Arsenic Removal Using a Biopolymer Chitosan Sorbent

An agricultural waste, chitosan, was converted to bead form to evaluate the feasibility of its use to remove As(III) and As(V) from water in both batch and continuous operations. In batch tests, the effect of pH, temperature, coexisting ions, and arsenic concentrations were studied. Studies of kinetic adsorption, recovery of arsenic by desorption solution, and reuse of chitosan beads were also carried out. Additionally, wastewater containing arsenic discharged from the manufacturing of GaAs supports was treated in a continuous operation. Results indicated that chitosan beads favored the adsorption of As(V), but not As(III). The optimal pH value for As(III) and As(V) removal was near 5. The insignificant difference for As(V) and As(III) adsorption by chitosan beads was found in the 25–40°C range. Ion coexistence below 50 mg/L did not affect arsenic removal. The optimal desorption solution for the arsenic recovery was H₂SO₄ with a 71% efficiency for As(V), which was amenable to efficient regeneration for multiple reuse (about 15 times). In continuous tests, the chitosan bead column exhibited excellent arsenic removal from actual wastewater without any pretreatment. The results provide strong evidence of the promise the application of chitosan bead has for arsenic removal.

Keywords:

• Arsenic
• Chitosan
• Adsorption
• Sorbent.

ACKNOWLEDGMENTS

This work was supported by Grant NSC 92-2622-E-157-006-CC3 from the National Science Council.