Preparation of mercaptoacetyl chitosan and its removal performance of copper ion and turbidity

In order to extend the application range of natural polymer flocculants chitosan (CTS), the macromolecule flocculant-mercapto-acetyl chitosan (MAC) which traps heavy metals was prepared by amidization reaction with CTS and L-cysteine. The optimum preparation conditions of the MAC were investigated through orthogonal experiment and its performances on removing copper ion and turbidity at different conditions were tested. The experimental results show that: (1) The optimal preparation conditions of MAC are as follows: the mass ratio of m(chitosan):m(mercaptoacetic acid) is 1:2, pH value is 4.5 and the reaction time is 2.5 h. (2) Compared with CTS, MAC has better water solubility and higher efficiency for removing copper ions and turbidity. The removal rate of Cu2+ is promoted by the presence of coexisting cations. (3) With pH value increasing the removal efficiency of Cu2+ by MAC is enhanced. However, the influence of the pH value to turbidity is not significant. (4) The removal efficiencies of heavy mental ions and the turbidity are greatly promoted by the cooperation effects for the water sample containing heavy metal ions and turbidity causing substances. The maximum removal rate of turbidity is up to 100%.