is mainly used to remove organic compounds, such as carboxylic acids, alcohols, and esters, which helps the reduction of organic foulants within membrane pores [100]. This can be attributed to the non-selective strong oxidant of hydroxyl radical formed in Fenton cleaning [138,139]. Soesanto et al. [140] studied the Fenton oxidation process in crossflow DM cleaning, and found that Fenton cleaning could recover 28% initial filtration flux. Angelis et al. [138] verified the flux recovery of 97% for HA, 86% for BSA, and 88% for SA with Fenton treatment in membrane cleaning. ...
... Soesanto et al. [140] studied the Fenton oxidation process in crossflow DM cleaning, and found that Fenton cleaning could recover 28% initial filtration flux. Angelis et al. [138] verified the flux recovery of 97% for HA, 86% for BSA, and 88% for SA with Fenton treatment in membrane cleaning. All these confirm the effectiveness of Fenton cleaning in membrane foulants control. ...
Dynamic membrane (DM) technology has attracted much attention due to low operating pressure and easy fouling layer removal in wastewater treatment, but correlationship between DM and microfiltration/ultrafiltration (MF/UF) has not been well elaborated. Much work on fouling layer and fouling control strategies has been conducted for better understanding and application of MF/UF and DM. Therefore, membrane fouling and cleaning strategies with MF/UF and DM are analyzed and compared in this review. Firstly, membrane fouling and influencing factors of membrane pore size, membrane material, membrane reactor configuration, and membrane hydrophobicity in MF/UF and DM are discussed, which indicates that potential influence of membrane characteristics should be valued for better fouling layer control. Secondly, different cleaning strategies of physical, chemical, physical-chemical, and biological cleaning were summarized for future optimization of membrane fouling in MF/UF and DM. The advanced fouling control strategies with MF/UF can be referenced for further fouling layer control in DM system. Finally, implication and potential future directions are presented for sustainable developing of MF/UF and DM in water and wastewater treatment. Overall, this review attempts to bridge the connections between MF/UF and DM, which can provide new insights for better fouling control, fouling utilization, and improved operating efficiency.
... The Fenton oxidation processes on the membrane surface aim to attack the anchoring sites at the catalytic membrane/foulant interface, which would result in fouling layer detachment. De Angelis and de Cortalezzi reported that Fenton reactions on an iron-oxide modified ceramic membrane achieved a flux recovery of 80% with bovine serum albumin degradation percentage of 40%, indicating an underlying detachment or relaxation of the fouling layer by Fenton oxidation [14]. According to Sun et al. ...
... UV/H 2 O 2 photo-Fenton oxidation on a α-FeOOH-coated ceramic membrane was able to limit the increase of TMP to a plateau level, during continuous filtration of humic acid solutions [15]. Above mentioned studies, however, only have paid attention to the viability of using membrane-surface-localized Fenton reactions for fouling control, but in water treatment by ceramic membranes, a persistent fouling layer (i.e., gel-like foulants) on the membrane surface may affect the reactivity of Fenton processes, which is still unresolved and poorly understood [14,15]. ...
Ceramic nanofiltration (NF) is a newly-developed technology for water recycling, but is still limited to pilot-scale applications. Lacking efficient and eco-friendly strategies for cleaning ceramic NF membrane impedes its scaling-up in industries. Forward flush, backwash and acidic/caustic cleaning are not efficient enough. In this work, a novel oxalic acid-aided Fenton process was proposed for synergistic relaxation/oxidation of persistent Ca²⁺-mediated gel-like fouling of ceramic NF membrane. A reactive catalyst layer was online pre-coated on top of the membrane via a pressure-driven cross-flow pre-filtration of Fe3O4 hydrosols. The gel-like fouling was simulated by alginate in the presence of Ca²⁺ ions. Results show that the Fe3O4 loading could be readily tuned from 0.16 to 1.34 g m⁻² by altering the permeate flux during the pre-coating. The membrane permeability loss due to the pre-coating was minimal (<10%). The combination of oxalic acid chelation and Fenton-based oxidation resulted in high flux recovery (85.07%) for the iron-oxide pre-coated membrane, whereas the single treatment by hydrogen peroxide (H2O2) or oxalic acid was inefficient. This synergistic effect was attributed to relaxation of the Ca²⁺-mediated gel layer via oxalic acid/Ca²⁺ chelation, which presumably facilitated H2O2 diffusion at the Fe3O4/foulant interface. The iron-oxide pre-coated membrane maintained stable initial normalized fluxes (83.33–90.15%) through the oxalic acid/H2O2 cleaning over five cycles, with no need of refreshing the iron-oxide pre-coat. Additionally, the leaching of iron from the iron-oxide pre-coat by oxalic acid was suppressed by the oxalic acid/H2O2 combination, owing to a reactive shielding by competitive sorption of H2O2 onto the Fe3O4 surface. Overall, the synergistic relaxation/oxidation method, demonstrated in this study, provides new insights into improving reactivity of Fenton-based processes on hybrid catalytic ceramic membranes for water treatment or fouling control.
... The studies so far on hybrid systems combining Fenton/photo-Fenton and membrane processes show that such systems are effective in the removal of organic pollutants (Zhanga et al. [36]; Angelis and Cortalezzi [37]), the treatment of flax wastewater (Fan et al., [26]), removal of micropollutants (Miralles-Cuevas et al. [38]), treatment of oil refinery effluents (Estrada-Arriaga et al., [25]); purification of winery effluent wastewater (Ioannou et al., [24]), textile industry (Aydiner et al., [34]; Mirza et al., [30]), as well as the treatment of wastewater produced in paper industry (Gholami et al., [9]; Romanos et al. [39]). However, studies to guide the choice of optimal integrated AOP/membrane separation processes for various treatment applications focused on wastewaters produced by important industries are still scarce. ...
... In Fenton process, iron and H 2 O 2 are used as the chemicals introduced. The present study employed MOR technologies, introducing iron to facilitate the decomposition of organic matter, as discussed in the literature, whereas the membrane enabled reuse of iron over and over, while H 2 O 2 helps remove fouling on the membrane (Angelis and Cortalezzi [37]; Fan et al. [26]). It should also be noted that iron added in small amounts acts as a catalyst while H 2 O 2 is continuously consumed to produce hydroxyl radicals (Ponnusami and Muthukumar [52]; Ribeiro et al. [21]). ...
Excessive amounts of wastewater produced by the paper industry, often containing a wide range of toxic and recalcitrant pollutants based on raw materials used, should be subjected to efficient treatment processes before discharging to the environment. This experimental work examined hybrid Fenton and photo-Fenton enhanced (UVC254 and UVA365) UF system performances in treating raw wastewater from pulp and paper industry by membrane oxidation reactor (MOR). By response surface analyses of Taguchi experimental design, the systems were compared onto hybrid efficiencies, in settings optimized for maximal responses with minimum chemical needs, regarding the performance metrics of TOC and COD removal efficiencies and UF water flux. Organics were removed slightly better than Fenton in both photo-Fenton, and H2O2 and Fe²⁺ spends per TOC were accomplished as more efficient than anticipated in every MOR system. Optimal TOC-COD removals were found as 64.0-74.9% by 85.2 L/m²h at Fenton system, and as 66.5-76.1% by 138.1 L/m²h at UVA-Fenton with the lowest chemical spending, while 69.7-82.1% by 90.0 L/m²h at UVC-Fenton. Hybrid MORs studied were at desirable operational costs of 2.11, 4.15 and 3.13 /g TOC removed. This study revealed that by synergistic MOR performances, effluents, after pH adjustment, are directly dischargeable in sewage infrastructure ending with complete treatment. In a near future, such innovative approaches towards industrial wastewater treatments, at less resource demands, will unambiguously gain importance, as pressures to reuse wastewater increase and discharge limits become stricter.
... However, ceramics can be particularly prone to fouling by natural organic matter [23], which partially offsets the mentioned benefits. Proteins were identified as the most damaging fraction of the organic matter content, due to their high potential for irreversible adsorbing to metal oxide materials when present in a dominant concentration, as well as their capacity to magnify fouling effects due to synergistic interactions with humic substances and polysaccharides [24]. ...
... The fouling experiments were conducted as follows: 150 mL of BSA solution were filtered; then, the membrane was tangentially rinsed with 100 mL of ultrapure water, to simulate hydraulic cleaning as well as to determine the degree of irreversible fouling. This procedure was repeated twice to simulate the life of a membrane in operation undergoing multiple cleanings [24]. ...
Ceramic membranes suffer from rapid permeability loss during filtration of organic matter due to their fouling propensity. To address this problem, iron oxide ultrafiltration membranes were coated with poly(sulfobetaine methacrylate) (polySBMA), a superhydrophilic zwitterionic polymer. The ceramic-organic hybrid membrane was characterized by scanning electron microscopy (SEM) and optical profilometry (OP). Membranes with and without polySBMA coating were subjected to fouling with bovine serum albumin solution. Hydraulic cleaning was significantly more effective for the coated membrane than for the non-coated one, as 56%, 66%, and 100% of the fouling was removed for the first, second, and third filtration cycle, respectively. Therefore, we can highlight the improved cleaning due to an increased fouling reversibility. Although some loss of polymer during operation was detected, it did not affect the improved behavior of the tested membranes.
... Park et al. reported higher NOM degradation, removal, and fouling propensity in a hybrid ozonation-filtration process upon doping iron oxide NPs onto alumina ceramic membranes [45]. Enhanced cleaning performance and flux recovery of fouled alumina membranes dip-coated in iron oxide NP suspensions were reported by De Angelis et al. [46]. Through detailed analysis of surface properties of the metal oxide filtration layer, Lu et al. [47] observed that a layer of deposited Fe 2 O 3 NPs resulted in the least fouling tendency owing to the high hydrophilicity of the NPs. ...
... Major differences between methods used in the literature [43][44][45][46][47][48][49][50] to modify ceramic membranes with iron oxide NPs and the approach used in this study. Location of deposited NPs -Deposition of NPs on the membrane surface mainly -NP formation on the membrane surface and within the membrane pores -Lower physical/chemical attachment of foulants within the membrane pores Measurement of the intrinsic resistance of the membrane showed that the storage time did not influence the membrane performance. ...
A facile technique for impregnating commercial ceramic membranes with in situ grown iron oxide nanoparticles (NPs) and their use for synthetic produced water treatment is presented. Unlike most literature, our technique led to NPs forming on the surface as well as within the pores of the membrane. The antifouling properties of the membrane were evaluated in terms of surface characteristics, hydrophilicity, fouling characteristics, organic rejection, and regeneration capacity. The contact angle and the rate of water penetration were used to determine optimum precursor concentration for which membrane hydrophilicity is improved without major pore blockage due to NP agglomeration and deposition. At such concentration, in situ generation of the NPs, mostly with sizes less than 4 nm, did not affect membrane morphology, porosity or the intrinsic hydraulic resistance. Membrane organic rejection and fouling behavior showed considerable enhancement in humic acid, a model natural organic matter also existing in produced water, retention at different transmembrane pressures. Organic rejection along with the permeate flux suggest fouling transition from concentration polarization and pore plugging to gel/cake layer formation occurs at higher critical gel concentration for the modified membranes. The steady permeate flux for modified and unmodified membranes are comparable, especially at higher humic acid concentration, and flux recovery and fouling ratios reveal enhanced antifouling properties. A new dimensionless number, membrane performance number, is introduced to couple the performance of the membrane in terms of permeate flux and contaminant rejection.
... As advanced oxidation processes (AOPs) enable reactive oxygen species generation and thus hold promise for contaminant degradation, UF membranes have been exploited by integrating with AOPs for achieving lower membrane fouling potential, higher foulant removal efficiency, and/or efficient membrane cleaning effect (Byun et al., 2011, De Angelis andFidalgo de Cortalezzi, 2016;Park et al., 2012). Among numerous UF membrane materials, ceramic membranes (CM) with strong chemical and thermal resilience possess appealing features in enduring harsh operation environment and integrating with AOPs for synergistic enhancement of membrane performance (Lu et al. 2015(Lu et al. , 2016Zhao et al., 2018). ...
... The analysis of the four classic fouling models also consisted with the higher reversible fouling resistance and lower irreversible fouling resistance of PMS/CuFeCM hybrid filtration, as compared with those of CuFeCM single filtration. In previous studies, the reversible fouling resistance was reported to be caused mostly by external fouling due to the accumulation of foulant above membrane (i.e., intermediate blocking and complete blocking) and the formation of cake/gel layer (i.e., cake fouling), thus could be easily removed by hydraulic cleaning (Chang et al., 2017, De Angelis andFidalgo de Cortalezzi, 2016;Lu et al., 2016;Lu et al., 2015). Similarly, in PMS/CuFeCM hybrid filtration, the HA AOP particles that aggregated more on CuFeCM surface likely caused more external fouling, which resulted in higher reversible fouling resistance and more efficient hydraulic cleaning compared to those in single filtrations. ...
