A nitric acid route for processing a nickel/copper sulphide concentrate

This paper is concerned with the processing of an indigenously available pyritic sulphide concentrate for the recovery of the associated nickel and copper values by nitric acid leaching. Two different processing schemes have been investigated. In the first, the concentrate as such has been acid leached at ambient pressure in a stainless steel vessel. The influence of time, temperature, and the quantity of acid in the leaching process has been studied. Data on acid regeneration have been collected. It has been possible to achieve high recoveries of nickel and copper with acid regeneration amounting to about 60% of the total input for leaching. In the second, the concentrate after pre-roasting has been leached using a smaller quantity of nitric acid as compared with the straight leaching procedure. The influence of various pre-roasting temperatures on the leaching behaviour has been studied. High recoveries of nickel and copper have been obtained by leaching the sulphide concentrate after pre-roasting at about 450°C. Based on these results an attempt has been made to propose a flowsheet for the treatment of sulphidic resources of nickel and copper.