An environmental-friendly approach to remove cyanide in gold smelting pulp by chlorination aided and corncob biochar: Performance and mechanisms

In this study, a new process was developed using ClO− and corncob biochar (CB) combined with HAS (a stabilizer) to remove cyanide from gold smelting pulp. The Box-Behnken design was employed to optimize the doses of treatment reagents during cyanide removal. Results showed that the optimal doses of the three reagents were as follows: ClO− dose of 20 mg/g dry solid (DS), CB dose of 22 mg/g DS, and an HAS dose of is 24 mg/g DS. The cyanide concentration in the filtrate was the lowest (0.114 mg/L), with a 98.36% removal efficiency after a contact time of 2 h at 25 °C under optimized conditions. Compared with those of ClO− and HAS, it was found that the dose of biochar was the dominant factor influencing cyanide removal. Batch sorption experiments of cyanide to biochar indicated that the Langmuir isotherm model fit the sorption data, and the maximum cyanide sorption capacity was expected to be 2.57 ± 0.06 mg/g. Density functional theory (DFT) calculations (interaction energy was −74.42 kcal/mol) indicated that the adsorption peak resulted from cation-π interactions between the cyanide and CB. This study could lead to a novel environmental-friendly approach for the removal of cyanide from gold smelting pulp.