Adsorption of As^III, As^V and dimethylarsinic acid onto synthesized lepidocrocite

Abstract

The trapping of arsenic by zero valent iron is strongly dependant on iron by-products. Among these, lepidocrite has been scarcely studied. In this work, we studied the adsorption of two inorganic (As^III, As^V) and one organic (dimethylarsinic acid, DMA) arsenic species onto lepidocrocite. pH influence was considered in the range 5 to 9, which corresponds to natural water pH. Langmuir model was used to simulate As adsorption isotherms. Our results showed that lepidocrocite offers high adsorption capacities: up to 0,25, 0,41 and 1 mol for As^V, DMA and As^III could be respectively trapped per kilogram of zero-valent iron. pH influence varied from one arsenic species to another: increasing pH improve As^III and DMA sorption whereas it has a very low effect on As^V sorption.

Keywords:

• Sorption
• iron oxide
• inorganic and organic arsenic species
• pH

Acknowledgments

This work was financially supported by the Project “COBIAS” of the French Research Agency (ANR PRECODD 2007) and the “Conseil Régional du Limousin.” The authors thank Pr. J.-C. Bollinger for his useful comments.