Research on the Use of Low-Selenium Additives in the Electrodeposition of Manganese Metal and Co-production of Electrolytic Manganese

This study addresses the problems of low product purity, low current efficiency, and environmental pollution caused by the excessive use of selenium additives in the electrolytic manganese (Mn) industry.It investigates the effects of composite additives on reducing selenium (Se) usage while enhancing the quality and current efficiency of Mn products.The primary additive is an industrial minimum amount of selenious acid (H2SeO3), with sodium sulfite (Na2SO3) and sodium dodecyl sulfate (SDS) as auxiliary additives.This research explores their impact on the membrane electrowinning process.The results show that the use of composite additives significantly enhances cathodic polarization of the coating, thereby inhibiting the hydrogen evolution reaction (HER) and playing a crucial role in forming dense and smooth coatings.When Na2SO3 is utilized as an auxiliary additive, it achieves a higher current efficiency than SDS, resulting in better quality Mn deposition.With a composite additive ratio of H2SeO3 at 0.0175 g/L and Na2SO3 at 1.5 g/L, the cathodic and anodic current efficiencies reach 84.59% and 80.13%, respectively, with an acid increment of 23.88 g/L.Additionally, the voltage stands at 3.9 V, the cathodic energy consumption at 4498.02 kW h t -1 , and the anodic energy consumption at 3001.41 kW h t -1 .The Mn surface after electrolysis is smooth, with a metallic luster and uniform thickness, exhibiting α-type crystal morphology, while electrolytic manganese dioxide (EMD) appears as a powder, black in color, with uniform size and γ-type crystal morphology.Thus, the use of Na2SO3 effectively reduces Se content in composite additives, enhancing current efficiency and product quality, and provides theoretical guidance for the study of low-Se composite additives in the coelectrolysis process of EMD.