Zinc Electrowinning Al-based Pb-wc-zro <sub> 2 </ Sub> Composite Electrode Material

In this paper, study status of inert anode for zinc electrowinning is systematically summarized, firstly. According to different base material, the lead-base alloy anode and dimensionally Stable Anode(DSA) are elaborated. At present, anode material, which has widely application in zinc electrowinning, is Pb-Ag(lwt%) alloy. Although it can basically meet needs of industrial production, there are still some shortcomings, as follows: high potential of oxygen evlution, high energy consumption, low mechanical strength and so oa One of key ways to solve these questions is to seek novel anode material with outstanding function.Process of composite electrodepositing Al/Pb-WC-ZrO₂ composite electrodes is studied in this paper, Al/Pb-WC-ZrO₂ composite electrodes are obtained, possessing better electrochemic performance. By means of PARSTAT2263 electrochemic synthesis instrument, EPMA-1600 electron probe as well as 3015-type X-ray diffractometer and so on, electrochemic performance, surface chemistry composition, surface morphology, phase structure of composite electrode material are studied.Through the orthogonal experiment, effects of solid particle concentrations and process conditions on potential of oxygen evlution, a value and exchange current density(i⁰) of coatings are studied and analyzed, and optimum process conditions of composite electrodepositing Pb-WC-ZrO₂ are determined as follows: WC 50g/L, ZrO₂ 40g/L, temperature 20℃, current density 1.5A/dm², plating time 1.5h. Moreover, through the condition experiment, effects of solid particle concentrations and process conditions on surface chemical composition and stable-state polarization curve of oxygen evolution of coating are analyzed, and process conditions above are optimized. The optimized process conditions are shown as follow: WC 50g/L, ZrO₂ 40g/L, temperature 20℃, current density 1.5A/dm², plating time 2h. In these conditions, kinetic parameters of oxygen evlution of coating are shown as follow: a 771mV, b 140mV, i⁰ 3.11×10^-6A·cm^-2 and η 1009mV. In addition, WC and ZrO₂ contents in composite coatings are ±10.02wt% and ±3.55wt%, respectively.Additionally, electrochemic property, composition and others properties of coatings prepared in composite bath above containing silver and CeO₂ solid particle are researched. Study shows that, when Ag concentration and CeO₂ concentration is at 3-4g/L and 10-20g/L, respectively, composite elrctrodes possessing better catalytic activity of oxygen evolution are obtained, kinetic parameters ofoxygen evolution are shown as follow: a 680mV, b 186mV, i° 2.21><104A-cm"2, r\ 996mVand a 792mV, b 121mV, i° 8.92xlO"7A-cm'2, r| 996mV, respectively. In these condition, WC, ZrO2 and Ag contents of Al/Pb-WC-ZrO2-Ag composite coating are 9.93%, 3.59%, 0.85% and WC, ZrO2and CeO2 of Al/Pb-WC-ZrO2-CeO2 composite coating 5.84%, 2.29% and 1.32%, respectively.Effect of solid particle concentration and process conditions on surface morphology of Al/Pb-WC-ZrO2, Al/Pb-WC-ZrO2-Ag and Al/Pb-WC-ZrOrCeQ, composite electrodes is studied, also. The research indicates that, crystal grain inscreases with the rise of current density and temperature;effect of concentrations of various solid particles on coating grain is very little;Moreover, the CeC^ particles, adding to plating solution, have certain effect of refined grain.Finally, phase structure, intensifying lifetime, cell voltage and current efficiency of eledtrodes prepared at optimum condition are researched. X-ray diflraction shows that, lead as well as WC and ZrO2 exist in the coatings, and the coatings are crystal status as deposited. Furthermore, Comparing diffraction peak of WC wth that of ZrO2, the former is stronger than the latter, showing that depositing effect of WC is better than that of ZrC^ during composite electrodeposition. In comparison with Pb-Ag anode, overpotential of oxygen evolution of Al/Pb-WC-ZrC^, Al/Pb-WC-ZrCh-Ag and Al/Pb-WC-ZrO2- CeO2 composite electrodes is lower 20-30mV, exchange current density is higher two magnitudes above, accounting for good catalytic activity of oxygen evolution and suitable for acting as anode with oxygen evolution reaction. Intensifying lifetime of Al/Pb-WC-ZrO2 composite electrodes is proportional to the coating thickness, and the thicker the coating is, the longer the electrode material lifetime is.In summary, through chemistry and electrochemistry method, Pb-WC-ZrO2 composite electrodes are electrodeposited on aluminum base, having certain application prospect.