Electrorefining of high purity manganese

Abstract

Manganese is an important industrial metal used as an additive for production of various steels, non-ferrous alloys, electronic components and special chemicals. The traditional electrowinning process is not suitable for the production of high-purity manganese. Therefore, a novel ion exchange -electrorefining process for production of high-purity manganese is proposed to solve the problems.The ammonium chloride -manganese chloride electrolyte was selected as the most promising for refining. The physical properties of the electrolyte were first studied. The density increases when increasing concentrations of the ammonium chloride and manganese chloride. The maximum electrical conductivity is obtained with high concentrations of ammonium chloride and high temperature. Viscosity is minimized by high temperature and by low concentrations of manganese chloride.The electrorefining process introduces impurities into the anolyte from the dissolving anode. The purification of the electrolyte by cementation and ion exchange were investigated. This thesis reports the uptake of copper, nickel, cobalt, cadmium, zinc and manganese from manganese chloride solution onto the chelating resin Lewatit® MDS TP220 and Purolite S930Plus in batch and column experiments. The results demonstrate the ability for Lewatit® MDS TP220 to remove contaminants to an extent satisfying the quality criteria required for electrorefining. However, cementation of impurities by manganese powder and ion exchange with PuroliteS930Plus are not suitable for purification to satisfy the quality criteria.iii In the electrorefining process, the individual and synergistic effects of selected impurities on manganese deposit quality were first investigated. The purity of manganese deposit did not change significantly in the presence of impurities. An addition of 0.15-5.0 mg/l Zn 2+ to the catholyte increases the cathodic current efficiency. The parameters of current density, deposition time, and cathode usage frequency were investigated. Current density, deposition time and cathode usage frequency could affect current efficiency, specific energy consumption and surface morphology. With increasing the current density, the cathodic current efficiency first increased, reached a maximum value and then decreased. With increasing deposition time from 24 hours to 48 hours, the manganese current efficiency decreased and the deposit became more dendritic. The more times the cathode was used, the lower the current efficiency.iv

Electrochemical Approaches for the Recovery of Metals from Electronic Waste: A Critical Review

“…Moreover, the selective recovery of metals from a solution containing complex mixtures of metal species (especially in the case of e-waste) is the most difficult problem to solve because of the M n+/ M couples' close redox potentials values [85]. Thus, to ensure such desired selectivity and to obtain high purity metals, one of the more feasible strategies is first to remove some of the metal species from the considered complex solutions through chemical precipitation, solvent extraction, or ion exchange [79,[86][87][88]. Interest- Moreover, the selective recovery of metals from a solution containing complex mixtures of metal species (especially in the case of e-waste) is the most difficult problem to solve because of the M n+ /M couples' close redox potentials values [85].…”

“…Electrorefining differs from electrowinning in that now the anode of the former consists of unrefined metals containing many impurities. During the electrorefining process, the anode gets partially dissolved into the solution via its direct or indirect electrooxidation, while some of these electroleached metal ions are selectively deposited into their pure forms onto the cathode [79]. Based on this principle, some electronic waste solids/powders can be packed together (for cohesion and electrical conductivity) and used as the anode where the base metals (e.g., Cu, Zn, Sn, Ni) are oxidized, and can then be electrowinned into their purified forms at the cathode.…”

“…For instance, since Mn is an active material exhibiting a fast dissolution during anodic oxidation, it is not suitable when mixed with copper for the latter conventional electrorefining. To address this issue, some authors proposed a method combining purification and electrorefining that enable the recovery of high purity Mn at the cathode [79]. To that end, an ion exchange is first performed that removes low concentration metals ions (Cu, Zn, Co, Cd, Ni) from the anolyte.…”

Phase Equilibria of the Ternary Systems ((NH4)2SO4–MNSO4–H2O) and ((NH4)2SO4–MGSO4–H2O) at 303.15 K

“…Rapidly growing demand for manganese has made it increasingly important to develop the technology for economical recovery of manganese from manganese ores and other sources . Either pyrometallurgical or hydrometallurgical processes can produce manganese . Similarly, manganese from the water–salt system can be recovered through the crystallization industry, for example, the leachate of electrolytic manganese slag and the electrolyte in electrolysis process, etc.…”

“…There is usually magnesium ammonium in the system containing manganese, therefore, the phase equilibrium data of the two systems ((NH 4 ) 2 SO 4 –MnSO 4 –H 2 O+(NH 4 ) 2 SO 4 –MgSO 4 –H 2 O) at T = 303.15 K provide theoretical data for the crystallization process of MnSO 4 ·H 2 O and (NH 4 ) 2 Mg­(SO 4 ) 2 ·6H 2 O, and in order to better carry out the analysis of the crystallization process. There is a certain research basis for the two ternary systems . However, at different temperatures, the solubility of the solution is different, which leads to a certain difference in the division and size of the crystallization zone.…”