Cellulose/chitin beads for adsorption of heavy metals in aqueous solution

We successfully prepared the biodegradable cellulose/chitin beads by coagulating a blend of cellulose and chitin in 6 wt% NaOH/5 wt% thiourea aqueous solution with 5 % H2SO4 as coagulant, and investigated the adsorption of heavy metals (Pb2+, Cd2+, Cu2+) from an aqueous solution on the beads by atomic absorption spectrophotometer. Batch adsorption experiments were carried out as a function of ion concentrations, initial pH, ionic strength, temperature, adsorption time and desorption time. The results revealed that the cellulose/chitin beads could adsorb effectively Pb2+, Cd2+ and Cu2+ ions, and the uptakes of Pb2+, Cd2+ and Cu2+ ions on cellulose/chitin beads were 0.33 mmol/g at pH0 4, 0.32 mmol/g at pH0 5 and 0.30 mmol/g at pH0 4, respectively. Experimental results also showed that the adsorption of these heavy metals was selective to be in the order of Pb2+>Cd2+>Cu2+ in a low ion concentration solution. The adsorption equilibrium time of these heavy metals on beads was 4–5 h, but the desorption time was 5–15 min.Moreover, these beads could be regenerated up to about 98% by treating with 1 mol/L HCl aqueous solution. The mechanisms for the removal of free heavy metal ions by cellulose/chitin beads was based on mainly complexation adsorption model, as well as a affinity of hydroxyl groups of the materials on metals. Therefore, we developed new environment-friendly beads prepared by a simple produce process for removal and recovery of heavy metals.