High-efficiency and green recycling of manganese, nickel, cobalt, and zinc in a hydrogen peroxide–sulfuric acid system from electrolytic manganese dioxide sulfide slag

Abstract

Electrolytic manganese dioxide sulfidation slag (EMDSS) is a hazardous waste generated during the production of electrolytic manganese dioxide (EMD), containing strategic metal resources such as nickel (Ni), cobalt (Co), and manganese (Mn), with a total content exceeding 10.00 ​%. Currently, the recovery of strategic metals from EMDSS has received limited attention, and existing methods are inefficient, accompanied by the risk of H₂S gas generation. This study proposes a hydrogen peroxide-sulfuric acid (H₂O₂-H₂SO₄) leaching process to address these challenges and recover strategic metals such as Mn, Ni, Co, and zinc (Zn) from EMDSS. Optimal process parameters were determined through single-factor and response surface optimization experiments. Thermodynamic, kinetic, and characterization analyses were conducted to elucidate the reaction process and mechanism of H₂O₂-H₂SO₄ leaching. In an acidic environment, sulfide ion (S²⁻) and oxygen ion (O⁻) exhibit strong redox reactivity, directly converting into sulfate ion (SO₄²⁻) without generating hydrogen sulfide (H₂S) gas. The 20 ​× ​magnified experiments demonstrated that the average leaching rates of Mn, Ni, Co, and Zn exceeded 99.20 ​%, with deviations between the measured and predicted values within 1.00 ​%. The proposed new process achieves over 99.00 ​% recovery of strategic metals such as Ni, Co, Mn, and Zn, providing raw materials for the subsequent resource utilization of strategic metals. Moreover, stable large-scale experimental results indicate its potential for industrial-scale application, expanding the raw material sources for Ni, Co, and Mn new energy metals.