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Review of the use of mesoporous silicas for removing dye from textile wastewater
Abstract
The textile industry is a major user of dyes and hence an important source of water pollution, which poses a threat to aquatic as well as human life. Adsorption is a widely used technique for separating and removing dye from wastewater. Recently the use of mesoporous silica (MPSs) as an adsorbent in wastewater treatment has received considerable attention. MPSs are emerging as potential adsorbents because of their surface area, tunable and uniform pore structure, high pore volume, ordered pore structure, thermal and mechanical stability, and extraordinarily wide possibilities for functionalization to increase their adsorption capacity. In this paper the ability of MPSs to absorb dyes from aqueous solutions is reviewed. This article provides information on adsorption studies carried out under different operational conditions such as contact time, solution pH, temperature, agitation speed, etc. This review also summarizes and attempts to compare the equilibrium isotherm and kinetic models, and the thermodynamic studies that report the adsorption of dyes onto MPSs. The literature reviewed, indicate that SBA-MPSs have a higher adsorption capacity than MCM-MPSs and functionalized MPSs a better adsorption capacity than MPSs. It is evident from the literature that the potential of MPS based nano-sorbents being used for removing dyes from aqueous solution is very high. However, still more research work is needed on developing cost effective and more efficient MPS based nano-sorbents for use commercially.
... An alternative, using RH to create highly functional silica, is an attractive research to scientists. Many shapes of silica have been made from RH such as spheres, rods, and plates for applications in construction, environment, energy storage, and catalyst [3,[5][6][7], where the mesoporous silica and its composite have been proven as an effective material in the adsorption and degradation of organic substances in wastewater due to its high surface area, good thermal stability, and favorable hydrothermal stability [8]. ...
... The rapid development of industry, agriculture, and services in developing countries leads to a large amount of wastewater being discharged into the environment every year [8]. Water sources are seriously polluted from wastewater causing serious impacts on ecosystems and human health. ...
... In addition, with the appearance of free radicals, Fe 3+ and Fe 2+ ions will be regenerated according to equation (8) [1,36]. However, this process is quite slowly. ...
SiO2 was prepared from rice husk (RH) with the assistance of cetrimonium bromide (CTAB), and the CuO•Fe3O4/SiO2 composite was prepared by a simple coprecipitation method to enhance the Fenton-like degradation of dyes in a wide pH range. SiO2 was a mesoporous material with a relatively large surface area of 496.4 m2/g and a highly relative pore volume of 1.154 cm3/g. The Fe3O4 and CuO particles with the size of 20–50 nm were well dispersed in the composite, making the composite tighter and causing the disappearance of large pores in the range of 20–55 nm. The surface area and pore volume of the composite were reduced to 248.6 m2/g and 0.420 cm3/g, respectively. Fe3O4/SiO2 and Fe3O4 samples only exhibited high catalytic activity in an acidic medium, while the CuO•Fe3O4/SiO2 composite could effectively work in a wide pH range of 3–7. Besides, the effects of reaction conditions such as catalyst dosage, H2O2 concentration, and initial dye concentration on the catalytic performance of the composite were studied. The optimal conditions for the degradation of dye were tartrazine (TA) concentration of 50 mg/L, dosage catalyst of 0.5 g/L, H2O2 concentration of 120 mM, and pH 5. The CuO•Fe3O4/SiO2 composite reached the highest activity at pH 5, showing a degradation efficiency (DE) of 93.3% and a reaction rate of 0.061 min−1. The reusability of the catalyst was investigated by cyclic experiments. The DE of the 3rd reuse remained at 55.1%, equivalent to 93.5% of the first use. The catalytic mechanism for the Fenton system has also been proposed.
... Dyes exhibit substantial structural diversity and can be categorized in several ways such as on the basis of their sources (e.g natural, synthetic), chemical structure (e.g azo, triphenylmethane, anthraquinone, indigo) and domain of usage or application to the fiber type (e.g reactive, disperse, direct, mordant, vat, sulphur, metal complexes, pigments, chromic) [27,29,32]. The classification on the basis of application is depicted in Table 2. Dyes can also be classified on the basis of their solubility: soluble dyes which comprise of basic, acid, reactive, direct, metal complex and mordant dyes; and insoluble dyes which include sulfur, vat, disperse and azo dyes [8,33,34]. ...
... They include varying chemical structures based on substituted aromatic groups [39]. The major chemical classes of cationic dyes are: triarylmethane, acridine, diazahemicyanine, cyanine, hemicyanine, oxazine and thiazine [8,18,32]. Cationic dyes are stable due to the presence of aromatic and various functional groups which in turn render recalcitrant effect of the dyes [40]. Among all commercially available synthetic dyes, cationic dyes are the brightest class of soluble dyes used by the textile industry [41]. ...
... The approaches generally employed to treat dye effluent can be grouped into three categories: (i) chemical (ii) physical and (iii) biological processes [32,71]. Some of the dye remediation technologies lying in the aforementioned categories include membrane filtration [72], photo-Fenton processes [73], coagulation [74], biodegradation [75], sono-chemical degradation [76], ultrafiltration [77], advanced oxidation process [78], ion exchange [79], precipitation [80], ozonation [81], reverse osmosis [82], microbial reduction [83], electrolytic methods [84], photocatalytic degradation [85] and adsorption. ...
One of the most pressing environmental problems is the existence of synthetic dyes in industrial wastewaters. The presence of dyes in wastewater can cause severe problems to human beings and aquatic life, and that warrants removal from aqueous medium. Amongst the multiple strategies to treat dye-contaminated water, adsorption is considered superior because of low cost, flexibility, ease of operation and lower energy consumption. Many adsorbents, including carbon-based materials, biomaterials, nanomaterials, Schiff bases, metal-organic frameworks as well as natural and synthetic polymers, have been successfully applied in cationic dyes remediation. The current review article provides literature information about cationic dyes, various treatment strategies, principles of adsorption and recent trends in adsorbents application were discussed at length. The applicability of various isotherms and kinetic models for cationic dyes removal by diversified adsorbents is also highlighted here. Conclusions have been drawn from the literature reviewed and recommendations for future research perspectives are proposed.
... The treatment of wastewater containing organic dyes has received considerable attention because the discharge of dye effluents to river streams is a major concern [39,40]. Many dyes are carcinogenic, mutagenic, and teratogenic compounds, resulting that dye-containing wastewater not only contaminates surface and ground water, but also harms human health and disrupts the ecological system [41,42]. ...
... For water purification, there is a need for technologies that have the ability to remove toxic contaminants from the environment to a safe level and to do so rapidly, efficiently and within a reasonable framework of costs [43]. Compared with other conventional methods for the removal of organic dyes from wastewater, such as ultrafiltration, reverse osmosis and ion exchange [40], adsorption has been considered as the most popular method. It is now recognized as an effective, efficient and economic technique [2]. ...
... Adsorption of toxic pollutants from wastewater has a predominant significance in the removal of dyes more effectively compared to conventional method water purification [40]. Thus, the development of novel and cost-effective materials with good adsorption properties and which are easily to be separated from the aqueous media has attracted considerable attention. ...
Water pollution by synthetic organic dyes is mainly regarded as environmental and ecological issues worldwide and requires feasible solutions in face of the short-term risk to human health and stability of eco-systems. Therefore, in this paper, the magnetic mesoporous composites (MMC) were synthesized by surfactant template sol–gel method, using cetyl-trimethylammonium bromide (CTAB) as mesoporous structure generator and investigated for anionic and cationic dyes removal from aqueous solutions. The magnetic iron oxide nanoparticles were obtained by reverse co-precipitation, followed by mesoporous silica coating through modified sol–gel method. The obtained materials were characterized by FT-IR spectroscopy, X-ray diffraction, transmission electron microscopy, Mössbauer spectroscopy, nitrogen adsorption, small-angle X-ray scattering and magnetization measurements. The influence of CTAB amount on the morpho-textural and structural properties of nanocomposites was studied. XRD and Mössbauer spectroscopy showed that the obtained nanocomposites were composed of pure maghemite nanoparticles, and TEM images revealed particles size around 10 nm, embedded in silica matrix. The combination of magnetic properties and high surface area values, up to 695 m²/g, made suitable the obtained nanocomposites to be used as adsorbents. The dye removal efficiency was higher than 90% after the first adsorption and remained above 65% after four adsorption–desorption cycles, indicating that the as-prepared magnetic mesoporous nanocomposites can be considered excellent adsorbent materials for the removal of both anionic and cationic dyes from wastewaters, and the recycling performance revealed the stability of MMC.
... These materials have inherent drawbacks such as low adsorption capacity and poor selectivity (Salahshoor & Shahbazi 2014). So, we need to look for new, efficient adsorbents. ...
... These include a high surface area and a large pore size (Diagboya & Dikio, 2018). Furthermore, the surface of mesoporous silica can be altered by functionalizing it with a variety of functional groups, which are highly selective and capable of adsorbing a wide range of dyes (Al-Amrani et al., 2022;Salahshoor & Shahbazi, 2014). Among the mesoporous materials, SBA-15 is one of the best candidates with a high surface area (500-1500 m 2 /g). ...
SBA-15/Pr-Im Schiff base was synthesized and characterized by low and wide-angle XRD, TGA, FTIR, FESEM, HRTEM, and BET analyses. It was used for the adsorption of sunset yellow, indigo carmine, titan yellow, and orange G from aqueous solutions. The maximum adsorption was noted at pH 7, dye concentration 50 mg/L, time 120 min, temperature 25 °C, and adsorbent doses for sunset yellow and orange G 15 mg, indigo carmine 12 mg, and titan yellow 9 mg. The dye removal efficiency for sunset yellow 91.23%, indigo carmine 94.02%, titan yellow 96.35%, and orange G 91.08%. The results of adsorption isotherms followed the Langmuir model, with maximum adsorption capacities for sunset yellow 125.00 mg/g, indigo carmine 138.88 mg/g, titan yellow 227.27 mg/g, and orange G 142.85 mg/g. The adsorption was verified to follow pseudo-second-order kinetics, and it was spontaneous and exothermic. The regenerated adsorbents could potentially be reused four times with little loss of removal efficiency.
Graphical Abstract
... In its production, textiles, leather, and paper use coloring agents (dyes) [1] [2] [3]. A side effect of dyes in producing textiles, leather and paper is the production of liquid waste containing dyes (wastewater) [1] [2] [3] [4]. Wastewater causes environmental pollution problems when released into the water and soil environment. ...
... Various efforts to overcome the problem of contamination due to dyes have been and are being carried out using various methods including using adsorbents and photocatalysts [5]. The use of adsorbent is mostly done because the manufacturing is relatively easy and inexpensive, and the raw materials are available abundantly such as biomass and ceramics [1] [2] [3] [4] [5] [6]. The use of ceramics for adsorbents is very beneficial because it can be used repeatedly while the use of carbon from biomass cannot be used repeatedly. ...
... Pure OMS materials like MCM and SBA have been used for the adsorption of dyes, but also modied OMS materials with graed functional groups like carboxylic and amino groups or transition metal oxides have been utilized to enhance adsorption. 9 Furthermore, several carbon-based materials such as activated carbon, carbon nanotubes, and graphene oxide (GO) have been reported for the adsorption of many organic dyes as well as heavy metals. 10,11 Among these materials has GO, an oxidized form of graphene, received considerable attention in the eld of adsorption due to its high specic surface area as well as its numerous functional groups such as hydroxyl, carboxyl, and epoxyl groups. ...
... These results are in good accordance with previous works in literature which have reported that both, the adsorption of MB on GO and on silica are dominated by monolayer adsorption. 9,41 The obtained maximum adsorption capacity of MB, q m , on the graed COK-12-GO-2* samples is 197.5 mg g À1 , which is much higher than that observed for the pure COK-12, 20.2 mg g À1 , and other silica adsorbents reported in literature, Table 2. At this point it is to be noted that Liou et al. promote their SBA-15-GO with a maximum adsorption capacity of 242 mg g À1 , which is not the maximum monolayer adsorption capacity obtained from the Langmuir isotherm, but a value from a kinetic experiment with unknown initial dye concentration and pH. ...
Large-pore ordered mesoporous silica (OMS) COK-12, analogous to the well-known SBA-15, but synthesized in a more environmentally friendly way and exhibiting a shorter plate-like structure, was grafted with different amounts of graphene oxide (GO) for the first time in an inexpensive and rapid process, that was successfully upscaled. Samples were examined with nitrogen sorption analysis, SAXS, Raman spectroscopy, XPS, and zeta potential analysis. Adsorption experiments with the cationic dye methylene blue (MB) were conducted on the grafted materials and on pure COK-12, taking into account the influence of initial dye concentration (30–600 mg L⁻¹), adsorbent dosage (0.2–14 g L⁻¹), contact time (0.3–300 min), solution pH (4–10), and influence of salts and temperature (0–1 M NaCl, 80 °C) to simulate industrial dye effluent. The adsorption process was found to be represented best by the Langmuir isotherm model, i.e., adsorption is a monolayer process. The calculated maximum adsorption capacities were found to be 20.2 and 197.5 mg g⁻¹ at dosages of 5 and 0.5 g L⁻¹ for pure COK-12 and COK-12 grafted with 50 wt% GO, respectively, at pH 5.65 and MB concentration of 100 mg L⁻¹. Adsorption kinetics were found to follow the pseudo-second order model, i.e., chemisorption is the rate controlling step. The adsorption performances could be well preserved at simulated dye effluent. Desorption was found to be most effective with hydrochloric acid. The COK-12 grafted with GO presented in this work shows superior adsorption properties in comparison to other grafted OMS materials. In addition, grafting with GO remarkably improved the stability of COK-12 in aqueous solution.
