Sulphur and sulphur dioxide for separating copper from nickel-cobalt-copper sulphate solutions



In hydro-metallurgical processes for the production of nickel and cobalt, the leach solutions usually contains salts of nickel, cobalt and copper. To recover high purity nickel and cobalt metals from such solutions, the copper is removed prior to the nickel-cobalt separation.

During the course of extensive investigations to determine the most economical and efficient methods for separating the copper, it was established that copper in solution reacts with elemental sulphur in the presence of sulphur dioxide forming a copper sulphide precipitate. This reaction permits a simple and quantitative separation of copper from nickel and cobalt leach solutions.

The variables affecting this reaction were studied and the results are presented in this paper. Studies were conducted on: the sulphur concentration between 0 to 2.0/1 molar ratio of sulphur to copper, the sulphur dioxide concentration 0 to 17 gpl., the temperature in the range from 100°F. to 325°F., the copper concentration from 1 to 30 gpl. and pH from 1.0 to 9.0.

The results are correlated and a tentative mechanism for the reaction is discussed.