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Adsorption and chemical precipitation of lead and zinc from contaminated solutions in porous rocks: Possible application in environmental protection
Abstract
Natural porous rocks, like limestone and rhyolite tuff are able to reduce heavy metal pollution by adsorbing or precipitating them from heavy metal containing solutions due to the favourable physical and chemical properties of these rocks.In our experiment, two porous rocks, a porous limestone and rhyolite tuff were used. Petrophysical parameters namely apparent density, real density, capillary water absorption, ultrasonic pulse velocity, total porosity and open porosity of the two porous rocks were determined in water-saturated and dried conditions.Powdered rock samples and cylindrical specimens were placed in lead-nitrate and zinc-sulphate solutions (initial concentration: 1000 ppm) and the amount of lead (II) and zinc (II) ions were identified by titration (chelatometry) of the residual solution. According to the experiments, powdered rocks and rock specimens of limestone and rhyolite tuff reduced the lead (II) and zinc (II) ion concentrations in aqueous solution. The results were cross-checked by ICP-MS. Heavy metal removal capacity was relatively high, 92-99% in each case. The treated powdered rocks and rock specimens were also studied by scanning electron microscope (SEM-EDS) and new heavy metal precipitates were identified.According to the tests result, it could be confirmed that these types of lithologies are capable of removing heavy metals and can be used in environmental protection technologies in a form of permeable reactive barrier.
... According to the previous studies that explored the use of natural limestone and porous asphalt surfaces for the removal of heavy metals from stormwater runoff or aqueous solutions [29][30][31][32][33] and the pavement models used herein, the reduction of Pb 2+ concentration in the effluent samples observed in this study is possibly due to several processes occurring within PA system: (1) the adsorption onto materials at the air voids within pavement layers including the bitumen in the porous asphalt mixture and limestone gravel in the reservoir; (2) precipitation between the lead actions and the mineral in the limestone within the reservoir; and, (3) the retention of Pb 2+ by the geotextile layer. ...
... Because of the extension of residence time, the interactive reaction of Pb 2+ ions and limestone gravel in the reservoir is promoted. Based on the findings given by previous researchers [29][30][31]34], for the PA system containing a lower geotextile layer, the adsorption processes of Pb 2+ occur with the dissolution of limestone surfaces at the mineral-stormwater interface within the reservoir. This leads to the formation of lead-containing crystals growing on the surface of the calcite (the main component of limestone) and in the pores of the limestone gravel resulting in the decrease of Pb 2+ concentration in the outflow. ...
... These apparent changes are probably due to the sorption processes of Pb 2+ ions occurring in the reservoir. Various researchers [29][30][31]36,38] have confirmed that the removal of Pb 2+ ions from aqueous solutions by natural limestone is mainly due to both the adsorption and the chemical precipitation that is closely related to the dissolution of the solid surface. ...
Porous asphalt (PA) pavement systems with and without a geotextile layer were investigated in laboratory experiments to determine the impacts of the geotextile layer on the processes leading to lead ion (Pb²⁺) removal from stormwater runoff. Two types of geotextile membranes that were placed separately at upper and lower levels within the PA systems were tested in an artificial rainfall experiment while using synthetic rainwater. The effect of storage capacity within the system on Pb²⁺ removal was also investigated. Results indicated that the use of a geotextile layer resulted in a longer delay to the onset of effluent. The non-woven geotextile membrane that was placed below the reservoir course improved the Pb²⁺ removal rate by 20% over the removal efficiency of the system while using a woven geotextile placed just below the surface but before the choker course. Pb²⁺ ions were reduced by over 98% in the effluent after being held for 24 h in reservoir storage. Results suggest that temporary storage of stormwater in the reservoir course of a PA system is essential to improving Pb²⁺ ion removal capability.
... According to the previous studies that explored the use of natural limestone and porous asphalt surfaces for the removal of heavy metals from stormwater runoff or aqueous solutions [27][28][29][30][31] and the pavement models used herein, the reduction of Pb 2+ concentration in the effluent samples observed in this study is possibly due to several processes occurring within PA system: (1) the adsorption onto materials at the air voids within pavement layers including the bitumen in the porous asphalt mixture and limestone gravel in the reservoir; (2) the precipitation between the lead actions and the mineral in the limestone within the reservoir; and (3) the retention of Pb 2+ by the geotextile layer. ...
... Because of the extension of residence time, the interactive reaction of Pb 2+ ions and limestone gravel in the reservoir is promoted. Based on the findings given by previous researchers [27][28][29]32], for the PA system containing a lower geotextile layer, the adsorption processes of Pb 2+ occur with the dissolution of limestone surfaces at the mineral-stormwater interface within the reservoir. This leads to the formation of lead-containing crystals growing on the surface of the calcite (the main component of limestone) and in the pores of the limestone gravel resulting in the decrease of Pb 2+ concentration in the outflow. ...
... These apparent changes are probably due to the sorption processes of Pb 2+ ions occurring in the reservoir. Various researchers [27][28][29]34,36] have confirmed that the removal of Pb 2+ ions from aqueous solutions by natural limestone is mainly due to both the adsorption and chemical precipitation that is closely related to the dissolution of the solid surface. ...
Porous asphalt (PA) pavement systems with and without a geotextile layer were investigated in laboratory experiments to determine the impacts of the geotextile layer on processes leading to lead ion (Pb2+) removal from stormwater runoff. Two types of geotextile membranes placed separately at upper and lower levels within the PA systems were tested in an artificial rainfall experiment using synthetic rainwater. The effect of storage capacity within the system on Pb2+ removal was also investigated. Results indicated that the use of a geotextile layer resulted in a longer delay to the onset of effluent. The non-woven geotextile membrane placed below the reservoir course improved the Pb2+ removal rate by 20% over removal efficiency of the system using a woven geotextile placed just below the surface but before the choker course. Pb2+ ions were reduced by over 98% in the effluent after being held for 24 hours in reservoir storage. Results suggest that temporary storage of stormwater in the reservoir course of a PA system is essential to improving Pb2+ ion removal capability.
... Porosity analyses are instrumental in hydrogeological issues, such as the ability of groundwater to move in underground water reservoirs, water resource management, and source water protection [10,11]. Knowledge of porosity parameters also influences broadly understood environmental protection issues [12,13]. Porosity studies are also applied in geotechnical engineering in construction projects like roads, bridges, and buildings. ...
... It consists of hydroxides, hydrated aluminum oxides, and iron hydroxide [60]. The texture 12 of the rock is random, slightly porous, and it crumbles easily into smaller fragments. Two types of sediment are visible in the microscopic image -these are fragments of micritic calcite (Figure 7a-c) and sparitic (Figure 7a-c) and microsparitic calcitic, or dolomitic fragments. ...
Slags and ashes generated in thermal waste treatment facilities require proper management. In line with the principles of the circular economy, new, more economical and ecological possibilities for utilizing these substances are sought. These waste materials exhibit characteristics similar to rocks in many aspects. This study focuses on analyzing the similarities and differences between nine selected rocks and three samples of slags and ashes obtained from municipal waste incineration. The main research device used was a polarizing microscope, using reflected, transmitted and fluorescent light. Additionally, low-pressure gas adsorption equipment, as well as helium and quasi-liquid pycnometers, were used for complementary analysis. The parameters analyzed mainly covered broadly defined petrographic properties of rocks and slags, with a particular emphasis on porosity, porous structure and the spatial distribution of pores and fractures. The conducted analyses confirmed a significant similarity between slags and ashes and clastic sedimentary rocks such as sandstones and mudstones. The research results underscore the importance of petrographic microscopic studies for analyzing materials other than rocks. They also allow for exploring applications for slags and ashes in areas traditionally reserved for natural rock resources. The findings also indicate the necessity of using methods other than microscopic ones to describe the pore space of rocks. The lower measurement range of the optical microscope is limited to approximately 1 μm, covering only macropores. Other methods extend this characteristic to micro- and mesopores. Therefore, a combination of different methods is often employed to obtain a more comprehensive characterization of rock porosity.
... The soft and porous tuffs from Northern Hungary exhibit a diverse and severe deterioration, jeopardizing the preservation of monuments and artworks. Although their durability can be inferred from relevant petrophysical and mechanical properties [6][7][8][9][10][11], only one study has documented the weathering of the monumental stone: the most recurring decay patterns, i.e., differential erosion, crust formation, crumbling, and other detachment morphologies, are dependent on mineralogy, pore-size distribution, and proportions of matrix, lithics, and pumice [7]. Indeed, the literature about tuffs in cultural heritage generally gives much broader consideration to technical characterization, and relatively few works deal with weathering-related mineralogical and geochemical changes of the stone in historical sites and buildings, this being a matter traditionally focused on carbonate rocks (the known case studies, from Europe, Asia, and Central America, are in [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]). ...
... The soft and porous tuffs from Northern Hungary exhibit a diverse and severe deterioration, jeopardizing the preservation of monuments and artworks. Although their durability can be inferred from relevant petrophysical and mechanical properties [6][7][8][9][10][11], only one study has documented the weathering of the monumental stone: the most recurring decay patterns, i.e., differential erosion, crust formation, crumbling, and other detachment morphologies, are dependent on mineralogy, pore-size distribution, and proportions of matrix, lithics, and pumice [7]. Indeed, the literature about tuffs in cultural heritage generally gives much broader consideration to technical characterization, and relatively few works deal with weathering-related mineralogical and geochemical changes of the stone in historical sites and buildings, this being a matter traditionally focused on carbonate rocks (the Minerals 2020, 10, 376 3 of 15 known case studies, from Europe, Asia, and Central America, are in [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]). ...
Volcanic tuffs have a historical tradition of usage in Northern Hungary as dimension stones for monumental construction, Ottoman architecture, common dwellings, etc., admirable at its best in the medieval castles of Eger and Sirok. This research explores tuff deterioration in the castle walls, dealing with the mineralogical composition, microstructure, trace-element geochemistry, and microporosity of the surface weathering products and the near-surface stone substrate. The classic microscopic and mineralogical techniques–optical microscopy, SEM-EDS, and XRD–were supported by ICP-MS and nitrogen adsorption analyses. The textures and mineral assemblages of the tuffs are partly diverse, and so are the weathering characteristics, although including common features such as secondary crystallization of gypsum, swelling clay minerals, and iron oxides-hydroxides; deposition of airborne pollutants, i.e., carbon particles and heavy metals; formation of crusts and patinas; decreased surface microporosity. Nonetheless, the entity of deterioration varies, in relation to air pollution–involving changing emissions from road and rail transport–and the specific tuff texture, porosity, and durability–affecting pollutant absorption. The studied stone monuments offer the possibility to examine materials with analogue composition and petrogenesis but utilized in different environmental contexts, which allow pointing out the environmental and lithological constraints and cause-effect relationships related to surface weathering.
... En la tabla 2 se muestra un comparativo de la adsorción de Pb (mg/g) con los niveles de adsorción de algunos materiales basados en rocas. Existen otros estudios que utilizan rocas volcánicas para adsorción de Pb en medio acuoso (Németh, Mlinárik, & Török, 2016;Shinzato, Montanheiro, Janasi, Andrade, & Yamamoto, 2012), o han sido considerados en la tabla debido a que expresan la capacidad de adsorción en %, lo que no podría ser comparable con los resultados obtenidos en el presente trabajo. Evidentemente esta comparación es relativa dado que los cálculos hechos por los autores citados están hechos en base a resultados de adsorción de Pb utilizando soluciones sintéticas mono componente. ...