This work synthesized catalytic CuFe2O4 tailored ceramic membrane (CuFeCM), and systematically investigated the intercorrelated oxidation - filtration mechanism of peroxymonosulfate (PMS)/CuFeCM catalytic filtration for treating humic acid (HA). PMS/CuFeCM filtration exhibited enhanced HA removal efficiency while reduced the irreversible fouling resistance as compared with the conventional CM filtration. Results from HA characterizations showed that PMS/CuFeCM catalytic filtration oxidized HA into conjugated structures of smaller molecular weight. The unsaturated bonds further caused the re-agglomeration of HA, hence enhancing the size exclusion of CuFeCM. Meanwhile, oxidized HA particles with changing physicochemical properties reduced the total attractive interaction energy between CuFeCM and HA, mainly attributed to the reduced acid-base interaction energy according to the Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analysis. The changing of HA properties and HA-CuFeCM physicochemical interactions rendered more re-agglomerated HA particles retained above membrane with less attachment, which induced decreasing irreversible fouling resistance and facilitated easier external fouling removal by hydraulic cleaning. Overall, the PMS/CuFeCM configuration demonstrated in this study could provide a new insight into the synergistic oxidation - filtration interaction mechanism of hybrid catalytic ceramic membrane filtration process.
... They provide certain advantages such as modularity, scalability, and compactness, and feature the use of low-pressure systems that significantly reduce energy use and operation and maintenance costs [1,[15][16][17][18]. Additionally, the advanced oxidation technique such as Fenton reaction is an effective tool to treat POP-containing wastewater, in which the Fenton's reagent, a solution of hydrogen peroxide (H 2 O 2 ) with ferrous iron as a catalyst, can generate highly reactive hydroxyl radicals to degrade POP [19][20][21][22][23]. Combining with such advanced oxidation technique, the modified polymer-based catalytic membranes become known as promising candidates with high processability and low cost to simultaneously separate particulate pollutants and degrade organic pollutants [18,[24][25][26][27][28][29]. Recently, catalytic ceramic membranes combining with Fenton reaction are developed for degradation of POP, which are still related to the major challenges in the membrane fabrication, including synthesis of defect-free membranes, reduction of membrane thickness, and control of pore size distribution, etc [27][28][29]. ...
... Additionally, the advanced oxidation technique such as Fenton reaction is an effective tool to treat POP-containing wastewater, in which the Fenton's reagent, a solution of hydrogen peroxide (H 2 O 2 ) with ferrous iron as a catalyst, can generate highly reactive hydroxyl radicals to degrade POP [19][20][21][22][23]. Combining with such advanced oxidation technique, the modified polymer-based catalytic membranes become known as promising candidates with high processability and low cost to simultaneously separate particulate pollutants and degrade organic pollutants [18,[24][25][26][27][28][29]. Recently, catalytic ceramic membranes combining with Fenton reaction are developed for degradation of POP, which are still related to the major challenges in the membrane fabrication, including synthesis of defect-free membranes, reduction of membrane thickness, and control of pore size distribution, etc [27][28][29]. However, polymeric membranes are preferred to load Fenton reaction catalysts, which could have some advantages over the ceramic membranes, such as easy-fabrication, better control of the pore forming, higher flexibility, smaller spaces required for installation and lower costs [18,[24][25][26]. ...
A novel composite catalytic membrane is developed by blending silicon oxide coated ferroferric oxide (Fe3O4@SiO2) nanoparticles in polyether sulfone (PES) membrane as Fenton-like catalysts via liquid-induced phase separation (LIPS) method. By introducing Fe3O4@SiO2 nanoparticles in PES membrane matrix, the surface hydrophilicity, porosity and mean pore diameter of as-prepared composite catalytic membranes are improved due to the hydrophilic nature of the SiO2 coating layer on the Fe3O4@SiO2 nanoparticles. The as-fabricated catalytic membrane can filter large particles above ~100 nm and shows a high water flux of 2084 kg m⁻² h⁻¹ under 0.1 MPa. Importantly, the composite catalytic membrane shows efficient catalytic performance and satisfactory stability in the degradation of organic pollutants based on the Fenton-like reaction mechanism. The proposed strategy for membrane fabrication and the experimental results in this study provide valuable guidance for developing high-flux catalytic membranes with efficient catalytic performances for treatment of industrial and municipal wastewater.
... The focus of current studies has been mainly put on coating the outer and inner surfaces of ceramic membranes with a thin catalyst film [24,25,27]. As previously suggested, however, the surface Fenton reactions on thin iron-oxide film coated ceramic membranes suffered a considerable mass transfer hindrance, resulting from the formation of a thick and compact fouling layer on the membranes by sole NOM or NOM/colloid mixtures [23,28]. This is supposedly because the thin catalyst films, anchored on the membrane surfaces, lacked internal channels for the oxidant (i.e. ...
... This leads to water toxicity and pollution issues. To solve the problem of dispersed particle recovery and catalyst recycling after AOPs reactions, scientists have proposed a method combining membrane separation and AOPs to prepare graded membranes with excellent photocatalytic performance (Damodar et al., 2009;De Angelis & de Cortalezzi, 2016;Lee et al., 2016;Leong et al., 2014;Pablos et al., 2013;Wang et al., 2016). It is well known that MnO 2 has photocatalytic properties that can effectively prevent membrane contamination and significantly improve membrane permeability. ...
The photocatalytic degradation of pollutants in wastewater shows promise as a potential sustainable water treatment technology. The main challenges in the application of nanocatalysts are catalyst recovery and toxic effects. In this paper, a simple vacuum filter was used to fix a photocatalyst on a membrane surface, which alleviated the problem of catalyst recovery. These synthetic membranes were able to filter and degrade contaminants, alleviating the problems of reduced separation efficiency and shortened membrane life. In this work, K-birnessite MnO2 photocatalyst was prepared by a simple hydrothermal reaction, and K-birnessite MnO2 photocatalytic film was prepared by a simple vacuum filtration method. This membrane showed excellent catalytic activity for the degradation of methylene blue (MB). The photocatalytic membrane prepared in this paper was able to catalyze the oxidation of peroxymonosulfate (PMS) to degrade organic dyes in aqueous solution at a constant flow rate of 1 ml/min under simulated sunlight. Furthermore, the membrane also showed good performance under dark conditions. A mechanism analysis showed that the OH. and SO4.− produced by PMS interacting with the different oxidation states of Mn were the main causes of dye degradation. The catalytic filtration process using the K-birnessite MnO2 catalytic membrane provides a new method for wastewater purification with high efficiency and low energy consumption.
... The FCNM system allows efficient degradation of contaminants even under neutral condition . Current studies mainly focus on the foulants removal by in situ Fenton catalytic coupled MF membrane (IFCM) (Gao et al., 2021;Li et al., 2020b;Li et al., 2018b;Plakas et al., 2019;Sun et al., 2020;Wang et al., 2021a;Yang et al., 2019;Zhang et al., 2019b;Zhang et al., 2020b;Zheng et al., 2017;Zheng et al., 2019) or in situ Fenton catalytic coupled UF membrane (IFCU) (De Angelis & de Cortalezzi, 2016;Lin et al., 2020;Olvera-Vargas et al., 2018;Sun et al., 2018a;Wang et al., 2019;Wang et al., 2021b). Nevertheless, some studies have demonstrated that the reaction rate (Eq. ...
The integration of nanofiltration with catalysis enables high-efficient removal of micropollutants due to its remarkable high selectivity and superior degradation efficacy. Meanwhile, the catalysis-assisted nanofiltration can largely alleviate the issues of inferior low-molecular-weight micropollutants selectivity, membrane fouling and tradeoff limitation. Two different technical routes, catalytic coupled nanofiltration system and catalytic nanofiltration membrane, have been developed based on nanofiltration module and material design for micropollutants separation enhancement. In this review, we first summarize the underlying governing principles of the latest progress of catalysis coupled nanofiltration and catalytic nanofiltration membrane for micropollutants removal. The catalysis and filtration performance of these two routes were initially discussed and compared based on various catalytic oxidation conditions and target substances. We then discussed the corresponding catalytic membrane material innovation and preparation strategies (e.g. coating, bottom-up synthesis, blending, etc.). Finally, we point out the prospects and challenges of catalysis-assisted nanofiltration for micropollutants removal. This review provides directions and guidance for further catalysis-assisted nanofiltration module development and technical industrialization.
... Nanomaterial loading up to 15%, either in the membrane matrix (Albukhari et al., 2019;Hong & He, 2014;Kangwansupamonkon et al., 2010;Song et al., 2012Song et al., , 2014b or on the membrane surface (Balkenov et al., 2020) has been reported. Polymeric membranes are common though commercial Al 2 O 3 membrane has also been tested (De Angelis & de Cortalezzi, 2016;Mendret et al., 2013). For photocatalysis, both ultraviolet (UV) and visible light have been studied. ...
This book chapter summarized the efficiency of marine derived biopolymers such as chitosan, alginate, and carrageenan as both an excellent replacement for synthetic polymers and as a source of sustainable environmental tools for water remediation process. Such a sustainable exploitation of natural marine-derived resources constitutes a really interesting arena for the development of novel biomaterials, with both economic and environmental benefits. The emphasis is given on the composites developed from these three biopolymers with different promising additives such as carbon, metal nanoparticles, and ionic liquids. Their specific biological, physicochemical, and structural properties together with relevant applications in control and removal of water pollutants have been included. Using these biopolymers in various crucial water remediation processes not only controls potable water issue, in addition civil society can very well evade the algal blooms-related pollution to natural water resources. Finally, this chapter ends with the summary and future perspectives of these cost-effective and eco-friendly biobased polymers and their composites and establishing them as versatile material tools for water treatment processes for large-scale applications.
... The traditional AOPs, which include the Fenton reaction [142], ozonation [143] and photocatalysis [144], are mainly correlated to the production of hydroxyl radicals (•OH). Among those recently studied, sulfate radicals, another reactive type of oxidative species with relatively high reactivity and potential, have gained increasing attention [145]. ...
Ceramic membranes are being increasingly applied in water/wastewater treatment, chemical, beverage and pharmaceutical industry, due to their excellent filtration/separation performance, chemical, mechanical, thermal and long-term stability. This work presents a comprehensive review on the structure design, chemistry manipulation and functionalization of advanced ceramic membranes for their better performance in water/wastewater treatment. It begins with looking into engineering the microstructure features of advanced ceramic membranes, especially the intermediate and top active layers, aiming at reducing the mass transport resistance and the likelihood of membrane fouling. Strategies to tune both the porosity and pore configuration in the intermediate layer, minimize their thickness and even complete elimination are then analyzed. Recent advances in surface patterning of ceramic membranes enabled by additive manufacturing techniques are also highlighted. In parallel, emerging methodologies in manipulating the chemistry aspects of the top layer, in terms of surface hydrophilicity and surface charges, are examined, in order to regulate the interactions between the membrane surface and water/foulant molecules. Going beyond the conventional membranes, these functionalized ceramic membranes with the coupling of external stimulus are further involved for high-efficiency filtration and antifouling ability, with the focus on structural optimization at various scales. Finally, perspectives and opportunities on the marriage between microstructure and chemistry are discussed for new generation ceramic membranes and their application in water and wastewater treatment.
... Likewise, Fenton-like catalysis usually requires the retention and separation of catalysts from the treated water [19,20]. Thus, AOPs, especially heterogeneous Fenton oxidation technology that are integrated into the membrane filtration system immobilize catalysts and mitigate membrane fouling [21][22][23]. The hybridized membrane filtration system has been proven to have the excellent photocatalytic degradation of water pollutants and anti-fouling properties [24][25][26]. ...
Membrane fouling has always been a problem restricting the industrial applications of membrane technology. We synthesized FeOOH/g-C3N4 submicron particles exhibiting a visible light response and PAN(polyacrylonitrile)@FeOOH/g-C3N4 nanofibers by electrospinning. By coating a dense, smooth and nondestructive layer of chitosan (CS) on the surface of the support layer, a highly hydrophilic CS/[email protected]/g-C3N4 membrane with self-cleaning ability was successfully prepared. The mechanistic studies revealed that the hydroxyl radicals (OH·) produced by the photo-Fenton reactions are the main agents responsible for the degradation of contaminants. Compared with the use of the CS/[email protected]/g-C3N4 membrane alone, the addition of photo-Fenton reactions could effectively recover the water flux of the membrane polluted by methylene blue and erythromycin, and increase the rejections. In this study, the electrospun membrane was combined with a photo-Fenton reaction for the first time, and this combination provides a new alternative solution for membrane fouling mitigation.