... Additionally, increases in absorption intensities of O-H bending at 1600 cm -1 , O-H stretching at 3500 cm -1 , and a new peak at 960-1100 cm -1 corresponding to Si-O were observed. These peaks were believed to be the active sites for adsorption [8][9][10]. ...
... This was indicated by the sharp increase in the Q m of activated zeolite. The activated zeolite possessed more silanol (Si-OH) groups indicated by the occurrence of a new peak at 960-1100 cm -1 [9,10] (Fig 1). The role of chemisorption mechanism is also supported by the good fit of the adsorption data with Langmuir isotherm model. ...
... Textile industries produce large volumes of dye effluents, because of the high amounts of water used in dyeing processes [7]. A number of different treatment methods for dye removal from effluent water have been investigated. ...
... There have been several review reports published on the removal of dye from water using sorbents. These include reviews on the use of activated carbon [52,53], agricultural waste [3,4], agricultural solid waste [54], activated carbon and low-cost sorbents [10], carbon nanotubes [55], mesoporous silicas [7], nanoparticles [56], low cost sorbents [57][58][59][60][61][62][63], cost-effective and non-conventional sorbents [64], biosorbents [65], functional oxide nanomaterials and nanocomposites [66], nano zero-valent iron oxide [67], alternative sorbents [68], immobilised fungi [69], whole bacterial cells [70], chitosan and its derivatives [71] and clay and modified clay [72]. In addition, several groups have published reviews focussing on the removal of dye from wastewater [10,[73][74][75]. ...
Dyes are priority pollutants, commonly found at significant concentrations in textile effluents. The presence of dyes stuffs in wastewater can cause severe problems to aquatic life and human beings. Therefore, the removal of dyes from wastewater is important in order to minimize their hazardous effects on the environment. One way of removing dyes is to use nanosized manganese oxides (MnOs). To date, there has been much work reported on the use of nanosized MnOs as sorbents for dyestuffs. They are promising sorbents for commercial use due to their amorphous nature, high specific surface areas (SSA), mesoporous structure, and low to the moderate point of zero charge (pHPZC). This review summarizes the toxicity and recent advances for removing dyes from wastewater using nanosized MnO sorbents. The article also describes the various experimental parameters necessary for adsorption optimization, such as adsorption time, pH, initial dye concentration, amount of sorbent and temperature. Adsorption mechanisms investigated by various modeling approaches are also discussed. In particular, it was observed that much work has been reported on the use of birnessite and its composites for dye removal. There are many papers reporting on the use of MnO in batch mode dye removal, but very few that report on the use of MnO in continuous column removal systems. Therefore, there is still a considerable need for further research to develop effective and economical large scale MnO column systems for commercial use.
... 8 Anirudhan et al. reported polyacrylamide/bentonite composites with amine functionality for the removal of cationic dyes malachite green (MG), methylene blue (MB), and crystal violet (CV). The adsorption capacity decreased in the order MG> MB> CV. 9 Diverse nano-, meso-, and micro-structured materials like silica, 1,10−20 zeolites, 21−23 metal−organic frameworks, 24 aerogels, 25 SBA, 10,12,14 mesoporous carbon, 26,27 etc. have been established as promising adsorbents for different types of metal ions and organic pollutants owing to their advantage of high surface area, tunable surface porosity, high pore volume, and robustness. SBA-15 possesses higher adsorption capacity than MCM-48 because of their high pore volume, which allows the easier diffusion of dye molecules to the pores. ...
... SBA-15 possesses higher adsorption capacity than MCM-48 because of their high pore volume, which allows the easier diffusion of dye molecules to the pores. 12 Recently, Salahshoor et al. have carried out the adsorption kinetics study and statistical optimization studies by response surface methodology (RSM) on the removal of MB by SBA-15 mesoporous silica. 14 Efficient adsorbents for field approach can be narrowed down from the pool of adsorbents via modeling and optimization studies. ...
In this work, a lightweight inorganic−organic
hybrid foam adsorbent is processed out of economically cheap
“double-silicate” precursors employing natural bentonite and
water glass through a facile cross-linking and polymerization
technique. Poly(vinyl alcohol) was used to provide structural
strength to the three-dimensional framework. The foam
adsorbent possessed an apparent density of 0.083 g cm−3,
indicating its internetworks and exposed surface area for the
uptake of dyes. The foam was systematically studied for the
treatment of textile dye effluent. Multivariate optimization
process was carried out using response surface methodology.
The Box−Behnken model was used for the design of
experiments and to study the interplay between the variables.
Batch adsorption and continuous column adsorption studies were carried out at respective levels of initial concentration (200−
1000 μM), adsorbent dose (1−10 g L−1), and contact time (0−120 min). The results revealed that the hybrid silicate foam
exhibits adsorption capacity as high as 99.9, 98.9, and 98.2% for 200, 600, and 1000 μM concentrations of methylene blue in
120 min, respectively, and 100% adsorption for 200, 600, and 1000 μM concentrations of crystal violet in 120 min for 10 g L−1
of adsorbent. Adsorption equilibrium data fitted well to Langmuir isotherm, and the kinetics followed second-order kinetic
model. Synthetic industrial effluent with 1000 μM dye concentration was also prepared and studied with continuous column for
determining the working capacity of the adsorbent, and the results are presented. The silicate hybrid foam is a cheap adsorbent
that does not produce any secondary waste and can be repeatedly used making it attractive for dye industries.
... However, the search continues for inexpensive adsorbents with longer lifetimes and higher adsorption capacities (Chen et al., 2016;Chen et al., 2019;Cho et al., 2019;Gao et al., 2019aGao et al., , 2019bIryani et al., 2019;Jha et al., 2023;Okoro et al,. 2022;Salahshoor & Shahbazi, 2014;Samy et al., 2023;Üner et al., 2016;Xing et al., 2017;Yuan et al., 2016). ...
In response to the water contamination problem, this study presents a novel method to remove methylene blue (MB), a typical water pollutant, using synthesized porous silicon dioxide (SiO2). The SiO2 was synthesized via a cost-effective sol–gel method and characterized for its thermal stability, structural, textural, morphological properties, and elemental composition using techniques such as TGA, FT-IR, XRD, BET-BJH, SEM, TEM, and STEM-EDS. A unique aspect of this study is the evaluation of SiO2 reusability in MB removal through multiple adsorption and thermal regeneration cycles, a critical factor for practical applications. The results demonstrated the successful synthesis of thermally stable, amorphous, porous SiO2 with a surface area of 811 m²g⁻¹ initially, reducing to 600 m²g⁻¹ after the adsorption and regeneration cycles, indicating its stability and durability. The removal efficiency of MB was consistent across cycles, achieving 71.19 ± 0.94%, 75.55 ± 0.69%, and 73.49 ± 0.15% after 20 min, and the adsorption capacity at equilibrium was 3.73 ± 0.025, 4.08 ± 0.045, and 3.48 ± 0.021 mgMB gads⁻¹ during the first, second, and third cycles, respectively. These findings highlight the potential of the synthesized porous SiO2 as a reusable and efficient adsorbent for MB removal in water treatment, contributing to the advancement of sustainable and effective solutions for water pollution.
... Furthermore, the M41S family has received considerable attention because of their high surface area, slightly higher pore diameters compared with the diameters of the adsorbate, and effective performance as adsorbents [73]. Moreover, their adsorption capacity can be enhanced by modifying their surface chemistry using various functional groups [101]. MCM-41 composites with imprinted nickel ions through co-condensation were used as mesoporous adsorbents to remove Ni +2 cations from wastewater, with high recovery. ...
Silica-based mesoporous materials are a class of porous materials with unique characteristics such as ordered pore structure, large surface area, and large pore volume. This review covers the different types of porous material (zeolite and mesoporous) and the physical properties of mesoporous materials that make them valuable in industry. Mesoporous materials can be divided into two groups: silica-based mesoporous materials and non-silica-based mesoporous materials. The most well-known family of silica-based mesoporous materials is the Mesoporous Molecular Sieves family, which attracts attention because of its beneficial properties. The family includes three members that are differentiated based on their pore arrangement. In this review, the major applications of the Mobil Mesoporous Molecular Sieves family, such as catalysts, adsorbents, and drug delivery agents, have been surveyed. Furthermore, the synthesis of the Mesoporous Molecular Sieves materials, the silica sources, the importance of templates, and the mechanisms of the synthesis are discussed herein. Members of this material family are characterized by many physicochemical properties that are closely related to their high silica content, crystalline structure, and pore arrangement. Commonly, the members of this family have large surface areas, high pore volumes, small pore sizes, and narrow and uniform particle size distributions. These properties enable numerous industrial applications and opportunities for scientific studies to further develop existing materials or manufacture new ones.
... [146] Previously, silica based material have attracted due to properties, that is, mesoporous, high adsorption capacity and surface area and even pore distribution made it as an ideal adsorbent for the removal of pollutants from water by adsorption. [147] Sulistiyo et al. investigated silica gel adsorption performance which is 62.70% higher than fly ash for methylene blue removal. The maximum adsorption capacity of silica gel and fly ash are 23.31 and 14.32 mg/g. ...
Adsorption is often considered to be the most competent and investigated treatment technique among wastewater technologies. The purpose of sequestration from wastewater is not validated through preferred utilization of costly starting material which pave way for the development of low-cost adsorbents. This review asserts the augmentation of both economically and environmentally sound sorbent material. The review encompasses gathering information from the literature insights dispersed over decades for the remediation of toxic pollutants especially dyes and heavy metals by various categories of adsorbents. Additionally, this review highlighted the adsorption of various emerging contaminants and pharmaceuticals. The review targeted to showcase various categories of adsorbent that can be refashioned and efficiently employed toward water treatment process. The review outlines and purposes the classification of diverse adsorbents involved in water treatment. Various Isotherm models and kinetic models employed in adsorption were also discussed. Mechanism of removal of pollutants was also outlined. The process of desorption gives the regeneration and recovery possibility of adsorbent providing opportunity of waste minimization, reusing it repeatedly was also reviewed here. Lastly, the significance of review and the future perspective for further adsorbent advancement were also detailed out. Hence, this review sufficiently authorizes the various adsorbent conceivability toward water treatment.
... Dyes are widely used in paper printing, plastics manufacturing, pulp mills, leather industries, and textiles (Forgacs et al. 2004). Mainly, the textile industry produces large amounts of dye effluents due to the high volume of water used in the dying process (Salahshoor and Shahbazi 2014). Further, the effect of some dyes on human ranges from skin irritation, eyes burning, and if swallowed, vomiting, diarrhea, and nausea (Borodoloi et al. 2018), whereas some dyes like Rhodamine-B and Terasil red are revealed as carcinogens (Nestmann et al. 1979). ...
The hazardous dyes on mixing with water resources are affecting many life forms. Granite stone is popular worldwide for decorating floors, making other forms of decorative materials and items. Granite stone powder waste can be obtained free of cost from marble factories as factories spend on the disposal of this waste. In the present study, novel granite stone powder waste composite has been prepared and utilized for the effective removal of Terasil dye. Two types of granite including gray granite and white granite were used in pure, calcinized, and chemically modified forms. Freundlich adsorption isotherm model best explained the adsorption mechanism of dye removal using granite composites as compared to other adsorption isothermal models. Characterization techniques like scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were used for the determination of morphological features and functional groups of granite composites. The obtained results were statistically analyzed using analysis of variance (ANOVA) along with the post hoc Tukey test. An extraordinarily high Terasil dye uptake capacity (more than 400 mg/g) was exhibited by granite composites prepared using sodium metasilicate. The synthesized novel nano-constructed composites provided a viable strategy as compared to the pure granite stone for dye removal from wastewater water.
Graphical abstract
... On the one hand, the increasingly frequent discharge of organically polluted wastewater during various human activities continues to pollute freshwater systems and terrestrial ecosystems. Organic contaminants are widespread in the environment, including pesticides, personal care products, pharmaceuticals, and organic dyes [1][2][3][4][5]. Generally, these emerging pollutants are harmful, bioaccumulating, and persistent and pose a potential threat to aquatic organisms and human beings. ...
A natural amino acid-doped polyaniline nanostructure was prepared by a simple in situ chemical polymerization method in an aqueous medium. The structure and morphology of composite material were characterized by FESEM, TEM, FT-IR, and XRD. The results showed that the product possesses a large aspect ratio and a hollow tubular morphology. As-synthesized products were further applied to remove dyes and heavy metal ions from the aqueous solution, which exhibited good removal capacity toward Congo red (955.6 mg·g−1) and Cr(VI) (60.0 mg·g−1). The adsorption data for the former were found to be well described by the pseudo-first-order kinetic and Langmuir adsorption isotherm model. Thermodynamic studies show that the adsorption of Congo red by GluP is a spontaneous and endothermic process. Moreover, cyclic experiment results show that the polyaniline composites exhibited good recyclability. Therefore, these amino acid-doped polyaniline nanotubes can be expected to be an ideal candidate for the removal of organic dye and heavy metal ions from wastewater.