Tumbes River is the main source of water for the city of the same name in northwest Peru. However, under current conditions it is negatively affected by activities such as artisanal mining in the upper part of the basin. It causes water pollution with heavy metals such as lead, which is potentially a cause of chronic diseases. On the other hand, ignimbrite is a volcanic rock extracted in the city of Arequipa. It is used as construction material and when it is cut into blocks, produces residual material that is normally discarded. This research aimed to produce and characterize adsorbent materials based on ignimbrite to directly remove Pb from the water of the Tumbes River. The ignimbrite was used in particle sizes of 150 µm and 250 µm, and the materials were activated by slow pyrolysis with and without the presence of ZnCl2. Then thermal treatment, the materials were impregnated with ZnO nanoparticles (NPs) using the in-situ impregnation technique. The thermal treatment manages to modify the structure of the materials, increasing their crystalline phase; however, apparently the concentration of ZnO NPs impregnated on the pyrolyzed ignimbrite samples was too low to be detected by X-ray diffraction. In the Pb adsorption kinetic tests using water samples directly from the Tumbes River, it is shown that adsorbents based on ignimbrite showed limited adsorption capacity compared to other adsorbents derived from rocks, obtaining adsorption values between 0.009 – 0.017 mg of Pb/g of the adsorbent. However, the final concentrations after the adsorption experiments were below the limit of 0.05 mg/l established by the WHO for drinking water. Despite this, it is important to conducted experiments using other types of ignimbrite and other types of modifications to corroborate the potential use of ignimbrite as an adsorbent.
... Porosity analyses are instrumental in hydrogeological issues, such as the ability of groundwater to move in underground water reservoirs, water resource management, and source water protection [10,11]. Knowledge of porosity parameters also influences broadly understood environmental protection issues [12,13]. Porosity studies are also applied in geotechnical engineering in construction projects like roads, bridges, and buildings. ...
Slags and ashes generated in thermal waste treatment facilities require proper management. In line with the principles of the circular economy, new, more economical, and ecological possibilities for utilizing these substances are sought. These waste materials exhibit characteristics similar to rocks in many aspects. This study focuses on analyzing the similarities and differences between nine selected rocks and three samples of slags and ashes obtained from municipal waste incineration. The main research device used was a polarizing microscope, using reflected, transmitted, and fluorescent light. Additionally, low-pressure gas adsorption equipment, as well as helium and quasi-liquid pycnometers, were used for complementary analysis. The parameters analyzed mainly covered broadly defined petrographic properties of rocks and slags, with a particular emphasis on porosity, porous structure, and the spatial distribution of pores and fractures. The conducted analyses confirmed a significant similarity between slags and ashes and clastic sedimentary rocks such as sandstones and mudstones. The research results underscore the importance of petrographic microscopic studies for analyzing materials other than rocks. They also allow for exploring applications for slags and ashes in areas traditionally reserved for natural rock resources. The findings also indicate the necessity of using methods other than microscopic ones to describe the pore space of rocks. The lower measurement range of the optical microscope is limited to approximately 1 μm, covering only macropores. Other methods extend this characteristic to micro- and mesopores. Therefore, a combination of different methods is often employed to obtain a more comprehensive characterization of rock porosity.
... The results show the relationship of a Freundlich isotherm, where the exponential fitting displayed the best correlation ( Fig. 2A). The exponential relationship can be explained either by precipitation or substantial multi-layer adsorption of TBT 62,63 . Multi-layer adsorption occurs when the sorbed TBT provides additional binding sites for adsorption, allowing more TBT to become sorbed in multiple layers. ...
Despite laws prohibiting its usage, butyltin (TBT) is a legacy pollutant and antifouling agent that is still prevalent in marine systems and has been shown to have negative effects on...
... The removal of Pb(II) ions, and other toxic metal ions, from wastewater is an essential and critical issue [4,5]. There are several methods that can be applied for example, adsorption [6], coagulation [7], membrane filtration [8], chemical precipitation [9], electrodialysis [10], etc. The method used in this work is adsorption, not only because it is simple and cost-effective method but also, due to the progress in materials science, which permits researchers to prepare novel and efficient sorbents materials. ...
LaFeO3 perovskite is prepared by the cellulose-modified microwave-assisted citrate method using two different biomasses as a cellulose source; rice straw (RS) and banana peel (BP). The prepared samples are assigned as LaFeO3/cellulose-RS and as LaFeO3/cellulose-BP, respectively. Raman Spectra prove the presence of perovskite and cellulose phases, as well as biochar resulted from the thermal treatment of the cellulose. LaFeO3/cellulose-RS has a cauliflower morphology while, two phases are observed for LaFeO3/cellulose-BP, mesoporous cellulose phase and octahedral LaFeO3 nanoparticles as shown by scanning electron microscope (SEM) images. LaFeO3/cellulose-BP has higher porosity and larger BET surface area than LaFeO3/cellulose-RS. Both samples are applied for the removal of Pb(II) ions from aqueous solution by adsorption. The adsorption follows Langmuir isotherm, with maximum adsorption capacities of 524 and 730 mg/g for LaFeO3/cellulose-RS and LaFeO3/cellulose-BP, respectively. Cellulose precursors from different biomasses affect structural and morphological properties of LaFeO3/cellulose samples as well as the sorption performance for Pb(II) ions. BP is more recommended than RS, as a biomass, in the present study.
... (3) Pseudo-second-order kinetic model [28,29]. ...
By utilizing low-grade bauxite desilication solution as raw material and adding lime after thermal reaction, adsorbent MCS was synthesized. X-ray diffraction, Brunauer–Emmett–Teller, Fourier transform infrared spectroscopy, and scanning electron microscopy were used to characterize the MCS, MCS-Pb, and MCS-Cu. The Freundlich model was found to be more suitable for isothermal adsorption, suggesting that the adsorption of Cu²⁺ and Pb²⁺ by MCS is not limited to monolayer adsorption. According to the results of the experiment, the maximum adsorption capacities of lead ion and copper ion were found to be Pb²⁺ (1921.506 mg/g) > Cu²⁺ (561.885 mg/g), and the adsorption was controlled by chemical reactions following pseudo-second-order kinetics. Electrolyte study results indicated that the presence of background electrolyte did not affect the adsorption of Cu²⁺ and Pb²⁺ by MCS.
... [22] The prepared activated carbon is washed several times with distilled water to obtain an activated carbon free from sodium hydroxide and mineral residues, and the washing continues with distilled water until it is proven that it is free from the base substance, then it is washed with 25 ml of a solution (10%) of hydrochloric acid until the ions are removed, and it is washed with distilled water also several times to remove any traces of acid, , the product is dried at a temperature of 130 0 C and grinded well using ceramic mortar and kept in isolation from air. [23] ...
The research included preparing activated carbon from apricot seeds. Activated carbon in this way was distinguished by its good quality in terms of its high surface area and Its pH is neutral. Activation was carried out using varying proportions of sodium hydroxide. Physical and chemical tests were performed.. Physical and chemical tests have been carried out for the prepared samples, including determination of low density, low ash content, iodine number (I.N), external surface area measurement by adsorption of methylene blue dye from its aqueous solution, ash content and moisture measurement.
... In recent decades, a variety of techniques have been developed to remove Pb from wastewater, such as ion-exchange [10], membrane processes [11], chemical precipitation [12], filtration [13], electrocoagulation [14], coagulation [15], and adsorption [16][17][18][19]. Among these methods, adsorption is one of the most common removal technologies and has attracted wide attention owing to its advantages of low cost, simple process, and high removal efficiency [20][21][22]. ...
Industrialization has resulted in the discharge of a certain amount of lead (Pb) from industrial sources causing damage risk to water quality and human health. Adsorption is an effective technique to remove Pb, and biochar has been widely studied owing to its advantages of low cost and high adsorption capacity. This review summarizes the influence of raw materials and modification methods on the adsorption capability of biochar. The adsorption isotherms and kinetics of biochar were summarized, and the main Pb removal mechanisms were studied systematically. In addition, the challenges and future perspectives were discussed comprehensively. It is expected that the review could provide insightful fundamentals for the experimental research and practical applications of biochar.
... In order to deal with the pollution of HMs, various treatment measures have been put into effect, including but not limited to ion exchange, coagulation, solvent extraction, chemical precipitation (Németh et al. 2016), membrane filtration (Fang et al. 2017), and electrochemical treatment (Mourya et al. 2019). While effective adsorption performances have been achieved, some critical shortcomings still exist, such as high energy consumption and secondary pollution. ...
The treatment of heavy metal (HM) wastewater is a critical and considerable challenge. Fruit peel-based HM adsorption is a promising way for the water pollution control and the reuse of agricultural waste. In this study, a novel adsorbent based on orange peel was synthesized for the first time by introducing abundant-COO groups with ethylenediaminetetraacetic dianhy-dride (EDTAD) to eliminate Cd(II) and Co(II) of sewage solution. The synthesized adsorbent displayed excellent adsorption capacity of 51.020 and 40.486 mg/g for Cd(II) and Co(II), respectively, and the adsorption equilibrium was achieved within 5 min, following the Langmuir isotherm model and the pseudo-second-order model. Surface characterization of adsorbents by scanning electron microscopy-energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy confirmed that ion exchange, complexation, and physical adsorption could occur during the adsorption process. The rapid and highly efficient adsorption performance suggests EDTAD-modified synthesized orange peel possesses great potential for HM removal from sewage systems.
... Current methods of Pb removal involve sorption to a solid substrate (Fu & Wang, 2011;Zhu et al., 2019), or precipitation of insoluble Pb compounds (Fu & Wang, 2011;Owen et al., 2019Owen et al., , 2021. In an environmental setting, precipitation of Pb will occur at high pH, requiring addition of carbonate minerals to raise the pH to a level where precipitation is possible (Németh et al., 2016). Iron sulfates, iron oxy(hydroxides) and persisting sulfides provide common surfaces for sorption of liberated heavy metals in a wastewater streams or wetland settings (Akcil & Koldas, 2006;Sheoran & Sheoran, 2006). ...
Even low levels of lead (Pb) contamination result in significant disruption to the surrounding ecology as Pb accumulates in soils and water and can be taken up by plants, which are then consumed by higher order animals. Understanding how Pb partitions between solids and the aqueous phase underpins prediction of bioavailability and locales of high toxicity, and the development of effective treatment options. This paper aims to unify our empirical understanding of the interaction between Pb(aq) and various common minerals associated with many large sulfide ore-bodies mined for their base- and precious metal contents, by measuring the sorption of Pb onto hematite (Fe2O3), pyrite (FeS2), chalcopyrite (CuFeS2), bornite (Cu5FeS4) and barite (BaSO4) as a function of solution pH and Pb(aq) concentration. In general, all minerals displayed a linear relation on a log–log plot of sorbed portion versus Pb concentration in the coexisting solution (Freundlich isotherm) over a wide range of Pb concentrations at pH 6. Hematite had two different domains (dual Freundlich behaviour), with Pb(aq) showing higher affinity for sorption at low Pb(aq) concentrations compared to high Pb(aq) concentrations. For the sulfide minerals (pyrite, chalcopyrite, bornite), Pb sorption/precipitation on the oxidised surface is favoured at low pH, while Pb sorption to Fe(oxyhydr)oxide and/or co-precipitation as anglesite is favoured at high pH. Isotherm modelling highlights the dual roles of Pb(aq) concentration and pH in controlling Pb scavenging in these natural minerals, and it is important to consider these parameters when predicting the Pb-geochemical cycle and its dynamic uptake in natural and engineered systems.
... It is noted, however, that the stabilization/solidification dynamics between Pb and other ligands and cations in more complex systems may affect the ranges in which removal of Pb by APS is most effective (e.g. Martınez and Motto, 2000;Németh et al. 2016;Ram et al. 2019b;Shi et al. 2019). These complex trends of Pb sorption with pH, solution and APS mineral compositions are interpreted to arise from the interplay between initial surface sorption and subsequent incorporation into APS phases. ...
The ability of aluminium-phosphate-sulfate (APS) phases to preferentially sorb lead and its radionuclides, particularly ²¹⁰Pb, from metallurgical processing streams has been recently recognised empirically. This suggests that APS minerals may be suitable for the removal of lead from environmental and anthropogenic processes. We investigated the Pb sorption capabilities of APS with different Ca:Sr and SO4:PO4 ratios over a range of aqueous Pb concentrations (10–1000 ppm) and pH (1.5–5.5) typical of metallurgical processes and acid drainage conditions. Through a combination of characterization techniques including electron probe microanalysis, (laser ablation-) inductively coupled plasma mass spectrometry and X-ray absorption spectroscopy, we confirm the rapid (< 8 h) incorporation of Pb into the crystal lattice of APS phases. We also provide a mechanistic pathway for the sorption mechanism, with Pb sorption favoured at pH 3.5–5.5 via the direct replacement of lattice-bound Ca by Pb within the APS crystal structure. The observed Pb-incorporation dynamics of APS minerals, along with their insolubility and high thermodynamic stabilities, support the use of APS minerals as a novel agent for the uptake of Pb, radiogenic and nonradiogenic, from process-, surface-, and groundwaters. Since Pb quickly enters the crystal structure of environmentally stable APS minerals, these phases have much potential for long-term storage of Pb waste, and in particular for sequestration of the highly radioactive ²¹⁰Pb isotope enriched in U-bearing geological materials.
