Response Surface Methodology for the Competitive Sorption of Metal ions from Aqueous Medium using Starch-Graft-CopolymerAuthor(s): Ekebafe LO, Ogbeifun DE, Okieimen FE and Amenaghawon AN
The competitive sorption of Cu (II), Pb (II) and Cd (II) by graft copolymer of cassava starch and acrylic acid was investigated using the response surface methodology. Optimization of the medium conditions was studied through experimental design. Response surface methodology including central composite design was successfully applied to develop a response surface to optimize the medium conditions. The most influential medium parameters were determined as initial concentration, contact time and temperature. The optimum conditions were evaluated to be 41.89 mg/l, 5.66 h, and 26.11°C, for all the ions in solution, representing the initial concentration, contact time, and temperature. At these optimum conditions, the sorption yield, sorption capacity and the coefficient of determination were evaluated as follows: for Cu (II) ions 92.05 %, 38.56 mg/l and 0.963 mg/lrespectively, for Pb (II) 66.60 %, 27.9 mg/l, and 0.941 and for Cd (II) 42.90%, 17.97 mg/l and 0.904 respectively. The sorption affinity for the metals follow the order Pb > Cu > Cd, this order suggests that electronegativity may be the most important factor as metal sorption increased with increasing electronegativity. Pb2+ sorption on the graft copolymer was competitively higher than Cd (II) and Cu (II).