... Up till now, various adsorbents such as activated carbon, metal organic frameworks (MOFs), zeolites, etc. were prepared and tested for adsorption of dyes from water [12][13][14][15][16]. ZSM-5 zeolite is attractive and considered more suitable for dyes adsorption due to acidic sites, crystalline three-dimensional structure and high porosity [16]. ...
Various industries are releasing dyes every year as waste water and causing different kind of problems to human beings and marine life. To overcome water pollution, various materials are available but still there is a great need of new materials and techniques. Herein, well-ordered micro-mesoporous silica, MMZ, was developed by combined dissolution and self-assembly strategy using ZSM-5 as silica-alumina source and CTAB as structure building unit. Different characterizations techniques such as N2 adsorption-desorption, XRD, SEM, TEM and elemental mapping distribution were utilized to characterize the structure and morphology of the samples. The application of both ZSM-5 and MMZ was investigated for the adsorption of methylene blue (MB) dye, and the influence of different factors affecting MB adsorption such as time of adsorption, pH of solution, initial MB concentration and adsorbent dosage were optimized. MMZ exhibited superior adsorption capacity towards MB dye from water compared with ZSM-5 due to strong electrostatic interactions. The equilibrium data for MB adsorption over MMZ material well fitted to Langmuir equation, with a maximum monolayer capacity (qm) of 303 mg/g. The adsorption of MB could be best described by the pseudo-second order model. Moreover, the MB adsorption activity of MMZ can be well recovered with no major loss.
... Therefore, there is an urgent need to install wastewater treatment systems to treat the dye-bearing wastewater before it is discharged directly into the environment to prevent further contamination. The adsorption technique Comparative Adsorption of Methylene Blue Dye on Hexane-Washed and Xanthated Spent Grated Coconut (Cocos nucifera L.): Isotherms, Thermodynamics, and Mechanisms using solid materials can be used to remove dyes from wastewater due to its ease of operation, low cost, and simplicity (Asem et al., 2009;Salahshoor and Shahbazi, 2014). Several MB adsorption studies have been reported using various low-cost biosorbents such as peanut stick wood (Ghaedi et However, as a model of cationic dye, the treatment of spent grated coconut (SGC) with hexane and carbon disulfide has not been investigated for the adsorption of MB-bearing wastewaters. ...
A batch system investigated the application of two types of chemically modified biosorbents derived from spent grated coconut (Cocos nucifera) powder to adsorb methylene blue (MB) from aqueous solutions. The biosorbents were characterised by spectroscopic and quantitative analyses. The assessment of MB adsorption onto the investigated biosorbents was studied at different experimental conditions with different pHs (2–9) and different initial concentrations of MB (10–400 mg/L) at three different temperatures (298, 308, and 318 K). The maximum adsorption capacity (qmax) of xanthated spent grated coconut (XSGC) was higher than that of hexane-washed spent grated coconut (HSGC). The thermodynamic study indicated that the MB adsorption process was spontaneous for both biosorbents. Desorption of MB-loaded biosorbents was carried out using HCl, NaOH, and Na2EDTA solutions. A desorption ratio of more than 90% was obtained over three adsorption/desorption cycles for HSGC. However, XSGC demonstrated poor MB desorption, implying a stronger MB interaction with XSGC, which could be attributed to H-bonding, Yoshida H-bonding, n-π, and π-π bonding. The study showed that HSGC and XSGC could be applied as biosorbents to remove low MB concentrations from aqueous solutions.
... But, mesoporous silica offer a number of potential advantages as adsorbents including larger pore volume and diameter, high surface area and regular channel type structures which increases the absorption capacity and repeatability of the results. High adsorption capacities make them ideal candidates for removal of organic compounds, heavy metal ions, and organic dyes [27][28][29][30][31][32][33][34][35]. Although, further studies are needed on cost effectiveness of using mesoporous silica adsorbent to removal of dye from industrial effluents, it is clear that high capacity of this adsorbents can be accommodated the cost.. ...
How to cite this article Hajiaghababaei L., Ashrafi L., Dehghan Abkenar Sh., Badiei AR., Ganjali MR., Mohammadi Ziarani Gh. Efficient removal of reactive Blue-19 from textile wastewater by adsorption on methyl Imidazolium modified LUS-1 and MCM-48 nanoporous. Int. Abstract In this study, N-methyl-N'propyltrimethoxysilylimidazolium modified LUS-1 and MCM-48 nanoporous materials were prepared and employed as adsorbent for removing Reactive Blue-19 from aqueous solutions. LUS-1 and MCM-48 were made based on the previous procedure and modified with N-methyl-N'propyltri methoxysilylimidazolium chloride. XRD analyses did not show any lattice alteration between modified and unmodified adsorbents. A hexagonal mesophase structure with the P6mm symmetry for LUS-1 and IM-LUS-1, and a cubic Ia3d space group for MCM-48 and IM-MCM-48 were observed. UV/Vis spectrophotometry was used to determine of the dye concentration in the solution. Batch studies were conducted in order to find the optimum adsorption conditions and investigation of different empirical parameters like the pH impact, contact time, the amount of adsorbent, and concentration of dye on adsorption process. The best dye removal efficiency of the adsorbents were more than 93% at pH= 3.0-7.0 after about 3 min for IM-LUS-1 and after 30 min for IM-MCM-48. RB-19 dye was desorbed from both of the adsorbents with 10 mL of sodium hydroxide 2 M during 5 min. There was well match between the data and the Langmuir model with maximum adsorption capacities 476.2 mg/g IM-LUS-1 and 277.8 mg/g IM-MCM-48. The reusability of the sorbents were higher than 4 cycles. In addition, removal percent of RB-19 dye from 50 mL of real textile wastewater with 20 mg of IM-LUS-1 and IM-MCM-48 were 93.0 (± 0.6) and 90.2 (± 0.7), respectively. The results showed that this method might be appropriate for removing the pollutant dyes from textile wastewater.
... Finding new adsorbent materials is a current requirement of great necessity. In recent years, mesoporous silica has been considered as an adsorbent for organic dyes (El-Safty et al., 2011;Salahshoor and Shahbazi, 2014) because of its high surface area, adjustable size of pores, evident surface properties, good mechanical stability, and reduced toxicity (Kittappa et al., 2015). The active SieOH bonds present on the surface of the pore walls can be modified with organic or inorganic functional groups, thus generating specific properties and high thermal and chemical stability (Deka et al., 2014). ...
... Chemical treatments, such as coagulation, electrolysis and oxidation and physical treatments such as membrane separation and adsorption, are typical methods used in this process. Adsorption is considered one of the most attractive techniques (Salahshoor and Shahbazi 2014). This efficient process of separation is characterized by the presence of two phases, the solute, also known as adsorbate and the adsorbent, which is a solid. ...
The adsorption of Basic Blue 41 (BB41), Methylene Blue (MB) and Basic Red 18 (BR18), three known basic dyes, was studied in shaped mesoporous adsorbent MCM-41. The granules were obtained by extrusion of the powder adsorbent and were analyzed by nitrogen adsorption, SEM–EDS, XRD, mercury porosimetry and helium picnometry. Adsorption equilibrium isotherms, kinetics, and breakthrough curves were performed with the selected adsorbent and dyes. The experimental results indicated that the Sips model better describes the equilibrium than the Langmuir and Freundlich isotherm models. Additionally, the co-adsorption equilibrium of two dyes was well predicted by the extended form of the Sips model. The kinetics results showed that the adsorption of Basic Blue 41 onto the selected adsorbent is faster than with the other studied dyes. The obtained adsorbed equilibrium amounts through the breakthrough curves were 308 mg g−1, 55 mg g−1 and 106 mg g−1 for the Basic Blue 41, Methylene Blue and Basic Red 18 dyes, respectively. The dye is concentrated during regeneration step, since the volume of regenerating solution, eluted during the regeneration, is considerably lower (about two orders of magnitude) when compared with the volume of effluent treated until the breakthrough point. This fact demonstrates the feasibility of a potential adsorption based process to treat dyed effluents, with the shaped MCM-41.
... implementations Albayati et al., 2017;Anbia and Moradi, 2009), such as a catalyst support and adsorbent for removing the organic pollutants, including phenolic compounds (Moreno et al., 2015), dyes (Zeid and Review, 2012), aromatics and as well as inorganic pollutants (Albayati and Doyle, 2013). Several investigations concentrate on the surface alteration of MCM-41 to improve its adsorption capacity for organic substances (Salahshoor and Shahbazi, 2016;Hu et al., 2014) or perform the chosen adsorption of some pollutants, like massive metals and the endocrine disrupters (Parida et al., 2012;Pallabi et al., 2018). In comparison with such functionalized mesoporous silica, non-calcined MCM-41 includes many surfactant templates and its fabrication process is relatively easy. ...
Adsorption techniques were tested for the removal of naphthalene (C10H8) polycyclic aromatic hydrocarbon (PAH) from aqueous solution in a batch and fixed-bed column systems. Three various types of prepared mesoporous silica MCM-41 were investigated such as; calcined, non-calcined (retained templates) and functionalized with amine groups (NH2-MCM-41). It was found that adsorption data resulted from non-calcined and functionalized adsorbents, fitted well with Langmuir and Freundlich adsorption isotherms, respectively. The total adsorption process was fitted with both pseudo-second-order
kinetic model and intra-particle diffusion model, successfully. Thermodynamic results specified that the adsorption capacity of C10H8 was reduced with increasing temperature, proving spontaneous nature and exothermic process. In a fixed-bed continuous system, C10H8 was efficiently separated using MCM-41. Breakthrough curves were tested at various bed heights, flow rates, and initial C10H8 concentrations. Thomas and Yoon models were applied to find kinetic constants and to predict naphthalene breakthrough curves. Both non-calcined and functionalized MCM-41 were regenerated five times in a batch system, while calcined MCM-41 was regenerated four times in a fixed-bed system without any significant loss in adsorption capacity and found to be convenient for reuse in consecutive adsorption desorption cycles. The results suggested that non-calcined and functionalized MCM-41 can be applied as efficient adsorbents for removal of naphthalene from aqueous solution in a batch adsorption system and the calcined MCM-41 in a fixed bed continues system.
... implementations Albayati et al., 2017;Anbia and Moradi, 2009), such as a catalyst support and adsorbent for removing the organic pollutants, including phenolic compounds (Moreno et al., 2015), dyes (Zeid and Review, 2012), aromatics and as well as inorganic pollutants (Albayati and Doyle, 2013). Several investigations concentrate on the surface alteration of MCM-41 to improve its adsorption capacity for organic substances (Salahshoor and Shahbazi, 2016;Hu et al., 2014) or perform the chosen adsorption of some pollutants, like massive metals and the endocrine disrupters (Parida et al., 2012;Pallabi et al., 2018). In comparison with such functionalized mesoporous silica, non-calcined MCM-41 includes many surfactant templates and its fabrication process is relatively easy. ...
Adsorption techniques were tested for the removal of naphthalene (C10H8) polycyclic aromatic hydrocarbon (PAH) from aqueous solution in a batch and fixed-bed column systems. Three various types of prepared mesoporous silica MCM-41 were investigated such as; calcined, non-calcined (retained templates) and functionalized with amine groups (NH2-MCM-41). It was found that adsorption data resulted from non-calcined and functionalized adsorbents, fitted well with Langmuir and Freundlich adsorption isotherms, respectively. The total adsorption process was fitted with both pseudo-second-order
kinetic model and intra-particle diffusion model, successfully. Thermodynamic results specified that the adsorption capacity of C10H8 was reduced with increasing temperature, proving spontaneous nature and exothermic process. In a fixed-bed continuous system, C10H8 was efficiently separated using MCM-41. Breakthrough curves were tested at various bed heights, flow rates, and initial C10H8 concentrations. Thomas and Yoon models were applied to find kinetic constants and to predict naphthalene breakthrough curves. Both non-calcined and functionalized MCM-41 were regenerated five times in a batch system, while calcined MCM-41 was regenerated four times in a fixed-bed system without any significant loss in adsorption capacity and found to be convenient for reuse in consecutive adsorption-desorption cycles. The results suggested that non-calcined and functionalized MCM-41 can be applied as efficient adsorbents for removal of naphthalene from aqueous solution in a batch adsorption system and the calcined MCM-41 in a fixed bed continues system.
... Adsorption is one of the most used techniques for dye separation due to facility of use, low cost, high selectivity, and its widespread application [25]. A special surface structure and the ability to modify the surface chemistry of mesoporous silica by incorporating various functional groups increase the adsorption capacity to a high level [184][185][186]. Removal of crystal violet dye from aqueous solution onto MCM-41 and sulfated-MCM-41 mesoporous was done. ...
