Experimental Evaluation of the Treatment of Cyanide Effluents from a Gold Mining Company by the Taguchi Method

Abstract

Metallurgical plants processing gold minerals use cyanide solutions to dissolve gold contained in these minerals, generating effluents from contaminated tailings whose final disposal causes severe environmental impacts to aquatic ecosystems if they are not previously treated. The environmental harmfulness of these tailings effluents depends directly on the type and concentration of the chemical agents they carry, of which cyanide is the most representative and harmful to the environment. The objective of this study is to determine the effect of the variables provided by the use of various types of chemical reagents and their reaction time, used in four methods of treatment by advanced oxidation, applied to obtain a clarified effluent with a total cyanide content that complies not only with the environmental regulations but also to be able to recirculate the water and reuse it in the processes of the metallurgical plant. The experimental design applied here is done with the Taguchi approach using an orthogonal matrix L16 (43) and analysis of variance (ANOVA) to identify the effect of the parameters on the response variables. The experimental results revealed that the joint action treatment of 70 % hydrogen peroxide and 10 % sodium hypochlorite (Singlet method), supplemented with coagulation and flocculation was the most effective to achieve the proposed objective. The rest of the treatments were relatively less effective to achieve it.