Diego A Nieto Monteros
Universidad Tecnica Particular de Loja, Ecuador
Title: Chemical and biological treatment of effluents containing cyanide from a gold mine
Biography
Biography: Diego A Nieto Monteros
Abstract
Cyanide is a chemical compound used per excellence for gold leaching in the mining industry. However, it is highly toxic for the environment and its organisms. This work focused on determining the optimum conditions for the degradation of free cyanide (CN-) using chemical compounds and a microbial consortium. Chemical and biological treatments were performed separately using samples of mining effluents at different CN- concentrations (280 and 10 mg CN- L-1). For chemical treatment, a factorial design 24 was developed to analyze: Three different oxidizing compounds (sodium hypochlorite, Caro’s acid and hydrogen peroxide at different concentrations), pH (10-11) and degradation times (4.71, 10.13 and 20.75 h). A rotating biological contactor was used for the biological treatment. It was operated in continuum, 16 rpm, 20±5° C and different HRT (4.71, 10.13 and 20.75 h). The alimentation flux contained: Effluent with CN- and liquid medium at pH=11. Free cyanide concentration, pH and the biomass concentration were measured. Chemical treatment results showed that the best oxidizing compound was hydrogen peroxide (8:1 g H2O2/gCN-) and pH (10) thus obtaining a 92.73% removal of CN- in 45 minutes (280 mg CN- L-1) and 91.01% removal in 25 minutes (10 mg CN- L-1). Whereas in the biological treatment, the CN- removal was 84.30% (280 mg/L CN-) and 50.49% (10 mg/L CN-) during 10.13 h. Finally, just the chemical treatment allowed to reach standard limits for CN- on both waste water samples (0.099 mg CN- L-1) according to US EPA (2000) and TULAS Ecuador (2011) (0.2 mg CN- L-1).