Study On Nickel Recovery By Electrodeposition Of Titanium-Iridium Tin Oxide Anode Modified By Rare Earth Cerium Doping

With the continuous progress of industrial production technology,the problem of heavy metal wastewater discharge is becoming more and more serious,which needs to be solved urgently.Anode is a very important component in electrodeposition process,which not only affects current density,energy consumption and reaction rate,but also directly affects the quality and composition of electrodeposited nickel.Therefore,the correct anode selection and use is very important for the successful implementation of electrodeposition process and the quality control of electrodeposited nickel film.The simple use of IrO₂ as oxide coating can not meet the current requirements for higher efficiency,energy saving and environmental protection of water treatment.Tin has good electrical conductivity and a large amount of free charge exists outside the nucleus.Rare earth elements have unique 4f electron shell structure and abundant electron energy levels,which are easy to form compounds of different valence states,showing excellent electrocatalytic effect.Rare-cerium doping can improve the physical,chemical and electrochemical properties of the anode,including forming a stable oxide film,increasing catalytic activity,increasing defects and holes,improving electron conductivity and charge transfer capacity,and enhancing the photocatalytic activity of the anode.In summary,rare earth cerium doping can improve the stability,electrochemical performance,degradation performance and photoelectric conversion efficiency of anode,so it becomes an effective anode material choice.In this paper,Ti/IrO₂+SnO₂+CeO₂anode by thermal decomposition method is used to solve the problems of high preparation cost and short service life.The electrocatalytic activity,surface morphology,coating stability and working life of anode oxygen evolution were investigated by scanning electron microscopy（SEM）,oxygen evolution polarization curve（LSV）,cyclic voltammetry curve（CV）,AC impedance（EIS）and anode accelerated life test（ALS）.The effects of molar distribution percentage of active elements,calcination temperature and coating load on the electrode properties of titanium oxide anode coating were investigated,and the optimal technological parameters were determined.Finally,through the experiment of nickel recovery by electrodeposition,current efficiency,tank voltage and electrodeposition energy consumption were used as evaluation indexes.The effects of different anode materials on electrodeposition were studied and compared.The results show that the influence of Ce doping on the surface morphology of Ti/IrO₂+SnO₂+CeO₂ electrode varies with the doping amount.With the change of Ce doping amount,the number,depth and width of cracks also change obviously.The existence of cracks can increase the contact surface area between the electrode surface and the electrolyte,thus increasing the electrocatalytic activity of the electrode.However,excessive Ce doping will densify the coating and reduce the number of cracks.The accelerated life test shows that the accelerated life increases first and then decreases with the increase of Ce content.When X is10%,that is,Ir:Sn:Ce=0.45:0.45:0.1,the surface morphology of the anode is the best,and the electrocatalytic performance and acceleration life of the anode reach the maximum value.With the increase of calcination temperature,the number of cracks in the coating increases,and with the increase of temperature to 425℃,the cracks become wider and deeper,and they are connected to form network structure.When the calcination temperature is lower than 425℃,the porosity factor of the electrode surface increases with the increase of doping ratio.When the calcination temperature is higher than 425℃,the porosity factor decreases with the increase of temperature,and the impedance value also reaches the minimum value at 425℃.With the increase of coating load,the voltammetry charge,current density,porosity factor and accelerated life increased first and then decreased,and gradually decreased when the coating load was greater than 6g/m²,and reached the maximum value when the coating load was 6g/m².Nickel recovery experiments were carried out by electrodeposition using graphite,lead-silver alloy and Ti/IrO₂+SnO₂+CeO₂ as anode.The results show that the energy consumption of graphite anode,lead-silver alloy anode and Ti/IrO₂+SnO₂+CeO₂ anode are 4300k Wh/t,5200k Wh/t and 3600k Wh/t,respectively,at the current density of 200A/m^-2.Compared with the first two anode materials,the energy consumption of self-made anode is reduced by 16.3%and 30.8%,respectively.Compared with the other two materials,Ti/IrO₂+SnO₂+CeO₂ anode has higher current efficiency,lower cell voltage,and lower electrodeposition energy consumption.