ABSTRACT
Inorganic arsenate and arsenite are the main forms of arsenic in groundwater. They have different mobility, toxicity and bioavailability in the natural environment. It is essential to clarify whether As(III) and As(V) will compete for active sites on certain minerals in sediments. A series of laboratory batch experiments in 10 mM PIPES and 25 mM NaCl mixed solution have been carried out to study the competitive adsorption between As(III) and As(V) on aquifer sediments. The results demonstrated that arsenic is more easily enriched in organic layer, iron-aluminum oxide and clay layer deposits with large specific surface area. The amount of As(III) and As(V) alone adsorbed on sediment was approximately the same. When the As(III)/As(V) molar ratio is very high, the adsorption of As(V) on the sediment can be inhibited by As(III) and there will be a more obvious inhibition with the increasing of As(III) concentration. However, the competitive adsorption between As(III) and As(V) on sediment can be neglected when the As(III)/As(V) molar ratio is low. As(V) seems to promote the adsorption of As(III) on sediment, especially when the concentration of As(V) is low.