... Moreover, combination of AOPs and membrane filtration has gained a great deal of attention recently as AOPs show synergistic roles in membrane filtration by enhancing pollutant degradation [18,19], improving filtration performance [20], and mitigating membrane fouling [21][22][23]. For example, our previous work [24,25] and a few others [26,27], heterogeneous photo-Fenton reaction was coupled with ceramic membrane filtration and increased the removal efficiency of 55 ± 5% and surface foulants (e.g., BSA and humic acid). Yang Guo developed a novel catalytic ceramic membrane with a coating layer of CuMn 2 O 4 particles that increased ozonation and filtration performances. ...
Pharmaceutical residuals are increasingly detected in natural waters, which made great threat to the health of the public. This study evaluated the utility of the photo-Fenton ceramic membrane filtration toward the removal and degradation of sulfamethoxazole (SMX) as a model recalcitrant micropollutant. The photo-Fenton catalyst Goethite (α-FeOOH) was coated on planar ceramic membranes as we reported previously. The removal of SMX in both simulated and real toilet wastewater were assessed by filtering the feed solutions with/without H2O2 and UV irradiation. The SMX degradation rate reached 87% and 92% respectively in the presence of UV/H2O2 for the original toilet wastewater (0.8 ± 0.05 ppb) and toilet wastewater with a spiked SMX concentration of 100 ppb. The mineralization and degradation by-products were both assessed under different degradation conditions to achieve deeper insight into the degradation mechanisms during this photo-Fenton reactive membrane filtration. Results showed that a negligible removal rate (e.g., 3%) of SMX was obtained when only filtering the feed solution through uncoated or catalyst-coated membranes. However, the removal rates of SMX were significantly increased to 67% (no H2O2) and 90% (with H2O2) under UV irradiation, respectively, confirming that photo-Fenton reactions played the key role in the degradation/mineralization process. The highest apparent quantum yield (AQY) reached up to approximately 27% when the H2O2 was 10 mmol·L−1 and UV254 intensity was 100 μW·cm−2. This study lays the groundwork for reactive membrane filtration to tackle the issues from micropollution.
... Furthermore, the filtration process may enhance the convective mass transfer rates of pollutants on the coated catalysts and thus improve the reaction kinetics compared to reactors with suspended catalysts . The surfaceenhanced reactions could lead to improved antifouling or defouling characteristics during membrane filtration as demonstrated previously (De Angelis and de Cortalezzi, 2016;Sun et al., 2018;Yu et al., 2017). Besides the improved antifouling capabilities, reactive membrane filtration could also be effective toward the degradation of refractory water contaminants, which however has not been extensively investigated. ...
... With the contribution of Fenton reaction, it is expected that the membrane fouling reduces and the permeability increases. Furthermore, the membrane may remove some Fenton shortcomings, as it is a substrate for the Fenton reaction to avoid the trouble of iron precipitation and catalyst lost from the treated water (Angelis and de Cortalezzi, 2016). In general, the combination of membrane and Fenton processes in the wastewater treatment systems can be accomplished through one of the following ways: (a) applying the membrane process following the Fenton process (Kumar and Pal, 2012), (b) applying the Fenton process following the membrane process (Miralles-Cuevas et al., 2013), (c) inserting the membrane module into the Fenton reactor (Zhang et al., 2011), and (d) inserting the Fenton catalysts on the surface or the pores of the membrane (Alpatova et al., 2015;Wang et al., 2019;Sun et al., 2018;Gui et al., 2012). ...
In this study, nanofiltration (NF) membrane process was combined with Fenton reaction (FT) by incorporating Fe-based nanoparticles (NPs), i.e., goethite (Goe) and maleate ferroxane (Mf) in the structure of polyacrylonitrile (PAN) film to improve the antifouling property and filtration performance of the membrane for amoxicillin (AMX) removal. The relation between the microstructure of the resulted composite with the antifouling properties and membrane performance is extensively investigated. It was found that by NF/FT combined process, foulants could be degraded and the AMX separation efficiency enhanced by 92.3 and 86.3% for PAN/Mf and PAN/Goe membranes, respectively. The permeate fluxes were also increased to 1.4 and 1.2 times of NF membrane filtration alone, respectively. Due to degradation of foulants, the combined NF/FT process exhibited better antifouling properties including flux recovery ratio (FRR) of 97.3 and 96.2% for PAN/Mf and PAN/Goe, respectively. The ratio of irreversible fouling to reversible fouling for NF/FT was lower than individual membrane process. Furthermore, the four cycles of AMX rejection, indicated the good stability and reusability of Fe-based NPs in composite membranes with FT reaction. Consequently, this research proves the successful combination of FT and NF membrane processes.
... Cortalezzi et al. developed a new route for the fabrication of iron oxide ultrafiltration membranes: ceramic membranes derived from ferroxane nanoparticles (Cortalezzi et al., 2003). Laura et al. explored the application of Fenton-type reactions in the cleaning of iron oxide ceramic membranes during filtration of water containing humic acid (HA), bovine serum albumin (BSA) and sodium alginate (SA) (De Angelis and de Cortalezzi, 2016). TiO 2 -incorporated membranes have proven excellent antifouling properties (Yu et al., 2017). ...
... Although membrane separation has many advantages, a major problem of this technique is membrane fouling [1]. Therefore many researchers try to develop novel solutions, such as combined methods [3,10,28,29], modified membrane surfaces [2,25,27,30] or cleaning techniques [21,31,32] to solve this problem. There are many reports in the literature in which membrane separation combined with pre-ozonation resulted in lower filtration resistances and/or fouling or even higher purification efficiency in case of different water contaminants [28,[33][34][35][36][37]. ...
In the present study membrane filtration was applied for the purification of crude oil containing stable oil in water emulsions (c oil = 100 ppm; d oil droplets < 1.5 µm) with and without pre-ozonation using polyethersulfone (PES) microfiltration membrane (d pore = 0.2 µm). The effect of ozonation on the size of oil droplets and on Zeta-potential was determined by dynamic light scattering measurements. The effects of applied transmembrane pressure, stirring speed and duration of ozonation were investigated in detail. Removal efficiency was determined by measuring turbidity, chemical oxygen demand (COD), total organic carbon content (TOC) and extractable oil content (TOG/TPH). Results pointed out, that short pre-ozonation (absorbed ozone was 30 ± 5 mg L-1) causes increased fluxes and decreased resistance without notable change in the purification efficiency in case of low transmem-brane pressure (0.1 MPa). However longer pre-ozonation or higher transmembrane pressure results in increased irreversible resistance, lower permeate fluxes or even lower purification efficiency.
... [14] The main disadvantage of FO, is that under high salt concentrations, scaling and fouling can occur on the membrane surface, significantly reducing water permeability. [23] To mitigate these issues, backwashing, increased cross-flow velocities, and rinsing has been performed on FO membranes to ensure proper operation and prevent excessive fouling and scaling [14,42,43]. ...
Hydraulic fracturing has become a reliable source for oil and natural gas, yet widespread use has led to significant issues with water consumption and sustainable sourcing. Research into the reuse of produced water and flowback water have focused on mitigating water demand in this industry through membrane separation technology. In general, nanofiltration and reverse osmosis have been thought to be more economically viable for the treatment of produced and flowback water at high flowrates. However, electrodialysis and electrodeionization are generally more flexible for production of produced water and brackish water for reuse in fracturing operations when contaminant concentrations in produced water and flowback water are low. Electrodialysis and electrodeionization can also significantly reduce wastewater produced from water treatment, decreasing the amount of water that must be disposed by deep well injection. Thus, there are many cases where electrically driven processes compete well with pressure driven processes due to high water recovery and each case must be analyzed in terms of water quality variability and overall desired water treatment rate. This paper finds that at low ion concentration of inlet water, electrodialysis and electrodeionization are energy-efficient, cost-effective attractive technologies for water recovery.
Water scarcity and environmental pollution are the major global concerns that require innovative solutions to circumvent the challenges associated with conventional wastewater treatment (WWT) methods. One promising approach involves integrating biological processes, such as activated sludge systems and microbial fuel cells, with cutting-edge nanotechnological interventions. This combination offers potential improvements in the efficiency and sustainability of wastewater treatment processes. The chapter overviews the current state of wastewater treatment, alongside the limitations of prevailing technologies. The principles and mechanisms supporting advanced biological processes and their ability to influence microorganisms’ inherent competencies to degrade various pollutants are explored. In addition, nanotechnological applications in wastewater treatment, accentuating nanomaterials’ exceptional properties that improve catalysis, adsorption, and separation processes, are accounted. A synergistic effect of nanotechnology and advanced biological processes that address problems like microbial resistance, emerging contaminants, and enhance treatment efficiency are also briefly discussed. Transformative potential of combinatorial approaches for sustainable achievement of wastewater treatment is comprehensively discussed. This underscores the inevitability of ongoing research and technological invention to augment this integration and plan the field for resource-efficient and an eco-friendlier future.
All species on this planet, both living and non-living, require water. It is well known that the availability of clean water sources is dwindling and that the rapid development of industry and technology has increased the number of hazardous effluents released into the environment. Before being released into the environment, industrial, agricultural, and municipal wastewater must be treated to remove dangerous contaminants such as organic colours, pharmaceutical wastes, inorganic compounds, and heavy metal ions. They pose major threats to human health and can pollute our environment if not controlled. Membrane filtration is a tried-and-true technique for removing germs and numerous hazardous substances from water. Carbon nanoparticles are used in wastewater treatment because of the promising surface area of sorbents. With the growth of nanotechnology, carbon nanomaterials (CNM) are being created and used in membrane filtration (MF) for effluent treatment before being terminated. To remove wastewater contaminants, this paper investigates using CNMs such as fullerenes, graphene’s, and CNTs. By examining sorption rate, selectivity, permeability, antimicrobial disinfectant properties, and environmental compatibility, we concentrate on these CNM-based membranes and this approach due to its attributes and utilization and how they can improve the performance of the frequently used membrane filtration system.
We perform the treatment of paper industry raw wastewater by using Fenton or photo-Fenton reactions with a submerged UF process within a MOR, aiming to meet current discharge standards and to provide water recovery by producing industrial reuse water with MD.
Water makes up 71% of the earth's surface, but due to the release of transitional metal ions, morbific microorganisms, and viruses, less than 1% is suitable for human use. Worldwide, heavy metal ions in wastewater are a severe environmental problem. Heavy metals on the surface of microorganisms and inside their cells can significantly affect their metabolic cycles. Heavy metals are the most prevalent ions in water. The metal ion chromium is poisonous, human carcinogenic , and has several harmful effects. They can cause dia-tom deaths by damaging the lamellae, kidneys, and liver of freshwater fish, hindering development and reducing sprouting in certain shrubs, boosting reproductive ratios, and causing impermanence in other surviving things like wig-glers [1,2]. Conventional water treatment techniques cannot remove most heavy metal ions. The most popular water treatment techniques now use membranes and nanotechnology.
Ceramic membranes incorporating CoFe2O4 (CoFeCM) were synthesized to activate peroxymonosulfate (PMS), and the performance and mechanisms of its oxidation-filtration were comprehensively investigated. The catalytic filtration performance of CoFeCM/PMS was evaluated by degradation of organic pollutants and the mitigation of membrane fouling. Results indicated that CoFeCM/PMS effectively removed toxic micropollutants, including phenol (82.56%), atrazine (93.42%), and carbamazepine (87.40%), ensuring the permeate quality and safety. Also, this synergistic process notably improved the degradation of natural organic matter (NOM) in the secondary effluent and Songhua River water. CoFeCM/PMS filtration effectively mitigated membrane fouling caused by three typical model organics, reducing their irreversible membrane fouling resistance by 70.85–83.62%, and increasing the normalized flux to 48.74–82.61%. The membrane fouling derived from two actual water systems was also greatly alleviated by CoFeCM/PMS. Based on the Extended Derjaguin-Landau-Verwey-Overbeek theory analysis, NOM was oxidized by reactive oxide species into hydrophilic small molecular fractions, resulting in remarkably increased repulsive interaction between NOM and CoFeCM surface. Density functional theory calculation results confirmed the nanoconfinement effect in CoFeCM pores, which can slow down the growth of foulants in pores and effectively alleviate irreversible membrane fouling. Consequently, standard blocking transformed into the dominant membrane fouling pattern due to the synergistic effects of nanoconfinement catalysis (in membrane pores) and repulsive interactions (on membrane surface) during oxidation-filtration.
