Optimizing Cd2+ adsorption performance of KOH modified biochar adopting response surface methodology

Chemical modification can enlarge biochar yield and increase its Cd adsorption capacity, so as to reduce production cost of the biochar and add its value. To efficiently use banana waste for preparation of biochar, response surface methodology based on central composite design (RSM-CCD) was used to establish a quadratic model of Cd adsorption capacity and yield in the present study. Analysis of variance (ANOVA) was used to examine accuracy and fitness of the models. The efficacy of variables and their interaction was illustrated by 3D surface plots and contour maps. The desirability function was used for multi-objective optimization to obtain the maximum Cd adsorption capacity and the maximum biochar yield simultaneously. The optimal parameters were 1.33 mol L−1, 721 ℃, 76 min. Under the conditions, the biochar yield ratio and Cd adsorption capacity were 36.41% and 480.94 mg g−1, respectively. The experimental results were consistent with the predicted results, which further verified the accuracy and fitness of the model. The results could provide the optimal process conditions and guidance for design and manufacture of biochar in the future.