... Thus, the Pb 2+ removal from wastewater is indispensable. Until now, a great many of techniques have been applied to the removal of Pb 2+ , which are coagulation/flocculation [12] , ion exchange [13] , adsorption [14] , membrane filtration [15] , chemical precipitation [16] , etc. In the middle of these techniques, adsorption has been known as one of the conventional methods owing to its easiness of process, cost-effectiveness, high efficiency, easy recovery and restoration of capacity [17] . ...
... Thus, the Pb 2+ removal from wastewater is indispensable. Until now, a great many of techniques have been applied to the removal of Pb 2+ , which are coagulation/flocculation [12] , ion exchange [13] , adsorption [14] , membrane filtration [15] , chemical precipitation [16] , etc. In the middle of these techniques, adsorption has been known as one of the conventional methods owing to its easiness of process, cost-effectiveness, high efficiency, easy recovery and restoration of capacity [17] . ...
Multi-wall carbon nanotubes functionalized with 3-Amino-5a, 10a-dihydroxybenzo [b] indeno [2,ld]furan-10-one (ADIF), (MWCNT-ADIF), were used as the adsorbent to remove lead ions (Pb²⁺) from aqueous solutions. The samples were characterized by FT-IR, SEM, TGA and DTG. Effects of pH, initial Pb²⁺ concentration, adsorbent dosage and contact time on adsorption kinetics and equilibrium were investigated in a batch mode. Adsorption isotherms of Pb²⁺ ions were investigated using four two-parameter models (Langmuir, Freundlich, Tempkin, Dubinin-Radushkevich) and six three-parameter models (Redlich-Peterson, Khan, Sips, Radke-Prausnitz, Toth, Hill). Adsorption kinetics were investigated by the pseudo first-order kinetic model, the pseudo second-order kinetic model and the intra particle diffusion model. Three error analysis methods, correlation coefficient, chi-square test and average relative errors, were used to determine the best fitted isother. Results indicated that adsorption kinetics was best described by the pseudo second-order kinetic model. Error analysis indicated that three-parameter models described the Pb²⁺ sorption data better than the two-parameter models . The isotherm data were best fitted by the Langmuir, Hill and Sips models. Pb²⁺ ions could be desorbed from MWCNT-ADIF up to 92% at pH=3 and the recycled MWCNT-ADIF could be reused for 5 regeneration cycles.
... The remediation of zinc-contaminated wastewaters may be performed through methodologies, such as precipitation [6], solvent extraction [7], electrocoagulation [8], adsorption [9], and biosorption [10][11][12][13]. The later one stands out because of the possibility of using alternative and low-cost adsorbents that allow removing metal ions in low concentrations based on selectivity differences [14][15][16][17]. ...
In this study, the by-product generated in the alginate extraction process (termed as RES) was recuperated and employed as biosorbent, without modifications, for Zn bioremoval from synthetic effluent. Different zinc concentrations (1, 1.5, and 2 mmol/L) and temperatures (293.15, 303.15, 313.15, and 323.15 K) were evaluated through kinetic and equilibrium studies. The involvement of ion exchange mechanism was observed during the kinetic assays with predominance of external diffusion. Within the evaluated zinc concentration range, there was no strong influence of concentration increase on experimental sorption capacity and the best results were achieved at 1.5 mmol/L. The temperature rise favored the process, as well as the affinity between RES and zinc. Langmuir best fitted the equilibrium experimental data and the highest sorption capacity was found at 323.15 K as 0.781 mmol/g. The thermodynamic parameters revealed that Zn bioremoval using RES occurred by physisorption, besides being endothermic and spontaneous. The selectivity study revealed that the alkali and alkaline earths metals ions naturally found in seaweeds (Ca, Na, Mg and K) may compete with Zn ions for the same binding sites, being that Ca has the greater potential for affecting the process. Mercury porosimetry and XRD analyzes revealed a macroporous and semi-crystalline structure. Similar contents of C, N, H and S were found before and after zinc removal by CNHS analysis, while thermal analysis indicated that RES remains stable up to 150 °C. The results indicated that RES has a great potential for being used as biosorbent, providing information that contribute to its valorization.
... The experimental results are consistent with the literature about Demjén and Eger tuffs (Forgó and Török, 2004;Török et al., 2007aTörök et al., , 2018Stück et al., 2008;Wedekind et al., 2013;Németh et al., 2016), although the variability of the petrophysical properties previously reported does not meet the standard deviations calculated here, which are non-significant. ...
Volcanic tuffs are notoriously very heterogeneous materials exhibiting a recurrent lithological diversity, which, in turn, can be associated with changing petrophysical and mechanical properties. This variability was investigated on a small scale in different Miocene acid tuffs extracted in the same quarry region, within just a few km radius from the town of Eger in Northern Hungary. They have been exploited since the Middle Ages and used for common construction and historical monuments – castles, churches, Ottoman architectures – or excavated and carved for creating wine cellars, cave houses, ritual sites, etc. These pyroclastic rocks are compositionally analogue but turn out to show unexpected major differences in texture and technical properties, which affect their resistance to decay. The rate and intensity of weathering, examined in laboratory conditions by freeze-thaw and salt attack tests, is governed mainly by the following properties: open porosity; relative abundance of pumice, crystals, and groundmass; pore-size distribution; and tensile strength. Nevertheless, open porosity – proportional to water absorption and indirectly related to mechanical performance – is considerably different among the tuff varieties, and this seems to be the most significant factor marking the diverse durability. That is questionable in case of unpredicted textural diversities, e.g., enrichment in pumice and higher concentration of groundmass. Therefore, without rejecting the importance of complementary tests, a basic and fast study involving thin-section examination and open-porosity measurement would be sufficient for providing many indications on the quality of these materials and for the selection of dimension stones for restoration of historical heritage and construction.
... As a result of the toxicity of this element and its compounds, removal has become an urgent priority. There are various available means to reduce heavy metals levels from water including ion exchange [6], [7], membrane filtration [8], [9], chemical precipitation [10], [11] and electrocoagulation [12], [13], but these methods generally require high cost and produce more lethal products [14]. ...
Due to the broad range uses of chromium for industrial purposes, besides its carcinogenic effect, an efficient, cost effective removal method should be obtained. In this study, cow bones as a cheap raw material were utilized to produce active carbon (CBAC) by physiochemical activation, which was characterized using: SEM to investigate surface morphology and BET to estimate the specific surface area. The best surface area of CBAC was 595.9 m2/gm which was prepared at 600 ᵒC activation temperature and impregnation ratio of 1:1.5. CBAC was used in aqueous chromium ions adsorption. The investigated factors and their ranges are: initial concentration (10-50 mg/L), adsorption time (30-300 min), temperature (20-50 ᵒC) and solution pH (2-11). Isotherm of adsorption and its kinetics were studied. The adsorption process was modeled statistically and was represented by an empirical model. Equilibrium data were fitted to the Langmuir and Freundlich isotherm models and the data best represented by Freundlich isotherm. Pseudo- first order and pseudo- second order kinetic equations were utilized to study adsorption kinetics, where chromium adsorption on CBAC fitted pseudo- second order fitted the data more adequately. The best removal efficiency was found to be 94.32%.
The conventional point-estimate human health risk assessment (HHRA) primarily uses average concentrations of a limited number of samples due to the high monitoring costs of heavy metals in groundwater. The results can be erroneous when concentrations significantly deviate from the average across the collected samples in an investigation region. The present research developed a hierarchical fuzzy-based HHRA (F-HHRA) framework to handle variations in limited data sets and subjectively established a broader range of risks for various exposure groups. Groundwater samples from 80 to 120 m deep in shallow wells were collected from agricultural farms along Wadi Rumah in the Qassim Region of Saudi Arabia. Laboratory testing found total dissolved solids much higher than the promulgated drinking water quality standards. As the aftertaste issue eliminated the raw water potability, the study considered dermal exposure for HHRA. The collected samples were tested for thirteen potential heavy metals (HMs), including barium (Ba), boron (B), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), lithium (Li), manganese (Mn), silver (Ag), strontium (Sr), thallium (TI), and zinc (Zn). Cu, Fe, Pb, Ag, and TI were lower than the detectable limit of the inductively coupled plasma mass spectrometry device. Concentrations of the remaining HMs in wastewater outfalls that were much less than the groundwater eradicated the impact of anthropogenic activities and affirmed natural contamination. Apart from 10% of the samples for Mn and 90% of the samples for Sr, all the other HMs remained within the desired maximum allowable concentrations. Point-estimate and fuzzy-based approaches yielded ‘low’ dermal non-cancer risk and cancer risk for all groups other than adults, where dermal cancer risk of Cr remained in the ‘acceptable’ (1 × 10⁻⁶ and 1 × 10⁻⁵) risk zone. Although dermal risk does not require controls, scenario analysis established the rationality of F-HHRA for more contaminated samples. The proposed hierarchical F-HHRA framework will facilitate the decision-makers in concerned agencies to plan risk mitigation strategies (household level and decentralized systems) for shallow well consumers in Saudi Arabia and other arid regions.
LaFeO3/biochar composite is prepared by cellulose-modified microwave-assisted method at 450 °C. The structure is identified by Raman spectrum which, consists of characteristics biochar bands and octahedral perovskite chemical shifts. The morphology is examined by scanning electron microscope (SEM); two phases are observed, rough microporous biochar and orthorhombic perovskite particles. The BET surface area of the composite is 57.63 m²/g. The prepared composite is applied as a sorbent for the removal of Pb²⁺, Cd²⁺, and Cu²⁺ ions from aqueous solutions and wastewater. The adsorption ability reaches a maximum at pH > 6 for Cd²⁺, and Cu²⁺ ions, and is pH-independent for Pb²⁺ ions adsorption. The adsorption follows pseudo 2nd order kinetic model, Langmuir isotherm for Pb²⁺ ions, and Temkin isotherms for Cd²⁺, and Cu²⁺ ions. The maximum adsorption capacities, qm, are 606, 391, and 112 mg/g for Pb²⁺, Cd²⁺, and Cu²⁺ ions, respectively. The electrostatic interaction is responsible for the adsorption of Cd²⁺, and Cu²⁺ ions on LaFeO3/biochar composite. In case of Pb²⁺ ions form a complex with the surface functional groups of the adsorbate. LaFeO3/biochar composite shows high selectivity for the studied metal ions and excellent performance in real samples. The proposed sorbent can be easily regenerated and effectively reused.
