Biosorption of Cu2+, Pb2+, Cd2+ and their mixture from aqueous solutions by Michelia figo sawdust.

The study aimed at investigating copper, lead, and cadmium removal from both single and mixed metal solutions by Michelia figo (Lour.) Spreng. wood sawdust treated with 0.5 mol l-1 NaOH for four hours. In order to evaluate the effects of each factor and interactions between factors on metal ion biosorption, a 23 factorial experimental design was applied. FTIR results showed that the metal ions would bind to the hydroxyl and carboxyl groups of M. figo wood sawdust biomass. The main effects and interactions of three factors pH (3 and 5), initial metal ion concentration (C0, 0.157 and 1.574 mmol L-1), and dosage of biomass (D, 4 and 10 g L-1) at two levels were analyzed. The most significant variable regarding Cu2+ and Pb2+ biosorption was initial metal iron concentration. For Cd2+, pH was found to be the most significant factor. The maximum removal efficiencies were 94.12 and 100% for Cu2+ and Cd2+, respectively, at conditions of (+ 1, - 1, + 1): pH 5, initial metal concentration 0.157 mmol L-1 and dosage of biomass 10 g L-1, while 96.39% for Pb2+ at conditions of (- 1, - 1, + 1): pH 3, initial metal concentration 0.157 mmol L-1 and dosage of biomass 10 g L-1. There were some interactions between factors: pH*C0 and C0*D for Cu2+, pH*C0, pH*D and C0*D for Pb2+, pH*C0 and C0*D for Cd2+. Biosorption from a multi metal system showed that the presence of Cu2+ and Cd2+ had no significant influence on the Pb2+ removal, while Pb2+ in solution significantly decreased the removal efficiencies of the other two metals.