Preparation and characterization of an organic/inorganic hybrid sorbent (PLE) to enhance selectivity for As(V)

For the selective removal of arsenate (As(V)) a hybrid sorbent was prepared using a non-toxic natural organic material, chitosan, by loading a transition metal, nickel. The immobilization of nickel was achieved by coordination with a deprotonated amino group (NH₂) in the chitosan polymer chain. The amount of nickel was directly correlated to the presence of the amino group and was calculated to be 62mg/g. FTIR spectra showed a peak shift from 1656 to 1637cm^-1 after Ni²⁺ loading, indicating the complexation between the amino group and nickel, and a peak of As(V) was observed at 834cm^-1. An increase of sulfate concentration from 100mg/L to 200mg/L did not significantly affect As(V) sorption, and an increase in the concentration of bicarbonate reduced the As(V) uptake by 33%. The optimal pH of the solution was determined at pH 10, which is in accordance with the fraction of HAsO₄ ^2- and AsO₄ ^-3. According to a fixed column test, a break through behavior of As(V) revealed that selectivity for As(V) was over sulfate. Regeneration using 5% NaCl extended the use of sorbent to up to uses without big loss of sorption capacity.