Sugarcane bagasse-based activated carbon (AC) was produced via a physical activation method using CO2, to remove lead (Pb) ions from an aqueous solution. The physical and chemical properties of ACs were examined by scanning electron micrograph (SEM), Brunauer–Emmett–Teller (BET) surface area, and Fourier-transform infrared spectroscopy (FTIR) analysis. The effect of both pH and contact time on adsorption was studied via a batch process. Based on the BET results, we have identified that BET surface area and micropore volume decreased at the highest activation temperature, while the intensity of the functional groups increased when the activation temperature was raised. The adsorption isotherms were best fitted with the Langmuir equation, which was used to describe the adsorption process and to examine the adsorption mechanisms of Pb(II) on the AC. The maximum adsorption capacity of Pb(II) was 60.24 mg g⁻¹ with AC850. The adsorption kinetic study closely followed the pseudo-second order (R² > 0.99). AC has the potential to economically remove metal ions in the purification process of wastewater. AC850 was also utilized in the manufacture and testing of pouch cell supercapacitors to demonstrate the potential of the sugarcane bagasse family of materials in energy storage applications. The devices made with the unmodified, nonoptimized material used for Pb(II) sorption demonstrated high rate and power-energy characteristics (>50% capacitance retention with 10-fold increase in current density, 10 Wh Kg⁻¹ at 2500 W Kg⁻¹, active material mass) but there remains a need for further optimization, particularly the removal of oxygen functionality, to enhance lifetime and specific capacitance. This work demonstrated the potential for sugarcane bagasse carbons across environmental applications.
p>A presença de metais pesados pode tornar-se motivo de preocupação em função da possibilidade de movimentação e consequente contaminação de camadas superficiais do solo e águas subterrâneas, comprometendo a saúde de plantas e animais. Dentre os métodos de descontaminação, a bioadsorção tem apresentando bons resultados econômicos e ecológicos. Neste trabalho, folhas da planta comigo-ninguém-pode (CNP) foram utilizadas na remoção de íons Cu2+ de soluções aquosas. Realizou-se a desidratação das folhas da planta em estufa, até massa constante, em seguida procedeu as etapas de pulverização e peneiramento. Os ensaios de adsorção foram realizados em batelada, sendo composto por 0.5 g das folhas desidratas com 100 mL de soluções aquosas de CuSO4 com diferentes concentrações. Uma avaliação do teor de íons oxalatos presentes nas folhas foi realizada pela técnica de permanganimetria. A caracterização e quantificação foi realizada pelas técnicas de difração de raios-X e espectroscopia de absorção atômica. Os resultados dos ensaios de adsorção mostraram que as folhas de CNP apresentaram 93% de remoção de Cu2+ quando testados em uma solução cuja concentração do metal foi de 600 mg L-1. Os difratogramas de raios-X confirmaram que o metal adsorvido incorporou na estrutura das folhas. O estudo cinético mostrou que a adsorção de Cu2+ pelas folhas de CNP obedecem ao modelo matemático de pseudossegunda ordem. O bioadsorvente testado neste trabalho apresentou elevada eficiência na descontaminação de efluentes contendo íons Cu2+. A utilização do processo utilizado propõe um mecanismo de descontaminação eficiente, de baixo custo e elevado valor ecológico, além de promover uma funcionalidade a uma espécie de planta tóxica.
Palavras chave : Bioadsorção, oxalatos, cinética.</p
In this study, the sorption capacity of local sugarcane waste (SW) for aqueous Pb(II) was investigated. The SW was fully characterized using Scanning microscopy (SEM), Energy-dispersive X-ray Analysis (EDX), Fourier Transform Infrared Spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) area measurements. The uptake efficiency of SW was assessed via the batch mode. Also, the effect of several process variables on the Pb(II) uptake efficiency was elucidated. The Freundlich (R² = 0.991; ARE = 0.340) and pseudo-second-order (R² = 0.999; ARE = 0.056) model, respectively merged as the best fit models for equilibrium and kinetic studies. The maximum adsorption capacity was found to be 132 mg/g (at pH 5 and 30 °C) from the Langmuir model. A very short equilibrium time of 10 min recorded in the study distinguishes SW as fast and efficient in aqueous Pb(II) uptake.
The pollution of heavy metal ions in water poses a serious threat to human being and ecosystems. Here, we report polyamidoxime (PAO) brush grafted graphene oxide (GO) as a highly efficient adsorbent for extraction of toxic metal cations from water. Surface‐initiated atom transfer radical polymerization was used to grow polyacrylonitrile (PAN) brushes on GO, followed by conversion of the nitrile groups in PAN into amidoxime groups, which had high binding affinity toward heavy metal cations. The PAO brush grafted GO demonstrated significantly fast adsorption kinetics and large adsorption capacity. At optimal pH 5, the PAO brush grafted GO can achieve maximum adsorption capacities of 116.7 mg g−1 for Pb(II), 258.6 mg g−1 for Ag(I), 192.2 mg g−1 for Cu(II), and 167.9 mg g−1 for Fe(III), which were significantly larger than those of small molecule functionalized GO. Mechanism analysis suggested that the enhanced adsorption performance was due to the myriads of functional groups in PAO brushes that were easily accessible to metal ions because of the swelling of the polymer brushes in water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48156. Schematic showing the adsorption of metal ions by polymer brush grafted graphene oxide.
Sodalite/Magnetite was efficiently fabricated by a one-step hydrothermal route using natural tourmaline as a silicon-aluminum source. The obtained products were characterized by X-ray diffraction, field emission scanning electron microscope, and elemental analysis (ICP) and N2 adsorption-desorption isotherm. In addition, the adsorption characteristics of metal ions (Cu²⁺, Co²⁺, Cr³⁺) on the sodalite were investigated. The results show that sodalite covered by octahedral particles of Fe3O4 was successfully obtained under hydrothermal treatment temperature at 300 °C. Nitrogen adsorption studies of sodalities showed the pore size around 0.7 nm and BET surface area over 0.315 m²/g. The adsorption capacities of Cu²⁺, Co²⁺and Cr³⁺ on sodalite/magnetite were 25.95, 8.90 and 4.1 mg/g.
Three Schiff base-functionalized mesoporous silicas: MCM-41@salen, HMS-C12@salen and HMS-C16@salen have been synthesized by a post-synthetic grafting strategy and their sorption capacities toward Pb(II) from synthetic aqueous solutions have been assessed. FTIR spectra, TG/DSC analyses, X-ray powder diffraction, X-ray photoelectron spectroscopy (XPS), N2 adsorption isotherms and HRTEM micrographs were used to characterize the novel functionalized mesoporous silicas. The novel adsorbents have been tested for their capability in the remediation of synthetic aqueous systems containing Pb(II). The Langmuir maximum values of sorption capacities of these adsorbents toward Pb(II) are: 138.88 mg Pb(II) per g MCM-41@salen, 144.92 mg Pb(II) per g HMS-C12@salen, and 181.81 mg Pb(II) per g HMS-C16@salen, therefore, the functionalized silicas (MCM-41@salen, HMS-C12@salen, HMS-C16@salen) could be used as effective adsorbents of Pb(II) ions from wastewater.
In this study, urea-modified D301 resin, UD301, was obtained successfully. The surface properties, chemical functional groups, element content, and surface morphology were investigated. The adsorption properties of UD301 for toxic heavy metal ions (Pb(II), Hg(II), Cd(II), and Ni(II)) were studied by batch method and the practical application value was evaluated by column method. The experimental results showed that UD301 possesses strong adsorption ability for Pb(II), Hg(II), Cd(II), and Ni(II). pH and temperature has a great influence on the adsorption capacity in the studied range. The adsorption capacities of UD301 towards Pb(II), Hg(II), Cd(II), and Ni(II) could reach 412.8, 396.9, 210.2, and 121.9 mg·g⁻¹ at 293 K and pH of 6, respectively. The adsorption process was a typical monolayer chemical adsorption and could be well described by the Lagergren-first-order model. The adsorption was also an endothermic and spontaneous process drived by entropy. In addition, UD301 could be reused almost without any loss in the adsorption capacity.
BACKGROUND
The alginate extraction residue from Brazilian Sargassum filipendula was employed as biosorbent for Zn(II) removal through a fixed‐bed column in order to explore its adsorptive properties and to establish a new use for this waste.
RESULTS
The best operating conditions were 0.5 mL min ‐1 and 1.0 mmol L ‐1 (inlet concentration), providing lower mass transfer zone and higher uptake. Elution percentages of 52 and 73% were obtained for the first and second desorption cycles, respectively, using CaCl 2 as eluent. The Yan et al. model was more representative of the experimental data. Characterization revealed that ion exchange is involved between zinc ions and light metals (Ca, Na, K and Mg). A decrease was observed in real and apparent densities of biomass, with an increase in particle porosity of the residue after process.
CONCLUSION
The study revealed that this biomass has potential for Zn removal from aqueous solution, encouraging its application as a biosorbent in future studies involving multicomponent systems. © 2017 Society of Chemical Industry
A pot experiment was conducted to investigate the effects of halloysite and activated carbon mixtures on the biomass and distribution of macronutrients (Mg, K, Ca, Na, P) in ryegrass grown in Pb-contaminated soil. The soil was spiked with four different levels of lead contamination, i.e. 0 (control), 200, 400, 800 mg·kg⁻¹ were applied in an analytical grade Pb(NO3)2 solution mixed thoroughly with the soil. Raw halloysite (3%) and activated carbon (1% relative to soil mass) mixtures were used to reduce the effect of soil lead contamination. Ryegrass of the Bokser variety was harvested after 42 days, and soil samples were collected for laboratory tests. The mixture of sorbents applied in the experiment which turned out to be most effective at doses of lead amounting to 400 and 800 mg·kg⁻¹ of soil, with the increase in the yield of ryegrass being the highest. Increasing contamination of soil with lead in the series without the mixture of sorbents increased the contents of phosphorus, sodium, calcium and magnesium in ryegrass. The applied mixture of halloysite and activated carbon changed the macronutrient concentration in ryegrass, with the greatest changes found in that of potassium and sodium.
High adsorption capacity, fast adsorption rate, easy regeneration and good reusability were very important for qualified adsorbents used in removing toxic heavy metals from wastewater. Based on this, a novel adsorbent was well designed and synthesized by functionalizing D301 resin with iminodiacetic acid (IDA). The physicochemical characteristics of IDA-functionalized D301 (ID301) were characterized by the scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR) and elemental analysis. The adsorption performances of ID301 towards toxic heavy metal ions were systematically performed from kinetics to isotherms and thermodynamics by batch technique. The effects of contact time, initial metal concentration, pH, temperature and adsorbent dosage on adsorption performance were investigated. ID301 possesses strong adsorption ability for Cu(II), Pb(II) and Cd(II). pH and temperature has a great influence on the adsorption capacity. The adsorption capacities of ID301 towards Cu(II), Pb(II) and Cd(II) could reach 4.48, 2.99 and 2.26 mmol·g− 1 at 293 K and pH of 5, respectively. Langmuir isotherm and pseudo-second-order equation could satisfactorily describe the experimental data. The adsorption thermodynamic experiment indicated that adsorption of ID301 towards Cu(II), Pb(II) and Cd(II) was an endothermic and spontaneous chemisorption process drived by entropy. In addition, ID301 could be reused without losing adsorption capacity significantly.
In this research, ultrasonic assisted fishtail palm Caryota urens seeds (UACUS) has been prepared for the effective removal of Zn(II) ions from aqueous solution in a packed bed column studies. The effect of various operating parameters such as bed depth, initial Zn(II) ions concentration and flow rate on breakthrough curves have been investigated. The dynamic response for the adsorption of Zn(II) ions onto UACUS was described in terms of the breakthrough curves. The results demonstrated that the maximum removal of Zn(II) ions was attained at low flow rate, influent concentration and high bed depth. The results showed that breakthrough time and exhaustion time were increased with increase of bed height and decreased with increase of flow rate, initial Zn(II) ion concentration. The experimental column data were fitted with different mathematical models, namely Adams–Bohart, Yoon–Nelson, and Bed depth service time (BDST) models. Amongst the models, BDST model was fitted well with the experimental data. The adsorbent was characterized by FTIR, ESEM, EDX and TGA analyses. The experimental results concluded that the prepared UACUS can be utilized as a potential and low-cost adsorbent for the removal of Zn(II) ions from the contaminated liquid.
The metal adsorption by clays is widely studied. The classical method consists in mixing a volume of metal solution with a mass of clay and making a series of agitation and centrifugation. The supernatant is analyzed by an atomic absorption method to determine the concentration adsorbed by clay. But this method has several disadvantages as the extract may contain impurities which are suspensions that can yield wrong analysis results. This work aims at studying the influence of a new method that uses membrane filtration to determine the maximum amount of zinc adsorbed by clay. To prove the effectiveness of such method, several identification techniques are used. The local clay extracted from Oued Tfal south west Tunisia, has been characterized. The mineralogical and chemical compositions of the materials have been determined. Gives the adsorption of Zn(II) studies, experimental data demonstrated a high regression coefficients with the pseudo-second order kinetics. The equilibrium data showed the best most suitable model fit to Freundlich and Langmuir models.
