| Although lead alloy electrodes are still the main anode materials in hydrometallurgy, there exist some problems of high internal resistance, high oxygen evolution potential, high weight, low intensity and high dissolubility. Because of the high bath voltage in the process of Zn electrodeposition, it causes25%?30%electric energy to be wasted, and because of the electric field force, the electrode plates will bend and the stability of production is destroyed. Also because lead anode is easily dissolved, it will cause the low quality of cathode product and a lead anode consumption of12kg per ton of Zn. In consequence, to develop a novel good electrical conductivity, energy-saving, high strength, anti-corrosion and low-cost anode material becomes an important issue in hydrometallurgy industry.In this research, the concept that the organization structures of composite substrate are changed to improve the anode performance is proposed base on the early work. And this work was supported by the Development Program of China (National863plans projects) and National High Technology Research and Development. This article embarks from improving conductivity of the substrate, choose Ti/Al composite material as the electrode substrate for the first time, by reducing the electrode impedance to improve the performance.And the low-cost, high adhesive force and good electrical conductivity SnO2+Sb2O4is selected as the intermediate coating.Using PbO2which is suitable for zinc sulfate electrolysis system. The novel energy-saving anode of Ti/Al/Ti/SnO2+Sb2O4/(3-PbO2is proposed. The technology thoughts are as follow:By changing the component and structural pattern of traditional composite and using Ti/Al/Ti anode layered composite matrix structure. Through the performance superposition of titanium aluminum clad, using Ti to keep high strength, strong corrosion resistance of the anode, at the same time, with the help of a metal A1core to improve the conductivity of the electrode substrate, homogenizing current distribution. Augment the transmission rate of electrons in the process of electrolysis, improve the reaction rate of electrolysis system. The SnO2+Sb2O4are selected to be middle layer to enforce the bonding strength between substrate and surface active layer. Also this middle layer can interdict the acid electrolyte to corrode the Ti substrate which is the main cause of electrode degradation. Through better electrodeposition process for ?- active layer on Ti/Al composite substrate, to improve the catalytic activity of zinc anode and cathode product quality.In this paper, the research work is mainly from the following three aspects:firstly, the influence relationship between synthetic mechanism of composite interface of titanium aluminum clad and performance. With the testing methods of SEM, XRD and HRTEM, the influence of composite substrate interface diffusion layer of microstructure and phase structure to electrical conductivity and mechanical properties of electrode substrate are analyzed; secondly, preparation technology and properties of the SnO2+Sb2O4middle layer and the ?-PbO2active layer. Electrodeposition mechanism and process of Ti/Al composite substrate are studied. And testing methods of SEM, XRD and LSV were used to analyzed the sedimentary phase structures, micro hardness, surface fractal dimension and the electrochemical performance in different technologies, and to reveal influence rule of different parameters to electrodeposition process; and the matching between Ti/Al composite substrate preparation process and the electrodeposition process of ?-PbO2active layer is studied; thirdly, comparative study on the production application of ?-PbO2coated electrode of Ti/Al substrate. The Ti/Al/Ti/SnO2+Sb2O4/?-PbO2anode in enterprise production experiment is simulated. By contrast with conventional Pb-1%Ag alloy anode, Al/Pb laminated composite anode and Ti/PbO2anode, energy saving mechanism of it is also analyzed. The study results are as following:(1) The phase formtion mechanism of interfacial diffusion layer is researched. And TiAl3single phase layer is the lowest resistivity of interface diffusion layer of which preparation process conditions is540?diffusion temperature and90min diffusion holding time. The best optimized thickness of Ti and Al plates are:0.3mm and6mm, respectively. The results of the growth kinetics of composite substrate interface diffusion layer show that diffusion temperature on the influence of its thickness is far greater than the influence of the time; the optimum diffusion layer thickness, phase and experimental results were confirmed by the calculation of Ti and Al element concentration and diffusion distance; and the growth of diffusion layer dynamic equation is y=1.09×1012t306027-0.00358T exp(-(RT)/(193252)). (2) The related experiments of non-precious metals SnO2+Sb2O4middle layer shows that: coating number of times have the most influence on ?-PbO2electrodeposition layer in the following electrodeposition technology, and its optimized coating number of times is15.(3) Through analysis the rmodynamic mechanism of P-PbCO2electrodeposition process on Ti/Al composite substrate shows that the conditions of solution are as follows:PH value<3.84, potential<0.82V. When electrodepositing P-PbO2, the influence factors of comprehensive effect are as follows:number of middle layer coating> current density> electrodeposition time; The best conditions of P-PbO2electrodeposition are as follows:current density3.3A·dm-2, electrodeposition time2h.(4) The impedance spectrum test of Ti/Al/Ti/SnO2+Sb2O4/?-PbO2anode shows that:Internal resistance of the anode can be reduced by43%than pure Ti electrodes, its active layer of oxygen evolution reaction of the charge transfer resistance is reduced by70%. Anodes in an acidic environment have a better stability, long life of10.4years, and50%pure Ti substrate PbO2electrode higher. The oxygen kinetics show that the exchange current density j0is the traditional Ti-based PbO2electrode15times in lmol/L H2SO4solution; the oxygen overvoltage ? was down3.3V from traditional anode material under industrial current density (1000A/m2).(5) The simulated test results of the novel Ti/Al/Ti/SnO2+Sb2O4/?-PbO2anode in enterprise show that under500A·m-2current density, the fluctuation of bath voltage is small and the mean value of bath voltage has fallen by3.2%compared with traditional Pb-1%Ag alloy anode; Zinc yield on cathode is increased by4.5%, Pb content in production is reduced by50.3%, the current efficiency of electrolysis is88.8%which is up4.5%to conventional electrode; Single-tons zinc of power consumption is reduced by3.2%, corrosion rate of anode is reduced by42.7%.(6) From influencing factors that changing of substrate materials mechanics and optimizing the ?-PbO2active coating, analyzes the anode energy-saving mechanism of Ti/Al/Ti/SnO2+Sb2O4/?-PbO2in this paper:Ti/Al composite substrate reduces the internal resistance and homogenizes the current distribution, at the same time, it makes the transfer rate of internal electron and electrochemical activity of electrode increasing. And the improvement of electrical conductivity is improved sediments morphology of (3-PbO2on the surface of electrode, increased the catalytic activity of anode. After bonding heterogeneous materials of Ti and Al, the composite substrate will produce12.1mV reverse contact potential, which is the anodic polarization potential series-opposing, and suppress the increase of polarization potential. Meanwhile, the decrease of the electrode quality can reduce the consumption and cost of. The novel anode of Ti/Al/Ti/SnO2+Sb2O4/?-PbO2gives full expression to its excellent energy saving effect and economic value in the test of zinc production simulation. |
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