A review about the use of fabricated mesoporous materials with emphasis on silica in water treatment is presented. The problem of water supply is a well-known global problem because many areas around the world are suffering due to the lack of water, and therefore, the treatment and reuse of wastewater is crucial. Mesoporous materials have some unique features, such as a high surface area, which is normally associated with wide pore volume in addition to good thermal and mechanical stability. These properties have attracted researchers to study the use of mesoporous materials in water treatment. The first section of the current review is focused on traditional materials that are used for water purification from different pollutants, in addition to the different techniques that are using for the preparation of the mesoporous materials. The second section discusses the several functionalization tactics of mesoporous materials and their role in the efficiency enhancement towards pollutant removal from water. Finally, the third section presents the use of mesoporous materials in two of the most popular applications in water treatment: adsorption and photocatalysis techniques.
... There are mainly two types of adsorption: chemical adsorption (chemisorptions) or physical adsorption (physisorption). Chemical adsorption involves the formation of strong chemical bonds between adsorbate and adsorbent occurring due to exchange of electrons and the process is generally irreversible while physisorption involves the weak van der Waals intraparticle bonds between adsorbent and adsorbate or hydrogen bonds or dipole-dipole π-π interactions and hence the process mostly irreversible in most cases [10][11][12][13][14]. Different types of low cost adsorbents utilized for waste-water treatment can be classified as follows [10][11][12][13][14][15][16][17][18] The mechanism of adsorption of pollutant (dyes, metal ions etc.) on adsorbate can be briefly explained by occurrence of series of following consecutive steps [11,13,19,20]: The properties of dye solution affecting the removal efficiency of dye from aqueous solution are ionic strength, presence of other contaminants, pH, and initial concentration, dosage of adsorbent, temperature and agitation time. Removal efficiency of dye from aqueous solution is also influenced by adsorbent properties like specific surface area, pore volume, grain size, pore size distribution and particle size [11,13]. ...
... As an alternative, silica nanomaterials with mesoporous structure have registered a great progress. Due to their specific properties such as regular mesoporous structure, high specific surface areas, high reactivity, thermal and mechanical stability, high adsorption capacity and countless possibilities of functionalization, mesoporous silica materials like MCM-41, MCM 48, MCM-50 and SBA-15 can be used as promising absorbents for contaminants in wastewater and as catalytic support (Hoffmann et al. 2006;Vinu et al. 2005;Salahshoor and Shahbazi 2014;Chen et al. 2012). Unlike the other types of mesoporous silica, SBA-15 has a strong hydrothermal stability due to its dense wall of structure; thus, it can be used in liquid medium adsorption processes (Rashed Nageeb 2013). ...
Thermal processing of materials is used in a very broad sense to cover all sets of technologies and processes for a wide range of industrial sectors and it refers to material development with a specific application potential due to its advantages over conventional synthesis methods. By applying hydrothermal technique, the development of advanced materials has been pursued, in order to retain heavy metals from wastewater. This research refers to nanosilica-based materials, specifically mesoporous silica, for which the heavy metal retention properties were improved by using nano-TiO2 and nano-CeO2, considering the properties of titanium and cerium. Advanced methods have been used to characterize the materials obtained as X-ray fluorescence (XRF) and energy-dispersive X-ray spectroscopy (EDS) for chemical composition; X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for microstructural properties and BET analyser for pores and specific surface area characterization. The results showed higher retention efficiencies for the doped nanosilica.
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... Natural zeolite is the hydrated aluminosilicates porous mineral, found abundantly in nature, low-cost resource, and significantly used as an adsorbent for decontamination of wastewater (Meshko et al. 2001;Armağan et al. 2004;Alver and Metin 2012;Humelnicu et al. 2017). From the earlier decade, explosive interest has also been shown in ordered mesoporous silica-based materials, high-specific surface area, uniform pore distribution, and high adsorption capacity; these attractive features make silica an ideal adsorbent for a d s o r p t i v e r e m o v a l o f p o l l u t a n t s f r o m w a t e r (Salahshoor and Shahbazi 2014). Because of the low cost, abundance, and good adsorption characteristics, the siliceous materials like silica beads, dolomite, and perlite have also been exploited for the decontamination of polluted water. ...
Several industries release varying concentration of dye-laden effluent with substantial negative consequences for any receiving environmental compartment. The control of water pollution and tighter restriction on wastewater discharge directly into the environment to reduce the potential ecotoxicological effect of dyes is forcing processors to retreat and reuse process water and chemicals. Among the different available technologies, the adsorption process has been recognized to be one of the finest and cost-effective wastewater treatment technologies. Various adsorbents have been utilized to remove toxic dyes from water and wastewater. Here, we review the application of polyaniline-based polymeric adsorbent for the adsorption of dyes which have been received considerable attention. To date, various modifications of polyaniline have been explored to improve the adsorption properties. Review on the application of polyaniline for adsorption of dyes has not been present till date. This article provides relevant literature on the application of various polyaniline composites for removing dyes, and their adsorption capacities with their experimental conditions have been compiled. It is evident from the literature survey that polyaniline provides a better opportunity for scientists for the effective removal of various dye.
Introduction
The development and applications of biological products have been seriously hindered by conventional immobilization for its low efficiency and high cost. The immobilization of solid supports is an area of intense research due to their widespread use in synthetic chemistry and various industries. This paper highlights a great interest in the adsorption of an enzyme on the solid porous structured material and the design of new controlled delivery systems. The enzyme immobilized on solid supports and synthetic materials of the reaction mixture with strong mechanical force and easy separation serves as a high selective catalyst.
Objective
A novel protein delivery system for hemoglobin (Hb) enzyme was proposed by incorporating the molecular molecules into the mesopores of well-ordered hexagonal nanometer MCM (Mobil Composition of Matters) - 41. The prepared adsorbents were successfully applied to the design and synthesis of new functionalization materials. Various parameters affecting adsorption process, such as adsorption time, adsorption isotherm, and the reusability of adsorbent, were investigated.
Method
The interaction between Hb and MCM-41 was investigated using powder X-ray diffraction (XRD), Fourier infrared spectroscopy, UV-visible solid diffuse reflectance spectroscopy and 77 K low-temperature N2 adsorption-desorption study.
Results
The experimental parameters were optimized, including the concentrations of Hb, the MCM-41 amount, and the interior surface of phenyl-functionalized MCM-41 materials. Under the optimized conditions, the biocatalytic performance was studied for Hb/MCM-41 and Hb/Ph-(MCM-41). The adsorption process of Hb by MCM-41 / Ph-(MCM-41) was in agreement with the quasi-two-order kinetic model. Process of Hb adsorption by MCM-41 / Ph-(MCM-41) belongs to an exothermic reaction, the reaction is not reversible at 4 ℃ and it is a spontaneous reaction. The Freundlich model can better describe the adsorption of hemoglobin on MCM-41 / Ph-(MCM-41). During the desorption process of composite (MCM-41)-Hb / [Ph-(MCM-41)]-Hb in 0.1 mol/L NaOH solution, the desorption rate can reach above 70% at 2 min. At 60 min, the desorption reached equilibrium and the desorption rates were 99.58% and 91.36%, respectively. The reuse activity experimental results indicated that the immobilized enzyme exhibited high catalytic activity. Reusability stability studies suggested that the prepared composites retained their activity even after five recycling runs. This shows that the phenylation of MCM-41 reduced the "leakage" of enzyme in the main material.
Conclusion
The results of the present study demonstrated that Hb/MCM-41 and Hb/Ph-(MCM-41) are highly efficient potential nanobiocatalysts for the immobilization of enzymes onto mesoporous materials.
Conclusion
The adsorption process of Hb by MCM-41 / Ph-(MCM-41) was in agreement with the quasi-two-order kinetic model. The reuse activity experimental results indicated that the immobilized enzyme exhibited high catalytic activity. Reusability stability studies suggested that the prepared composites retained their activity even after five recycling runs. The results of the present study demonstrate that Hb/MCM-41 and Hb/Ph-(MCM-41) are highly efficient potential nanobiocatalysts for the immobilization of enzymes onto mesoporous materials.
Waste foundry sand (WFS), an industrial waste mainly comprising silicon dioxide was used to generate low-cost and efficient adsorbents for the expulsion of toxic pollutants from water through adsorption. The WFS was converted into particles by top-down approach followed by subsequent activation and functionalization. Activated sand particles (ASPs) with-OH groups and amino-functionalized sand particles (AFSPs) with-NH 2 groups were synthesized and fully characterized using FESEM, EDX, ATR-FTIR, XRD, TGA, and BET analyses. The adsorption capacities at experimental conditions for cationic dyes namely methylene blue(MB), malachite green(MG), methyl violet (MV), rhodamine B(Rh B) were 38.16, 26.31, 55.24 and 35.84 mg g −1 while for anionic dyes namely methyl orange (MO), patent blue VF(PB VF), quinoline yellow(QY), reactive Red 2(RR 2) were 7.28, 4.63, 7.84 and 6.91 mg g −1 as well as for metal ions namely Cd(II)), Ni(II)), Co(II)), and Cr(VI)were 23.81, 43.06, 17.03 and 3.47 mg g −1 respectively. The adsorption equilibrium isotherms optimally fit the Langmuir isotherm model, indicating homogeneous surfaces and monolayer adsorption. A pseudo-second-order model showed a strong agreement with the experimental data, thus identifying chemisorption as the rate-limiting step. Additionally, these particles were verified to be reusable for a minimum five adsorption-desorption cycles without loss of efficiency.
In this study, a hydrogel composite based on natural jute fiber (JF) has been prepared and employed for the removal of methylene blue (MB) dye from aqueous solution. Polyacrylamide (PAAm) hydrogel was synthesized by thermal polymerization in presence of N,N□-methylene bisacrylamide (MBAA) as the cross-linker and potassium per sulfate (KPS) as the initiator. JF reinforced hydrogel (JFRH) composite was prepared by incorporating JF into PAAm matrix prior to the polymerization. The prepared JFRH was characterized by FTIR spectroscopy and scanning electron microscope. It was found that, JFRH composite demonstrated strong mechanical properties with a compressive strength of 1.5 MPa at a deformation of above 80%. The prepared JFRH composite can remove more than 90% of MB from an aqueous solution and be separated easily from the solution after the adsorption process. Therefore, the synthesized JF based hydrogel composite could significantly expand the use of our natural golden fiber for reinforcement of composite materials and removal of dyes from water bodies. Dhaka Univ. J. Sci. 70(2): 59-64, 2022 (July)
Aim
Catalytic degradation of azo dye.
Background
Azo dyes are toxic agents and pollutants and the degradation of these dyes has an important application in the treatment of textile industry wastes. Catalytic decolorization of fast yellow dye by hexacyanoferrate (III), abbreviated as HCF(III) using polyvinylpyrrolidone abbreviated as PVP stabilized Ir-Ni bimetallic nanocrystals has been evaluated by kinetic spectrophotometric method at 440nm wavelength of the reaction mixture.
Methods
The impact of various operational factors such as fast yellow dye abbreviated as [FY], oxidant [HCF(III)] ions, promoter iridium-nickel bimetallic nanoparticles abbreviated as [(Ir-Ni)] BMNPs, and solution pH on the rate of the reaction have been examined.
Results
The results represent that the reaction follows first -order kinetics model with respect to [oxidant] at optimum pH 8 and fix temperature 40±0.1◦C. Thermodynamic parameters such as activation energy (Ea), enthalpy (ΔH#), entropy (ΔS#), frequency factor (A), and free energy of activation (ΔF#) have been evaluated by examining the reaction rate at four temperatures i.e. 40⁰C, 45⁰C, 50⁰C, and 55⁰C. On the basis of experimental outcomes, an appropriate mechanism involving complex formation has been proposed.
Conclusion
Analytical techniques such as UV-Vis spectroscopy, FTIR, and LCMS of degraded products represent the formation of easier and less harmful compounds.
A volcanic tuff of clinoptilolite type has been assessed in regards to its efficiency on Basic Blue 41 (BB‐41) cationic dye removal from aqueous solutions. Optimal working conditions were established by considering influences of the particle sizes, initial pH, dye concentration, contact time, and temperature. Tuff samples have been characterized by using SEM/EDX, FT‐IR, and N2 gas adsorption‐desorption techniques. Experimental data at equilibrium showed a better fitting of adsorption kinetics on pseudo‐second‐order and Langmuir models, whereas the thermodynamic parameters indicate an endothermic spontaneous process. Tuff particles of 47 μm medium sizes, which own the highest zeolite content, were found to be the most suitable for practical use as adsorbents, attaining a maximum adsorptive capacity of 123.5 mg g⁻¹ pure dye at 323 K, equivalent to 303 mg g⁻¹ commercial product containing 40 % dye. A potential interference involving the retention pattern was furthermore evaluated within binary systems with other two cationic dyes, Rhodamine B (RhB) and Methylene Blue (MB). The adsorbent shows a relevant selectivity towards BB‐41, influenced by commercial dye additives, structural configuration, molecular size, and contact time, with the 99.7 % dye removal efficiency at 24 hours only slightly depressed in binary systems with RhB ‐ 97.4 %, respective MB ‐ 90.2 %. This study confirmed the tuff particles as efficient adsorbents for the treatment of textile wastewater effluents.
