Effect of Magnesium Ion on the Zinc Electrodeposition from Acidic Sulfate Electrolyte
- PDF / 615,714 Bytes
- 6 Pages / 593.972 x 792 pts Page_size
- 111 Downloads / 216 Views
RODUCTION
THE presence of impurities in the zinc electrolyte is problematic for the electrowinning process. Up to now, there have been a large number of research reports investigating the effects of various metallic impurities on zinc electrodeposition, which includes copper,[1–3] iron,[2–4] cadmium,[2] germanium,[5–7] manganese,[8,9] cobalt, nickel,[10–12] and so on. It has been reported that, although these metallic impurities have great influence on the zinc electrodeposition, most of them can be removed through the purification process. Recently, the effects of alkaline earth metals, especially magnesium ions, have increasingly attracted considerable concern; unfortunately, there is still little research to systematically investigate the effect of Mg2+ ion on zinc electrodeposition in the zinc hydrometallurgy process.[13–15] For example, Saloma and Holtan[13] pointed out that the Na+, Ca2+, and Mg2+ ions acted by an adsorption mechanism to suppress the inhibiting action of hydrogen on zinc electrodeposition. Krauss[14] found that the magnesium ion presented no cathode problems, but MgSO4 can adversely affect filtering, settling, and electrolyte conductivity. Mackinnon and Brannen[15] concluded that the current efficiency (CE) was a small increase with increasing MgSO4 concentration to 20 g L1 and this was accompanied by a change in the preferred deposit orientation from intermediate to basal. A further increase in the MgSO4 concentration resulted in a small decrease in CE, and the preferred
deposit orientation reverted to intermediate. However, their conclusions were incomplete due to earlier research. With the cycle of electrolyte, magnesium ion continuously accumulated and reached some extent. Its effect on zinc electrodeposition is very serious. It can increase viscosity of electrolyte and decrease electrical conductivity of electrolyte, and then increase power consumption (PC) and decrease CE.[14] Moreover, MgSO4 can adversely affect filtering and obstruct pipeline due to its crystallization. So, the objective of this research was to study the effects of Mg2+ on zinc electrodeposition concerning the CE, PC, morphology, cathodic polarization, and so on.
II.
EXPERIMENTAL
A. Materials and Instructions The zinc electrolyte used in this study was prepared with analytical reagent (AR) ZnSO4Æ7H2O and industrial sulfuric acid (H2SO4 98 pct). The desired electrolyte was obtained by adding MgSO4Æ7H2O (AR) to the base electrolyte (the zinc ion concentration of 60 g L1 and H2SO4 concentration of 150 g L1). Experimental instruments mainly were the Gamry PC14/300 (Gamry, Warminster, PA) and EPMA-1600 electron probe (Shimadzu, Tokyo, Japan). B. Electrolysis
LIN TIAN, GANG XIE and RONG-XING LI, Professors, and XIAO-HUA YU, Lecturer, are with the Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, P.R. China. Contact e-mail: [email protected] GUI-SHENG ZENG, Professor, is with the School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 3300
Data Loading...
