Adsorption of aurocyanide complexes onto carbonaceous matter from preg-robbing Goldstrike ore

Abstract

Aurocyanide complex adsorption by naturally occurring carbon in Goldstrike ore has been implicated in a form of gold refractoriness known as “preg-robbing”. The aim of this work was to establish a relationship between the aurocyanide uptake capacity of Goldstrike ore carbonaceous matter and the preg-robbing behavior of the parent ore. The effect of varying contact time between the aqueous gold–cyanide and the carbonaceous matter on the uptake of aurocyanide complexes was also investigated. In column adsorption experiments, the adsorbed gold concentration from 100 mL of a gold–cyanide solution depended on the flow rate of the solution. The concentration of adsorbed gold increased with solution flow rate, reaching a maximum concentration at a flow rate of approximately 0.05 mL/min. As solution flow rate increased to more than 0.05 mL/min, the concentration of gold adsorbed on the carbon decreased. Desorption of adsorbed gold into 75-mL sodium cyanide solution also depended on solution flow rate. Maximum desorption of gold occurred at a flow rate of approximately 0.14 mL/min. The gold adsorbed at the lowest and highest flow rates was more slowly desorbed than the additional gold adsorbed at the intermediate flow rates. The concentration of gold remaining on the carbon after desorption at 0.14 mL/min correlated to the amount of gold adsorbed at the highest and lowest flow rates in the adsorption experiments. This amount of slowly desorbed gold correlated to the preg-robbing behavior of the ore, whereas the amount of additional adsorbed gold (i.e., gold adsorbed at intermediate flow rates) was similar for all of the ores. For all of the carbonaceous matters studied, the concentration of gold sorbed in both batch and column experiments increased after autoclaving.