Mesoporous KIT-5 was functionalized with g-C3N4 nanoparticles using trichloroacetic acid and terephthalic acid as acid modulators under hydrothermal conditions. The surface morphology, elemental composition, stability, surface area, pore size and pore volume of the functionalized KIT-5-g-C3N4 nanomaterial were determined using SEM, EDAX, Zeta potential analysis and BET surface area analysis respectively. The functionalized mesoporous KIT-5 material was screened for cationic dye degradation. The material was found to decolorize and degrade the cationic dye methylene blue completely under visible light conditions. The adsorption and degradation of the dye by functionalized KIT-5-g-C3N4 nanomaterial were studied using UV spectrophotometer. The photo degradation efficiency of the functionalized KIT-5-g-C3N4 nanomaterial was found to be 85.5%. The recyclability and reusability of the functionalized KIT-5-g-C3N4 nanomaterial in dye degradation was studied. The mechanism for the successful dye degradation by functionalized KIT-5-g-C3N4 nanomaterial was also discussed based on electro static interaction.
In this study, MIL-68(Al), a metal-organic framework, and SBA-15 (Santa Barbara Amorphous-15), a well-known silica material, were chosen for fabrication of composite material 1 by reflux method. The composite 1 named MIL-68(Al)@SBA-15 was characterized fully. TEM images and BET results confirmed the crystallization of MIL-68(Al) inside SBA-15 channels. Interestingly the BET surface area increased from 797 m² g⁻¹ for SBA-15 to 947 m² g⁻¹ for composite 1. Herein for the first time, we synthesized and used composite 1 for the adsorption of dye pollutants from water. The adsorption ability of composite 1 was investigated towards different dye solutions and was compared with the ability of bare MIL-68(Al) and SBA-15. The results revealed that the composite 1 adsorbed 100 % of MB solution in 0.5 min with a maximum adsorption capacity of 68.93 mg g⁻¹. Furthermore, the composite 1 was used for adsorption of binary, ternary, and quaternary mixed dye solutions and showed high adsorption efficiency for removal of all the mixed dye solutions in short time. The kinetics of the adsorption process follows the pseudo-second-order model, and the Langmuir isotherm model provides the best fitting for the adsorption of MB onto composite 1. Also, for investigation of the effect of synthesis route on the prepared composite material, the composite 2 named MIL-68(Al)/SBA-15 was synthesized by solid-state grinding and its adsorption ability toward dye solutions was compared with composite 1.
Present study reports the adsorption of aromatic amine, 4-chloro-o-toluidine (4-COT), onto synthesized mesoporous Mobil Composition of Matter No. 41 (MCM-41) silica nanoparticles, in batch mode. Synthesized MCM-41 was characterized by XRD, BET, FTIR, SEM and TEM analysis. The effects of pH, MCM-41 dose, 4-COT concentration, contact time and temperature were studied, and interaction of 4-COT with the surface of MCM-41 and adsorption process controlling mechanism were investigated. BET analysis of MCM-41 showed 502.77 m² g–1 of surface area. Kinetic experimental data were well represented by the pseudo-second order kinetic model. Freundlich and Temkin isotherm models well represented the adsorption equilibrium isotherm data.
The very high adsorption efficiency of Direct Blue (DB), an anionic toxic azo dye, onto amino grafted mesoporous silica nanoparticles (MCM-41), was studied in this paper, for possible industrial applications. Interesting challenges and advances are proposed in this field, presenting an adsorbent able to efficiently and rapidly remove the anionic dye from water. The important added value of this work regards the system recycle, which allows both the DB and adsorbent material recover, with a global reduction of the environmental impact, in the viewpoint of the green economy. Indeed, this paper is the first example of very fast removal and recycle of great amounts of DB with adsorbent materials characterized by impressive adsorption/desorption capacities, at least of around 300 mg/g for each adsorption cycle, potentially increasable by performing consecutive cycles of DB adsorption/desorption. In detail, the MCM-41 amino functionalization (MCM-41-NH2) was obtained after (MCM-41-POST) and during (MCM-41-PRE) the synthesis of MCM-41, obtaining materials with different behavior towards the DB adsorption. The MCM-41-NH2 surface features and porous structure, before and after the dye adsorption, were carefully characterized. Considering the adsorption process, for investigating the nature of the DB/MCM-41-NH2 interaction, several parameters were studied: the contact time, the DB solutions pH values, adsorbent material and dye amount, with the additional analysis of how the adsorption process was influenced by the presence of electrolytes. The isotherms of adsorption were also considered. Although MCM-41-PRE exhibited a higher affinity towards DB molecules, the MCM-41-POST were able to rapidly desorb it, thus recycling both DB and the adsorbent material.
The solution conditions such as the ion concentration and pH have a profound effect on the behaviour of the silica/water interface, which dictates many of the surface properties of mesoporous silica nanoparticles (MSNs) and their utility in a range of nanotechnology applications. The interaction of water molecules with a model silica surface, α-quartz (101), at different surface charge densities, is investigated to evaluate the influence of pH on structure (density profile, radial distribution function) and dynamics (diffusion coefficient D) of the interfacial water in the presence of biologically relevant ions, Na+, K+ and Rb+ ions. Classical molecular dynamics were performed using a recently developed force field (Kroutil et al, J. Phys. Chem C, 2015, 119, 9274-9286). Our results show the interfacial water is more structured and the diffusion of interfacial water molecules becomes slower as the surface charge becomes more negatively charged, as we increase the pH from acidic to neutral to basic pH. The self-coefficient diffusion (D) of water molecules and ions decrease with an increase in pH and is affected by concentration and type of ions in the system. The diffusion of water molecules around deprotonated oxygen atoms is slower than the diffusion of water molecules around oxygen protonated. The presence of the ions near to deprotonated oxygen atoms further decreases the diffusion of water molecules.
In this paper, the ability of chitosan film to remove dyestuff from wastewater was evaluated for environmental applications, using three commercial direct azo dyes. Two chitosan films were adopted: the standard one prepared following a well-known procedure to form it, and a novel one, with a weakly acidic character. Moreover, to improve the adsorption process, the hydrophobic character of the films was investigated. The pH of the dye solutions was also changed, showing an excellent ability in dye removal at pH 12. The films were characterized by means of spectroscopic and morphologic methods to better understand the nature of interactions between dyes and chitosan chains. Swelling ratio measurements were also performed. All analyses suggest that all dyes showed a strong affinity to chitosan polymer chains, with the presence of extended hydrogen bonds and Van der Waals forces perturbing the chitosan network. Interestingly, very good results were obtained in recycling experiments related to the dyeing capacities of chitosan blended films in the presence of textiles. An ecofriendly application is thus presented in this paper. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45945.
Being abundant and hazardous solid waste, the utilization of fly ash was sought. This study aimed to convert coal fly ash into zeolite using reflux method combined with microwave and ultrasonic pretreatments. Fly ash was reacted with NaOH 2 M, ultrasonicated for 30 minutes and irradiated using microwave for 45 minutes. The resulting solution was then refluxed for 24 hours. The zeolite formation was confirmed by FTIR and XRD analysis. The zeolite was then activated by 20% HCl for 2 hours. Fly ash, zeolites and activated zeolite were characterized for their adsorptive properties using a cationic dye via batch experiment. The maximum adsorption capacity (Qm) of fly ash, zeolite, and acid activated zeolite were 0.0003 mg g, 51 mg/g, and 101 mg/g, respectively. BET analyses indicated that the surface area of fly ash was 7 m2/g, while that for zeolite and acid activated zeolite were 82.4 m2g and 82.6 m2/g, respectively. The FTIR showed the Si-OH groups were significantly enhanced upon acid activation indicated by absorption peak at 960-1100 cm-1. It can be concluded that the chemisorption via cation-exchange or monolayer interaction played a major role in the adsorption mechanism of zeolite, supported by the allignment of the adsorption data plots to Langmuir isoterm adsorption model.
Mesoporous silicas MCM-48 and SBA-15 were synthesized and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. Adsorption capacity of two mesoporous silica for removing naphthalene from waste water was determined. The results indicate that under similar conditions, SBA-15 had a better adsorption capacity than MCM-48. In this context, SBA-15 was modified using 3-aminopropyltrimethoxysilane and the effect of contact time, adsorbent dose, solution pH and concentration of naphthalene was investigated in batch adsorption systems. Solution pH appeared to be a key factor affecting the adsorption of naphthalene by NH2-SBA-15. The adsorption experiments revealed that a higher percentage of up to 79.3% of naphthalene was adsorbed in highly acidic media (pH of 2). The equilibrium data were analyzed using Langmuir and Freundlich isotherms and nonlinear regression analysis. This revealed that based on the correlation coefficient (R2 = 0.979) the Langmuir model provided the best fit to the results. The adsorption kinetic was determined using the pseudo-first order, pseudo-second order and Elovich kinetic models. Of the kinetics models tested, the pseudo-first-order equation provided the best fit to the results (R2 = 0.991) of the absorption of naphthalene by the adsorbent.
Yellow dye (YD) adsorption was carried out on some mesoporous materials such as calcined and uncalcined Al-MCM-41. These two matrices were synthesized by variation of Si/Al molar ratio (20, 40 and 80) under thermal conditions. The obtained materials were characterized by various methods: XRD diffraction (XRD), nitrogen adsorption at 77 K, Fourier transformed infrared spectroscopy (FTIR) and energy dispersive spectroscopy by X-rays (EDX). Elimination of YD as a function of both pH and shaking, contacting time, and reaction temperature was studied. The uncalcined Al-MCM-41 had the highest adsorption capacities with adsorption rate of about 92%. Both the uncalcined and calcined materials which contain a very little amount of aluminum seem to have a high affinity toward YD molecules.
Silicate mesoporous materials have received widespread interest because of their potential applications as supports for catalysis, separation, selective adsorption, novel functional materials, and use as hosts to confine guest molecules, due to their extremely high surface areas combined with large and uniform pore sizes. Over time a constant demand has developed for larger pores with well-defined pore structures. Silicate materials, with well-defined pore sizes of about 2.0-10.0 nm, surpass the pore-size constraint (< 2.0 nm) of microporous zeolites. They also possess extremely high surface areas (> 700 m(2) g(-1)) and narrow pore size distributions. Instead of using small organic molecules as templating compounds, as in the case of zeolites, long chain surfactant molecules were employed as the structure-directing agent during the synthesis of these highly ordered materials. The structure, composition, and pore size of these materials can be tailored during synthesis by variation of the reactant stoichiometry, the nature of the surfactant molecule, the auxiliary chemicals, the reaction conditions, or by post-synthesis functionalization techniques. This review focuses mainly on a concise overview of silicate mesoporous materials together with their applications. Perusal of the review will enable researchers to obtain succinct information about microporous and mesoporous materials.
Color removal from wastewater has been a matter of concern, both in the aesthetic sense and health point of view. Color removal from textile effluents on a continuous industrial scale has been given much attention in the last few years, not only because of its potential toxicity, but also mainly due to its visibility problem. There have been various promising techniques for the removal of dyes from wastewater. However, the effectiveness of adsorption for dye removal from wastewater has made it an ideal alternative to other expensive treatment methods. In this review, an extensive list of sorbent literature has been compiled. The review evaluates different agricultural waste materials as low-cost adsorbents for the removal of dyes from wastewater. The review also outlines some of the fundamental principles of dye adsorption on to adsorbents.
Dye pollutants from the textile, paper, and leather industries are important sources of environmental contamination. In the present study an agricultural waste from potato plant (potato stem powder, PSP and potato leaves powder, PLP) was used as an adsorbent for removal of the methylene blue (MB) and malachite green (MG) dyes from aqueous solution. The adsorbent materials were characterized by scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy. Batch experiments were performed to investigate the effect of physico-chemical parameters, such as pHpzc, ionic strength, adsorbent dose, contact time, initial dyes concentration and temperature. The kinetics of adsorption was studied by applying the pseudo-first order, pseudo-second order and intraparticle diffusion models. The pseudo-second order model better represented the adsorption kinetics and the mechanism was controlled by surface adsorption and intraparticle diffusion. Equilibrium data were analyzed using Langmuir and Freundlich isotherm models. The thermodynamic parameters such as change in enthalpy (ΔH°), entropy (ΔS°) and Gibb’s free energy (ΔG°) of adsorption systems were also determined and evaluated.
Investigations were conducted to study the adsorption behavior of heavy metal Cu(II) on the mesoporous silicate SBA-15 (CONH(2)-SBA-15) in aqueous medium by varying parameters such as contact time, temperature, ionic strength, and competing ions. Heavy metal adsorption was broadly independent of initial metal concentration. Competing ions in the aqueous solution had a small effect on the adsorption of Cu(II) on CONH(2)-SBA-15. The adsorption data for Cu(II) fit well with the Langmuir and Redlich-Peterson models. Kinetic studies showed that the kinetic data are well described by the pseudo second-order kinetic model. Initial adsorption rate increases with an increase in temperature. The intraparticle diffusion model was the best in describing the adsorption kinetics for the Cu(II) on CONH(2)-SBA-15. Thermodynamic analysis indicates that the adsorption is spontaneous and endothermic.
