Removal of arsenite and arsenate using hydrous ferric oxide incorporated into naturally occurring porous diatomite (original) (raw)
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Hydrous ferric oxide incorporated diatomite for remediation of arsenic contaminated groundwater
Environmental Science and Technology, 2007
Two reactive media [zerovalent iron (ZVI, Fisher Fe0) and amorphous hydrous ferric oxide (HFO)-incorporated porous, naturally occurring aluminum silicate diatomite [designated as Fe (25%)-diatomite]], were tested for batch kinetic, pH-controlled differential column batch reactors (DCBRs), in small- and large-scale column tests (about 50 and 900 mL of bed volume) with groundwater from a hazardous waste site containing high concentrations of arsenic (both organic and inorganic species), as well as other toxic or carcinogenic volatile and semivolatile organic compounds (VOC/SVOCs). Granular activated carbon (GAC) was also included as a reactive media since a permeable reactive barrier (PRB) at the subject site would need to address the hazardous VOC/SVOC contamination as well as arsenic. The groundwater contained an extremely high arsenic concentration (341 mg L-1) and the results of ion chromatography and inductively coupled plasma mass spectrometry (IC-ICP-MS) analysis showed that the dominant arsenic species were arsenite (45.1%) and monomethyl arsenic acid (MMAA, 22.7%), while dimethyl arsenic acid (DMAA) and arsenate were only 2.4 and 1.3%, respectively. Based on these proportions of arsenic species and the initial As-to-Fe molar ratio (0.15 molAs molFe-1), batch kinetic tests revealed that the sorption density (0.076 molAs molFe-1) for Fe (25%)-diatomite seems to be less than the expected value (0.086 molAs molFe-1) calculated from the sorption density data reported by Lafferty and Loeppert (Environ. Sci. Technol. 2005, 39, 2120-2127), implying that natural organic matters (NOMs) might play a significant role in reducing arsenic removal efficiency. The results of pH-controlled DCBR tests using different synthetic species of arsenic solution showed that the humic acid inhibited the MMAA removal of Fe (25%)-diatomite more than arsenite. The mixed system of GAC and Fe (25%)-diatomite increased the arsenic sorption speed to more than that of either individual media alone. This increase might be deduced by the fact that the addition of GAC could enhance arsenic removal performance of Fe (25%)-diatomite through removing comparably high portions of NOMs. Small- and large-scale column studies demonstrated that the empty bed contact time (EBCT) significantly affected sorpton capacities at breakthrough (C = 0.5 C 0) for the Fe0/sand (50/50, w/w) mixture, but not for GAC preloaded Fe (25%)-diatomite. In the large-scale column tests with actual groundwater conditions, the GAC preloaded Fe (25%)-diatomite effectively reduced arsenic to below 50 μg L-1 for 44 days; additionally, most species of VOC/SVOCs were also simultaneously attenuated to levels below detection. © 2007 American Chemical Society. http://www.ncbi.nlm.nih.gov/pubmed/17539544
Arsenic adsorption onto hematite and goethite
Comptes Rendus Chimie, 2009
Surface complexation reactions on mineral affect the fate and the transport of arsenic in environmental systems and the global cycle of this element. In this work, the sorption of As(V) on two commercial iron oxides (hematite and goethite) was studied as a function of different physico-chemical parameters such as pH and ionic strength. The main trend observed in the variation of the arsenic sorbed with the pH is a strong retention in acidic pH and the decrease of the sorption on both sorbents at alkaline pH values. The sorption experiments for these iron oxides show that there is no effect of the ionic strength on arsenate adsorption suggesting the formation of an inner sphere surface complex. At pH values corresponding to natural pH water, both hematite and goethite are able to adsorb more than 80% of arsenic, whatever the initial concentration may be. The iron oxides used in this work should be suitable candidates as sorbents for As(V) removal technologies. To cite this article: Y. Mamindy-Pajany et al., C. R. Chimie 12 (2009).