Eight different types of acid tuffs of the Eger Castle (Hungary) and two tuffs from nearby quarries have been studied in detail. Mapping of wall sections reveals that tuffs show weathering forms that are similar to common sedimentary rocks, such as limestones or sandstones. Different lithologies display various weathering features. On pumice-rich tuff ashlars relief due to selective weathering, weathering crusts, multiple flakes and scales occur, while crumbling is common on layered flow tuffs. Conversely, cemented tuff types do not show deep weathering. Pore-size distribution rather than effective porosity controls the weathering susceptibility of tuffs. Frequent larger micropores are the main causes of freeze - thaw-related weathering. Besides clays, newly formed gypsum and calcite are the weathering-related index minerals. Schmidt hammer rebound values mark the weathering process when quarry stones and ashlars of historic walls are compared.
Bryozoan and Lithothamnion limestones (BLL) from central-southern Italy, commercially known as Perlato Royal Coreno, were used for a long time in the monumental architecture of the Campania and Lazio regions. In this paper, new mineralogical-petrographical and engineering-geological data about BILL are reported and the relations between the lithofacial and technical features of this stone are investigated. A field survey of the main limestone outcrops allowed a lithostratigraphic reconstruction of this formation to be drawn and the eight main lithotypes presently used as dimension stones to be recognized. Mineralogical and petrographical characterization was performed by means of X-ray powder diffraction and optical microscopy observation of thin sections (under transmitted, UV-reflected light and cold cathodoluminescence). Petrophysical characterization enabled to compare some engineering-geological properties and to evaluate the influences of rock fabric, chemical composition, fractures and stylolithes on the technical features of the stone. Ageing tests were also performed. Finally the main weathering phenomena affecting the stone were recognised through a detailed study on the facades of the bell tower of the Santa Chiara monastery in Naples.
The water treatment performances of two anoxic limestone drains (ALDs) were evaluated. Anoxic limestone drains are buried beds limestone that are intended to add bicarbonate alkalinity to flow-through acid mine drainage. Both ALDs received mine water contami-nated with Fe 2+ (216-279 mg -I) and Mn (41-51 m g L -~). F low through the Howe Bridge ALD increased alkalinity by an average 128 mg L-~ (CaCO3 equivalent) and Ca by 52 mg L -i, while concentrations of Fe, K, Mg, Mn, Na, and SO~-were unchanged. The Morrison ALD increased alkalinity by an average 248 mg L -I and Ca by III mg L-~. Concentrations of K, Mg, Mn, and SO~-all decreased by an average 17%, an effect attributed to dilution with uncontaminated water. Iron, which decreased by 30%, was partially retained within the Morrison ALD. Calcite dissolution was enhanced at both sites by high Pco2. Untreated mine waters at the Howe Bridge and Morrison sites had average calculated Pco~ values of 6.39 kPa (I0-1.z0 atm) and 9.24 kPa (I0 -I'°~ atm), respectively. At both sites, concentrations of bicarbonate alkalinity stabilized at undersaturated values (SIc~k~t~ I0 -I"~ at Howe Bridge and I0 -°'s at Morrison) after flowing through approximately half of the limestone beds. Flow through the second half of each ALD had little additional effect on mine water chemistry. At the current rates of calcite solubilization, 17.9 kg d-i CaCO3 at Howe Bridge and 2.7 kg d-i CaCO3 at Morrison, the ALDs have theoretical effective lifetimes in excess of 20 yr. By significantly increas-ing alkalinity concentrations in the mine waters, both ALDs increased metal removal in downstream constructed wetlands.
The Cappadocian tuff contains unique erosional features, the so-called fairy chimneys, some of which in the past were dwelled
in and contain valuable wall paintings. These historical heritages, however, are undergoing chemical and physical deterioration
due to atmospheric effects. For the conservation studies, understanding of the deterioration phenomenon of the tuff is essential.
In this study, engineering geological and physicochemical characteristics of the tuff were determined. The durability of the
tuff was assessed through wetting-drying, freezing-thawing, and salt crystallization. The test results suggest that chemical
weathering may be traced to a depth of 2 cm below lichen-covered surfaces and 20 cm adjacent to discolored joint walls. Based
on durability assessment methods, the tuff may be classified as having poor to very poor durability.
Effects of impurities on the removal of heavy metals by natural limestones in aqueous solutions were studied by evaluating various factors including limestone concentration, pH, contact time and temperature. Solutions of Pb(II), Cd(II), Cu(II) and Zn(II), prepared from chloride reagents at a concentration of 10 mg/L, were studied in a batch method. Four natural limestone samples, collected from the Campanian-Maastrichtian limestone beds in Tunisia, were used as adsorbents. Sorption experiments indicated that high removal efficiencies could be achieved. Limestone samples containing impurities, such as silica, iron/aluminum oxides and different kinds of clay minerals, demonstrated enhanced sorption capacity, nearing 100% removal in some cases. Kinetic experiments showed that the sorption of metal ions occurred rapidly at a low coverage stage, and that solutions were nearly at equilibrium after 60 min. Data trends generally fit pseudo-second order kinetic, and intra-particle diffusion, models. The following conditions were found to promote optimum, or near-optimum, sorption of heavy metals: 1) contact time of more than 60 min, 2) pH = 5, 3) >3 g/L limestone concentration and 4) T = 35 °C. The results of this study suggest that the limestones from northern Tunisia, that contain higher amounts of silica and iron/aluminum oxides, are promising adsorbents for the effective removal of toxic heavy metals from wastewaters.
The contamination of groundwater by heavy metal, originating either from natural soil sources or from anthropogenic sources is a matter of utmost concern to the public health. Remediation of contaminated groundwater is of highest priority since billions of people all over the world use it for drinking purpose. In this paper, thirty five approaches for groundwater treatment have been reviewed and classified under three large categories viz chemical, biochemical/biological/biosorption and physico-chemical treatment processes. Comparison tables have been provided at the end of each process for a better understanding of each category. Selection of a suitable technology for contamination remediation at a particular site is one of the most challenging job due to extremely complex soil chemistry and aquifer characteristics and no thumb-rule can be suggested regarding this issue. In the past decade, iron based technologies, microbial remediation, biological sulphate reduction and various adsorbents played versatile and efficient remediation roles. Keeping the sustainability issues and environmental ethics in mind, the technologies encompassing natural chemistry, bioremediation and biosorption are recommended to be adopted in appropriate cases. In many places, two or more techniques can work synergistically for better results. Processes such as chelate extraction and chemical soil washings are advisable only for recovery of valuable metals in highly contaminated industrial sites depending on economical feasibility.
Preface
Groundwater is one of mankind’s most important natural resources because it is the main source of drinking water. Contaminated sites resulting from industrial activity, mining, improper waste disposal or accidents involving hazardous substances pose a permanent threat to aquifers. Harmful chemicals can leach from polluted areas, for instance through rain water infiltrating the soil, and migrate downwards until they reach an underlying aquifer. The groundwater may become contaminated as a result and no longer usable as drinking water. It is, therefore, very important to develop and implement methods of preventing and reducing groundwater pollution. Pump-and-treat, the most frequently used conventional method for groundwater remediation, exhibits a number of shortcomings, while permeable reactive barriers (PRBs) represent a new and innovative technology with many advantageous features.
PRBs enable physical, chemical or biological in situ treatment of contaminated groundwater by bringing it into contact with reactive materials. The reactive material is inserted underground in a natural aquifer and intercepts the pollution plume as it is carried along within the aquifer, and thus the contaminants are treated without either wholesale soil excavation or water pumping. This cost-effective clean-up technology has much less impact on the environment than other methods, and since it requires hardly any energy input during operation, it is generally more economical over the long term than methods such as pump-and-treat that require continuous energy input.
While extensive research has been performed on many technological aspects of PRBs, and a number of contaminants have already been successfully treated by PRB systems, long-term performance has not been extensively considered and little is known about the processes influencing the long-term behaviour. This gap in our knowledge is all the more problematic because design life has a decisive influence on the economic viability of PRBs.
This book describes methods for the evaluation and enhancement of the long-term performance of PRB systems, especially of those targeting heavy metals such as uranium and organic contaminants, by sorption and/or precipitation mechanisms. The contents originate mainly from original research work performed within an international collaborative project funded by the European Commission. The project was called “Long-Term Performance of Permeable Reactive Barriers Used for the Remediation of Contaminated Groundwater” (acronym: “PEREBAR”) and was undertaken between the years 2000 and 2003. Processes that impair the barrier performance during PRB operation, and technologies to enhance the long-term efficacy of PRB systems were studied qualitatively and quantitatively. Two case study sites formed the central part of the project. The primary case study site was the former Hungarian uranium ore mining and processing area near the city of Pe´cs in Southern Hungary. The second site is located in Brunn am Gebirge, Austria, where an activated carbon PRB system is installed to treat a plume of organic contaminants at a former industrial site.
The first two chapters of this book introduce the field of PRBs as an innovative technology for passive groundwater remediation. Chapter 1 gives a brief introduction to the concept of PRBs. Potential reactive materials and the major biogeochemical mechanisms that can be utilised in PRBs are presented, and design considerations discussed. Particular attention is given to an up-to-date review on the application of PRBs, especially on the experiences and lessons learnt about the long-term performance of fullscale installations. Chapter 2 describes the practical aspects of PRB construction. In the first part of this chapter, cut-off wall construction methods are described, since PRB construction techniques are based firmly on experience gathered with these methods and because cut-off walls are integral parts of some PRB designs (e.g. funnel-and-gate systems). In the second part, PRB design considerations and construction techniques (including some innovative techniques) are explicitly discussed.
The next four chapters focus on the removal of uranium from contaminated groundwater by a selection of reactive materials including zeolites, hydroxyapatite (HAP) and elemental iron (Fe0, also widely referred to as “zero-valent iron” (ZVI)). The driving force behind the investigations described in these chapters was the case study site in Pe´cs, Hungary. Therefore the experimental conditions develop, chapter by chapter, towards the actual field conditions at that site. Chapter 3 describes the results of batch experiments conducted to evaluate the effectiveness of natural zeolitic tuff, hydroxyapatite, activated carbon, hydrated lime, elemental iron and iron oxides in removing uranium from aqueous solution. The experiments were conducted with simple solutions of uranyl nitrate dissolved in deionised water. It was found that elemental iron and hydroxyapatite are the most effective materials in removing uranium from water. Therefore, further experiments focused on these two materials.
Column experiments described in Chapter 4 showed that elemental iron and hydroxyapatite have strong uranium attenuation capabilities. The column experiments also showed the susceptibility of elemental iron to corrosion effects and the formation of secondary mineral precipitates due to the extreme geochemical conditions inside the iron matrix. A special feature of the column experiments was the development of a nondestructive method to measure the propagation of the uranium front during an experiment using a radiotracer. The column experiments were conducted with an artificial groundwater with a composition close to that of the case study site in Pe´cs. Chapter 5 describes the set-up and results of laboratory experiments conducted with groundwater taken from monitoring wells at the site in Pe´cs. These experiments focussed again on elemental iron and hydroxyapatite, and were conducted as column experiments and floor-scale box experiments (at cubic meter scale). The results of the experiments showed that the composition of the local groundwater, with its high concentrations of Ca, Mg, HCO3 and SO4, has a significant impact on the long-term functioning of PRB systems based on elemental iron.
Laboratory-based experiments are usually subject to rather artificial boundary conditions, and a number of crucial parameters and groundwater constituents may differ significantly from real field conditions. Therefore, with the experiments described in Chapter 6, the step from the laboratory to the field was taken. On-site column experiments with elemental iron and hydroxyapatite were designed and operated at a field test location on the former Hungarian uranium ore-processing site near the city of Pe´cs. The test site was located downstream of a large uranium-bearing waste rock pile where the shallow local groundwater showed significantly elevated concentrations of dissolved uranium. To simulate different flow conditions, small-scale columns were installed and operated within monitoring wells, and large-scale column experiments were located and operated very close to the monitoring wells used to supply their influent groundwater. The results of these on-site (and even partly in situ) column experiments showed that both elemental iron and hydroxyapatite effectively remove uranium from contaminated groundwater under field conditions. For elemental iron it could also be shown that the residence time of the contaminated groundwater in the reactive material controls, to some extent, the change of overall groundwater composition. It can be concluded that the volume of the reactive zone and the groundwater flow-velocity through the reactive zone are important design parameters for controlling adverse effects that occur within the elemental iron barriers (such as precipitation of secondary minerals) and are thus important to the long-term performance and operating life of iron-based PRBs.
