Gold Cementation by Dendritic Zinc Powders in Percolation Mode

Abstract

In present article gold cementation features from cyanide solutions using dendritic zinc powders are studied. The powders were obtained by electroextraction from alkaline solutions. Powders with different physical properties were obtained by means of change in current density (from 0.5 to 2 A/m2) and NaOH concentration in solution (from 100 to 400 g/dm3) at the constant zinc concentration (10 g/dm3). The physical properties of mentioned powders were studied using SEM (Jeol JSM-6390LA), BET (Gemini VII 2390) and laser diffraction (Sympatec HELOS & RODOS). It is shown that electrolytic powders have high specific surface area, which is 1.8–2.6 times larger than the surface area of ​​the zinc powder currently used for cementation. At that electrolytic powders particle size is 8-22 times larger than the particle size of powder currently used for cementation. The reason of high specific surface area is the electrolytic zinc powders dendritic structure. It was found that the obtained powders precipitate gold from cyanide solutions with a greater efficiency in a wide range of productivity. Laboratory unit simulating Merrill-Crow technology was used for cementation. Immediately ahead conducting the experiments, Na2SO3 was added to the solution in excess to remove dissolved oxygen. Zinc powders were plated by dendritic lead before loading into the laboratory setup by cementation. Lead was added as acetate (Pb (CH3COO)2). The consumption of lead acetate was 10% by weight of zinc. Correlation between the powders physical properties and the gold extraction is shown.