IntroductionToxicology and Toxicity Assessments Acute ToxicitySensitizationMutagenicityCarcinogenicityEnvironmental Assessment/Fate IntroductionTreatment of Dye-Containing WastewaterLegislation Registration/Notification of New SubstancesPrincipal Chemical Legislation also Relevant to DyesSpecial Regulations for Dyes (Colorants)Material Safety Data Sheets Acute ToxicitySensitizationMutagenicityCarcinogenicity IntroductionTreatment of Dye-Containing Wastewater Registration/Notification of New SubstancesPrincipal Chemical Legislation also Relevant to DyesSpecial Regulations for Dyes (Colorants)Material Safety Data Sheets
The rates of adsorption of a basic dye, Astrazone Blue, and an acidic dye, Telon Blue, on wood have been studied. The rate controlling step is mainly intraparticle diffusion, although a small resistance due to a boundary layer is experienced. The activation energies for the adsorption of Astrazone Blue and Telon Blue on wood are 16.8 kJ mol-1 and 9.6 kJ mol-1, respectively. The diffusion coefficients vary from 6 X 10-13 cm2s-1 to 18 X 110-13 cm2s-1 for Astrazone Blue at 18°C and from 3 X 10 -1:3 cm2s1 to 8 X 110-13 cm2s-1 for Telon Blue at 18°C. The variation in diffusivities is attributed to boundary layer effects.
Research in supramolecular-templated mesoporous materials began in the early 1990s with the announcement of MCM-41 and the M41S family of molecular sieves. These materials are highly unusual in their textural characteristics: uniform pore sizes greater than 20 Å, surface areas in excess of 1000 m2g-1, and long-range ordering of the packing of pores. The mesoporous materials are derived with supramolecular assemblies of surfactants, which template the inorganic components during synthesis. Many researchers have since exploited this technique of supramolecular templating to produce materials with different compositions, new pore systems, and novel properties. This article reviews the current state of the art in mesoporous materials research in three general areas: synthesis, catalytic properties, and other applications that take advantage of bulk morphologies. Various mechanisms formulated to explain the formation of mesostructures are discussed in the context of compositional control. The catalytic applications of mesoporous materials are examined, with a significant fraction based on recent patent literature. Other directions in the utilization of mesoporous materials are also presented.
Organofunctionalized nanostructured silica SBA-15 with tri(2-aminoethyl)amine tetradentate-amine ligand was synthesized and applied as adsorbent for the removal of Cu2+, Pb2+, and Cd2+ from both synthetic wastewater and real paper mill and electroplating industrial effluents. The prepared materials were characterized by XRD, N-2 adsorption-desorption, TGA, and FT-IR analysis. The Tren-SBA-15 was found to be a fast adsorbent for heavy metal ions from single solution with affinity for Cu2+, Pb2+, than for Cd2+ due to the complicated impacts of metal ion electronegativity. The kinetic rate constant decreased with increasing metal ion concentration due to increasing of ion repulsion force. The equilibrium batch experimental data is well described by the Langmuir isotherm. The maximum adsorption capacity was 1.85 mmol g(-1) for Cu2+, 1.34 mmol g(-1) for Pb2+, and 1.08 mmol g(-1) for Cd2+ at the optimized adsorption conditions (pH=4, T=323 K, t=2 h, C-0=3 mmol L-1, and adsorbent dose=1 g L-1). All Gibbs energy was negative as expected for spontaneous interactions, and the positive entropic values from 103.7 to 138.7 J mol(-1) K-1 also reinforced this favorable adsorption process in heterogeneous system. Experiment with real wastewaters showed that approximately a half fraction of the total amount of studied metal ions was removed within the first cycle of adsorption. Hence, desorption experiments were performed by 0.3M HCl eluent, and Tren-SBA-15 successfully reused for four adsorption/desorption cycles to complete removal of metal ions from real effluents. The regenerated Tren-SBA-15 displayed almost similar adsorption capacity of Cu2+, Pb2+, and Cd2+ even after four recycles. The results suggest that Tren-SBA-15 is a good candidate as an adsorbent in the removal of Cu2+, Pb2+, and Cd2+ from aqueous solutions.
In May 2001, at a diplomatic conference in Stockholm, Sweden, the international community adopted and opened for signature the new Stockholm Convention on Persistent Organic Pollutants (Stockholm Convention). Over ninety nations signed the convention at the conference, and one country—Canada—ratified it. The Stockholm Convention is designed to protect human health and the environment from persistent organic pollutants (POPs)—chemical substances that are persistent and toxic, that bioaccumulate in fatty tissue (achieving higher concentrations as they move up a particular food chain), and that are prone to long-range environmental transport. Among other things, the convention contains obligations to eliminate or severely restrict the production and use of a number of POP pesticides and industrial chemicals, to take strong measures to prevent or control the release of certain POPs that are formed as by-products of various combustion activities, and to ensure the safe and proper disposal or destruction of such substances when they become wastes.
The adsorption kinetics and thermodynamics of Maxilon Blue 5G, a cationic textile dye, onto perlite were investigated in aqueous solution in a batch system for determining the effect of contact time, stirring speed, initial dye concentration, initial solution pH, ionic strength and temperature. Experimental data were evaluated according to the pseudo-first, second-order and the Elovich equation, mass transfer and intra-particle diffusion models, and it was found that adsorption kinetics can be described according to the pseudo-second-order model, from which the rate constant and the adsorption capacity were determined. The thermodynamic activation parameters, such as activation energy, enthalpy, entropy and Gibbs free energy, were determined. The obtained results confirmed the applicability of this mineral as an efficient adsorbent for cationic dyes.
The pine leaves which are an agricultural residue were used in its natural form as biosorbent for the removal of Acid Yellow 220 (AY 220) dye from aqueous solutions. The sorption experiments were carried out as a function of solution pH, biosorbent dosage, biosorbent size, dye concentration, temperature, contact time and ionic strength. The sorption isotherms closely followed the Langmuir model. The monolayer sorption capacity of the pine leaves for AY 220 was found as 40.00 mg g(-1). It was shown that pseudo-second order equation could best describe the sorption kinetics. The thermodynamic data indicated that the sorption system was spontaneous. endothermic and physical process. Based on the results of present investigation, the pine leaves could be used as a suitable alternative biosorbent for the elimination of AY 220 from aqueous solutions.
This article reports the application of a crosslinked chitosan/bentonite composite as adsorbent for the removal of a cationic dye, methylene blue (MB), from aqueous solution. Batch experiments were conducted to study the effects of contact time, initial concentration of adsorbate (50–200 mg L−1), temperature (298–313 K), agitation speed (90–150 rpm), and pH (2–10) on adsorption. The equilibrium experimental data were analyzed by the Freundlich and Langmuir models. The kinetic data obtained with different initial concentration and temperature were analyzed using a pseudo-first-order, pseudo-second-order, and intraparticle diffusion equations. Maximum adsorption capacity (Q m) was calculated at different temperatures (298, 308, and 313 K) as 95.24, 97.09, and 142.86 mg g−1, respectively. The results showed that this novel adsorbent had a high adsorption capacity, making it suitable for use in the treatment MB-enriched wastewater.
Functionalised SBA-15 mesoporous silica with polyamidoamine groups (PAMAM-SBA-15) was successfully prepared with the structure characterised by X-ray diffraction, nitrogen adsorption–desorption, Fourier transform infrared spectra and thermogravimetric analysis. PAMAM-SBA-15 was applied as adsorbent for Cu(II), Pb(II) and Cd(II) ions removal from aqueous solution. The effects of the solution pH, adsorbent dosage and metal ion concentration were studied under the batch mode. The Langmuir model was fitted favourably to the experimental data. The maximum sorptive capacities were determined to be 1.74 mmol g−1 for Cu(II), 1.16 mmol g−1 for Pb(II) and 0.97 mmol g−1 for Cd(II). The overall sorption process was fast and its kinetics was fitted well to a pseudo-first-order kinetic model. The mean free energy of sorption, calculated from the Dubinin–Radushkevich isotherm, indicated that the sorption of lead and copper, with E > 16 kJ mol−1, followed the sorption mechanism by particle diffusion. The adsorbent could be regenerated three times without significant varying its sorption capacity. A series of column tests were performed to determine the breakthrough curves with varying bed heights and flow rates. The breakthrough data gave a good fit to the Thomas model. Maximum sorption capacity of 1.6, 1.3 and 1.0 mmol g−1 were found for Cu(II), Pb(II) and Cd(II), respectively, at flow rate of 0.4 mL min−1 and bed height of 8 cm, which corresponds to 83%, 75% and 73% of metallic ion removal, respectively, which very close to the value determined in the batch process. Bed depth service time model could describe the breakthrough data from the column experiments properly. © 2012 Canadian Society for Chemical Engineering
In this study, graphene oxide (GO) nanosheets have been used for the adsorption of methyl green, a cationic dye from aqueous solution. GO nanosheets consist of single layered graphite structure decorated with a number of oxygen containing functionalities such as carboxyl, epoxy, ketone, and hydroxyl groups which impart a negative charge density to it in aqueous solution at a wide range of pH. Thus, GO nanosheets can be predicted as a good adsorbent material for the adsorption of cationic species. The adsorption of the methyl green onto the GO nanosheets has been carried out at different experimental conditions such as adsorption kinetics, concentration of adsorbate, pH, and temperature. The kinetics of the adsorption data were analyzed using four kinetic models such as the pseudofirst-order model, pseudosecond-order model, intraparticle diffusion, and the Boyd model to understand the adsorption behavior of methyl green onto the GO nanosheets and the mechanism of adsorption. The kinetics of adsorption result shows that the adsorption maximum was reached at 60 min and follows the linear form of pseudosecond-order kinetics. The adsorption isotherm of adsorption of the methyl green onto the GO nanosheets has been investigated in the pH range of 4 to 9 at 25 °C. The equilibrium data were fitted well to the Langmuir model. Various thermodynamic parameters such as the Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) change were also evaluated. The negative value of ΔG indicates spontaneity of the adsorption process of the methyl green–GO system. The interaction of methyl green onto the GO nanosheets has been investigated by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy.
Ordered nanoporous silica SBA-15 was successfully synthesized and functionalized by tris(2-aminoethyl)amine (Tren), a multi-amine ligand, to develop efficient cationic dye adsorbent. The prepared materials were characterized by XRD, N2 adsorption–desorption, TGA, and FT-IR analysis. Tren-SBA-15 was used for the removal of malachite green (MG) from both aqueous solution and real textile effluent. The effects of various operational parameters including solution pH, adsorbent dosage, contact time, initial concentration and temperature on removal of MG using Tren-SBA-15 were investigated in batch adsorption mode. Within the optimum conditions, Tren-SBA-15 exhibited an excellent adsorptive capability of 2330 m g−1 (6.38 mmol g−1) with removal of 89.8%. Equilibrium data was best described by the Freundlich and Sips isotherm models indicated a favorable adsorption process (nF > 1) and heterogeneous system for dye adsorption (nS > 1). The adsorption kinetic behavior was influenced by intraparticle diffusion and pseudo-second-order kinetic model provided well-fitted to the experimental data. The kinetic rate constant increased with temperature. Qualitative estimates of the thermodynamic parameters showed that the overall adsorption process is spontaneous (ΔG < 0) and a bit endothermic (ΔH > 0), and adsorption mechanism was assumed to be a physisorption. Experiment with real textile wastewater showed 48.7% MG removal by the use of 0.01 g Tren-SBA-15. The reusability of the adsorbent in real wastewater was shown to be successful along with its regeneration possibility. Desorption experiments were performed by two deferent eluents to desorbs both cationic ions and dye molecules from Tren-SBA-15. The results showed that dye is removed completely from real effluent after two continues adsorption/desorption cycles. © 2014 American Institute of Chemical Engineers Environ Prog, 2014
Congo red was removed from aqueous solution using nano-crystalline agglomerates of calcium–iron mixed oxide (CaIMO) and iron–calcium mixed oxide (ICaMO) (CaIMO: 30–25 nm; ICaMO: 22–19 nm). The optimum pH was 8.0 (±0.1). Kinetically, pore diffusion with pseudo-second order equation governs the overall adsorption process. Langmuir and Redlich–Peterson isotherms describe the experimental data. Negative ΔGo (−20.78 to −15.25 kJ mol−1) and negative ΔHo (−26.21 and −105.59 kJ mol−1) indicated spontaneous and exothermic reaction. Adsorbents are 4th cycle regenerated using 0.05 M NaOH. Both CaIMO and ICaMO are competitive materials for CR removal from aqueous solution
In this work, a kind of novel full biodegradable magnetic adsorbent based on glutamic acid modified chitosan and silica coated Fe3O4 nanoparticles was prepared successfully by a one-step method. The structure of the glutamic acid modified chitosan magnetic composite microspheres (CS-Glu-MCMs) was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), vibrating-sample magnetometer (VSM), scanning electron microscope (SEM), and equilibrium swelling experiment. Then, CS-Glu-MCM was employed as adsorbent for removal of three different kinds of cationic dyes, methylene blue (MB), crystal violet (CV) and cationic light yellow 7GL (7GL), from aqueous solutions. Compared with chitosan magnetic composite microspheres (CS-MCMs) without modification, CS-Glu-MCM shows much higher dye uptakes. The fundamental adsorption experiments reveal that CS-Glu-MCM is more efficient in dye removal at pH higher than 5.0. Adsorption isotherms and adsorption kinetics of CS-Glu-MCM are all well described by Langmuir model and the pseudo-second order model, respectively, which indicates that the dyes adsorption behavior of CS-Glu-MCM is a homogeneous monolayer chemisorption process. Furthermore, the magnetic adsorbents could be easily regenerated at lower pH and reused with almost no loss of adsorption capacity.
