Optimization of process variables for a biosorption of nickel(II) using response surface method

The biosorption of nickel(II) was studied by using crab shell particles of diameter (d p =0.012 mm) under different initial concentrations of nickel(II) in solution (0.01–5.0 g/ l ), temperature (20–40 °C), pH (2–6.5), and biosorbent dosages (0.5–10 g/ l ). The maximum removal of nickel(II) occurred at pH 6.5 and temperature 40 °C for a biosorbent dosage of 6 g/ l . The results were modeled by response surface methodology (RSM), which determines the maximum biosorption of nickel(II) as a function of the above four independent variables, and the optimum values for the efficient biosorption of nickel(II) were obtained. The RSM studies were carried out using Box-Behnken design and the analysis of variance confirms the adequacy of the quadratic model with coefficient of correlation R 2 to be 0.9999. The quadratic model fitted the data well with Prob>F to be