Arsenite and arsenate sorption by hydrous ferric oxide/polymeric material
Desalination, 2008
The occurrence of arsenic in natural ground waters is due to geological composition of soil. There are several methods for removal of arsenic from drinking water, such as coagulation followed by filtration, membrane processes, ion exchange and adsorption. Adsorption methods proved to be effective, economic, easy to perform and construct. The objective of this study was to investigate the removal of arsenic from drinking water using adsorbents prepared by coating the surface of the following polymeric materials: natural alum silicate exchanger zeolite clinoptilolite and ionic exchanger Dowex Marathon C with hydrous ferric oxide. Modified adsorbents were saturated with Fe 3+ ions from the FeCl 3 solution in acetate buffer solution (pH 3.6) and then converted to hydrous ferric oxide by thermo chemical procedure (NaOH, NaCl, 50°C). Adsorption kinetics of arsenic was investigated as a function of initial arsenite and arsenate concentrations (ranging from 100 to 500 μg/L), contact time (from 15 to 360 min) and pH (6.4, 6.9, 7.4, 7.9). The results and sorption characteristics of the prepared hydrous ferric oxide/polymeric material adsorbents were determined using Freundlich and Langmuir adsorption isotherms.
Sorption materials for arsenic removal from water
Water Research, 2004
Five different sorption materials were tested in parallel for the removal of arsenic from water: activated carbon (AC), zirconium-loaded activated carbon (Zr-AC), a sorption medium with the trade name 'Absorptionsmittel 3' (AM3), zerovalent iron (Fe 0), and iron hydroxide granulates (GIH). Batch and column tests were carried out and the behavior of the two inorganic species (arsenite and arsenate) was investigated separately. The sorption kinetics of arsenate onto the materials followed the sequence Zr-ACcGIH=AM3>Fe 0 >AC. A different sequence was obtained for arsenite (ACcZr-AC=AM3=GIH=Fe 0). AC was found to enhance the oxidation reaction of arsenite in anaerobic batch experiments. The linear constants of the sorption isotherms were determined to be 377, 89 and 87 for Zr-AC, AM3 and GIH, respectively. The uptake capacities yielded from the batch experiment were about 7 g l À1 for Zr-Ac and 5 g l À1 for AM3. Column tests indicated that arsenite was completely removed. The best results were obtained with GIH, with the arsenate not eluting before 13 100 pore volumes (inflow concentration 1 mg l À1 As) which corresponds to a uptake capacity of 2.3 mg g À1 or 3.7 g l À1 .
ARSENATE ADSORPTION ONTO ALUMINIUM AND IRON (HYDR)OXIDES AS AN ALTERNATIVE FOR WATER TREATMENT
2007
The geochemical fates of iron and arsenic are so closely correlated that methods of arsenic removal from water are in general based on the high adsorptive affinity of this metalloid with iron (hydr)oxides. Under anoxic conditions, however, reductive dissolution of iron (hydr)oxides can take place, and arsenic may be released into the surrounding environment. The purpose of this study was to investigate the potential of Al-substituted goethites in adsorbing arsenic compared with other Fe and Al (hydr)oxides. Hematite (Hm), goethite (Gt), 2-line ferrihydrite (Fh), gibbsite (Gb), aluminium hydroxide, and three Al-substituted goethites (AlGt) were synthesized and characterized by X-ray powder diffraction (XRD), particle size analysis, and diffuse reflectance (DR) spectroscopy. Adsorption isotherms were obtained after shaking the samples with increasing concentrations of arsenate (40 -1600 mg L -1 ) in a 10 mmol L -1 CaCl 2 solution for 24 hours. The adsorption envelope was measured at pH ranging from 3 to 9. The As(V) adsorption maxima decreased in the following order: Al(OH) 3 > Fh > AlGt-15 > AlGt-25 > AlGt-35 > Hm > Gb > Gt. No relationship was observed between particle diameter and maximum adsorption, suggesting that re-aggregation could have taken place, or possibly that imperfections on the surface of the particles increased their surface net charge, resulting in high adsorption density. The behaviour of all samples was strongly dependent on pH, and the maximum adsorption was achieved in slightly acidic conditions. In general, Al-substituted goethites showed promising results for their potential use as an adsorbent to remove arsenic from water.