Sulfur dyes are inexpensive and are used mainly for dyeing textile cellulosic materials or blends of cellulosic fibers. Sodium sulfide is fairly cheap and a traditional reducing agent used for sulfur dyeing, but it is toxic and hazardous to handle. Its use may leave harmful residues in finished fabrics and generate effluents that are difficult to treat and damaging to the environment. Textile companies face the high costs of water and wastewater, as well as strict environmental legislation. In this review, a variety of methods, including physicochemical and biological methods, are surveyed for their application to the treatment of water and wastewater containing sulfur dyes. This survey is followed by suggestions for further actions that can be taken for the improvement of the treatment processes from both economic and technical viewpoints.
The nano-sized TiO2 powder and immobilized TiO2/SBA-15 photocatalysts were synthesized via a polyol method with an attempt to increase the quantitative effect by reducing the particle size and avoid the aggregation by immobilizing on hydrophilic SBA-15 support. The effect of reduction temperature on the TiO2 crystalline size was investigated. The X-ray diffraction (XRD) and Field-emission scanning electron microscopy (FE-SEM) results showed that the crystallite size of the TiO2 particles is in the nano-regime and indicated that depended on the nucleation and growth process, different sizes and shapes of monodisperse or polydisperse TiO2 powders are formed. The photocatalytic activities of the samples were evaluated for the decolorization of an ano dye, acid red 1 (AR1) were studied in aqueous solution under UV light irradiation. The effect of different parameters such as catalyst dosage, solution pH, TiO2 loading weight, and different support materials Al2O3 and glass bead on the decolorization efficiency of AR1 were studied. The results indicated that the self-synthesized TiO2 showed comparable decolorization efficiency than commercial P25, and the efficiency can be significantly improved by using SBA-15 as support material due to its hydrophilicity.
The preparation of organo-bentonite via microwave radiation using natural surfactant (i.e. rarasaponin) from the tropical soapfruit pericarps of Sapindus rarak was conducted in this work. The adsorption performance of bentonite and its modified form was studied for the removal of two dyes (i.e. methylene blue and malachite green) in single and binary systems. Langmuir and Freundlich models were applied to evaluate adsorption equilibrium data in single systems. From physical meaning interpretation of the model parameters, it was found that Langmuir model gave the best representation. A new approach in representing binary experimental isotherms with extended Langmuir model incorporating fractional surface coverage in 3D mesh plot was also verified. The results show that recently proposed modification of extended Langmuir model could be used to evaluate binary adsorption data well with reasonable fitted parameter value.
Amino functionalized silica gel (NH2–SG) and amino functionalized silica nano hollow sphere (NH2–SNHS) with rather monodispers shape and size were prepared and characterized by X-ray differaction, scanning electron microscopy (SEM), FT-IR, thermogravimetery, and N2 adsorption–desorption techniques. The synthesized nano particles were employed as a Cd2+, Ni2+, and Pb2+ adsorbent from aqueous solutions at room temperature. Adsorption performances of three different adsorbents prepared by functionalization of commercial silica gel (NH2–SG), silica nano hollow sphere (NH2–SNHS), and a non functionalized silica nano hollow sphere (SNHS) have been compared. Heavy metal adsorption process has been thoroughly studied from both kinetic and equilibrium points of view for all adsorbents. The adsorption isotherms were analyzed using the seven different isotherm models and correlation coefficients were determined for each isotherm. It was found that the Langmuir–Freundlich (Sips) isotherm showed better correlation with the experimental data than other isotherms. The adsorption kinetics was tested for the pseudo-first order, pseudo-second order and Elovich kinetic models at different experimental conditions. The kinetic data show that the process is very fast and the reactions follow pseudo-second-order kinetic models for amino functionalized adsorbents. Also, the maximum adsorption values for Cd2+, Ni2+, and Pb2+ under the experimental conditions were determined for all adsorbents.
Mesoporous molecular sieves with size-tunable mesopores have been well developed and have attracted a great deal of attention because of their controllable structures and compositions, which make them suitable for a wide range of applications in catalysis, adsorption, separation, chromatography, etc. The pore size of mesoporous silica is large enough to accommodate a variety of large molecules, and the high density of silanol groups on the pore wall is beneficial to the introduction of functional groups with a high coverage. Actually, various kinds of surface modifications have been conducted for providing new functions for the surfaces. Among various functional groups, the introduction of the amino groups onto the mesopores has enabled us to use amino-functionalized mesoporous materials as solid-base catalysts and adsorbents. Meanwhile, “anionic surfactant templated mesoporous silica (AMS)” has been synthesized via a novel templating route for preparing mesoporous silicas based on the self-assembly of anionic surfactants and inorganic precursors in the presence of aminosilane or quaternized aminosilane as a co-structure-directing agent. AMSs are synthetically interesting not only for their structural diversity, including chiral properties, but also for the chance of functionalizing the pore surface by removing the surfactant by solvent extraction, resulting in the formation of the mesoporous silica with aminopropyl groups intact. Thus obtained amino-functionalized AMS can be applied to solid-base catalysis, adsorption, drug delivery, etc.This review gives an overview on the recent development of amino-functionalized mesoporous silica. In particular, the difference in the state and catalytic activity of amino groups between the functionalized mesoporous silicas synthesized via anionic and cationic surfactants templating routes is featured. Interesting applications of amino-functionalized mesoporous silica besides solid-base catalyst are also described.
In the present study, titania nanoparticles were first constructed on mesoporous aluminosilicate Al-SBA-15 in supercritical carbon dioxide (Sc-CO2) and the resultant samples were characterized by a combination of various techniques, such as X-ray diffraction (XRD), nitrogen physisorption, 27Al MAS NMR, UV–vis diffuse reflectance spectroscopy, and transmission electron microscopy (TEM). It was identified that the Al species incorporated samples retained structures similar to that of the parent SBA-15. In addition, the content of titania loading varied with reaction temperature and time in Sc-CO2. As-synthesized TiO2/Al-SBA-15 samples were evaluated in terms of photocatalytic decolorization of methylene blue in aqueous solutions. It was observed that all TiO2/Al-SBA-15 samples showed satisfactory decolorization efficiency that was much higher than those of TiO2/SBA-15 and commercial TiO2 under identical conditions, which could be mainly attributed to the effective adsorption capability, resulting from the extension of specific surface area after substitution of Si species with Al species.
Quaternary ammonium polyethylenimine (PEI) was successfully modified to silica nanoparticle (QPEI/SiO2) as a new adsorbent to remove methyl orange from aqueous solution. The isotherm and kinetics of dye adsorption were studied, which showed that Langmuir isotherm fit the experimental results well. The maximum adsorption capacity of QPEI/SiO2 for methyl orange is 105.4 mg/g. The equilibrium time for methyl orange adsorption onto QPEI/SiO2 was as short as 10 min, indicating that the adsorbent has a strong affinity for methyl orange. The adsorption capacities of the methyl orange are slightly influenced by the pH in the range of 3.2–9.6. The QPEI/SiO2 adsorbent can be used in the wide pH range, which is different from other adsorbent. This may attribute to the quaternary ammonium carrying positive charges in acidic and basic solution.
Ordered mesoporous silica materials are one of the most extensively used adsorbents for trapping pollutants. They have many advantages such as good accessibility to active sites, rapid mass transport inside the nanostructures, and good hydrothermal stability, but most mesoporous materials do not themselves have the appropriate surface properties. To address this issue, we reported a simple method for immobilization of heteropolymetalate onto mesoporous, because they have potential sorption and ion exchange properties. Here we attempted to immobilized Tin (IV) molybdophosphate onto mesoporous silica SBA-15 and used for strontium removal from aqueous solution. The obtained products were characterized by inductively coupled plasma (ICP), XRD, N2 adsorption–desorption isotherms, scanning electron microscopy (SEM) and FT-IR. This work provides new methodology for the general synthesis of supported heteropolymetalate with large surface areas, and ordered nano porous structures.
The aim of the present work was to investigate the potential of multicarboxylic hyperbranched polyglycerol (HPG) modified mesoporous SBA-15 (SBA/HPG-COOH) as adsorbent for the removal of cationic dyes or/and heavy metal ions from aqueous media. The SBA/HPG-COOH adsorbents can be facilely synthesized through two steps: in situ anionic ring-opening polymerization of glycidol and further modification of hydroxyl groups by succinic anhydride. The resulting SBA/HPG-COOH was characterized by means of FTIR, TGA, XRD, SEM and nitrogen adsorption–desorption isotherms. The results demonstrate that the SBA/HPG-COOH was successfully synthesized and the density of carboxylic groups on the SBA/HPG-COOH is calculated to be as high as 1.5 mmol/g, posing a powerful base for adsorbing cationic adsorbates. Four kinds of dyes and copper ions were chosen as representatives to investigate the adsorption ability of SBA/HPG-COOH. The SBA/HPG-COOH adsorbent showed quick adsorption rate, high adsorption capacity (e.g., its saturated adsorption capacity for methylene blue (MB) can reach 0.50 mmol/g, while for unmodified SBA-15 is lower than 0.05 mmol/g), and high selectivity for cationic adsorbates. The fitness of Langmuir adsorption model and pseudo second-order kinetics on describing the adsorption isotherm and kinetics of SBA/HPG-COOH for MB dye was examined, respectively. It is believed that this robust SBA/HPG-COOH adsorbent will find important application in removal of cationic adsorbates from aqueous solution.
The objective of this work is development of a new adsorbent on the base of an organoclay with a chelating ligand covalently attached to the clay mineral surface. The presence of a chelating ligand in the clay structure significantly improves its ability to immobilize heavy metal ions from contaminated sludge of wastewater. Montmorillonite and kaolinite were chosen as typical examples of expandable and non-expandable clay minerals. A two-step modification procedure comprised of sequential modification with oxides and grafting of a chelating agent to the modified clay minerals was used. Modifications with silica and ferric oxide were conducted by reacting the dispersed raw clay minerals with tetraethoxysilane and ferric nitrate solution. A chelating ligand, N-[3-(trimethoxysilyl)propyl]ethylenediamine triacetic acid trisodium salt, was introduced into interlayer space of raw and modified clay minerals in aqueous solutions. Laboratory tests of the organoclay efficiency for purification of wastewater were conducted with the most promising sample, i.e., organoclay with the highest specific loading of chelating agent. Experiments were conducted with model wastewater containing either individual or mixed heavy metal ions. The modified organoclay displayed high adsorption capacity for heavy metal cations even in acidic media. The method of modification presented in this work can be used for synthesis of efficient adsorbents for applications in contaminated areas.
The adsorption characteristics of basic yellow 87 from aqueous solution were investigated using two mesoporous materials: MCM41 and carbon aerogel (MCA). The adsorbents were analyzed by N-2 adsorption-desorption technique and transmission electron microscopy to elucidate the effect of pore properties on the adsorption behavior of basic yellow 87. Three adsorption isotherms were used to model the equilibrium adsorption of basic yellow 87 on two mesoporous adsorbents. The result indicates that the Redlich-Peterson isotherm model describes the adsorption of basic yellow 87 extremely well. The adsorption process of MCM41 was exothermic and that of MCA was endothermic. Kinetic studies show that the adsorption of MCM41 and MCA followed the pseudo-second-order kinetic model. Batch experiments were conducted to study the effects of pH (1.2-13.0), dosage (0.025-0.200 g/50 mL). and particle size (5-10, 10-20, 20-40, and >= 200 mesh) on dye adsorption. The mesoporous adsorbents were highly effective as adsorbents for basic yellow 87 from aqueous solution. In particular, the initial adsorption rate of MCM41 was faster than that of MCA, but its adsorption capacity in dilute solutions was lower than that of MCA. The relatively low cost and high capabilities of MCM41 and MCA make them potentially attractive adsorbents for the removal of dyes from aqueous solution. (C) 2011 Elsevier B.V. All rights reserved.
The surface chemistry of a commercial activated carbon with a slightly basic nature was modified by appropriate treatments in order to obtain two additional samples, respectively with acidic and basic properties, without changing its textural parameters significantly. Different techniques (N2 adsorption at 77 K, temperature programmed desorption, and determination of acidity, basicity, and pH at the point of zero charge) were used to characterize the adsorbents. Kinetic and equilibrium adsorption data of a selected textile reactive dye (Rifafix Red 3BN, C.I. reactive red 241) on the mentioned materials were obtained at the pH values of 2, 7, and 12. The kinetic curves are fitted using the second-order model. The respective rate constants seem to diminish progressively with the initial concentration for the more diluted solutions tested, reaching a constant value at higher concentrations, which depends on the experimental system under consideration (adsorbent and pH). In general, the Langmuir model provides the best fit for the equilibrium data. The different uptakes obtained are discussed in relation to the surface chemical properties of the adsorbents. It is shown that the adsorption of the reactive (anionic) dye on the basic sample (prepared by thermal treatment under H2 flow at 700 °C) is favored. This conclusion is explained on the basis of the dispersive and electrostatic interactions involved. Moreover, it is also shown that the optimal adsorption condition for all the activated carbons tested corresponds to solution pH values not higher than the pHpzc of the adsorbents, which may be interpreted by taking into account the electrostatic forces present.