The next two chapters address innovative ideas on improving the performance of PRBs, especially with respect to their long-term behaviour. Chapter 7 describes the development and testing of a new reactive material designed to sequester uranium (VI) from contaminated groundwater. This material, named PANSIL, consists of a polymeric resin coated onto the surface of quartz sand. The advantage of PANSIL is that it is selective towards the uranyl ion, available in a granular and durable form (important considerations for materials to be used in a PRB system), and does not have any side-effects on either the groundwater composition or the geochemical conditions in the barrier, and thus avoids secondary effects such as coating or clogging of the reactive matrix. Chapter 8 evaluates the feasibility of electrokinetic methods to positively affect the long-term efficiency of PRBs. The approach of coupling electrokinetic processes with PRB systems to reduce the advective transport of groundwater constituents that may impair the barrier function was studied in a series of laboratory experiments. The results described in this chapter suggest that the installation of an electrokinetic fence upstream of the barrier could indeed electrokinetically trap such groundwater constituents outside the barrier.
Chapters 9–11 report investigations and research work conducted at the two case study sites in Hungary and Austria. The characteristics of the former Hungarian uranium ore mining and processing site near the city of Pe´cs in Southern Hungary, including its pollution history, hydrogeology and ongoing remediation activities, are presented in Chapter 9. The chapter also describes the site investigations carried out to find and characterise a suitable location for an experimental PRB system to treat the uraniumcontaminated groundwater. In Chapter 10, the design, construction and operation of an experimental elemental iron barrier at the Pe´cs case study site are described. The aim of this pilot-scale barrier is the removal of dissolved uranium from the local groundwater. It consists of 38 tonnes of shredded cast iron placed in a shallow aquifer in a small valley downstream of a large, uranium-bearing waste rock pile. During the first year of operation uranium removal from the groundwater by the experimental barrier has been very successful. At the same time the change in overall groundwater composition of the barrier effluent indicated that strong geochemical processes were taking place inside the barrier material. These processes include the formation of significant amounts of precipitates, mainly carbonates, which in the long-term might lead to changes in the hydraulic properties of the system. Chapter 11 describes the geological, hydrogeological and environmental characteristics of a former industrial site in Brunn am Gebirge, Austria which is heavily contaminated with organic contaminants such as polycyclic aromatic hydrocarbons (PAH), hydrocarbons, BTEX, phenols and chlorinated hydrocarbons. A groundwater remediation scheme, called a “Adsorptive Reactor and Barrier (AR&B) System”, has been implemented at the site. This system is designed as a hydraulic barrier with four gates that funnel the groundwater through adsorptive reactors containing activated carbon. This chapter also describes the routine monitoring applied at the site to document the groundwater clean-up efficiency of the AR&B system and additional sampling and testing conducted at the activated carbon reactors to investigate those hydrogeochemical parameters that may allow an assessment of the long-term performance of the system.
In the final chapter, Chapter 12, some issues concerning the regulatory acceptance of PRBs and cost data currently available for PRBs are discussed. By addressing the issue of long-term performance of PRBs, an important aspect of this technology, we aim to advance PRB technology as an accepted, scientifically sound, costeffective and stable tool for passive groundwater remediation. Thus we hope to contribute, with this book, to an improvement in pollution management and a reduction in the exposure of groundwater resources to harmful pollutants, and thereby safeguard water resources for future generations.
Karl Ernst Roehl, Karlsruhe, Germany
Tamas Meggyes, Franz-Georg Simon, Berlin, Germany
D. I. Stewart, Leeds, United Kingdom
The goal of developing the present biotest and the X-ray fluorescent spectroscopic (XRF) analysis was to acquire rapid methods useful for assessing heavy-metal polluted areas. The testing organism, a Bacillus subtills bacterial strain, is especially sensitive to Cu, Zn and Cd. XRF is a multielement, nondestructive method. Both methods are suitable for direct measuring of soil and other solid phase samples, e.g. sediments, ore or barren materials. The methods were worked out and applied for assessing and controlling a former lead-zinc mine-waste pollution in Northeast Hungary, in the Mátra-hills, a center of tourism.
To provide for the rational design of limestone neutralization processes, the kinetics of the chemical reactions involved were evaluated by experiment, and an analysis made of the chemical and physical boundary conditions that control the extent to which the reactions are completed. The rate limiting reactions are the attack of limestone by hydrogen ions, and the exsolution of carbon dioxide which is thereby generated; the latter reaction has an increasing effect on process effciency above pH 5. Rate constants for the limiting reactions were evaluated each as a function of temperature, ionic strength, water turbulence, and for the first reaction bicarbonate ion concentration, which catalyzes the attack of limestone by hydrogen ions. A mathematical model of limestone neutralization processes was simplified to obtain a graphical procedure for the process design for neutralization. These graphs indicate the quantity of crushed limestone of given size that is required to neutralize a specified flow of acid waste from the initial pH to the required final pH.
The main cause of degradation in tuffeau, a soft siliceous and clayey limestone extensively used in the construction of the castles of the Loire Valley in France, is scaling. The most damaging form of weathering is spalling. Over time, a plaque several centimetres in thickness gradually forms under the stone surface and eventually falls away, leaving the resulting new surface powdered. Hypotheses regarding the initiation and development of such degradation have not yet met scientific consensus. The objective of the present paper is to improve existing knowledge of scaling degradation by analysing in situ samples representing different stages of the same degradation process. The analysis of the stones at the Castle of Chambord, revealed the presence of gypsum (CaSO4·2H2O), mainly located in cracks parallel to the stone surface. This gypsum was then studied in terms of its crystal morphology and distribution with depth. For comparison purposes, another form of scaling identified at the Castle of Chambord but rarely studied, flaking, was also examined. A first attempt at explaining the origin and formation of the observed gypsum in both scaling processes was conducted by interacting and comparing the characterisation results with historical and environmental data.
Heavy metals wash from tires, automobile exhausts, road asphalt, fuel combustion, parking dust, and recreational land into urban stormwater runoff and its subsequent discharge into surface and subsurface water sources can create public health and environmental hazards. An in-ground permeable reactive filter system is proposed to treat contaminated urban stormwater. However, the filter materials should be carefully selected. Several series of batch experiments were conducted with synthetic stormwater containing individual metal contaminants at different concentrations to determine the adsorption and removal behavior of four potential permeable inorganic filter materials (calcite, zeolite, sand, and iron filings) for six common toxic heavy metal contaminants (Cd, Cu, Pb, Ni, Cr, and Zn). The adsorbed metals, pH, oxidation-reduction potential and electrical conductivity of batch samples were determined. Isotherm modeling was performed to assess the mechanisms and quantify the adsorption of each filter material for the contaminants. The extent of adsorption and removal of metals was found to depend on the type and concentration of metal as well as the filter material. Langmuir or Freundlich isotherm proved best to describe the metal adsorption behavior. The maximum removal achieved for individual metals were: 95-100% Cd, Cu, Pb and Zn by calcite, zeolite and iron filings, 90% Ni by zeolite, and 100% Cr by iron filings. Sand produced low results with maximum levels of 8 to 58%. Based on the maximum adsorption capacity of each filter material, the typical filter size and volume of stormwater that can be treated were estimated. No single filter material was capable of removing all metals to the maximum extent; therefore, a combination of filter materials should be investigated for the simultaneous removal of multiple heavy metals.
The removal of Cd, Cu, Ni and Zn from dilute mine water by using several geological materials including pure limestone, sand, carbonaceous limestone and brecciated limestone was performed on a laboratory scale. The results showed that to add geological materials in combination with sodium carbonate injection would notably enhance the efficiency of heavy metal removal to varying degrees. Pure limestone was found the best one among the four materials mentioned above for removing heavy metals from mine water. The removal efficiencies of pure limestone when it is ground as fine as 30–60 meshes are 58.6% for Cd, 100% for Cu, 47.8% for Ni, and 36.8% for Zn at 20°C. The optimum pH is about 8.9 to 9.1. The mechanism of higher effective removal, perhaps, is primarily due to co-precipitation under the control of calcite-related pH value. According to this research, Na2CO3 injection manners, including slug dosing and drip-wise, seemed to have little impact on the efficiency of heavy metal removal.
Hazardous metal cations enter water through the natural geochemical route or from the industrial wastes. Their separation and removal can be achieved by adsorptive accumulation of the cations on a suitable adsorbent. In the present work, toxic Pb(II) ions are removed from water by accumulating it on the surface of natural zeolite in three different forms; one untreated and two treated samples, one sample treated with 2 M HCI solution and other is treated with 3 M NaOH solution. Natural zeolite is mainly composed of clinoptilolite, and mordenite, with amount of non-zeolite phase (smectite and illite) and C and CT opal. The adsorption experiments are carried out using a batch process in environments of different pH, initial Pb(II) concentration, interaction time and amount of zeolites. Treated zeolite samples show high exchange capacity for Pb(II) compared to untreated sample, however, acid-treated sample shows an exceedingly good exchange capacity. Equilibrium data fitted well with the Langmuir isotherm model with maximum adsorption capacity of 115, 126, and 132 mg g−1 of untreated natural zeolites, alkali-treated zeolites and acid-treated zeolites respectively. The rates of adsorption were found to confirm to pseudo-first order kinetic with good correlation and the overall rate of lead ions uptake.
The Maltese Islands measure only 316 km(2), have a population of just over 405 000 and are situated in the central Mediterranean. They are composed of sedimentary rocks, of which the Globigerina and Coralline Limestones have been used as building materials since prehistoric times. This paper gives an overview of the use of these materials, and other imported materials, for building from prehistoric times to the present day, and also looks at the exploitation of the underground environment through the ages.
The impact of mining and smelting of metal ores on environmental quality is described. Mines produce large amounts of waste because the ore is only a small fraction of the total volume of the mined material. In the metal industry, production of Cu, Pb, and Zn causes the greatest degradation of the environment. Copper mining produces extensive mine wastes and tailings and Cu smelling emits approximately 0.11 Mg of S per Mg of Cu produced in the USA. Zinc and Pb smelters release large quantities of Cd and Pb into the environment. Metal smelting and refining produce gaseous (CO2, SO2, NO(x), etc.) and particulate matter emissions, sewage waters, and solid wastes. Soil contamination with trace metals is considered a serious problem related to smelting; however, mining and smelting are not main sources of global metal input into soils. Other sources like discarded manufactured products, coal ash, agriculture, and transportation take a lead. Smelters are the main sources of atmospheric emissions of As, Cu, Cd, Sb, and Zn on a global scale and they contribute substantially to the overall emissions of Cr, Pb, Se, and Ni. A quantitative evaluation of the environmental health effects of mining and smelting is difficult because of the complexity of factors involved and lack of consistent methodology. Nevertheless, the case studies described indicate that negative health effects could arise from Pb mining and smelting. Risk assessment revealed that food chain contamination by Cd from soils contaminated by smelting is very unlikely under the western diet.
This article reviews the technical applicability of various physico–chemical treatments for the removal of heavy metals such as Cd(II), Cr(III), Cr(VI), Cu(II), Ni(II) and Zn(II) from contaminated wastewater. A particular focus is given to chemical precipitation, coagulation–flocculation, flotation, ion exchange and membrane filtration. Their advantages and limitations in application are evaluated. Their operating conditions such as pH, dose required, initial metal concentration and treatment performance are presented. About 124 published studies (1980–2006) are reviewed. It is evident from the survey that ion exchange and membrane filtration are the most frequently studied and widely applied for the treatment of metal-contaminated wastewater. Ion exchange has achieved a complete removal of Cd(II), Cr(III), Cu(II), Ni(II) and Zn(II) with an initial concentration of 100mg/L, respectively. The results are comparable to that of reverse osmosis (99% of Cd(II) rejection with an initial concentration of 200mg/L). Lime precipitation has been found as one of the most effective means to treat inorganic effluent with a metal concentration of higher than 1000mg/L. It is important to note that the overall treatment cost of metal-contaminated water varies, depending on the process employed and the local conditions. In general, the technical applicability, plant simplicity and cost-effectiveness are the key factors in selecting the most suitable treatment for inorganic effluent.
