Study On Compound Additive Of Electrolytic Manganese

At present, SO₂ and SeO₂ were both widely used as additives for electrolytic manganese at home and abroad. When SO₂ was used as electrolysis additive, the purity of products was satisfactorily high (Mn>99.9%). However, sulfur contained in products was the main impurity (Se≈0.04%), and the current efficiency was lower than 65%. When SeO₂ was used as electrolysis additive, although the current efficiency was 75% or so, the purity of products was low (Mn≤99.8%). At the same time, SeO₂ has some fetal drawbacks, and it's virulent inorganic agent. Therefore, the single additive (SO₂ or SeO₂) will be difficult to meet the development of electrolytic manganese industry and implement energy saving & Emission Reduction policy.In this study, four kinds of compound additive for electrolytic manganese which were beneficial for improving the current efficiency and reducing selenium content in manganese products were successfully invented. The effect and mechanism of these additives were investigated. The effect was validated in manganese factory. The main content of the dissertation are as follows:(1) SeO₂ was used as the main additive with minimal dosage of plants, while compound TJA, TJB, TJC and TJD were invented as auxiliary additives based on the existing production process. Elementary selecting the additives by simulating the industry process in organic glass electrobathes. The results show that the ideal dosage of TJA, TJB, TJC, TJD is 5 mg·L^-1, 0.2 g·L^-1, 1.0 mL·L^-1, 1m g·L^-1, respectively, while the dosage of SeO₂ is fixed at 0.03 g·L^-1.(2) Electrochemical measurements including Cyclic Voltammeter (CV) and Linear Sweep Voltammetry (LSV) techniques were carried out to investigate the mechanism of the compound additives. The results show that the auxiliary additives made the reduction potential of Mn²⁺ become more positive. The surface status of the cathode manganese was observed by SEM, and the crystallization of it was investigated by XRD. The SEM micrographs of Mn obtained in presence of these additives show all large coarse clusters. XRD patterns corresponding to the manganese deposits obtained in the presence of these additives show that the crystal structure of manganese deposits are allα-Mn, the crystal structure of deposits remains essentially unchanged with these different additives. Considering all these effects of the compound additives, the mechanism of them is suggested as"ψ1 effect"and"Selected Adsorption". (3) In order to fit realistic industry produce, SeO₂-TJA, SeO₂-TJB and SeO₂-TJC were put into industry process. The results show that the three compound additives have better performance than the additive which is actually used in the plant, and SeO₂-TJA is the best.