Photocatalysis water treatment without artificial energy is cost‐effective, waste‐free and sustainable. Coventional powder photocatalysts have tiny contact surfaces, low catalytic efficiency, and are difficult to recycle and reuse, restricting their usage. Herein, a Lignin@t‐FeC2O4/g‐C3N4 material is developed by engineering hollow quadrangle t‐FeC2O4 and g‐C3N4 nanosheets on lignin membranes through facile impregnation coating and precipitation reaction. Fast mass transport, catalytic activity and accessibility characterize hollow tetragonal FeC2O4·2H2O. TEM, SEM and FTIR show that lignin binds t‐FeC2O4 and g‐C3N4. The g‐C3N4 nanosheets are uniformly wrapped on the surface of lignin fibers, and t‐FeC2O4 is loaded between them. This structure increases visible light absorption and active site‐contaminant contact. The chain reaction produces extremely active hydroxyl radicals from hydrogen peroxide because the Lignin@t‐FeC2O4/g‐C3N4 modules are rich inFeII, according to XPS. Transient photocurrent response curves and electrochemical impedance spectroscopy suggest a promoted charge migration and isolation at the redox reaction interface in the Lignin@t‐FeC2O4/g‐C3N4 system. As a result, Lignin@t‐FeC2O4/g‐C3N4 degrades 99% Rhodamine B within 40 minutes, and this performance is stable even under difficult conditions, such as low hydrogen peroxide concentration and high pH. This study combines lignin membranes with the photo‐Fenton reaction, and thus provides new concept for the development and application of membranes and photocatalysis.
Fouling of ultrafiltration (UF) and microfiltration (MF) membranes by proteins is a major challenge in the bioprocessing and dairy industries, as well as in surface and wastewater treatment applications. This review attempts at presenting a comprehensive state-of-the-art understanding on protein fouling of membranes. Effects of operating conditions, along with properties of proteins and membranes, are discussed. Various tools and techniques used to characterize and monitor fouling are described. Different mitigation techniques and cleaning methods used are also presented. Two main factors have been identified as playing important roles in governing protein fouling, namely, ratio of protein size to membrane pore size and interfacial interactions (i.e., protein-protein and protein-membrane). Some directions for future research are suggested: (1) explore a wider range of proteins and their mixtures with respect to their fouling tendencies; and (2) create a comprehensive dataset that can be used to develop machine-learning models to enhance both predictive capabilities and mechanistic understanding.
Membrane separation is emerging as a key technology in wastewater treatment solutions particularly where high quality of treated water is targeted. Wastewaters from industrial processes are complex and based on the constituents, a combination of physico-chemical-biological steps are used to comply with discharge standards. Domestic wastewaters are also increasingly contaminated with recalcitrant (difficult to biodegrade) components such as pharmaceutically active compounds and personal care products. To improve industrial water security and meet zero liquid discharge norms (where applicable), there is growing interest in options that lead to (1) treated wastewater of suitable quality that can be reused/recycled on-site and/or (2) recovery of resources (chemicals, etc.) that can be reused in the production process. Resource recovery and removal of emerging contaminants in domestic wastewaters is also becoming a priority. Consequently, hybrid processes comprising membrane technologies integrated with other treatment steps have been developed. Biological treatment is combined with microfiltration/ultrafiltration/nanofiltration/forward osmosis in membrane bioreactors for wastewater reclamation. To enhance removal of recalcitrant compounds, adsorption and catalysis have been employed. Other membrane processes such as reverse osmosis membrane distillation, and electrodialysis have been coupled with MBRs for tertiary treatment. Nanomaterials-based membrane systems have evolved aiming to enhance overall performance, e.g., higher flux (flow rate per unit membrane area), higher removal of targeted contaminants, and lower membrane fouling. This chapter provides an overview of state of the art and challenges in nanomaterial-based membranes and corresponding hybrid treatment systems.
Water plays a crucial role in every animate life. There are a multitude of problems that can be occurred without water; thereafter, mankind’s lives can be extinct. Several solutions should be implemented in order to protect water supplies and to treat water used in industries. Among solutions, wastewater treatment is sounded economical and convenient way to overcome water scarcity. Physical, chemical, biological, and mixed treatment systems provide ample opportunity to use water over and over again. However, by using nanotechnology in these systems wastewater treatment can reach much more quality and overcome their drawbacks. Nano-membranes in MBR technology is one of most appropriate treatment technologies that have such potential to postpone water shortage until several years.
Novel self-cleaning catalytic membranes are prepared for water treatment via an integration of heterogeneous Fenton and membrane process. Polysulfone (PSF) based functional copolymers with pendant ferrocene groups are facilely synthesized via a combination of controlled radical polymerization and ester coupling reaction. Different catalytic membranes with tuned surface hydrophilicity are then prepared through non-solvent phase inversion method based on functional ferrocene- and hydroxyl-containing PSF. These membranes have demonstrated high activity in catalyzing Fenton-type reactions, which also lead to outstanding antifouling performance for the membrane. Finally, the catalytic membranes are successfully used for treatment of waste water containing different dyes. The proposed strategy in this work may provide worthy guidance to catalytic membranes, which is promising for water purification through simultaneous Fenton reaction and membrane separation.
The present study evaluated a photo-Fenton reactive membrane that achieved enhanced 1,4-Dioxane removal performance. As a common organic solvent and stabilizer, 1,4-Dioxane is widely used in a variety of industrial products and poses negative environmental and health impacts. The membrane was prepared by covalently coating photocatalyst of goethite (α-FeOOH) on a ceramic porous membrane as we reported previously. The effects of UV irradiation, H2O2 and catalyst on the removal efficiency of 1,4-Dioxane in batch reactors were first evaluated for optimized reaction conditions, followed by a systematical investigation of 1,4-Dioxane removal in the photo-Fenton membrane filtration mode. Under optimized conditions, the 1,4-Dioxane removal rate reached up to 16% with combination of 2 mmol/L H2O2 and UV365 irradiation (2000 µW/cm2) when the feed water was filtered by the photo-Fenton reactive membrane at a hydraulic retention time of 6 min. The removal efficiency and apparent quantum yield (AQY) were both enhanced in the filtration compared to the batch mode of the same photo-Fenton reaction. Moreover, the proposed degradation pathways were analyzed by density functional theory (DFT) calculations, which provided a new insight into the degradation mechanisms of 1,4-Dioxane in photo-Fenton reactions on the functionalized ceramic membrane.
The combination of membrane filtration with catalytic ozonation has been promoted in this study, to develop self-cleaning in situ for membrane fouling and micropollutants degradation. A novel CuMn2O4/g-C3N4 catalytic ceramic membrane (CG/CM) was developed and a catalytic ozonation membrane reactor was established. Firstly, powder catalyst CuMn2O4/g-C3N4 was optimized for the degradation of micropollutant benzophenone-4 (BP-4) and elimination of toxic byproduct bromate (BrO3⁻). Secondly, the thickness, roughness, and hydrophilicity/hydrophobicity of CuMn2O4/g-C3N4 deposition on CG/CM, was adjustable by changing the loading time. The obtained CG/CM showed good in situ self-cleaning for membrane fouling, BP-4 degradation, and BrO3⁻ elimination through interface catalytic ozonation, as sodium alginate (SA) selected as the model probe. [Ozone] and transmembrane pressure (TMP) showed a significant inflence on dependence on CG/CM performance. The operation parameters were optimieized as [ozone]=20 mg/L, TMP=0.2 bar, and cross flow velocity=1600 mL/min, with the normalized flux recovering to 87% and a BP-4 removal efficiency three times that of sole ozonation. Furthermore, the effect of [SA], [bovine serum albumin], and [BP-4] on the performance was studied. This represents a promising strategy for developing catalytic ceramic membranes coupled with catalytic ozonation for water treatment.
Catalytic membranes have gained increasing interest in water treatment due to their improved performance on contaminants removal, fouling mitigation, and cleaning efficiency. The reactive species generated in the catalytic membrane system play a critical role in the process. However, the performance of SO4•–-based catalytic membrane has been considerably less studied. The current research investigated the performance of a novel SO4•–-based ceramic ultrafiltration membrane on organics removal, fouling mitigation, and cleaning efficiency. The catalytic membrane was prepared through the filtration of a MnO2-Co3O4 nanoparticle solution, followed by sintering and sonication. Characterization results demonstrated the successful deposition of nanoparticles onto the membrane surface. Besides, the influence of 0.06 mg/cm² of coating on membrane permeability was negligible. The production of SO4•– (i.e., with the presence of peroxymonosulfate (PMS)) as predominant radical species was confirmed using para-chlorobenzoic acid (pCBA) and nitrobenzene (NB) as probe compounds. Due to the reaction with SO4•–, a higher NOM removal rate was observed with the coated membrane as compared to the pristine membrane. However, the permeate flux of the coated membrane was only slightly increased in the presence of PMS (i.e., 8% increase in normalized flux), possibly due to the formation of small molecules leading to internal pore fouling. Contrariwise, the PMS cleaning efficiency with the coated membrane was remarkably higher than the pristine membrane and stable within three cycles of membrane filtration. The results of this study would significantly assist in the optimization of SO4•–-based catalytic membrane processes for future successful industrial implementation.
A novel CuO modified ceramic hollow fiber membrane for in-situ peroxymonosulfate (PMS) activation was developed and employed in surface water treatment. The performance of membrane fouling control and organic pollutants removal was systematically investigated. The results indicated that compared with pristine membrane, CuO modified ceramic hollow fiber membrane significantly improved the removal of dissolved organic carbon (DOC) and UV absorbance at 254 nm (UV254) in surface water. The removal rate increased with the increase of CuO loading content because of the reduction of the membrane surface pore size, but declined with the increase of PMS dosage due to the degradation products of incomplete mineralization passing through the membrane. The fluorescent compounds in surface water were efficiently removed by the CuO modified ceramic hollow fiber membrane and enhanced with the increase of PMS dosage and CuO loading content. The CuO modified ceramic hollow fiber membrane with in-situ PMS activation exhibits excellent antifouling property to natural organic matter (NOM) in surface water. Both the reversible and irreversible fouling decreased with the increase of PMS dosage while the membrane fouling would be slightly intensified with increased loading of CuO on the membrane, suggesting the trade-off relation between PMS dosage and CuO loading content. In addition, the degradation efficiency of organic pollutants in surface water was dramatically enhanced by the CuO modified ceramic hollow fiber membrane via incorporation of in-situ PMS oxidation process. High removal performance after five cycles of experiments showed the superior stability and reusability of the CuO modified ceramic hollow fiber membrane.
Membrane technologies have broad applications in the removal of contaminants from drinking water and wastewater. In recent decades, ceramic membrane has made rapid progress in industrial/municipal wastewater treatment and drinking water treatment owing to their advantageous properties over conventional polymeric membrane. The beneficial characteristics of ceramic membranes include fouling resistance, high permeability, good recoverability, chemical stability, long life time, contaminant degradation, and self-cleaning, which have found applications with the recent innovations in both fabrication methods and nanotechnology. Therefore, ceramic membranes hold great promise for potential applications in water treatment. This paper mainly reviews the progress in the research and development of ceramic membranes, with key focus on porous ceramic membranes and nanomaterial-functionalized ceramic membranes for nanofiltration or catalysis. The current state of the available ceramic membranes in industry and academia, and their potential advantages, limitations and applications are reviewed. The last section of the review focuses on ceramic membrane fouling and the efforts towards ceramic membrane fouling mitigation. The advances in ceramic membrane technologies have rarely been widely reviewed before, therefore, this review could be served as a guide for the new entrants to the field, as well to the established researchers.
In this study, we investigated the performance of powdered activated carbon dynamic membranes (PAC DMs) in fouling mitigation strategies during cross-flow microfiltration for high-efficiency seawater pretreatment. By altering the fouling mechanism and water molecule pathway, PAC DMs successfully enhanced the pseudo-steady-state filtration flux and rejection of cross-flow microfiltration by 53% and 29%, respectively, compared to filtration without a PAC DM. Moreover, Fenton oxidation processes (FOPs) application in the DMs’ cross-flow cleaning was studied and showed promising results, recovering up to 28% of the initial filtration flux when used alone and 52% when combined with alkaline cleaning. This study provides insight into the utilization FOPs cleaning technology for PAC DMs cross-flow cleaning, allowing the automation and optimization of DMs operation.
