Patent ID: 7799114
Filing Date: 2010-09-21
Classification: C22B,Y02P

Abstract:
1. A method for recovering gold from an essentially copper-free leaching residue or intermediate containing iron and sulphur, which is generated in an atmospheric chloride leaching process of copper sulphidic raw material, comprising leaching gold from the residue or intermediate by: contacting the residue or intermediate with an aqueous solution of copper (II) chloride and alkali chloride at atmospheric pressure to form a suspension; introducing an oxygen-containing gas to the suspension; maintaining the oxidation reduction potential of the suspension to a maximum value of 650 mV vs. Ag/AgCl electrode; adding alkali bromide to the suspension in an amount such that the amount of dissolved bromide ions in solution the suspension is 0.5-30 g/L; maintaining the pH of the suspension at a value of 0.5-2.5; and recovering the leached gold, and an undissolved precipitate formed in the gold leaching stage comprising waste sulphur and iron; wherein said recovering an undissolved precipitate comprises: filtering and water washing the undissolved precipitate to obtain a filtrate wherein the filtrate and wash water contain an amount of bromide that is 0.5-10% of the total amount of dissolved bromide ions in the suspension; and oxidizing the filtrate and wash water in an oxidation stage of a copper sulphide concentrate leaching process, whereby bromide in the filtrate and wash water is oxidized into bromine gas by means of chlorine gas; recovering the resulting bromine gas by a scrubber in the oxidation stage; and recirculating a washing fluid of the gas scrubber containing said bromine gas to the gold leaching stage.