Harmless Impact of Electrolytic Manganese Residue by Low Temperature Thermochemical Method with Carbide Slag

This study introduced a low-temperature thermochemical method for the treatment of EMR in the presence of carbide slag （CS） to achieve an economical and efficient harmless effect.The experimental results indicate that,under suitable conditions,the NH4+ and Mn2+ contents in EMR decrease notably with the increasing CS content,accompanied by an increase in pH value.Furthermore,the concentration of NH4+ in EMR considerably decreases with the increasing liquid-to-solid ratio,eventually stabilizing.Similarly,the pH value first increases and then decreases,ultimately stabilizing.At a CS content of 12% and a liquid-to-solid ratio of 0.7,the leaching concentrations of NH4+ and Mn2+ in EMR （127.7 mg/kg and 0.15 mg/L,respectively） fall below the standard detection limit （2 mg/L）,with the pH measuring 8.26,meeting the conditions outlined in the GB 8978.NH4+ is converted to NH3,while Mn2+ is transformed into solid precipitates such as Mn（OH）2,Mn2O3,MnO2,Ca3Mn2O7,and Ca2MnO4.The majority of manganese ions exist in trivalent or tetravalent states and remain stable over time.The cost of using CS as a reagent for treating 1 ton of EMR is merely $1.01.The high OH? concentration provided by CS enables the effective removal of NH4+ from EMR and the solidification of Mn2+ during thermal reactions.