Innovative co-treatment technology for effective disposal of electrolytic manganese residue

Abstract

Electrolytic manganese residue (EMR) stockpiles contain significant amounts of Mn²⁺ and NH₄⁺-N which pose a risk of environmental pollution. For EMR safe disposal, an innovative approach is proposed that involves direct sodium silicate-sodium hydroxide (Na₂SiO₃-NaOH) collaborative technology. This approach utilises Na₂SiO₃ and NaOH as the solidifying agent and activator, respectively, to treat EMR without hazardous effects. The study also provides insights into the kinetics of Mn²⁺ leaching under the effect of Na₂SiO₃-NaOH. Leaching efficiency was determined by varying parameters such as stirring rate, reaction temperature, pH of the initial solution, Na₂SiO₃ concentration, and reaction time to investigate the efficacy of this method. The study indicates that the co-treatment technology of Na₂SiO₃-NaOH can achieve maximum solidification efficiencies of 99.7% and 98.2% for Mn²⁺ and NH₄⁺-N, respectively. The process can successfully solidify Mn²⁺ by synthesising Mn(OH)₂ and MnSiO₃ in an alkaline environment under optimal conditions including stirring rate of 450 rpm, initial solution pH of 8, test temperature of 40 °C, test time of 420 min, and Na₂SiO₃ content of 5%. The findings of this study have confirmed that surface chemistry plays a vital role in regulating the test rate and the proposed equation accurately describes Mn²⁺ leaching kinetics. Overall, the co-treatment technology involving Na₂SiO₃-NaOH is a viable solution for EMR resource utilisation without compromising environmental safety. This method has the potential to be implemented for other waste streams with comparable compositions, ultimately promoting the sustainable management of waste.

Keywords: Electrolytic manganese residue; Environmental pollution; Harmless disposal; Leaching kinetics; Synergistic technology.