The anion exchange resin (AER) process successfully removed dissolved organic matter (DOM) from various water matrices. To restore AER capacity by routine DOM removal from the regenerant is an attractive strategy to solve the spent brine disposal problem. This study investigated the long-term removal (from the feed) and accumulation (in the inorganic regenerant) characteristics of typical DOM molecules (including anionic pharmaceuticals, short-chain aliphatic acids, humic substances and amino acids) during ˜50 adsorption–regeneration cycles of an AER-based fixed-bed process with the routine physico-chemical purification treatment of the regenerant. All anionic DOM molecules complied with common long-term removal and accumulation mechanisms driven by both electrostatic and non-electrostatic interactions in a multicomponent system, regardless of aromatic structure, hydrophobicity/hydrophilicity, or water solubility. A high anionic DOM removal (˜90%) from the feed could be stably achieved after anionic DOM accumulated in the regenerant was effectively removed (˜80%) by more frequent regenerant-purification treatments. The AER presented here did not selectively remove aromatic and/or hydrophobic DOM molecules from water matrices during the long-term cyclic operation. These findings will enable the development of new designs of AER-based fixed-bed processes for DOM removal from various water matrices.
Membrane fouling is an obstacle impeding the wide applications of ceramic membranes and organics are responsible for most of the membrane fouling issues in wastewater treatment. In this study, Fenton cleaning strategy was firstly proposed to clean ceramic membrane fouling in wastewater treatment. Fe2+ efficiently catalyzed fouling cleaning with H2O2 (1.5%) to recover the filterability of ceramic membrane. The maximum ∆TMP recovery (over 99%) was achieved at an optimal Fe2+ dosage of 124 mg/L after 6 hr of immersion cleaning. The total residual membrane fouling resistance decreased gradually from this optimum value as the Fe2+ dosage increased above 124 mg/L. The residual hydraulically reversible fouling resistance accounted for most of the membrane fouling and was basically removed (≤3.0 × 109 m-1) when Fe2+ dosages higher than 124 mg/L were used. The foulants responsible for the formation of a residual hydraulically reversible fouling layer (DOC (dissolved organic carbon), proteins, polysaccharides, EEM (fluorescence excitation-emission matrix spectra), SS (suspended solids), and VSS (volatile suspended solids)) were gradually removed as the Fe2+ dosage increased. These residual organic foulants were degraded from biopolymers (10-200 kDa) to low molecular weight substances (0.1-1 kDa), and the particle size of these residual foulants decreased significantly as a result. The strong oxidation power of hydrogen peroxide/hydroxy radicals towards organic foulants was enhanced by Fe2+. Fe2+ played a significant role in the removal of hydraulically reversible fouling and irreversible fouling from the ceramic membrane. However, Fe2+ (≥124 mg/L) increased the likelihood of forming secondary iron-organics aggregates.
Palm oil mill effluent (POME), which is rich in organic matter, is one of the major contributors of water pollution. To date, biological treatment has been employed before it is released into water bodies to minimize the environmental hazards. However, the dark brownish colour of the effluent is still a big challenge to be addressed. In regard to this concern, membrane separation can serve as an attractive solution for this issue. This paper aims to investigate the performance of ultrafiltration nanocomposite membrane embedded with coupled zinc-iron oxide (ZIO) for the decolourization of POME. The ZIO was synthesized through the solution combustion technique by employing zinc nitrate hexahydrate and iron (III) nitrate nonahydrate as the precursors and urea as the fuel. The nanocomposite flat sheet membrane was prepared via phase inversion process. The physico-chemical properties of the MMMs were analysed using zeta potential analysis, SEM, BET and contact angle. Continuous filtration test was carried out to evaluate the capability of the MMMs for colour and COD removal. The results showed that the increase in the ZIO loading has drastically increased the membrane surface negativity and led to the colour removal of 70%. In addition, with the addition of M0.5, the permeation and colour removal had increased 25% and 17% respectively, compared to the pristine PVDF membrane. However, the long term filtration test revealed that the structure of M0.5 collapsed after 4 cycles of washing, but M2.0 still retained its performance. In a nutshell, this study demonstrated that negative surface charge has improved the antifouling properties meanwhile hydrophilicity has contributed to increased water flux during the colour removal process.
This research describes the heterogeneous catalytic reactions of H2O2 with granular size goethite (α-FeOOH) particles in aqueous solution under various experimental conditions. This is an important reaction for the environment since both H2O2 and iron oxides are common constituents of natural and atmospheric waters. Furthermore, iron oxides function as catalysts in chemical oxidation processes used for treatment of contaminated waters with H2O2. The results of this study demonstrated that the decomposition rate of H2O2 over goethite surface can be described by the second-order kinetic expression −d[H2O2]/dt = k[FeOOH][H2O2], where k = 0.031 M-1 s-1, at pH 7 in the absence of any inorganic or organic chemical species. The apparent reaction rate was dominated by the intrinsic reaction rates on the oxide surfaces rather than the mass transfer rate of H2O2 to the surface. The activation energy of the reaction of H2O2 with the iron oxide surface was determined to be 32.8 kJ/M. The reaction mechanism for the decomposition of H2O2 on goethite surface was proposed on the basis of the fundamental reactions describing the surface complexation chemistry for iron oxide and the interaction of H2O2 with the surface sites. The kinetic model, which was developed according to the proposed mechanism, was found to be similar to the classical Langmuir−Hinshelwood rate model. The model was calibrated and verified successfully. For low concentrations of H2O2, the Langmuir−Hinshelwood model is reduced to the observed second-order kinetic expression.
Increasingly stringent regulations for drinking water quality have stimulated the application of ultrafiltration to water treatment. In addition to removing particulate materials from water (including microorganisms, bacteria and viruses), the use of membrane treatment also meets purification requirements. However, irreversible fouling curtails the economic viability of such a process. Experiments in stirred-cells were conducted to evaluate the effects of surface water composition on rejection and fouling of two ultrafiltration membranes with different molecular weight cut-offs (10 and 100 kDa). Experimental solutions consisted of natural organic matter or humic substances in a background electrolyte. The effect of calcium concentration decreased rejection of humic acid under certain circumstances. This is believed due to reduced molecular size with an initial increase in calcium concentration. However, at about 2.5 mM CaCl2, IHSS humic acid aggregates. This aggregation increased rejection, and also caused irreversible fouling of the 100 kDa membrane, presumably as a result of pore size reduction due to internal deposition of aggregates. This was confirmed by blocking law analysis. The variation of transmembrane pressure indicated the importance of a ‘critical flux’ effect. The organics and their various fractions showed differences both in rejection and flux decline. The larger and more UV-absorbing fraction of humic acid was shown to be responsible for irreversible pore adsorption and plugging. The fulvic acid and the hydrophilic fraction showed a smaller and mostly reversible flux decline.
The oxidative removal of natural organic matter (NOM) from waters using hydrogen peroxide and iron-coated pumice particles as heterogeneous catalysts was investigated. Two NOM sources were tested: humic acid solution and a natural source water. Iron coated pumice removed about half of the dissolved organic carbon (DOC) concentration at a dose of 3000 mg l(-1) in 24 h by adsorption only. Original pumice and peroxide dosed together provided UV absorbance reductions as high as 49%, mainly due to the presence of metal oxides including Al(2)O(3), Fe(2)O(3) and TiO(2) in the natural pumice, which are known to catalyze the decomposition of peroxide forming strong oxidants. Coating the original pumice particles with iron oxides significantly enhanced the removal of NOM with peroxide. A strong linear correlation was found between iron contents of coated pumices and UV absorbance reductions. Peroxide consumption also correlated with UV absorbance reduction. Control experiments proved the effective coating and the stability of iron oxide species bound on pumice surfaces. Results overall indicated that in addition to adsorptive removal of NOM by metal oxides on pumice surfaces, surface reactions between iron oxides and peroxide result in the formation of strong oxidants, probably like hydroxyl radicals, which further oxidize both adsorbed NOM and remaining NOM in solution, similar to those in Fenton-like reactions.
Membranes are thin films allowing for selective transport of mass species, such as gases, liquids, or ions. The major advantages of inorganic membranes as compared to polymeric membranes are their better thermal, chemical, and mechanical stability and higher permselectivity. The disadvantages are higher membrane costs and an increased difficulty toward making membrane modules with high packing densities. Inorganic membranes will find applications that require high permselectivity and good chemical and thermal stability beyond what can be offered by polymeric membranes. The most important properties of inorganic membranes include permeance and selectivity. These properties of microporous and mesoporous membranes are determined by the pore size, porosity, and membrane thickness. Chemistry plays a very important role in controlling these properties. Microporous amorphous silica membranes can be prepared by the acid catalyzed solegel method using an alkoxide precursor. The intercrystalline defects and zeolitic pores of crystalline zeolite membranes can be eliminated or narrowed by chemical vapor deposition through proper control of the surface chemistry of the zeolite framework. The membranes are very thick because synthesis chemistry gave large metal-organic framework crystals. Synthesis chemistry controls the pore size and structure of ordered mesoporous materials as well as orientation of the pore of the ordered mesoporous membranes.
The Major Iron OxidesLess Common or Rare Iron OxidesIron Oxides in the Environment
A comparative assessment of iron oxide ceramic ultrafiltration membranes fouling by model organic compounds was performed. To characterize this fouling phenomenon, humic acid (HA), bovine serum albumin (BSA) and sodium alginate (SA) were used as models of humic substances, proteins and polysaccharides respectively. Clean and fouled iron oxide membranes surfaces were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The influence of concentration, foulant mixtures and pH on the fouling mechanism was investigated. Fouling was observed to depend first on foulant-membrane interactions, followed by a second step where membrane material plays a less important role. Membrane surface chemistry and solution pH were significant factors affecting irreversibility of the fouling layer. A strong dependence was observed in foulant concentration and solution pH. Foulant mixtures showed synergetic results, determined by foulant-foulant interactions.
Increased protein fouling of polyether sulphone membranes after NaOCl cleaning was previously reported but not explained. Here we show that the cleaning increases the hydrophilicity, and the degree of increase linearly correlates with the amount of adsorbed protein. The high initial flux through the cleaned membrane is a result of the hydrophilization of the membrane surface and a promise for the enhanced fouling. We propose that the proper oxidative cleaning should target the restoration of the initial flux and not its increase over initial values. The previously reported pore size changes are subjective as higher hydrophilicity of the membrane surface increases water permeability and adsorption of size test solutes.
The aims of this study were (a) to evaluate the degradation of acetamiprid with the use of Fenton reaction, (b) to investigate the effect of different concentrations of H2O2 and Fe(2+), initial pH and various iron salts, on the degradation of acetamiprid and (c) to apply response surface methodology for the evaluation of degradation kinetics. The kinetic study revealed a two-stage process, described by pseudo- first and second order kinetics. Different H2O2:Fe(2+) molar ratios were examined for their effect on acetamiprid degradation kinetics. The ratio of 3mgL(-1) Fe(2+): 40mgL(-1) H2O2 was found to completely remove acetamiprid at less than 10min. Degradation rate was faster at lower pH, with the optimal value at pH 2.9, while Mohr salt appeared to degrade acetamiprid faster. A central composite design was selected in order to observe the effects of Fe(2+) and H2O2 initial concentration on acetamiprid degradation kinetics. A quadratic model fitted the experimental data, with satisfactory regression and fit. The most significant effect on the degradation of acetamiprid, was induced by ferrous iron concentration followed by H2O2. Optimization, aiming to minimize the applied ferrous concentration and the process time, proposed a ratio of 7.76mgL(-1) Fe(II): 19.78mgL(-1) H2O2. DOC is reduced much more slowly and requires more than 6h of processing for 50% degradation. The use to zero valent iron, demonstrated fast kinetic rates with acetamiprid degradation occurring in 10min and effective DOC removal.
Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species such as the hydroxyl radical and possibly others. In this review, the complex mechanisms of Fenton and Fenton-like reactions and the important factors influencing these reactions, from both a fundamental and practical perspective, in applications to water and soil treatment, are discussed. The review covers modified versions including the photoassisted Fenton reaction, use of chelated iron, electro-Fenton reactions, and Fenton reactions using heterogeneous catalysts. Sections are devoted to nonclassical pathways, by-products, kinetics and process modeling, experimental design methodology, soil and aquifer treatment, use of Fenton in combination with other advanced oxidation processes or biodegradation, economic comparison with other advanced oxidation processes, and case studies.