The process of electro deposition of heavy metals on bodies of different materials (for instance on non metallic objects to improve their look, their mechanical resistance and other physical properties) generates effluents contaminated by residues of valuable metal salts whose disposal is difficult and expensive. After several months of on site pilot testing it was possible to draw optimised flow schemes and to define the type of membrane more suitable to the recovery of metal salts from highly acidic solutions (pH close to 1) and to the production of high quality, reusable industrial water. The paper describes the various steps of the testing program, the comparison of mathematical models and results of plant operation, the optimised flow diagram of different applications (recovery of copper from the cleaning baths in a copper electro deposition plant, recovery of nickel sulphate and chloride from the cleaning baths in the electro deposition of nickel) and the operating costs and physical features of industrial plants.
In Budapest damage due to atmospheric pollution on many public buildings is severe. Black encrustations, white crusts and other decay features of a soft oolitic limestone have been studied in detail by using field measurements and laboratory analyses. Limestone weathering was assessed by description of weathering forms, by on-site petrophysical tests (Duroscope, Schmidt hammer, water absorption) and by laboratory mineralogical assessment and thermoanalysis (X-ray diffraction, Derivatograph). There is a clear correlation between the organic carbon content in stone and location of the site, particularly in the polluted city centre. Gypsum, which is not an indigenous mineral in the limestone, can contribute up to 70% of the crust composition and indicates the importance of air-derived SO 2. This mineralogical change in stone composition leads to changes in physical properties, by strengthening laminar black crust and white case hardened crusts and weakening the host rock.
This article aims to provide an overview of the upcoming technology of permeable reactive barriers for groundwater remediation. A comprehensive list of references and web-links are also provided for further in-depth understanding. A brief discussion on the Australian perspective on this emerging technology is also included.
Adsorption and ion exchange can be effectively employed for the treatment of metal-contaminated wastewater streams. The use of low-cost materials as sorbents increases the competitive advantage of the process. Natural and modified minerals have been extensively employed for the removal of nickel and zinc from water and wastewater. This work critically reviews existing knowledge and research on the uptake of nickel and zinc by natural and modified zeolite, bentonite and vermiculite. It focuses on the examination of different parameters affecting the process, system kinetics and equilibrium conditions. The process parameters under investigation are the initial metal concentration, ionic strength, solution pH, adsorbent type, grain size and concentration, temperature, agitation speed, presence of competing ions in the solution and type of adsorbate. The system's performance is evaluated with respect to the overall metal removal and the adsorption capacity. Furthermore, research works comparing the process kinetics with existing reaction kinetic and diffusion models are reviewed as well as works examining the performance of isotherm models against the experimental equilibrium data.
The reduction and control of water pollution in the manufacturing process is an important area for improvement. Current technology can be utilized to reduce water consumption and improve the efficiency of water use. The function of the paint shop is to apply an organic coating for protective and decorative reasons. The paint can be applied in various forms, including dry powder, solvent-diluted formulations, and waterborne formulations. The primary function of a paint booth, whether wet or dry, is to remove the paint overspray from the air of the work environment. A similar mechanism can be used in the downdraft paint booth, which is the most common in larger continuous operations, such as automotive assembly plants. Downdraft systems normally contain much larger volumes of water than side-draft systems, making the treatment and conservation of this water even more critical.
A program of research was initiated to study the treatment of spent rinse water from metal plating using reverse osmosis (RO) to meet the requirements for reuse as an alkaline rinse water. Four categories of spent rinses were treated in the laboratory using flat sheet membranes from different manufacturers. The experimental results showed that CPA2, ESPA1 and TW30 membranes were not suitable for treating the spent solvent rinse. A mechanism for the solvent to attack the composite RO membranes was proposed. For a combination of alkaline, acid and nickel-plating rinses, rejections of conductivity, nickel, nitrate and total organic carbon (TOC) were above 97, 99.8, 95 and 87%, respectively. The permeate conductivity and concentration in terms of nickel, nitrate and TOC were below 45 μS/cm, 0.01, 2.1 and 3.0 ppm, respectively, which met the requirements for reuse as an alkaline rinse water. An appropriate ultrafiltration (UF) pretreatment could reduce fouling of RO membrane and increase the flux of RO membrane by 30–50%. It was found that there was an optimum operating pressure for the treatment of nickel-plating rinses. The results also showed that the feed pH had a significant effect on the rejection of nickel.
The oolitic limestone blocks on the buildings of Budapest show extensive crust formation, which is related to atmospheric pollution and continental climate. Crusts can be grouped according to their colour and morphology. Two types of white crusts and two types of black crusts have been studied in detail. Physical properties (Schmidt hammer rebound, Duroscope rebound, water absorption) and mineralogical composition (XRD, DTA–DTG) were measured and compared. Most crusts have higher Duroscope and Schmidt hammer rebound values than their host rock. The strength of the crust is related to the thickness, to the mineral composition, to the crust morphology and to the water absorption capacity. Calcite-rich, impermeable, thick white crusts have the highest strength, which is followed by gypsum-rich laminar black crusts alongside with thin gypsum-rich white crusts. These differences in strength and mineralogy are attributed to differences in rain/wind exposure and conditions conducive to pollution entrapment.
Acid mine drainage (AMD) is one of the most significant environmental challenges facing the mining industry worldwide. Water infiltrating through the metal sulphide minerals, effluents of mineral processing plants and seepage from tailing dams becomes acidic and this acidic nature of the solution allows the metals to be transported in their most soluble form. The conventional treatment technologies used in the treatment of acid mine drainage are expensive both in terms of operating and capital costs. One of the methods of achieving compliance using passive treatment systems at low cost, producing treated water pollution free, and fostering a community responsibility for acid mine water treatment involves the use of wetland treatment system. These wetlands absorb and bind heavy metals and make them slowly concentrated in the sedimentary deposits to become part of the geological cycle. In this paper a critical review of the heavy metal removal mechanism involving various physical, chemical and biological processes, which govern wetland performance, have been made. This information is important for the siting and use of wetlands for remediation of heavy metals.
Peat has been investigated by several researchers as a sorbent for the capture of dissolved metals from wastestreams. Besides being plentiful and inexpensive, peat possesses several characteristics that make it an effective media for the removal of dissolved metal pollutants. The mechanism of metal ion binding to peat remains a controversial area with ion-exchange, complexation, and surface adsorption being the prevalent theories. Factors affecting adsorption include pH, loading rates, and the presence of competing metals. The optimum pH range for metals capture is generally 3.5–6.5. Although the presence of more than one metal in a solution creates competition for sorption sites and less of a particular ion may be bound, the total sorption capacity has been found to increase. Studies have also shown that metals removal is most efficient when the loading rates are low. In addition, recovery of metals and regeneration of the peat is possible using acid elution with little effect on peat’s sorption capacity.The utilization of peat and other biomass materials for the treatment of wastewater containing heavy metals is gaining more attention as a simple, effective and economical means of pollution remediation. Pelleting processes can now produce a robust media for a variety of applications where traditional methods of pollutant removal would be economically or technologically difficult.
The treatment of aqueous or oily effluents is one of the most serious environmental issues faced by the minerals and metallurgy industries. Main pollutants are residual reagents, powders, chemicals, metal ions, oils, organic and some may be valuable (Au, Pt, Ag). The use of flotation is showing a great potential due to the high throughput of modern equipment, low sludge generation and the high efficiency of the separation schemes already available. It is concluded that this process will be soon incorporated as a technology in the minerals industry to treat these wastewaters and, when possible, to recycle process water and materials. In this paper, the use of flotation in environmental applications is fully discussed. Examples of promising emerging techniques and devices are reported and some recent advances in the treatment of heavy metal containing waters and emulsified oil wastes are discussed.
Inadequate disposal of tailings resulting from processing and other mining and metallurgical activities causes often severe contamination of surface streams and groundwater reservoirs, due to oxidation of the inherent sulfide phases and the subsequent generation of leachates characterized by high acidity and elevated concentration of hazardous elements. A relatively low cost alternative to pump and treat approach aiming at prevention of contamination or clean up of contaminated groundwater involves the application of in-situ permeable reactive barriers (PRBs). A number of low cost compounds may be used as reactive media in order to provide alkalinity, activate precipitation and sorption mechanisms and finally lead to clean up of the contaminated plume.
Water plays a fundamental role in the phenomena of stone deterioration. A highly porous limestone called tuffeau used in the Loire castles in France is characterized. Several techniques for pore space investigation and anisotropy determination are presented and their range of application is discussed. Water retention and transfer properties related to the pore space characteristics are determined as a function of relative humidity. The experimental set-up and tests presented have been chosen for their simple execution and interesting data produced for both fresh and deteriorated stone.
The US Department of Energy (DOE) has been evaluating the unsaturated zone (UZ) at Yucca Mountain, Nevada, as a potential repository site for high level nuclear waste. A large number of boreholes have been drilled at the site, and an underground tunnel, the exploratory studies facility (ESF), has been constructed. A variety of boreholes and underground tests have been conducted that have provided large amounts of data from the UZ. This paper summarizes some of the current knowledge of geological and hydrological characteristics of the site and provides the framework for a series of technical papers that follow in this issue. A brief discussion is also given to the repository safety strategy for Yucca Mountain and the UZ site-scale flow model.
Long-term behaviour is a major issue related to the use of zero-valent iron (ZVI) in permeable reactive barriers for groundwater remediation; in fact, in several published cases the hydraulic conductivity and removal efficiency were progressively reduced during operation, potentially compromising the functionality of the barrier. To solve this problem, the use of granular mixtures of ZVI and natural pumice has recently been proposed. This paper reports the results of column tests using aqueous nickel and copper solutions of various concentrations. Three configurations of reactive material (ZVI only, granular mixture of ZVI and pumice, and pumice and ZVI in series) are discussed. The results clearly demonstrate that iron-pumice granular mixtures perform well both in terms of contaminant removal and in maintaining the long-term hydraulic conductivity. Comparison with previous reports concerning copper removal by ZVI/sand mixtures reveals higher performance in the case of ZVI/pumice.
Kinetic and equilibrium sorption experiments were conducted on removal of divalent heavy metals (Pb(II), Cu(II), Zn(II), Cd(II)) and trivalent arsenic (As(III)) from aqueous solutions by scoria (a vesicular pyroclastic rock with basaltic composition) from Jeju Island, Korea, in order to examine its potential use as an efficient sorbent. The removal efficiencies of Pb, Cu, Zn, Cd, and As by the scoria (size=0.1-0.2mm, dose=60gL(-1)) were 94, 70, 63, 59, and 14%, respectively, after a reaction time of 24h under a sorbate concentration of 1mM and the solution pH of 5.0. A careful examination on ionic concentrations in sorption batches suggested that sorption behaviors of heavy metals onto scoria are mainly controlled by cation exchange. On the other hand, arsenic appeared to be sensitive to specific sorption onto hematite (a minor constituent of scoria). Equilibrium sorption tests indicated that the removal efficiency for heavy metals increases with increasing pH of aqueous solutions, which is resulted from precipitation as hydroxides. Similarly, multi-component systems containing heavy metals and arsenic showed that the arsenic removal increases with increasing pH of aqueous solutions, which can be attributed to coprecipitation with metal hydroxides. The empirically determined sorption kinetics were well fitted to a pseudo-second order model, while equilibrium sorption data for heavy metals and arsenic onto scoria were consistent with the Langmuir and Freundlich isotherms, respectively. Natural scoria studied in this work is an efficient sorbent for concurrent removal of divalent heavy metals and arsenic.
