Optimization Study on Modified Starch Flocculants Conditions for Wastewater Treatment with Response Surface Methodology

The flocculant was synthesized by graft copolymerization of corn starch and acrylamide. The fourier transform infrared spectroscopy was used to characterize and analyze the flocculant structure. On the basis of single factor experiments, Response surface methodology (RSM) was employed to optimize the response variable (the COD removal rate) by varying flocculant dosage, the time and pH of flocculation process. The results indicated that flocculant was successfully synthesized. In the range studied, time and pH were the most significant variables affecting COD removal rate. The two main relative affecting fators of these variables for the COD removal rate were flocculant dosage and pH. Based on statistical analysis, the COD removal rate model proved to be highly significant with very low P-values (<0.0001) and R-2 was 0.9884, the optimal control parameters were determined as follows: flocculant dosage was 0.50 g/L, time was 40 min and pH was 9.7, the predict value was 89.31%. The experimental value of the COD removal rate was 87.24% under the optimum conditions, the relative error was 2.31%, and the experimental value was consistent with the predicted value.