CA2152770A1 - Process for treatment of volcanic igneous rocks to recover gold, silver and platinum - Google Patents

Abstract

The recovery of gold, silver and platinum group metals from volcanic cinders containing iron is achieved by mixing the cinders with a suitable flux, and metallic copper, and smelting the mixture at a sufficiently high temperature to produce a molten mass of metal containing iron and copper, and a molten slag. The molten slag is separated from the molten metal mass by a suitable means. The slag is discarded and the metal mixture is cooled to a solid state. The copper and iron are then dissolved in acid, leaving an undissolved portion which can then be separated from the resulting leach liquor by filtration. Alternatively, the iron and copper bearing metal can be cast into an anode and electrolyzed in a sulfuric acid solution where copper is deposited at the cathode and iron is put into solution as iron sulfate. The insoluble residue at the anode can be recovered from the sulfuric acid solution by filtration. The filtered solids from either acid dissolution or electrolysis contain a significant amount of the gold, silver, and platinum group metals that were present in the original ore. These solids can then be processed by well known technology to recover their gold, silver, and platinum group metal content in essentially pure form. The solution which contains most of the silver can be treated by conventional means to recover that metal. With electrolysis copper is recovered as a cathode deposit. With acid dissolution copper can be recovered by other conventional methods. With either method copper can be recycled to the process.