The adsorption of CN on sphalerite (1 1 0) surface and the effects of lattice impurities on the surface adsorption have been investigated using density-functional theory (DFT). The results show that CN adsorbs strongly on perfect sphalerite (1 1 0) surface, where C atom and N atom of CN molecule are bonding with two Zn atoms on the surface. The presence of Fe/Mn/Cu-impurity on sphalerite surface was shown to enhance the CN adsorption, however; Cd impurity worked in the opposite. The adsorption mode of CN on defective surfaces is mainly via C atom interacting with the impurity atom, and s orbital of C interacts with sp orbital of Fe/Mn/Cu to form the covalent bond, and d orbital of Fe/Mn/Cu donates electrons to the anti-bonding p orbital of C to form the back donating it bonding. While on the Cd-bearing surface, Cd 4d orbital donates fewer electrons to the vacant pi(2p)* of C. and thus no back donating pi bonding appears and the adsorption of CN on Cd-bearing sphalerite surface is weak. The simulations of CN adsorption show that Fe-bearing sphalerite could be easily depressed by cyanide, while Cd-bearing sphalerite is difficult to be depressed by cyanide. (C) 2010 Elsevier Ltd. All rights reserved.