Arsenic−Bicarbonate Interaction on Goethite Particles

• Published in: Environmental science & technology Vol. 41; no. 16; pp. 5620 - 5625
• Main Authors: Stachowicz, Monika, Hiemstra, Tjisse, van Riemsdijk, Willem H
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.08.2007
• Subjects: Adsorption; Applied sciences; Arsenic - analysis; Arsenic - chemistry; Arsenic content; bangladesh groundwater; Bicarbonates - chemistry; carbonate adsorption; Carbonates - chemistry; charge-distribution; competitive adsorption; dissolved carbonate; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environment; Exact sciences and technology; Geochemistry; Groundwaters; Hydrogen-Ion Concentration; ion adsorption; Iron Compounds - chemistry; metal (hydr)oxides; Mineralogy; Minerals; Models, Chemical; Natural water pollution; Pollution; Pollution, environment geology; ray-absorption spectroscopy; Research methodology; Sediment transport; Silicates; solution interface; Solutions; surface structural approach; Water geochemistry; Water treatment and pollution; Iron oxide; Arsenic; Arsenates; Liquid solid adsorption; Competitive reaction; Environmental factor; Desorption; Arsenites; Hydrogencarbonates; Aquifers; Biogeochemistry; Hydrochemistry; Water quality; Pollution source; pH; Water pollution; Goethite; Ground water
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es063087i

The As(V) and As(III) interaction with HCO3 has been studied for goethite systems using a pH and As concentration range that is relevant for field situations. Our study shows that dissolved bicarbonate may act as a competitor for both As(V) and As(III). In our closed systems, the largest effect of bicarbonate occurs at the lowest experimental pH values (pH ∼6.5), which is related to the pH dependency of the carbonate adsorption process. The experimental data have been modeled with the charge distribution (CD) model. The CD model was separately parametrized for goethite with “single ion” adsorption data of HCO3, As(III), and As(V). The competitive effect of HCO3 on the As(III) and As(V) release could be predicted well. Application of the model shows that the natural As loading of aquifer materials (∼ <0.01−0.1 μmol/m2 or <1−5 mg/kg) is at least about >1−2 orders of magnitude smaller than the As loading based on the competition of As−HCO3 alone. It indicates that another, very prominent competitor, like phosphate and natural organic matter, will strongly contribute to the control of As in natural systems.