Preparation And Electrochemical Performance Of Composite Inert Anode Materials For Zinc Electrowinning

The Pb-Ag?0.75-1.0wt%?alloy anodes is widely used in zinc electrowinning industry in view of their good stability and high corrosion resistance in acid solution.However,it has some shortcomings such as poor conductivity,high overpotential of oxygen evolution,and dissatisfactory mechanical performance.In this paper,based on the higher electrocatalytic activities of cobalt oxide?Co₃O₄?,manganese dioxide?MnO₂?and lead dioxide?PbO₂?,different component composite inert anodes were prepared by vacuum hot pressing technique from the mixtures of lead powders,Co₃O₄,MnO₂ and PbO₂ particles,which act as particle reinforcements.The influences of heating temperatures,soak at temperature,load pressures and different mixing ratios on the properties of the composite inert anodes were researched.The surface microstructures,phase structures and electrochemical properties were measured by X-ray diffraction,scanning electronic microscopy,anodic polarization curves,cyclic voltammetry curves and Tafel polarization curves.The cell voltage,current efficiency,power consumption and accelerated corrosion life of composite anodes were measured in the simulated zinc electrowinning system.The main research results are as follows:The influences of heating temperatures,soak at temperature,load pressures and different mixing ratios on properties of Pb-Co₃O₄ and Pb-MnO₂ composite inert anodes prepared by vacuum hot pressing technique were studied.The results showed that the uniform distributions of Co₃O₄ and MnO₂ in the composite inert anodes have been obtained by the vacuum hot pressing technique.A part of lead powders were melted and formed a uniform and compact matrix,in which the morphologies and properties of Co₃O₄ and MnO₂ particles were kept.The electrochemical property and corrosion resistance of the composite inert anodes in a zinc electrowinning simulation solution were improved with the rise of heating temperatures during the vacuum hot pressing.The excessive temperature were disadvantageous to the precipitation of the composite inert anodes at a certain pressure.Soak at 60 min is beneficial to the improvement of electrocatalytic activity,but too long soak at time does not improve the performance obviously.The optimum conditions of Pb-Co₃O₄ and Pb-MnO₂composite inert anode were heating temperature 320?,soak at 60 min,load pressure65 MPa and mixing ratio Pb:Co₃O₄=1:0.20,Pb:MnO₂=1:0.20.The electrochemical performances of Pb-Co₃O₄-MnO₂,Pb-Co₃O₄?MnO₂?-PbO₂and Pb-Co₃O₄-MnO₂-PbO₂ composite inert anode,such as oxygen evolution electrocatalytic activity and corrosion resistance,were measured in the simulated zinc electrowinning system.The results indicate that Pb-Co₃O₄-MnO₂ composite anode had higher electrocatalytic activity,lower overpotential of oxygen evolution and better corrosion resistance than other composite inert anodes.The electrochemical performances of the prepared composite inert anodes are all superior to that of Pb-0.8wt%Ag alloy anode.The cell voltage,current efficiency,power consumption and accelerated corrosion life of composite anodes were measured in the simulated zinc electrowinning system.The cell voltage of Pb-Co₃O₄-MnO₂ composite inert anode was 1.80 V,which was reduced 0.41 V compared with Pb-0.8wt%Ag alloy anode.The power consumption was 2483.8 kW·h/?t·Zn?,which was reduced 406.6 kW·h/?t·Zn?compared with Pb-0.8wt%Ag alloy anode.The new composite inert anode shows the remarkable energy-saving effect.The accelerated corrosion life of Pb-Co₃O₄-MnO₂composite inert anode was 25 h and its service life was 40000 hours under the general industrial current density of 500 A·m^-2.