Abstract:A novel macromolecule chelating-flocculant dithiocarboxyl chitosan (DTCTS) was synthesized by grafting a dithiocarboxylic group onto chitosan. Taking removal rate of Cd (Ⅱ) in water samples as the main indicator, the optimal conditions for preparing DTCTS were investigated with central composite design and response surface methodology (RSM) based on single-factor experiments. A quadratic polynomial regression model was established to predict the removal efficiency. The results showed that the regression of this model was significant while the lack of fit was not significant. The determination coefficient (R2) was 0.9829, which demonstrated the model had good agreements with experimental data. Determined by optimized response surface, the optimum conditions for the preparation of DTCTS were as follows: the molar ratio of CTS/CS2/NaOH was 1:1.5:2, pre-reaction time was 30min, and main-reaction temperature was 60℃. Under the optimum conditions, the removal rate of Cd(Ⅱ) could be reached 99.52%. The relative deviation between experimental and predicted value was only 0.05%, which proved the model was reasonable and feasible.