Addressed is the effect of heat treatment on the dissolution behavior of zinc, cadmium and nickel from Cd-Ni zinc plant residues. The proposal was considered for possible positive effect of heat treatment on the separation of nickel present in the residue, due to some phase transformations. The leaching experiments were carried out with the heat-treated residues at identical leaching conditions. The residues were heat treated at 100-1000 degrees C for 1 h and water-leached after subsequent cooling down to the room temperature. The results obviously showed that the heat treatment necessarily reduces the dissolution of zinc but does not affect the dissolution of cadmium. However, the recovery of nickel was increased by 83.80% upon the temperature increase from 25 to 800 C, whereas at temperatures above 800 C, the recovery of nickel did not change. This work offers a possible vehicle for the separation of nickel from the residues. The increase in nickel dissolution was attributed to the formation of water-soluble nickel sulfate which was further verified by the XRD detection. (C) 2010 Elsevier B.V. All rights reserved.