Effect of sodium alkyl sulfates on electrodeposition of manganese metal from sulfate solutions in the presence of sodium metabisulphite

Abstract

Electrodeposition of manganese in the presence of selenium compounds results in high current yield. However, selenium compounds are environmentally toxic and hence their use in manganese electrodeposition should be controlled. The main objective of the present study was to avoid the use of selenium compounds during electrodeposition of manganese without compromising with quality and current yield. Thus in the present study electrolytic manganese metal (EMM) has been produced from aqueous manganese(II) sulfate solutions in the presence of sodium alkyl sulfates (SAS) as organic additives. The alkyl sulfates used in the present study are sodium octyl sulfate (SOS), sodium lauryl sulfate (SLS) and sodium tetradecyl sulfate (STS). It was found that addition of SOS at a concentration of 20 mg.L-1 was most effective in increasing the cathodic current efficiency from 59% to 67% and in presence of 10 mg.L-1 SLS 63.5% cathodic efficiency was obtained. Further in presence of these additives bright and smooth manganese deposits were resulted. It was also observed that increase in alkyl chain length in the additives used in this work affected the deposit morphology and current yield adversely, however in all the cases alpha-manganese with (330, 411) as the most preferred plane of orientations were produced. Polarization of cathode takes place in presence of all the organic anionic additives used in the current study and the degree of polarization increases with increase in concentration and chain length of additives.