In this study, activated carbon, kaolin, bentonite, blast furnace slag and fly ash were used as adsorbent with a particle size between 100 mesh and 200 mesh to remove the lead and zinc ions from water. The concentration of the solutions prepared was in the range of 50-100 mg/L for lead and zinc for single and binary systems which are diluted as required for batch experiments. The effect of contact time, pH and adsorbent dosage on removal of lead and zinc by adsorption was investigated. The equilibrium time was found to be 30 min for activated carbon and 3h for kaolin, bentonite, blast furnace slag and fly ash. The most effective pH value for lead and zinc removal was 6 for activated carbon. pH value did not effect lead and zinc removal significantly for other adsorbents. Adsorbent doses were varied from 5 g/L to 20 g/L for both lead and zinc solutions. An increase in adsorbent doses increases the percent removal of lead and zinc. A series of isotherm studies was undertaken and the data evaluated for compliance was found to match with the Langmuir and Freundlich isotherm models. To investigate the adsorption mechanism, the kinetic models were tested, and it follows second order kinetics. Kinetic studies reveals that blast furnace slag was not effective for lead and zinc removal. The bentonite and fly ash were effective for lead and zinc removal.
Although consequences of zinc deficiency have been recognized for many years, it is only recently that attention has been directed to the potential consequences of excessive zinc intake. This is a review of the literature on manifestations of toxicity at several levels of zinc intake. Zinc is considered to be relatively nontoxic, particularly if taken orally. However, manifestations of overt toxicity symptoms (nausea, vomiting, epigastric pain, lethargy, and fatigue) will occur with extremely high zinc intakes. At low intakes, but at amounts well in excess of the Recommended Dietary Allowance (RDA) (100-300 mg Zn/d vs an RDA of 15 mg Zn/d), evidence of induced copper deficiency with attendant symptoms of anemia and neutropenia, as well as impaired immune function and adverse effects on the ratio of low-density-lipoprotein to high-density-lipoprotein (LDL/HDL) cholesterol have been reported. Even lower levels of zinc supplementation, closer in amount to the RDA, have been suggested to interfere with the utilization of copper and iron and to adversely affect HDL cholesterol concentrations. Individuals using zinc supplements should be aware of the possible complications attendant to their use.
The possibility of removing Zn2+ cations from wastewater by ion exchange using natural zeolites as exchangers has been investigated. The process of binding of zinc ions into zeolite structure has been established by several reaction mechanisms as a fast chemical reaction of ion exchange, accompanied by slower adsorption of different ionic species and possible precipitation or coprecipitation with the zeolite structure. The physicochemical phenomena such as hydrolysis and dissolution of surface layers are the result of interaction of zeolite with hydrogen or hydroxyl ions from the solution. Complexation of OH- with Zn2+ to form the zinc-hydroxy species strongly depends on pH value and affect the uptake mechanism as to lower dissolution of surface aluminosilicate layers. Structure imperfections as a surface property of mineralogical nonhomogeneous zeolitic grains can lead to formation of sorption surface sites with different energy, which affects the nonuniform distribution of different zinc species adsorbed. It is particularly possible in zeolitic tuff samples with relatively high content of aluminosilicates as minor mineralogical components, which is characteristic of Croatian deposits.
Acid mine drainage (AMD) causes environmental pollution that affects many countries having historic or current mining industries. Preventing the formation or the migration of AMD from its source is generally considered to be the preferable option, although this is not feasible in many locations, and in such cases, it is necessary to collect, treat, and discharge mine water. There are various options available for remediating AMD, which may be divided into those that use either chemical or biological mechanisms to neutralise AMD and remove metals from solution. Both abiotic and biological systems include those that are classed as "active" (i.e., require continuous inputs of resources to sustain the process) or "passive" (i.e., require relatively little resource input once in operation). This review describes the current abiotic and bioremediative strategies that are currently used to mitigate AMD and compares the strengths and weaknesses of each. New and emerging technologies are also described. In addition, the factors that currently influence the selection of a remediation system, and how these criteria may change in the future, are discussed.
The evolution of fluid chemistry and mineral alteration around a potential waste emplacement tunnel (drift) is evaluated using numerical modeling. The model considers the flow of water, gas, and heat, plus reactions between minerals, CO(2) gas, and aqueous species, and porosity-permeability-capillary pressure coupling for a dual permeability (fractures and matrix) medium. Two possible operating temperature modes are investigated: a "high-temperature" case with temperatures exceeding the boiling point of water for several hundred years, and a "low-temperature" case with temperatures remaining below boiling for the entire life of the repository. In both cases, possible seepage waters are characterized by dilute to moderate salinities and mildly alkaline pH values. These trends in fluid composition and mineral alteration are controlled by various coupled mechanisms. For example, upon heating and boiling, CO(2) exsolution from pore waters raises pH and causes calcite precipitation. In condensation zones, this CO(2) redissolves, resulting in a decrease in pH that causes calcite dissolution and enhances feldspar alteration to clays. Heat also enhances dissolution of wall rock minerals leading to elevated silica concentrations. Amorphous silica precipitates through evaporative concentration caused by boiling in the high-temperature case, but does not precipitate in the low-temperature case. Some alteration of feldspars to clays and zeolites is predicted in the high-temperature case. In both cases, calcite precipitates when percolating waters are heated near the drift. The predicted porosity decrease around drifts in the high-temperature case (several percent of the fracture volume) is larger by at least one order of magnitude than in the low temperature case. Although there are important differences between the two investigated temperature modes in the predicted evolution of fluid compositions and mineral alteration around drifts, these differences are largely within to the model uncertainty and the variability of water compositions at Yucca Mountain.
This paper provides a quantitative comparison between electrocoagulation and chemical precipitation based on heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) removal from acidic soil leachate (ASL) at the laboratory pilot scale. Chemical precipitation was evaluated using either calcium hydroxide or sodium hydroxide, whereas electrocoagulation was evaluated via an electrolytic cell using mild steel electrodes. Chemical precipitation was as effective as electrocoagulation in removing metals from ASL having low contamination levels (30 mg Pbl(-1) and 18 mg Znl(-1)). For ASL enriched with different metals (each concentration of metals was initially adjusted to 100 mg l(-1)), the residual Cr, Cu, Pb and Zn concentrations at the end of the experiments were below the acceptable level recommended for discharge in sewage urban works (more than 99.8% of metal was removed) using either electrocoagulation or chemical precipitation. Cd was more effectively removed by electrochemical treatment, whereas Ni was easily removed by chemical treatment. The cost for energy, chemicals and disposal of metallic residue of electrocoagulation process ranged from USD 8.83 to 13.95 tds(-1), which was up to five times lower than that recorded using chemical precipitation. Highly effective electrocoagulation was observed as the ASL was specifically enriched with high concentration of Pb (250-2000 mg Pbl(-1)). More than 99.5% of Pb was removed regardless of the initial Pb concentration imposed in ASL and, in all cases, the residual Pb concentrations (0.0-1.44 mg l(-1)) were below the limiting value (2.0 mg l(-1)) for effluent discharge in sewage works.
This paper presents the results of research on heavy metals removal from water by filtration using low cost coarse media which could be used as an alternative approach to remove heavy metals from water or selected wastewater. A series of batch studies were conducted using different particle media (particle size 2.36-4.75 mm) shaken with different heavy metal solutions at various pH values to see the removal behaviour for each metal. Each solution of cadmium (Cd), lead (Pb), zinc (Zn), nickel (Ni), copper (Cu) and chromium (Cr(III)) with a concentration of 2 mg/L was shaken with the media. At a final pH of 8.5, limestone has significantly removed more than 90% of most metals followed by 80% and 65% removals using crushed bricks and gravel, respectively. The removal by aeration and settlement methods without solid media was less than 30%. Results indicated that the removal of heavy metals was influenced by the media and not directly by the pH. Investigations on the removal behaviour of these metals indicated that rough solid media with the presence of carbonate were beneficial for the removal process. Adsorption and precipitation as metals oxide and probably as metals carbonate were among the two mechanisms that contributed to the removal of metals from solution.
The retention of lead by a Mexican, clinoptilolite-rich tuff from Oaxaca (Mexico) at different pH values was evaluated and the lead sorption mechanisms on the zeolitic material in this work were discussed.
Isotherms were determined using lead nitrate solutions (initial pH values between 2 and 5) at 303 K. After the equilibrium was reached, the content of lead in the liquid phases was determined by atomic absorption spectrometry. The elemental composition of the clinoptilolite-rich tuff before and after the lead sorption process was evaluated by electron microscopy.
The maximum ion exchange capacity of the Mexican, clinoptilolite-rich tuff for lead was 1.4 meq/g at pH 3, considering an ion exchange mechanism in the absence of any precipitated or hydrolyzed lead species in the sorption process or any change in the zeolite network. Langmuir and Freundlich isotherms were also considered in this work for comparison purposes.
It is important to consider the nature of the sorption processes before choosing a model to describe the interaction between the metal ions and the sorbent.
The chemical lead speciation, the pH, as well as the characteristics of the clinoptilolite-rich tuff are important factors to be considered on the lead sorption process by natural zeolites. The chemical species involved in that process are Na, from the zeolite and Pb2+ from the aqueous solution at pH 2 and 3, so that the ion exchange mechanism explains the lead sorption processes by the clinoptilolite-rich tuff through the ion exchange isotherms. The sodium, Mexican, clinoptilolite-rich tuff is a potential adsorbent for lead from aqueous solutions.
The natural zeolite-rich tuffs are very important as ion exchangers for the treatment of polluted water due to their sorption properties and low cost. The sorption behavior of each natural material depends on their composition. Mexican, clinoptilolite-rich tuff from Oaxaca (Mexico) could be used for the treatment of waste water contaminated with lead. It would be important to propose this material as an alternative as waste water treatment, because it shows good selectivity for the removal of heavy metals from water.
The feasibility of using two important and common clay minerals, kaolinite and montmorillonite, as adsorbents for removal of toxic heavy metals has been reviewed. A good number of works have been reported where the modifications of these natural clays were done to carry the adsorption of metals from aqueous solutions. The modification was predominantly done by pillaring with various polyoxy cations of Zr4+, Al3+, Si4+, Ti4+, Fe3+, Cr3+or Ga3+, etc. Preparation of pillared clays with quaternary ammonium cations, namely, tetramethylammonium-, tetramethylphosphonium- and trimethyl-phenylammonium-, N'-didodecyl-N, N'-tetramethylethanediammonium, etc, are also common. Moreover, the acid treatment of clays often boosted their adsorption capacities. The adsorption of toxic metals, viz., As, Cd, Cr, Co, Cu, Fe, Pb, Mn, Ni, Zn, etc., have been studied predominantly. Montmorillonite and its modified forms have much higher metal adsorption capacity compared to that of kaolinite as well as modified-kaolinite.
A number of industries currently produce varying concentrations of heavy metal laden waste streams with significant consequences for any receiving environmental compartment. In recent years, increasing emphasis has been placed on environmental impact minimisation and resulting from this the range and capability of natural and prepared materials capable of heavy metal removal has seen steady development. In particular considerable work has been carried out on the use of both natural materials and their modifications. These natural materials, in many instances are relatively cheap, abundant in supply and have significant potential for modification and ultimately enhancement of their adsorption capabilities. This review paper reviews the current state of research on the use of the naturally occurring material cellulose, its modified forms and their efficacy as adsorbents for the removal of heavy metals from waste streams. Adsorbents based on direct modification of cellulose are evaluated initially and subsequently modifications resulting from the grafting of selected monomers to the cellulose backbone with subsequent functionalisation are assessed. The heavy metal adsorption capacities for these modified cellulose materials were found to be significant and levels of uptake were comparable, in many instances, to both other naturally occurring adsorbent materials and commercial ion exchange type resins. Many of the modified cellulose adsorbents proved regenerable and re-usable over a number of adsorption/desorption cycles allowing recovery of the adsorbed heavy metal in a more concentrated form.
Overview of scientific investigations at Yucca 354
- G S Bodvarsson
- W Boyle
- R Patterson
- D Williams
Bodvarsson, G.S., Boyle, W., Patterson, R., Williams D., 1999. Overview of scientific investigations at Yucca
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Limestone in the Built Environment: Present Day Challenges for 361 Preservation of the Past
- M Heras
- H A Viles
- J Cassar
Heras, M., Viles H. A., Cassar, J. (eds) Limestone in the Built Environment: Present Day Challenges for
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Preservation of the Past. Geological Society of London Special Publication 331, 13-25.