Arsenic (V) Adsorption and Transport in Sediments As a Function of pH.

Arsenic (V) in drinking water is a health/regulatory concern above the 10?g/L level. Arsenic adsorption onto soils and subsurface materials via infiltration ponds is being considered as an inexpensive ground water remediation method for reducing As (V) concentrations to below the drinking water limit in ground water. Arsenic (V) adsorption was determined in batch studies as a function of solution pH and As solution concentration. Arsenic adsorption was described using an inner sphere adsorption mechanism in the constant capacitance model. We also conducted laboratory column transport studies to evaluate As (V) mobility at pH 6 and pH 8 on three materials, at input As (V) concentrations of 30 and 300 ug/L. After 50 pore volumes As (V) concentrations remained at the baseline level of 2 ug/L for all but the coarsest material at pH 8, where the output concentrations from the 300 ug/L As water rose relatively rapidly from the baseline to 6 ug/L after 47 pore volumes. The breakthrough curves indicate strong adsorption, affinity but limited adsorption capacity on the coarse material. These results are consistent with very strong affinity observed in the batch adsorption studies.