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

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 H 2 S gas generation. This study proposes a hydrogen peroxide-sulfuric acid (H 2 O 2 -H 2 SO 4 ) 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 H 2 O 2 -H 2 SO 4 leaching. In an acidic environment, sulfide ion (S 2− ) and oxygen ion (O − ) exhibit strong redox reactivity, directly converting into sulfate ion (SO 4 2− ) without generating hydrogen sulfide (H 2 S) 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. This study proposes an H 2 O 2 -H 2 SO 4 leaching process for electrolytic manganese dioxide sulfidation slag (EMDSS) and elucidates its reaction process and mechanism. In the optimized and methodological experiments, the leaching efficiencies of Mn, Ni, Co, and Zn all exceed 99.00 ​%, with no gaseous by-products such as H 2 S generated. • Valuable metals (Mn, Ni, Co, and Zn) were efficiently extracted, with leaching efficiencies exceeding 99.00 ​%. • In the acidic environment, S 2− was directly oxidized by O − to SO 4 2− , effectively preventing H 2 S generation. • The leaching mechanism of EMDSS in the H 2 O 2 –H 2 SO 4 system was systematically elucidated. • A 200 ​g scale-up experiment confirmed the process stability and its feasibility for industrial application.