Study on harmless treatment of electrolytic manganese residue by low temperature thermochemical method

The Electrolytic Manganese Residue (EMR) is a by-product of the electrolytic manganese metal (EMM) industry, containing high concentrations of potential pollutants such as NH₄⁺-N and soluble Mn²⁺. These components pose a serious threat to the ecological environment. To explore accurate, efficient, and harmless treatment methods for EMR, this study proposes a low-temperature thermochemical approach. The orthogonal experiment design investigates the effects of reaction temperature, reaction time, quicklime (CaO), sodium carbonate (Na₂CO₃), sodium phosphate (Na₃PO₄) (Reviewer #3), and water consumption on manganese solidified and ammonia removal from EMR. The results indicate that optimal conditions are a reaction temperature of 60 ℃ (Reviewer #3) and a reaction time of 10 min. CaO precipitates Mn²⁺ as manganese hydroxide (Mn(OH)₂) (Reviewer #3), achieving effective manganese solidified and ammonia removal. The addition of Na₂CO₃ causes Mn²⁺ to form manganesecarbonate (MnCO₃) (Reviewer #3)precipitate, while Na₃PO₄ makes Mn²⁺ form Manganese phosphate trihydrate (Mn₃(PO₄)₂·3H₂O) (Reviewer #3). Increased water consumption enhances the interaction adequacy between ions. Under optimal conditions (CaO 10%, Na₂CO₃ 1%, Na₃PO₄ 0.5%, and 80% water consumption), the removal rate of ammonium ions reaches 98.5%, and the solidification rate of soluble Mn²⁺ is 99.9%. The order of influence on ammonium ion removal is CaO > water consumption > Na₃PO₄ > Na₂CO₃. Therefore, this study provides a new method for low-cost process disposal and efficient harmless treatment of EMR (Reviewer #3).