A study has been conducted on the decomposition of 2-chlorophenol (2-CP) applying a heterogeneous Fenton reaction using goethite as catalyst at pH 3. The research was aimed at obtaining a workable kinetic expression apt for developing a kinetic model for scaling up purposes. Several aspects of the reaction have been described in the available literature but, for the moment, without a reasonable representation of the entire reaction behavior. In order to provide a more comprehensive and probable explanation of the whole observed performance, a set of experiments was carried out varying systematically all the significant variables. The proposal considers that the reaction is essentially a combination of four heterogeneous processes associated with one typical homogeneous Fenton reaction. Three of the surface reactions explain a very small iron leaching to the medium by a proton induced solubilization, a reductive dissolution reaction and a non-reductive iron release produced by detected 2-CP chemical decomposition byproducts, particularly, chlorohydroquinone (ClHQ) and oxalic acid (OxA). Iron concentration in the solution may be further increased in the final stages of the reaction after most of the 2-CP has been degraded, by the appearance of OxA that takes part in a third surface reaction. The fourth heterogeneous reaction rationalizes the unusual hydrogen peroxide consumption at high catalyst loadings. During the homogeneous reaction, the presence of ClHQ and ClBQ produces a homogeneous autocatalytic beneficial enhancement of the Fe3+→Fe2+ transformation. Consequently, the existence of phenolic derivatives either in the mixture or as reaction byproducts produces a beneficial enhancement of the reaction rate. Very low iron leaching is required to produce the onset of the homogeneous Fenton reaction, which was shown to be strongly dependent upon the reaction temperature. All the experimental findings were satisfactorily described by a set of 19-step feasible reaction scheme. The process could be useful for the treatment of wastewaters containing pollutants with phenolic derivatives, as long as iron leaching remains within tolerable limits.
This study study aimed to clarify the effect of interactions between membranes and natural organic matter (NOM), which is considered to be the major membrane foulant in wastewater treatment processes. Sodium alginate (SA), humic acid (HA) and bovine serum albumin (BSA) were used as NOM models. Hollow fiber membranes were prepared using cellulose acetate butyrate polymer (CAB). Filtration experiments were carried out using SA, HA and BSA solutions and the membrane fouling behavior was examined. NOM adsorption on CAB membranes was measured by quartz crystal microbalance with dissipation (QCM-D), where NOM solutions were flowed across CAB spin-coated quartz crystal sensors and adsorbed. SA showed more severe permeate flux decline during the early stage of filtration and lower recovery of permeate flux after backwashing compared with HA. The severe flux decline for SA was due to pore-plugging and cake formation with high molecular weight components. The BSA solution, with no high molecular components, showed a gradual permeate flux decline and resulted in lower permeate flux after 240 min filtration compared with HA. The gradual permeate flux decline with the BSA solution was due to ready adsorption of BSA on the CAB membrane. (C) 2011 Elsevier B.V. All rights reserved.
Membrane filtration plays a critical role in advanced wastewater treatment and reuse. However, alginate, one typical polysaccharide secreted by microorganisms in wastewater, may cause significant membrane fouling. This study explored the use of an enzyme, alginate lyase, to catalytically degrade alginate in order to decrease its fouling potential for 0.2 and 0.02 mu m gamma-Al(2)O(3) ceramic membranes. The results indicated that the enzyme significantly reduced membrane fouling and made the fouling easy to clean (i.e., reversible fouling). The enzymatic degradation of alginate followed Michaelis-Menten kinetics through the beta-elimination mechanism. When 20 mg L(-1) alginate lyase was added to 325 mg L(-1) alginate solution at pH 6.7 +/- 0.2, the weight-averaged molecular weight decreased from 35,500 to 2200 Da over a 2 h period. Meanwhile, polydispersity declined from 9.10 to 1.47. Membrane filtrations were compared between the original and the enzyme-reacted alginate at pH 6.7 +/- 0.2 and an ionic strength of 0.075 M. At the end of 50-min filtration, alginate lyase reduced the foulant resistance by 82% and 85% for the 0.2 and 0.02 mu m membrane, respectively, because the enzyme-reacted alginate had a higher diffusivity and less affinity/attachment to the membrane pores and surfaces. In addition, the enzyme improved the efficiency of backwash as well. Compared to the 0.2 mu m membrane, 0.02 mu m membrane had a more significant enhancement of backwashing with a 100% recovery rate obtained, because diffusivity is more important to clean tight membrane pores. A decline in the rejection rate of the membranes after enzymatic reactions was observed, which may be explained by decreased steric exclusion as evidenced by the size exclusion chromatography.
In this study, two ceramic nanofiltration membranes with a molecular weight cutoff of 450 Da (NF450) and 1000 Da (NF1000) were used to reduce the concentration of organic matter (OM) in natural water, and the effect on the formation of disinfection by-products (DBPs) was evaluated. The effects of pressure, conductivity and pH were studied. The formation of trihalomethanes, haloacetic acids, haloacetonitriles and haloketones was evaluated. The results of the study indicated that the permeation flow rate of NF1000 was greater than that of NF450. An increase in the operating pressure improved the efficiency of OM removal and reduced the formation of DPBs. Over 75% of the formation potential of trihalomethanes was eliminated using NF450 membrane. The NF1000 membrane produces smaller decreases in trihalomethanes. As the conductivity increased from 900 μS/cm to 4000 μS/cm, the reduction of trihalomethanes decreased from 51% to 22% and from 80% to 39% for NF1000 and NF450 respectively. The flow through NF450 and NF1000 decreased when the pH of the solution decreased from pH 8.3 to pH 4.5. The values of trihalomethanes rejections at pH 8.3 were 79% and 58% for NF450 and NF1000 respectively, and these values decreased to 65% and 40% at pH 4.5.Research highlights► The elimination of THMs and HAAs increases with the increase of pressure. ► When the conductivity increased, DBPs potential formation increased. ► The effect of the pH on the concentration of DOC was stronger than that of DBPs. ► Ceramic membrane (NF 450 Da) produces a rejection of HKs greater than 60%.
Oxidation of benzoic acid (BA) by H2O2 was performed with a novel supported γ-FeOOH catalyst in a circulating fluidized-bed reactor (CFBR). This study focused mainly on determining the proportions of homogeneous catalysis and heterogeneous catalysis in this CFBR. Also studied herein was how pH, H2O2 concentration, and BA concentration affect the oxidation of BA. Experimental results indicate that the decomposition rate of H2O2 was proportional to its concentration and that the oxidation rate of BA depended on both H2O2 and BA concentrations. The change in the rate constant of heterogeneous catalysis by pH was described in terms of ionization fractions of surface hydroxyl group. From the mathematical deduction, we can infer that the reaction rate associated with FeIIIOH2+ is markedly higher than that with FeIIIOH. Conclusively, although heterogeneous catalysis contributes primarily to the oxidation of BA at pH 4.4−7.0, the homogeneous catalysis is of increasing importance below pH 4.4 because of the reductive dissolution of γ-FeOOH.
This review provides updated information on the application of the Fenton process as an advanced oxidation method for the treatment of industrial wastewaters. This technology has been used in recent decades as a chemical oxidation process addressed to meet a variety of objectives including final polishing, reduction of high percentages of organic load in terms of chemical oxygen demand or total organic carbon and removal of recalcitrant and toxic pollutants thus allowing for further conventional biological treatment. The efficiency and flexibility of this technology has been proven with a wide diversity of effluents from chemical and other related industries or activities, including pharmaceutical, pulp and paper, textile, food, cork processing, and landfilling among others. Copyright © 2008 Society of Chemical Industry
The photodegradation of humic acid (HA) was carried out in the presence of the Fenton reagent. The absorbance decrease of HA was strongly influenced by the pH, and initial concentrations of H2O2 and Fe(II). An initial absorbances of HA (10 mg L−1) in 254 and 400 nm were completely disappeared after 8 h under the optimum conditions. The decrease of TOC as a result of mineralization of HA was observed during the photo-Fenton process. The degree of HA mineralization was about 80% under UV irradiation after 15 h. The molecular weight distribution changes of HA were evaluated by high performance size exclusion chromatography (HPSEC). The large molecular weight component in HA appears to be easily degraded by the photo-Fenton process than the smaller components. Furthermore, the photo-Fenton process was successfully applied to the degradation of HA in sea sediment of Ago Bay, Mie Prefecture, Japan. Based on these results, the photo-Fenton reaction could be useful technology for the treatment of environmental sample contaminated by HA.
In the last decades, the research done in the field of membrane technology applied to wastewater has drastically increased . However, the applicability of this technology is limited due to the fouling of membranes, directly affecting its performance. In this study, several parameters thought to be in some extent responsible for membrane fouling are evaluated. Ultrafiltration was the selected membrane process and membranes with different molecular weight cut off (MWCO) have been employed. The feed of the experiments consisted of solutions containing humic and fulvic acids, natural organic matter (NOM), alginic acid and cellulose. The influence of different sets of operating parameters, such as applied pressure, concentration of polymer, content of calcium and pH of the feed solution in the performance of the process has been investigated.
In this paper the results obtained from investigations on a polyamide reverse osmosis membrane fouled by precipitation of materials which exist in water are presented. In these studies, the effect of different cleaning agents on recovery of the fouled membrane has been shown. Results show that a combination of sodium dodecyl sulphate, Na-ED TA and sodium hydroxide must be used as a cleaning material to reach the optimum recovery of the polyamide membrane employed in petrochemical industries. It was found that cleaning efficiency depends on the type of cleaning agent and its concentration. It has been shown that the efficiency increases with increasing the concentration of the cleaning agent and reaches a maximum value. The concentration that provides the highest cleaning efficiency can be considered as the optimum concentration. This depends on the type of cleaning agents. Operating conditions such as cross flow velocity, turbulence in the vicinity of the membrane surface, temperature, pH and cleaning time also play an important role in the cleaning processes. Membrane cleaning requires deep understanding of the interactions between the foulants and the membrane as well as the effect of the cleaning procedure on deposit removal. In this paper the mechanism of deposit removal is also investigated.
a b s t r a c t The fouling and subsequent cleaning of RO membranes fouled by a mixture of organic foulants sim-ulating wastewater effluent has been systematically investigated. The organic foulants investigated included alginate, bovine serum albumin (BSA), Suwannee River natural organic matter, and octanoic acid, representing, respectively, polysaccharides, proteins, humic substances, and fatty acids, which are ubiquitous in effluent organic matter. After establishing the fouling behavior and mechanisms with a mixture of organic foulants in the presence and absence of calcium ions, our study focused on the clean-ing mechanisms of RO membranes fouled by the mixture of organic foulants. The chemical cleaning agents used included an alkaline solution (NaOH), a metal chelating agent (EDTA), an anionic surfactant (SDS), and a concentrated salt solution (NaCl). Specifically, we examined the impact of cleaning agent type, cleaning solution pH, cleaning time, and fouling layer composition on membrane cleaning effi-ciency. Foulant–foulant adhesion forces measured under conditions simulating chemical cleaning of a membrane fouled by a mixture of the investigated organic foulants provided insights into the chemical cleaning mechanisms. It was shown that while alkaline solution (NaOH) alone is not effective in dis-rupting the complexes formed by the organic foulants with calcium, a higher solution pH can lead to effective cleaning if sufficient hydrodynamic shear (provided by crossflow) prevails. Surfactant (SDS), a strong chelating agent (EDTA), and salt solution (NaCl) were effective in cleaning RO membranes fouled by a mixture of foulants, especially if applied at high pH and for longer cleaning times. The observed cleaning efficiencies with the various cleaning agents were consistent with the related measurements of foulant–foulant intermolecular forces. Furthermore, we have shown that an optimal cleaning agent con-centration can be derived from a plot presenting the percent reduction in the foulant–foulant adhesion force versus cleaning agent concentration.
A combined method of backpulsing and membrane surface modification was employed for the reduction of membrane fouling. A novel photoinduced grafting method was used to render polypropylene (PP) membranes hydrophilic with neutral or positively or negatively charged surfaces by grafting monomers of poly(ethylene glycol 200) monomethacrylate (PEG200MA), dimethyl aminoethyl methacrylate (DMAEMA), or acrylic acid (AA), respectively. Both unmodified and modified PP membranes, as well as commercial cellulose acetate (CA) membranes, were evaluated in a crossflow microfiltration system with and without backpulsing in the presence of Escherichia coli bacterial suspensions. Without backpulsing, the resulting permeate volume is nearly the same for the different membranes. With backpulsing, however, considerable improvement was obtained by surface modification, especially for low feed concentrations and for short filtration times. For example, the permeate volume for backpulsed filtration of 0.14 g/l E. coli for 1 h using the unmodified PP membrane is 1.7 times that without backpulsing, and it is even higher for the other membranes. The permeate volume with backpulsing is highest for the neutral, hydrophilically modified PP membrane and for the commercial CA membrane, approximately 2.6 times that of the unmodified PP membrane without backpulsing. Moreover, the recovered pure buffer flux after backwashing the fouled membranes for an extended period is approximately twice as high for these neutral hydrophilic membranes as it is for the unmodified hydrophobic PP membrane. However, the recovered flux after a long backwash of the membranes fouled with backpulsing is 20–40% lower than that of the membrane fouled without backpulsing, apparently due to greater adhesive internal fouling when the membrane surface is frequently exposed by rapid backpulsing.