Adsorption of acid dyes on SBA-3 ordered mesoporous silica, ethylenediamine functionalized SBA-3 (SBA-3/EDA), aminopropyl functionalized SBA-3 (SBA-3/APTES) and pentaethylene hexamine functionalized SBA-3 (SBA-3/PEHA) materials has been studied. The structural order and textural properties of the synthesized materials have been studied by XRD, FT-IR and nitrogen adsorption–desorption analysis. The adsorption capacity of the adsorbents varies in the following order: SBA-3/PEHA > SBA-3/APTES > SBA-3/EDA > SBA-3. The SBA-3/PEHA is found to have the highest adsorption capacity for all acid dyes. The adsorption mechanism which is based on electrostatic attraction and hydrogen bonding is described. Batch studies were performed to study the effect of various experimental parameters such as chemical modification, contact time, initial concentration, adsorbent dose, agitation speed, solution pH and reaction temperature on the adsorption process. The Langmuir and Freundlich isotherm models have been applied and the Freundlich model was found to be fit with the equilibrium isotherm data. Kinetics of adsorption follows the second-order rate equation.
Well-ordered cubic FDU-12 type mesoporous silicas functionalized with various contents of carboxylic acid group (-COOH), up to 40 mol% based on silica, were synthesized via co-condensation of tetraethyl orthosilicate (TEOS) and carboxyethylsilanetriol sodium salt (CES) under acidic conditions using Pluronic F127 triblock copolymer as template. The materials thus obtained were characterized by a variety of techniques including powder X-ray diffraction (XRD), nitrogen adsorption-desorption, transmission electron microscopy (TEM), C-13 and Si-29 solid-state nuclear magnetic resonance (NMR) measurements. The materials were used as adsorbents for removal of methylene blue (MB) in aqueous solutions and as an antidote for intoxication of herbicide paraquat (PQ). Due to the -COOH functionalization, three-dimensional pores, high surface areas, and electrostatic interactions between the adsorbent and the adsorbates, the prepared adsorbents possessed very high adsorption capacities and extremely rapid rates for MB and PQ adsorption. The kinetic regression results revealed that the overall adsorption process was controlled by external mass transfer and intra-particle diffusion jointly. The Langmuir isotherm model showed better fit with the experimental adsorption data than the Freundlich isotherm model, implying a monolayer adsorption mechanism. The present results show that the prepared -COOH functionalized cubic mesoporous silicas have great potentials for removing pollutants and herbicides from aqueous solutions in environmental and clinical applications. (c) 2013 Elsevier B.V. All rights reserved.
Mesoporous silica nanoparticles (MSN) with high surface area, tunable pore size and very narrow pore size distribution were functionalized by organic acid, organic base, metallic nanoparticles and organometallic complexes through co-condensation methods and/or post-synthesis grafting methods. And these surface-functionalized mesoporous materials were applied as heterogeneous catalysts in organocatalysis, metallic catalysis and organometallic catalysis.
Organocatalysis. First, Brynsted acid and base were confined into the mesoporous channels of MSN and they could co-exist as compatible catalysts for one-pot reaction cascades without neutralizing each other because they were confined in different MSN particles' channels. Brynsted acid and base also were site-separated by MSN's internal surface and external surface through co-condensation method to functionalize MSN's internal surface followed by grafting method to functionalize MSN's external surface. These internal and external surface-separated Brynsted acid and base could co-exist as compatible catalysts too.
Metallic catalysis. Water-soluble rhodium nanoparticles with well defined particle size were synthesized and immobilized on MSN during in situ MSN's synthesis. The obtained material (MSNRhNPs) had homogeneous rhodium nanoparticle size, homogeneous rhodium nanoparticle distribution in MSN, typical MSN's highly ordered structure and surface area and narrow pore size distribution as well. After MSNRhNPs were modified by manganese oxide, it could catalyze the hydrogenation of CO to produce the renewable energy alternative - ethanol with high selectivity and high activity. Additionally, after MSNRhNPs were functionalized by some chiral agents such as (-)-cinchonidine, it can used as a solid chiral catalyst which can be recycled and reused without any loss of reactivity and enantioselectivity.
Organometallic catalysis. Wilkinson-type rhodium phosphine complex was homogeneously immobilized on MSN surface by co-condensation method. This MSN- immobilized rhodium-phosphine complex (RhPMSN) had a new and total different catalytic performance: RhPMSN could enantioselectively catalyze the hydrogenation of pyruvate when (-)-cinchonidine was adsorbed on RhPMSN surface. However, RhCl(TPP)3 (TPP: triphenylphosphine) and (-)-cinchonidine could not enantioselectively catalyze the same reaction in homogeneous system.
An in-depth solid-state NMR study of RhPMSN has been presented. Functionalization of the ligand was confirmed by the presence of T sites in the 29Si CPMASNMR spectrum and quantification of these sites was achieved via integration of the 29Si DPMAS NMR spectrum. Both 1D and 2D SSNMR experiments showed that covalent attachment of the rhodium- phosphine ligand to the MSN surfaces was successful. Both 13C-1H and 31P-1H idHETCOR experiments provided structural details of oxidized and non-oxidized phosphine ligands, otherwise indiscernible in a conventional 1D CPMAS NMR experiments.
Organometallic complex (salen)Cr on MSN was synthesized and applied in the oxidation of tetramethylbenzidine (TMB) with iodosobenzene. MSN-(salen)CrIII as a heterogeneous catalyst exhibited both similarities and differences with the analogous (salen)CrIII(H2O)+ as catalyst in aqueous acetonitrile (10% H2O). It was shown that the covalently attached catalyst in mesoporous channels of MSN was still easily accessible to the reactants without diffusion problem.
Aminopropyl-functionalized MSN was synthesized and applied in the selective sequestration of carboxylic acids from biomass fermentation. Aminopropyl-functionalized MSN with a designed loading of functional groups could have a very high selectivity for carboxylic acid instead for ethanol, glucose, and protein. The regeneration of aminopropyl-functionalized MSN could be done easily by increasing pH to 10.5 because the adsorption reaction between carboxylic acids and aminopropyl-functionalized MSN was pH-dependent. And the regenerated aminopropyl-functionalized MSN showed adsorption capacity equivalent to the original.
Batch sorption experiments were carried out to remove dyes, methyl orange (MO), orange G (OG) and brilliant red X-3B (X-3B), from their aqueous solutions using a mesoporous silica SBA-3 as an adsorbent. The effect of surfactant template in SBA-3 on the removal of OG, MO and X-3B was investigated. Experiments were carried out to investigate the influence of contact time, initial concentration, pH, and adsorbent dosage on the adsorption performance. The adsorption results of anionic dyes on the uncalcined SBA-3 (noted as SBA-3) were compared with those of the calcined SBA-3 (noted as C-SBA-3). The uncalcined SBA-3 adsorbent has a large adsorption capacity and a strong affinity for the anionic dyes. Langmuir, Freundlich and Temkin isotherms were employed to model the experimental results, from which the Freundlich isotherm exhibited the most appropriate to predict the same. Freundlich isotherm exhibited the most appropriate to predict the experimental results. The kinetic data were also analyzed through pseudo-first-order and pseudo-second-order models. The pseudo-second-order kinetic model well depicted the kinetics of dyes adsorption on mesoporous SBA-3.
Superparamagnetic mesoporous silica microspheres embedded with a silica-coated superparamagnetic iron oxide nanoparticles core and mesoporous silica shell have been prepared using stearyltrimethyl ammonium bromide (STAB) as surfactant template. The superparamagnetic mesoporous silica microspheres then were modified with anhydride functionalized silane to graft carboxylic groups and developed for removing basic dye pollutants, e.g., Methylene Blue (MB) and Acridine Orange (AO) from wastewaters. The results show that the as-prepared adsorbent exhibits high adsorption capacity, extremely rapid adsorption rate and separation convenience for basic dye pollutants removal. Furthermore, the as-prepared adsorbent can be regenerated by simple washing with acid solution to recover both the adsorbents and the adsorbed dyes. The regenerated adsorbent can be reused for dye removal and the adsorption efficiency is still above 88% even after use for seven times. So it can be used as an economic recyclable tool for dyes pollutants removal from wastewater.
A review with ca. 400 references is provided dealing with the use of mesoporous silica and organically-modified silica-based materials for removal of inorganic and organic pollutants from aqueous solutions. After having briefly discussed the interest of functionalized mesoporous silica for environmental remediation purposes, the various synthetic methods to prepare such nanoengineered adsorbents are described. Then, their application to the removal of heavy metal species, toxic anions, radionuclides, and a wide range of organic pollutants is presented in a comprehensive way with the help of extensive tables and some illustrating figures.
With harmless reagents, a series of pore-expanded amino-functionalized mesoporous silicas (PEAFMS) were directly synthesized under mild alkali condition. During the preparation, dimethyldecylamine (DMDA) served as the expander. The PEAFMS samples (S0, S0.50, S1.00, S1.50 and S2.00), which were prepared using different DMDA/surfactant (cetyltrimethylammonium, abbr. CTAB) molar ratio of 0, 0.50, 1.00, 1.50 and 2.00, were characterized by FTIR spectroscopy, CHN elemental analysis, X-ray diffraction and N2 adsorption measurement. Results demonstrated that the addition of DMDA markedly influenced the porous structures of synthesized samples. Their pore sizes and pore volumes were adjusted in the range from 4.684 to 22.31nm and from 0.6046 to 1.360cm3/g, respectively. Subsequently, the adsorption mechanism of sulphonated azo dyes onto obtained PEAFMS samples was analyzed and the optimal pH was determined as pH 2. The synthesized decolorants were then compared for the removal of given dyes (acid mordant dark yellow GG and reactive red violet X-2R) from aqueous solutions and the degressive order of adsorption capacities for two dyes was S1.50>S2.00>S1.00>S0.50>S0. The experimental results confirmed that the use of DMDA could improve the decolorization performance of functionalized mesoporous silicas. The sample synthesized with DMDA/CTAB molar ratio of 1.50 owned the suitable pore size (19.04nm) and pore volume (1.360cm3/g), so it exhibited better decolorization ability than counterparts. The adsorbed amount of acid mordant dark yellow GG and reactive red violet X-2R reached 1.713 and 0.902mmol/g, respectively.
Dynamic adsorption of an organic dye, methylene blue, on mesoporous silica materials with different structures, MCM-41, MCM-48 and MCM-50, were investigated and it was found that dye adsorption presents reversible or irreversible behaviour in dye solution depending on the structure of mesoporous materials. MCM-41 and MCM-48 display a reversible adsorption after reaching equilibrium while MCM-50 exhibits irreversible adsorption. The kinetic studies show that the adsorption of dye on MCM-41, MCM-48 and MCM-50 mesoporous materials follows the second-order kinetics. The desorption of dye from MCM-41 and MCM-48 follows the pseudo-first-order kinetics and the desorption rate constants are much smaller than those of adsorption.
The adsorption behavior of methylene blue from aqueous systems onto mesoporous SBA-3 has been studied. Batch experiments were carried out to measure the adsorption as a function of contact time, initial concentration (50–150mgL−1), pH (4–12), and temperature (303, 313 and 323K). The equilibrium of the process was achieved within 1h. The sorption of methylene blue on the mesoporous silica SBA-3 slightly increases with increasing pH, and temperature, indicating an endothermic process. Adsorption isotherms were fitted with the Langmuir, Freundlich and Temkin models. The kinetic data were analyzed using pseudo-first-order and pseudo-second-order models. The adsorption kinetics of methylene blue on mesoporous SBA-3 matched well with pseudo-second order kinetic model.
Effluents of a large variety of industries usually contain important quantities of synthetic organic dyes. The discharge of these colored compounds in the environment causes considerable non-aesthetic pollution and serious health-risk factors. Since conventional wastewater treatment plants cannot degrade the majority of these pollutants, powerful methods for the decontamination of dyes wastewaters have received increasing attention over the past decade. This paper presents a general review of efficient electrochemical technologies developed to decolorize and/or degrade dyeing effluents for environmental protection. Fundamentals and main applications of typical methods such as electrocoagulation, electrochemical reduction, electrochemical oxidation and indirect electro-oxidation with active chlorine species are reported. The influence of iron or aluminium anode on decolorization efficiency of synthetic dyes in electrocoagulation is explained. The advantages of electrocatalysis with metal oxides anodes and the great ability of boron-doped diamond electrodes to generate heterogeneous hydroxyl radical as mediated oxidant of these compounds in electrochemical oxidation are extensively discussed. The effect of electrode material, chloride concentration, pH and temperature on the destruction of dyestuffs mediated with electrogenerated active chlorine is analyzed. The degradation power of these pollutants with an emerging electrochemical advanced oxidation process such as electro-Fenton, based on the mediated oxidation by homogeneous hydroxyl radical formed from Fenton's reaction between cathodically produced hydrogen peroxide and catalytic Fe2+, is examined. Recent progress of emerging photoassisted electrochemical treatments with UV irradiation such as photoelectro-Fenton and photoelectrocatalysis is also described.
