Sometimes gold deposits may contain a significant amount of copper or zinc, on the recovery process they form cyanide complexes that can be dissociate into weak cyanide, and be a competitor with gold for the cyanide available in the solution. This results in a high cyanide consumption, and a possible contamination of the final product.
For these particular cases a process called SART has been developed, the name came from the acronym of the operations involved: sulfidization, acidification, recirculation of cyanide, and thickening, in this article we will see briefly how this process works.
The process begins in a precipitation reactor where the acidification and sulphidation stage take place, by the addition of sulfuric acid and sodium hidrosulfhyde, with this acidification of the solution allowing the complexes formed with cyanide and metals such as copper have a chemical rupture, and the addition of NASH allows the precipitation of metal sulfides as is the case of copper.
The solids that are generated in the reactor are thickened, filtered and dried several times to obtain copper sulphide as final product.
On the other hand, the clarified solution of the thickener overflow is mixed with the filtered solution to form the treated rich solution, this solution is sent to a neutralization reactor where its PH will be increased by the addition of milk of lime, this transforms the dissolved cyanide in calcium cyanide and the gypsum obtained will precipitate and separated in the filtering process.
The overflow of this thickener also known as gypsum thickener, as well as the filtered solution of the cake obtained from his underflow, are the final products of the SART process, the solution is sent to the circuit of leaching solutions, and the cake obtained from the filtration process is discarded.
By using this process, gold recovery is optimized, copper sulphide is obtained as a secondary product and cyanide consumption is reduced, helping to improve operating costs.
Thanks for reading, best regards.