Removal of As(V) and As(III) from aqueous solution using hydrous ceric oxide

Removal of As(V) and As(III) from water using hydrous ceric oxide, CeO2 center dot xH(2)O (HCO) was investigated under different pH and As loading conditions, using batch equilibrium adsorption and FTIR methods. Adsorption of both As(V) and As(III) anions was virtually independent of pH and up to 100% removal can be achieved in the lower concentration range 0.5 - 5.0 mg L-1 As at sorbent dosage of 1.0 g L-1. As the initial As concentration increased to 50, 100 or 250 mg L-1 for the same sorbent dosage, distinct adsorption maxima of As(V) appeared and shift to lower pH, whereas that of As(III) was found at approximately pH 8. The effect of contact time was dependent on pH but adsorption equilibriums were reached after 6 h in all cases for the studied systems. The isotherms fit well in the Langmuir model of adsorption. Both As(V) and As(III) anions were adsorbed on HCO principally by forming inner-sphere complexes as revealed by the FTIR spectra.