Journal ArticleDOI
Competitive Sorption of Arsenate and Phosphate on Different Clay Minerals and Soils
Antonio Violante,Massimo Pigna +1 more
TLDR
In this article, the competitive sorption of PO 4 and AsO 4 on selected phyllosilicates, metal oxides, synthetic organo-mineral complexes, and soil samples as affected by pH (4.0-8.0), ligands concentration, surface coverage of the oxyanions on the samples and the residence time.Abstract:
Sorption and desorption of AsO 4 on or from different soil components may have a dominant role in regulating As mobility in soils. The objectives of this work were to provide information on the factors that influence the competitive sorption of AsO 4 and PO 4 in soil. We studied the competitive sorption of PO 4 and AsO 4 on selected phyllosilicates, metal oxides, synthetic organo-mineral complexes, and soil samples as affected by pH (4.0-8.0), ligands concentration, surface coverage of the oxyanions on the samples and the residence time. We found that Mn, Fe, and Ti oxides and phyllosilicates particularly rich in Fe (nontronite, ferruginous smectites) were more effective in sorbing AsO 4 than PO 4 . In fact, by adding AsO 4 and PO 4 as a mixture (AsO 4 /PO 4 molar ratio of 1) more AsO 4 , than PO 4 was usually sorbed on birnessite, pyrolusite, goethite, nontronite, and ferruginous smectite, but more PO 4 than AsO 4 was sorbed on noncrystalline Al precipitation products, gibbsite, boehmite, allophane, and kaolinite. For example, at pH 5.0 the sorbed AsO 4 /sorbed PO 4 molar ratio (rf) was 1.81 for bimessite, 1.05 for nontronite, but was only 0.45 for kaolinite and 0.14 for allophane. For montmorillonite, illite, and vermiculite the rf values were slightly <1. For soil samples, particularly rich in kaolinite, halloysite, allophane, and containing relatively large amounts of organic C, the rf values were usually much <1. For all the samples, the rf values increased by decreasing the pH and with the residence time of the oxyanions. The sorption of AsO 4 (or PO 4 ) on goethite and gibbsite decreased by increasing the initial PO 4 /AsO 4 (or ASO 4 / PO 4 molar ratio) up to 2.0. However, PO 4 inhibited AsO 4 sorption more on gibbsite than on goethite, whereas AsO 4 prevented PO 4 sorption more on goethite than on gibbsite. The data reported in this paper suggest that the mobility, the bioavailability, and the toxicity of As in soil environments may be greatly affected by the nature of soil components, pH, presence of anions (PO 4 ), and residence time.read more
Citations
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Journal ArticleDOI
Sorption characteristics of lead cations on microporous organo-birnessite
TL;DR: In this article, the adsorption characteristics of modified-birnessite for removal of Pb were examined using a batch isotherm test with powder X-ray diffraction (XRD), energy-dispersive Xray spectroscopy (EDS), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) specific surface area measurements.
Book ChapterDOI
Arsenic in Soil: Availability and Interactions with Soil Microorganisms
TL;DR: In this article, the concentration of total As in soils does not necessarily represent its biological availability or potential toxicity measures, which are much more important for assessing possible environmental impacts, and soil microorganisms may be involved in As pollution issues in an active and passive way at the same time.
Journal ArticleDOI
Modeling oxyanion adsorption on ferralic soil, part 2: Chromate, selenate, molybdate, and arsenate adsorption
TL;DR: The authors were able to use the charge distribution model to accurately describe the adsorption of these 4 oxyanions and thus to determine the surface speciation, and found the highest adsorptive behavior was found for arsenate ions, whereas the lowest was finding for selenate, with chromate and molybdate ions showing an intermediate behavior.
Book ChapterDOI
Interaction between Heavy Metals and Variable Charge Surfaces
TL;DR: In this article, the adsorption mechanisms of heavy metals and their competition for adorption sites on variable charge surfaces, as well as the effects of ionic strength, pH, surface chemical properties and accompanying anions on the adaption in this type of soil are summarized.
Journal ArticleDOI
Adsorption of arsenite onto a soil irrigated by sewage
TL;DR: In this paper, the authors investigated the adsorption of As (III) on a soil irrigated by sewage, as a function of reaction time, initial As(III) concentrations, pH, phosphate, and humic acid.
References
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Journal ArticleDOI
Arsenite and Arsenate Adsorption on Ferrihydrite: Kinetics, Equilibrium, and Adsorption Envelopes
TL;DR: In this paper, the authors compared the adsorption behavior of arsenite and arsenate on ferrihydrite, under carefully controlled conditions, with regard to adaption kinetics and the influence of pH.
Journal ArticleDOI
Surface chemistry of ferrihydrite: Part 1. EXAFS studies of the geometry of coprecipitated and adsorbed arsenate
TL;DR: In this article, the As and Fe K-edges were collected from samples of two-line ferrihydrite with adsorbed (ADS) and coprecipitated (CPT) arsenate prepared over a range of conditions and arsenate surface coverages.
Journal ArticleDOI
Arsenic contamination of groundwater and drinking water in Vietnam: a human health threat.
Michael Berg,Hong Con Tran,Thi Chuyen Nguyen,Hung Viet Pham,Roland Schertenleib,Walter Giger +5 more
TL;DR: The high arsenic concentrations found in the tubewells indicate that several million people consuming untreated groundwater might be at a considerable risk of chronic arsenic poisoning.
Journal ArticleDOI
Arsenate and Chromate Retention Mechanisms on Goethite. 1. Surface Structure
TL;DR: In this paper, the authors used Extended X-ray absorption fine structure (EXAFS) spectroscopy to deduce the local coordination environment of two environmental contaminants, arsenate and chromate, on the mineral goethite (α-FeOOH).