The vacuum-UV- (VUV-) photolysis of water is one of the advanced oxidation processes (AOP) based on the production of hydroxyl radicals (HO) that can be applied to the degradation of organic pollutants in aqueous systems. The kinetics of the VUV-photolyses of aqueous solutions of citric acid (1) or gallic acid (2) were investigated in the presence or absence of dissolved molecular oxygen (O2) and under different pH conditions. In the case of 1, the rate of consumption of the substrate was faster at pH 3.4 than in alkaline solution (pH 11), whereas, in the case of 2, the variation of pH (2.5–7.5) did not affect the course of the reaction. Unexpectedly, the rates of depletion of both 1 and 2 decreased in the absence of O2, this effect being much more pronounced in the case of 2. In order to explain these results, possible reaction pathways for the degradation of 1 and 2 are proposed, and the roles of the oxidizing (HO) and reducing (H and eaq−) species produced by the VUV-photolysis of water are discussed.
Ferroxane nanoparticles, obtained from reaction of lepidocrocite (FeOOH) and acetic acid at room temperature, were applied to the fabrication of ceramic membranes. The size of the nanoparticles and the kinetics of the reaction were investigated. Ferroxane derived membranes were prepared and characterized by nitrogen adsorption/desorption isotherms, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Permeability and molecular weight cut off measurements were conducted on asymmetric ferroxane-derived membranes. The average pore size was determined to be 24.11 nm and the BET surface area was 75.6 m2/g. Permeability was measured for membranes with one, two, and three coatings, to determine the effect of thickness of the ferroxane layer on the membrane hydraulic resistance. The MWCO of the ferroxane-derived membranes was 150,000 Da, which falls in the ultra-filtration range.
Whilst permeate flux is an important parameter in characterising synthetic membrane performance, it is a poor indicator of surface condition. Membrane pores may be fouled, but the charge of the fouled surface is critical in determining performance. Polyethersulphone (PES) and polysulphone (PSf) ultrafiltration membranes were fouled with spent sulphite liquor and cleaned using sodium hydroxide and Ultrasil 11 over several operating cycles. The Osmonics PSf membrane displayed a greater relative flux decline over several cycles than the Nadir PES membrane. After 15 fouling and cleaning cycles, the relative flux decline for the PSf membrane was 70% and 55% when cleaning with NaOH and Ultrasil 11, respectively. The corresponding relative flux decline figures for the PES membrane after 15 cycles were 45 and 30% for NaOH and Ultrasil 11 cleaning, respectively. Performance and zeta-potential graphs are presented that demonstrate the strong relationship between the fouling and cleaning history, the surface charge and the performance of the membranes in terms of flux recovery.
In this study, membrane filtration was used to treat a secondary effluent emanating from a sewage treatment works that treats a combined industrial and municipal wastewater. Three feed pretreatments for a spiral wound reverse osmosis (RO) membrane filtration were evaluated, including: (i) membrane ultrafiltration (System I); (ii) dual media filtration and granular activated carbon (GAC) adsorption (System II); (iii) dual media filtration with dosage of organic flocculant and GAC adsorption (System III). It is shown that System I yielded the best turbidity removal, with turbidity below 1.15 NTU. The combination of System I and RO showed the least flux decline between cleans. In addition, flux recovery was easily achieved with mechanical clean without chemicals. The overall total dissolved solids (TDS) rejection was well maintained at 81–89%. The dual media filter and GAC did not provide adequate pretreatment; this led to rapid fouling in the RO membrane. The impact on RO performance was a greater flux decline coupled with TDS rejection decrease from 78 to 66%. The addition of an organic flocculant (dosed at 15 mg/l to form filterable flocs) did not significantly improve the performance of the dual media filtration and the GAC. It was also observed that inadequate pretreatment had an adverse impact on the membrane flux recovery by cleaning. Simple mechanical cleaning was insufficient in recovering flux when Systems II and III were employed as pretreatment. Furthermore, longer chemical cleaning duration was required to recover membrane flux.
Fouling as well as the presence and growth of microorganisms necessitate regular cleaning and disinfection of membranes and membrane separation plants, especially those used for food and biotechnological applications.Factors of importance for membrane fouling reduction and for membrane cleaning, such as flow conditions, pretreatment, membrane properties, water quality, cleaning agents, and cleaning performance, are reviewed and discussed.
This paper reviews the published literature on potential membrane fouling components, available cleaning agents and possible interactions between cleaning agents and fouling components. It also lists the cleaning models available in the literature, and evaluates the advantages and disadvantages of these models. Based on this outcome, a new cleaning model is proposed to capture cleaning dynamics for 10 different cleaning agents, varying from acidic, alkali and oxidizing to sequestering agents and detergents that were used to clean dead-end ultra filtration membranes fouled by surface water. The model is effectively fitted to the experimental data of the different cleanings. Two criteria are subsequently introduced to quantify the overall cleaning effect of a cleaning agent in terms of cleaning rate and cleaning effectiveness. For membranes fouled by surface water with high organic content it was found that caustic-and oxidizing cleaning agents give the best overall cleaning results.
A major factor limiting the use of microfiltration for surface water treatment is membrane fouling by natural organic matter. The extent and mechanisms of humic acid fouling during microfiltration have been examined using stirred cell filtration experiments and scanning electron microscopy. The extent of fouling was strongly dependent on both the source and preparation of the humic acid solutions. The large flux decline observed during constant pressure microfiltration was caused by the formation of a humic acid deposit located on the upper surface of the membrane. Prefiltration of the humic acid solutions dramatically reduced the rate of fouling through the removal of large humic acid aggregates. The initial fouling in this system was determined almost entirely by the convective deposition of these large particles/aggregates on the membrane surface. This initial deposit accelerated the subsequent rate of humic acid fouling, possibly serving as a nucleation site for deposition of macromolecular humic acids.
Nanoscale iron oxide particles were synthesized and deposited on porous alumina tubes to develop tubular ceramic adsorbers for the removal of arsenic, which is an extremely toxic contaminant even in very low concentrations. In addition, its natural presence affects rural and low-income populations in developing countries in Latin America and around the world which makes it essential to develop an user-friendly, low energy demanding and low cost treatment technology. The system can be operated with minimal trans-membrane pressure difference and does not require pumping. The support tubes and final membrane have been characterized by surface area and porosity measurements, permeability tests and scanning electron microscopy (SEM) imaging. Arsenic concentrations were determined by ICP-OES. This easy to use and low cost process is effective in the removal of arsenic and may provide a valuable solution to the groundwater quality issue in Latin America.
The literature on chemical cleaning of polymeric hollow fibre ultrafiltration and microfiltration membranes used in the filtration of water for municipal water supply is reviewed. The review considers the chemical cleaning mechanism, and the perceived link between this and membrane fouling by natural organic matter (NOM)—the principal foulant in municipal potable water applications. Existing chemical cleaning agents used for this duty are considered individually and their cleaning action described, along with the most commonly applied cleaning protocols (i.e. the cleaning conditions, cleaning sequence and method of cleaning agent application).It is concluded that chemical cleaning is poorly understood and not extensively investigated, in marked contrast to the much more widely studied area of membrane fouling generally, for which there are thousands of published studies. Studies of chemical cleaning specifically have instead been generally limited either to qualitative measurements, such as the use of surface or other analytical tools to characterise membrane foulants and record their removal, or incidental permeability recovery recorded from cleaning events during pilot or full-scale trials. It is proposed that a chemical cleaning index is needed, analogous to the recently proposed general membrane fouling index, based on empirical data to inform cleaning protocols for specific duties and feedwater quality.
The role of chemical and physical interactions in natural organic matter (NOM) fouling of nanofiltration membranes is systematically investigated. Results of fouling experiments with three humic acids demonstrate that membrane fouling increases with increasing electrolyte (NaCl) concentration, decreasing solution pH, and addition of divalent cations (Ca2+). At fixed solution ionic strength, the presence of calcium ions, at concentrations typical of those found in natural waters, has a marked effect on membrane fouling. Divalent cations interact specifically with humic carboxyl functional groups and, thus, substantially reduce humic charge and the electrostatic repulsion between humic macromolecules. Reduced NOM interchain repulsion results in increased NOM deposition on the membrane surface and formation of a densely packed fouling layer. In addition to the aforementioned chemical effects, results show that NOM fouling rate increases substantially with increasing initial permeation rate. It is demonstrated that the rate of fouling is controlled by an interplay between permeation drag and electrostatic double layer repulsion; that is, NOM fouling of NF membranes involves interrelationship (coupling) between physical and chemical interactions. The addition of a strong chelating agent (EDTA) to feed water reduces NOM fouling significantly by removing free and NOM-complexed calcium ions. EDTA treatment of NOM-fouled membranes also improves the cleaning efficiency dramatically by disrupting the fouling layer structure through a ligand exchange reaction between EDTA and NOM-calcium complexes.
Fouling by natural organic matter, such as humic substances, is a major factor limiting the use of microfiltration for water purification. The objective of this study was to develop a fundamental understanding of the underlying mechanisms governing humic acid fouling during microfiltration using a combined pore blockage–cake filtration model. Data were obtained over a range of humic acid concentrations, transmembrane pressures, and stirring speeds. The initial flux decline was due to pore blockage caused by the deposition of large humic acid aggregates on the membrane surface, with a humic acid deposit developing over those regions of the membrane that have first been blocked by an aggregate. The rate of cake growth approaches zero at a finite filtrate flux, similar to the critical flux concept developed for colloidal filtration. The data were in good agreement with model calculations, with the parameter values providing important insights into the mechanisms governing humic acid fouling during microfiltration. In addition, the basic approach provides a framework that can be used to analyze humic acid fouling under different conditions.
One of the critical issues for the successful application of ultrafiltration in water treatment is membrane fouling due to dissolved organic matter, which negatively affects productivity, product quality, and process costs. The aim of the present study is to contribute to the understanding of fouling phenomena by organic matter and the efficiency of the backwashing technique, which is applied in practice to restore membrane flux. Fouling experiments are carried out, in a single fiber apparatus, using humic acid solutions as model substances representative of naturally occurring organic matter; they are aimed at identifying the significance of distinct fouling mechanisms and their degree of reversibility. A new model is presented which takes into account the simultaneous action of all fouling mechanisms and describes the experimental results successfully. An important parameter considered in the study is the concentration of calcium ions, which promote humic acid aggregation and influence the rate of flux decline, the reversibility of fouling and rejection. A relatively rapid irreversible fouling takes place due to internal pore adsorption, which persists for a long time. In parallel, with time, pore blocking becomes important and a fouling cake develops on the membranes. The effects of the latter are partly reversed by backwashing, but their combined influence persists over a long time giving rise to a prolonged flux decline.
Reverse osmosis (RO) is being increasingly used in treatment of domestic wastewater secondary effluent for potable and non-potable reuse. Among other solutes, dissolved biopolymers, i.e., proteins and polysaccharides, can lead to severe fouling of RO membranes. In this study, the roles of RO membrane surface properties in membrane fouling by two model biopolymers, bovine serum albumin (BSA) and sodium alginate, were investigated. Three commercial RO membranes with different surface properties were tested in a laboratory-scale cross-flow RO system. Membrane surface properties considered include surface roughness, zeta potential, and hydrophobicity. Experimental results revealed that membrane surface roughness had the greatest effect on fouling by the biopolymers tested. Accordingly, modified membranes with smoother surfaces showed significantly lower fouling rates. When Ca2+ was present, alginate fouled RO membranes much faster than BSA. Considerable synergistic effect was observed when both BSA and alginate were present. The larger foulant particle sizes measured in the co-existence of BSA and alginate indicate formation of BSA-alginate aggregates, which resulted in greater fouling rates. Faster initial flux decline was observed at higher initial permeate flux even when the flux was measured against accumulative permeate volume, indicating a negative impact of higher operating pressure.
