6533b7d8fe1ef96bd126a161

RESEARCH PRODUCT

Change of arsenite adsorption mechanism during aging of 2-line ferrihydrite in the absence of oxygen

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Abstract Arsenite was effectively immobilized by 2-line ferrihydrite at different pH values (4.0, 5.5 and 7.4) and adsorbent dosages (0.4, 1, and 2 g/L) in the absence of oxygen, showing an initial surface diffusion-controlled period (Stage I, 2 h). Dissolved δ 56 Fe increased during Stage I and decreased during Stage II, resulting from aging of ferrihydrite and equilibrium isotopic exchange, respectively. The ferrihydrite aging was hampered by both high As concentrations and high pH values close to the pH zpc , due to inhibition of mineral dissolution as a prerequisite for mineral transformation. During Stage I, As was adsorbed by both bidentate binuclear corner-sharing ( 2 C ) and monodentate mononuclear corner-sharing complexes ( 1 V ), while 2 C dominated during Stage II. At stage I, As stability was mainly controlled by As-complexation, by both mineral transformation and As complexation at stage II. It is suggested that adsorbed-As stability can be optimized by regulating As complexation and mineral phases, which are of great significance for remediation of As-contaminated groundwater.