Arsenic(V) sorption using chitosan/Cu(OH)2 and chitosan/CuO composite sorbents

The removal of As(V) ions from aqueous solution was carried out using composite sorbents based on chitosan (as the encapsulating material) and Cu(OH)2 or CuO. The sorbents were characterized using SEM, EDX and Zeta potential analysis. Sorption uptake was highly dependent on pH, temperature, initial As(V) concentration and sorbent dosage (SD): the optimum initial pH for arsenic removal was found close to 4. The sorption isotherm was described by the Langmuir equation. The metal ion can be bound through two different sorption sites: one having a strong affinity for As(V) (probably Cu(OH)2 or CuO) and the other having a lower affinity (probably the encapsulating material). The uptake kinetics was well fitted by the pseudo-second order rate equation. The effect of temperature was also evaluated, verifying the endothermic nature of the sorption process. Arsenic elution was performed using a saline solution (30 g L−1 NaCl) at pH 12. The recycling of the sorbent was tested, maintaining a removal efficiency and a metal recovery over 95% for five successive sorption/desorption cycles.