Aluminum Composite Inert Anode Materials For Zinc Eletrodeposition Performance Study

Non-ferrous metal resources are plentiful in our country. Although Pb-Ag alloy anodes are widely used in hydrometallurgy processes of Zinc electrowinning, but the following shortages as high oxygen evolution potential, low mechanics property and electroconductibility, anodic dissolution pollute the electrolyte, still exist. New composite inert anodes can give full play to the advantages of material multi-composite and synergies, and have attracted much attention.In this thesis, Al/Pb-PANI-WC composite inert anodes have been prepared on the surface of Al substrates by means of double pulse electrodeposition of doped conductive polyaniline (PANI) and tungsten carbide (WC) with Pb2+. The surface, cross-section microstructures and composition distributions of the composite inert anodes were researched. In the system of Zn2+-Mn2+-H2SO4, the electrochemical parameters, strengthening corrosion morphologies and service lifetime were investigated, and the corrosion failure reasons were discussed. In the simulation experiments of zinc electrowinning, the potentials of oxygen evolution for the composite inert anodes, cell voltages and Mn2+dilution rates, current efficiencies and power consumptions were also discussed. The main results are the followings.The surface, cross-section microstructures and composition distributions of Al/Pb-PANI-WC composite inert anodes (prepared by double pulse eletrodeposition of2hours) were tested, anodic polarization curves and cyclic voltammetry curves were also tested in the solutions of50g/L Zn+,150g/L H2SO4and35℃. The results show that the composite inert anodes prepared by double pulse eletrodeposition possess compact microstrutures, composition uniform composition distributions, closed interface bonding, few structure of less structural defects, high exchange current density, low overpotential of oxygen evolution and better reversibility to electrode reaction.The electrochemical parameters, strengthening corrosion morphologies and service lifetime for Al/Pb-PANI-WC composite inert anodes (prepared by double pulse eletrodeposition of4hours and8hours) were investigated in the solutions of50g/L Zn2+、5g/L Mn2+,150g/L H2SO4and35℃, and the corrosion failure reasons were discussed. The results show that compared with the composite inert anodes obtained by double pulse eletrodeposition of4hours and Pb-1%Ag alloy, composite inert anodes obtained by double pulse eletrodeposition of8hours have lower overpotential of oxygen evolution, better corrosion resistance and excellent electrocatalytic activity. The corrosion failure reasons are mainly caused by the falling out of a part of deposits which are affected by the occuring and expanding of local corrsosion. Under10000A·m-2current density, the service times for the composite inert anodes obtained by double pulse eletrodeposition of4hours and8hours are8hours and16hous, and the calculated using lifetimes in500A·m-2current density reach to.133days and267days.In the solutions of50g/L Zn2+、5g/L Mn2+、50g/L H2SO4,35℃and500A·m-2current density, the simulation experiments of zinc electrowinning for Al/Pb-PANI-WC composite inert anodes (prepared by double pulse eletrodeposition of4hours and8hours) were carried on, and the potentials of oxygen evolution for the composite inert anodes, cell voltages and Mn2+dilution rates, current efficiencies and power consumptions were tested. The results show that the potentials of oxygen evolution for the composite inert anodes obtained by double pulse eletrodeposition of4hours and8hours, are2.08V and2.06V, and decrease0.16V and0.18V than that of Pb-1.0wt%Ag. The cell voltages for the composite inert anodes obtained by double pulse eletrodeposition of4hours and8hours, are3.0V and2.9V, and decrease0.2V and0.3V than that of Pb-1.0wt%Ag. The Mn2+dilution rates for the composite inert anodes obtained by double pulse eletrodeposition of4hours and8hours, are4.76%and3.90%, and decrease8.52%and9.38%than that of Pb-1.0wt%Ag. The current efficiencies for the composite inert anodes obtained by double pulse eletrodeposition of4hours and8hours, are92.5%and93.2%, and decrease1.7%and2.4%than that of Pb-1.0wt%Ag. The power consumptions for the composite inert anodes obtained by double pulse eletrodeposition of4hours and8hours, are2659.5kW-h/(t-Zn) and2551.5kW-h/(t-Zn), and decrease230.4kW-h/(t-Zn) and338.4kW-h/(t-Zn) that of Pb-1.0wt%Ag.