Desalination, 2011
In this paper, adsorption of arsenic (V) was studied under different physico-chemical conditions onto four commercial adsorbents: hematite, goethite, magnetite and zero-valent iron (ZVI). The reversibility of adsorption process was also studied using chlorides and phosphates as competing ions. Results show that arsenate adsorption is related to the iron content of adsorbents, and adsorption rate increases in the following order: goethite b hematite b magnetite b ZVI. The modeling of adsorption isotherms by empirical models show that arsenate adsorption is fitted by the Langmuir model for almost all adsorbents, suggesting a monolayer adsorption of arsenic onto adsorbents. Desorption experiments show that arsenic is strongly adsorbed onto hematite and ZVI. Among adsorbents, hematite appears to be the most suitable for removing arsenate in natural medium since it is effective over large ranges of pH and arsenic concentration.
Arsenic Adsorption onto Pillared Clays and Iron Oxides
Journal of Colloid and Interface Science, 2002
Arsenic adsorption was carried out on simple materials such as goethite and amorphous iron hydroxide, and more complex matrices such as clay pillared with titanium(IV), iron(III), and aluminum(III). These matrices were synthesized from a bentonite whose montmorillonitic fraction was pillared according to optimized parameters. These sorbents were characterized by various methods: XRD, FTIR, BET, DTA/TGA, surface acidity, and zetametry. Elimination of arsenite and arsenate as a function of pH was studied. Arsenate elimination was favored at acidic pH, whereas optimal arsenite elimination was obtained at 4 < pH < 9. For pH values above 10, the pillared clays were damaged and elimination decreased. Equilibrium time and adsorption isotherms were also determined for arsenite and arsenate at each matrix autoequilibrium pH. Amorphous iron hydroxide had the highest adsorption capacities both towards arsenate and arsenite. Adsorption capacities of goethite and iron-and titanium-pillared clays toward arsenate were similar, but those toward arsenite were different. Desorption experiments from the various matrices were carried out. Iron-and titanium-pillared clays showed a desorption capacity above 95% and around 40% respectively, but no desorption rate could be obtained for iron (hydr)oxides as they were damaged during the process. C 2002 Elsevier Science (USA)
Arsenic Adsorption by Some Iron Oxide Minerals: Influence of Interfacial Chemistry
Ghana Mining Journal, 2020
The dramatic increase in hydrometallurgical extraction of gold from arsenic bearing gold ores has inevitably resulted in the release of arsenic into the environment worldwide. Residual arsenic minerals in tailings storage facilities can be oxidised and mobilise arsenic into the environment. This can contaminate soils, ground and surface waters and eventually biota. In spite of well-established technologies and recent advances in arsenic remediation, there are limited knowledge and understanding of the iron oxide substrate (goethite, hematite and magnetite) mineralogy and the fate of arsenic on the surface charge of these iron oxide substrates in an aqueous media during adsorption. The aim of the present study was to investigate the influence of interfacial chemistry on arsenic adsorption onto selected iron oxide particles to assist in developing a better understanding and new knowledge in arsenic removal from contaminated waters. Bulk mineralogy and partial chemical composition of s...
Combined effects of anions on arsenic removal by iron hydroxides
Toxicology letters, 2002
Batch experiments were conducted to investigate the combined effects of phosphate, silicate, and bicarbonate on the removal of arsenic from Bangladesh groundwater (BGW) and simulated groundwater by iron hydroxides. The apparent adsorption constants indicated that the affinity of the anions for iron hydroxide sites decreased in the following order arsenate>phosphate>arsenite>silicate>bicarbonate. Phosphate, silicate, and bicarbonate decreased the removal of As(III) even at relatively low concentrations and low surface site coverage. Phosphate (0-0.08 mM), silicate (0-0.8 mM), and bicarbonate (0-14 mM) in separate solutions had none to moderate effects on As(V) removal in a solution containing 6.7 mg/l Fe and 0.3 ppm As(V). In the presence of bicarbonate and silicate the adverse effect of phosphate on As(V) adsorption was magnified. The residual As(V) concentration after iron hydroxide treatment increased from less than 13 microg/l in separate bicarbonate (2.2 mM) and phos...