Utilization of N-carboxymethyl chitosan (N-CMCh) to limit the detrimental effect of serpentine on the flotation of pyrite is presented in this work. Flotation results show that the presence of hydrophilic serpentine slimes results in lower recoveries of the valuable pyrite. Utilization of N-carboxymethyl chitosan can limit the detrimental effect of serpentine on the flotation of pyrite. Zeta potential measurements illustrate that N-CMCh is with negative charge and the electrostatic interaction between serpentine and N-CMCh is occurred at pH 8.5, then the serpentine zeta potential will be changed from positive to negative, the electro-steric attraction converts into electro-steric repulsion between pyrite and serpentine and the pyrite recovery is improved. (C) 2017 Elsevier B.V. All rights reserved.