Destruction of cyanide and thiocyanate ions by bacterial and chemical methods

Abstract

This article deals with the destruction of cyanide and thiocyanate ions by bacterial and chemical methods. Adsorption with granulated activated carbon and oxidation with sodium pyrosulfite in the presence of a copper sulfate catalyst were used as methods of chemical destruction. The bacterial method of destruction was carried out using the bacterial consortium Agrobacterium tumefaciens AC-1, Agrobacterium tumefaciens AC-2 and Pseudomonas sp. AC-3. The control solutions were placed under identical conditions without the addition of any reagent. Sodium pyrosulfite was effective reagent at removing cyanide ions with 97 % efficiency in 1–1.5 hours, while the bacterial consortiumwas the most productive against thiocyanate ions, resulting 99 % removal at 120 hours. Thus, the significant amount of cyanide ions has been removed chemically in the first stage, to reduce the effect of high cyanide concentrations on the bacterial process. In the second stage, the cyanide ions have been removed until the MPC levels. In addition, thiocyanate ions were neutralized completely. Model experiments with technological solutions from the gold mining plant were carried out. According to the results of the studies, the respective degrees of bacterial destruction of CN- and SCNare 99 % and 99.9 %. The residual concentration of CN- and SCN-ions in the treated solution was ≤0.1 mg/l and ≤ 4 mg/l, respectively. These amounts correspond to the maximum permissible concentrations approved in the Republic of Kazakhstan and CIS countries.