Enhanced removal of Pb2+ from aqueous solution using modified extracts from food processing wastes: design of experiments

ABSTRACT The biosorption of lead from aqueous solution on chitosan and modified chitosan from crab shells was investigated. Response surface methodology (RSM) was employed to optimize the process parameters. Based on central composite design, a quadratic model was developed to correlate the process variables to the response. The most influential factor on each experimental design response was identified from the ANOVA. The optimum conditions for the biosorption of lead were found to be as follows: pH: 10, temperature: 55 °C, sorbent dosage: 2 g, metal concentration: 50 mg/L and contact time: 150 min. At these optimized conditions, the maximum removal of lead by the chitosan and modified chitosan was found to be 84.38% and 89.83%, respectively. From the analysis, the model's coefficient of determination (R2) (of 0.84 and 0.87, respectively, for chitosan and modified chitosan) and F-values (of 14.01 and 17.25, respectively, for chitosan and modified chitosan) obtained proved that the experimental design model is adequate and can be used to navigate the design space. The sorbents were characterized using FTIR, SEM, DSC and XRD. The Freundlich and Lineweaver–Burk isotherm model well expressed the lead biosorption onto the studied sorbent. The metal biosorption onto the sorbents correlated well with the pseudo-second-order kinetic model.