Two approaches were utilized to disperse rhodium metal particles onto the ultramicroporous silica separation layer of a composite inorganic membrane prepared by modification of a commercial alumina support. In one approach, the silica membrane surface was first amine-derivatized using the silylation agent H2N (CH2)2 NH (CH2)3 Si (OCH3)3, followed by reaction with the metal-organic compound [(1,5-COD) RhCl]2. This approach led to uniformly dispersed ca. 6 nm rhodium particles located only on the surface of the membrane (as revealed by cross-sectional transmission electron microscopy) after a hydrogen reduction at 200°C. The size of the [(1,5-COD) RhCl]2 molecule combined with a reduction of the pore size due to silylation apparently prevented significant penetration into the membrane separation layer. Modest reductions (ca. 50%) in helium and nitrogen permeability resulted from this treatment. An alternative procedure involved wet impregnation of the membrane with a (Rh(acac)3)/THF solution, followed by air calcination and hydrogen reduction. This approach produced a much lower coverage of ca. 4 nm rhodium particles. Helium and nitrogen permeability measurements indicated that considerable pore blockage existed after the calcination step, and that the reduction step led to defect or crack formation in the SiO2 membrane layer as evidenced by a sizeable increase in permeability. It was proposed that the silylation approach led to the [(1,5-COD) RhCl]2 precursor being located primarily on the surface with little pore penetration, while the Rh(acac)3 was able to penetrate the pores to a greater extent, leading to damage of the membrane layer during decomposition of the ligands. The silylation approach appears to be a general strategy to control the size, surface coverage, and location of catalyst in catalytic membrane design.
The fouling behaviours and membrane autopsy protocol for polysulfone (PSF) ultrafiltration membrane fouled with natural organic matter source waters were studied. Samples from Ulu Pontian river which has a relatively hydrophilic NOM source water and Bekok Dam river which has a relatively hydrophobic NOM source water have been used as the case study. Fouling characteristics of the NOM source waters were assessed by filtering the feed water with an immersed hydrophobic PSF ultrafiltration membrane. The asymmetric hollow fiber PSF membrane was spun by a dry–wet phase inversion spinning process. The membrane autopsy protocol was performed to identify the nature of the deposited foulants and their relative effects on membrane characteristics. Results for the relatively hydrophilic NOM source water (Ulu Pontian river) exhibited greater flux decline but lesser NOM removal considerably due to pore adsorption, indicating that the low molecular weight, aliphatic linear structure and neutral/base organic matter contained within the hydrophilic fraction were the prime foulants. In contrast, relatively hydrophobic NOM source water (Bekok Dam water) that possessed higher charge density, greater molecular weight and bulky aromatic structure has exhibited lesser flux decline and better NOM rejection noticeably due to cake deposition, despite filtering through a hydrophobic membrane, thus suggesting that the electrostatic repulsion was more influential than the steric hindrance mechanisms. In comparison a non-charged model compound (polyethylene glycol) of similar molecular weight was used to quantify the role of electrostatic charge repulsion on NOM rejection. Moreover, analyses on the permeate characteristics revealed that the hydrophobic NOM was preferentially removed by the negatively charged PSF membrane as opposed to the hydrophilic NOM, hence, suggesting that the charge interactions, in addition to size exclusion were more crucial to NOM removal. The membrane autopsies analyses confirmed the flux decline results and permeate analyses as the filtered-membrane was mainly fouled by the hydrophilic NOM components rather than humic compounds. Distinctive changes were observed in membrane characteristics in terms of ionizable functional groups, membrane wettability and zeta potential. ATR-FTIR analysis revealed that hydrophilic components such as the polysaccharides-like substances, alcoholic compounds and aliphatic amide of protein groups as the responsible materials covering the membrane surface. Morphological analyses using SEM indicated different fouling mechanisms occur for both NOM sources associated with differences in the relative NOM constituent distributions, NOM structural variations and NOM removal mechanisms.
A facile polyol synthesis was used for the deposition of Ag nanoparticles on electrospun TiO2 nanofibers for the subsequent fabrication of Ag/TiO2 nanofiber membrane. The permeate flux of the Ag/TiO2 nanofiber membrane was remarkably high compared to commercial P25 deposited membrane. The Ag/TiO2 nanofiber membrane achieved 99.9% bacteria inactivation and 80.0% dye degradation under solar irradiation within 30 min. The Ag/TiO2 nanofiber membrane also showed excellent antibacterial capability without solar irradiation. Considering the excellent intrinsic antibacterial activity and high-performance photocatalytic disinfection/degradation under solar irradiation, this novel membrane proved to have promising applications in water purification industry.
The elimination of Bisphenol A (BPA) from contaminated waters is an urgent challenge. This contribution focuses on BPA degradation by homogeneous Fenton reagent based on reactive ()OH radicals. Pronounced sub-stoichiometric amounts of H(2)O(2) oxidant were used to simulate economically viable processes and operation under not fully controlled conditions, as for example in in situ groundwater remediation. Aside from the most abundant benzenediols and the monohydroxylated BPA intermediate (which were detected as stable intermediates in earlier contributions), a wide array of aromatic products in the molecular weight range between 94 Da (phenol) and approximately 500 Da could be detected, the overwhelming majority of which have not been reported thus far. The identification was carried out by GC/MS analysis of trimethylsilyl ethers. The structural assignments were confirmed through the use of fully deuterated [(2)H(16)] BPA as the substrate, as well as using retention indices calculated on the basis of the increment system. The occurrence of aromatic intermediates larger than BPA, which typically share either a biphenyl- or a diphenylether structure, can be explained by oxidative coupling reactions of stabilized free radicals or by the addition of organoradicals (organocations) onto BPA molecules or benzenediols. The hydroxycyclohexadienyl radical of BPA was recognized to play central role in the degradation pathways. Ring opening products, including lactic, acetic and dicarboxylic acids, could be detected in addition to aromatic intermediates. Since some of those intermediates and products are recalcitrant to further oxidation under the conditions of sub-stoichiometric Fenton reaction, they should be carefully considered when designing and optimizing Fenton-driven remediation systems.
Fenton's reagent has been shown to be a feasible technique to treat phenolic-type compounds present in a variety of food processing industry wastewaters. A model compound, p-hydroxybenzoic acid was oxidised by continuously pumping two solutions of ferrous iron and hydrogen peroxide. Typical operating variables like reagent feeding concentrations and flowrate, temperature and pH were studied. A mechanism of reactions based on the classical Fenton's chemistry was assumed, and computed concentration profiles of the parent compound, ferrous ion and dihydroxybenzene were compared to experimental results. The model qualitatively predicted the influence of several operating variables, however, calculated results suggested the presence of parallel routes of substrate elimination and/or a initiating rate constant with a higher value. The low efficiency of a well-known hydroxyl radical scavenger (tert-butyl alcohol) also supports the contribution of oxidising species different from the hydroxyl radical to substrate removal. Further evidence of the presence of reactions different from the hydroxyl radical oxidation was observed from comparison of the simultaneous Fenton's or UV/H2O2 oxidations of p-hydroxybenzoic acid, tyrosol and p-coumaric acid.
Oxidation of benzoic acid (BA) by H2O2 was performed with a novel supported gamma-FeOOH catalyst in a circulating fluidized-bed reactor (CFBR). This study focused mainly on determining the proportions of homogeneous catalysis and heterogeneous catalysis in this CFBR. Also studied herein was how pH, H2O2 concentration, and BA concentration affect the oxidation of BA. Experimental results indicate that the decomposition rate of H2O2 was proportional to its concentration and that the oxidation rate of BA depended on both H2O2 and BA concentrations. The change in the rate constant of heterogeneous catalysis by pH was described in terms of ionization fractions of surface hydroxyl group. From the mathematical deduction, we can infer thatthe reaction rate associated with ...Fe(III)OH2+ is markedly higher than that with ...Fe(III)OH. Conclusively, although heterogeneous catalysis contributes primarily to the oxidation of BA at pH 4.4-7.0, the homogeneous catalysis is of increasing importance below pH 4.4 because of the reductive dissolution of gamma-FeOOH.
It is well known that the dissolution of goethite plays an important role in catalyzing the oxidation of organic chemicals. Therefore, this study investigates how surface dissolution of goethite affects 2-chlorophenol oxidation in the goethite/H2O2 process. Experimental results indicate that ligand and reductant can enhance the dissolution rate of goethite, which is surface-controlled. Our results further indicate 2-chlorophenol degradation depends on goethite concentration. In addition, the oxidation rate of 2-CP is correlated with reductive dissolution rate at various dosages of goethite. Moreover, the oxidation mechanism of 2-CP is also a surface-controlled reaction. A mechanism proposed herein indicates that, in addition to the contaminant, its intermediate species affect the oxidation rate as well.
We examined plasma protein adsorption and platelet adhesion to polysulfone (PSf) flat membranes coated with Pluronic with varying polyethylene oxide (PEO) block length. Adsorption of albumin, globulin and fibrinogen to Pluronic-coated PSf membranes was independent of plasma dilution when concentrations of human blood plasma above 20% were applied. Increasing coating concentrations of aqueous Pluronic solution resulted in decreased protein adsorption by the PSf membranes. Pluronic F68, which was more hydrophilic than Pluronic L62 or L64 and had 80% of PEO content, was the most effective at suppressing the adsorption of plasma proteins and platelet adhesion to PSf membranes. We developed a mixed protein solution containing human albumin, gamma-globulin and fibrinogen to attempt to mimic the competitive and cooperative binding effects found in plasma. Fibrinogen adsorption from plasma could be recapitulated by the mixed protein solution. The number of platelets adhering to the PSf membranes decreased as the coating concentration of Pluronic solution was increased, and platelet adhesion decreased in parallel with fibrinogen adsorption. These results suggest that the bioinert property of PEO segments in the Pluronic, which is ascribed to their high flexibility in aqueous media, suppresses the adsorption of plasma proteins and platelets to the Pluronic-coated PSf membranes.
Hydrogen peroxide (H(2)O(2)) is a strong oxidant and its application in the treatment of various inorganic and organic pollutants is well established. Still H(2)O(2) alone is not effective for high concentrations of certain refractory contaminants because of low rates of reaction at reasonable H(2)O(2) concentrations. Improvements can be achieved by using transition metal salts (e.g. iron salts) or ozone and UV-light can activate H(2)O(2) to form hydroxyl radicals, which are strong oxidants. Oxidation processes utilising activation of H(2)O(2) by iron salts, classically referred to as Fenton's reagent is known to be very effective in the destruction of many hazardous organic pollutants in water. The first part of our paper presents a literature review of the various Fenton reagent reactions which constitute the overall kinetic scheme with all possible side reactions. It also summarises previous publications on the relationships between the dominant parameters (e.g. [H(2)O(2)], [Fe(2+)], . . .). The second part of our review discusses the possibility of improving sludge dewaterability using Fenton's reagent.
Gallic acid (3,4,5-trihydroxybenzoic acid) is a major pollutant present in the wastewater generated in the boiling cork process, as well as in other wastewaters from food manufacturing industries. Its decay in aqueous solutions has been studied by the action of several oxidation systems: monochromatic UV radiation alone and combined with hydrogen peroxide, Fenton's reagent and the combination Fenton's reagent with UV radiation (photo-Fenton system). The influence of the pH is discussed and the quantum yields are determined in the UV radiation system. Also, the influence of operating variables (initial concentrations of H2O2 and Fe(II), and pH) is established in the Fenton's reaction. The apparent pseudo-first-order rate constants are evaluated in all the experiments conducted in order to compare the efficiency of each one of the processes. Increases in the degradation levels of gallic acid are obtained in the combined processes in relation to the single UV radiation system, due to reactions of the very reactive OH*. These improvements are determined in every process by calculating the partial contribution to the overall decomposition rate of the radical pathways. For the oxidant concentrations applied, the most effective process in removing gallic acid was found to be the photo-Fenton system. The rate constant for the reaction of gallic acid with OH was also determined by means of a competition kinetics model, being its value 11.0+/-0.1 x 10(9)l mol(-1)s(-1).
Microfiltration and Ultrafiltration: Principles and Applications
- J Zerman
- A L Zydney
J. Zerman, A.L. Zydney, Microfiltration and Ultrafiltration: Principles and Applications, Taylor &
Francis, 1996.
Fabricación y Caracterización de Membranas Cerámicas Derivadas de Nanopartículas de Ferroxanos para el Tratamiento Avanzado de Aguas
- L De Angelis
L. De Angelis, Fabricación y Caracterización de Membranas Cerámicas Derivadas de Nanopartículas
de Ferroxanos para el Tratamiento Avanzado de Aguas, in: Instituto de Investigación e Ingeniería
Ambiental, Universidad Nacional de San Martín, Argentina, 2013.
Membrane cleaning, Desalination
- G Trägårdh
G. Trägårdh, Membrane cleaning, Desalination, 71 (1989) 325-335.
- S.-S Lin
- M D Gurol
S.-S. Lin, M.D. Gurol, Catalytic Decomposition of Hydrogen Peroxide on Iron Oxide: Kinetics,
Mechanism, and Implications, Environmental Science & Technology, 32 (1998) 1417-1423.