Enhanced copper cyanide complex precipitation using polymer-surfactant aggregates

Precipitation of metal cyanide complexes using quaternary ammonium salts has been used in cyanidation so-lutions after gold leaching. Due to the high residual load of metal cyanide complexes and ammonium salts, this method does not apply to effluents containing moderate or low cyanide concentrations. To overcome these limitations, in this study, we introduce poly(sodium 4-styrenesulfonate) (PSS) into a solution containing cetyl-trimethylammonium bromide Sinpharm (CTAB), to form polymer-surfactant aggregates (PSAs) and enhance the removal efficiency of Cu and TCN. 93.8% and 97.0% of Cu and TCN, respectively, were removed from the syn-thetic solution (Cu 0.5 mM and CN 1.5 mM) under optimum dosage of 150 ppm PSS and 0.8 mM CTAB, resulting in 92.2% of substrate usage. The addition of 3.0 mM CTAB without PSS resulted in only 46.3% of substrate usage, even though the removals of Cu and TCN were 92.2 and 93.6%, respectively. The presence of thiocyanate ions significantly reduced the removal efficiency due to the competitive interaction with PSAs, whereas the pH of the solution and the temperature did not have any noticeable impact. Tests performed with an industrial effluent corroborated the results obtained with synthetic solutions: PSAs react with copper cyanide to form a precipitate that can be separated from the solution.

Automated summary

The precipitation of metal cyanide complexes using quaternary ammonium salts is not suitable for cyanide effluents with low or moderate concentrations. To overcome this limitation, this study introduces PSS into a solution containing CTAB to enhance the removal efficiency of Cu and TCN. The addition of PSS and CTAB resulted in high removal rates for Cu and TCN, while the presence of thiocyanate ions reduced the removal efficiency. Industrial effluent tests confirmed the effectiveness of PSAs in removing copper cyanide.