Efficient Clean Leaching Of Ruthenium From Superalloy Waste And Preparation Technology Of Nano-ruthenium Oxide

Superalloys will generate a large amount of waste during production and service,such as scraps,scrap parts,defective products,etc.,accounting for more than 70%of the total.These superalloy scraps have extremely high comprehensive recycling value and are important secondary resources of strategic metals.In this paper,by studying the electrochemical behavior of ruthenium-containing superalloys,the possibility and method of electrochemically dissolving and recovering ruthenium in the alloy were explored.The chlorine complex is treated to convert the product into nanometer-scale ruthenium oxide,so as to realize the improvement of the added value of the product.The main findings of this paper are as follows:Through the research on the relevant process parameters such as dissolution efficiency,current efficiency and electrolysis energy consumption in the electrolysis process of superalloy waste,the appropriate process parameters for the electrolysis process of superalloy waste diluted with aqua regia electrolyte are finally determined,that is,the electrolysis current is 8 A,the electrolysis time is 4 h,the current density is0.5 A/cm^-2,the current efficiency of diluting aqua regia by superalloy waste is155.39%,and the electrolysis energy consumption is 4.39 kw·h·kg^-1.As the electrolysis reaction progresses,the surface of the superalloy begins to corrode,and holes appear in the matrix.The soluble elements such as Ni and Co are preferentially dissolved,while the insoluble elements such as Ta and W form Ta₂O₅and WO₃and adhere to the surface of the superalloy waste.The reaction proceeds and gradually falls off to form anode slime.The easily passivating elements such as Al and Cr in the superalloy scrap form a passivation layer on the surface of the superalloy scrap,which hinders the electrolytic reaction of the superalloy scrap.During the electrolysis of superalloy waste,Ru mainly exists in the form of Ru（III）in the electrolysis residual solution.The electrochemical dissolution behavior of superalloy waste diluted aqua regia electrolyte can be divided into four stages:1)dissolution of external field oxide layer;2)formation of matrix microchannels;3)formation of anode product layer;4)formation of Cr-rich passivation layer.Through the research on the parameters of reaction time and reaction temperature,it is finally obtained that increasing the reaction temperature and prolonging the reaction time can improve the yield of ruthenium hydroxide in the direct precipitation method.The effect of reaction temperature on the precipitation rate is greater than that of reaction time.The effect of sedimentation rate.Through the analysis of XRD and XPS,it is concluded that the product obtained by the hydrothermal synthesis method is amorphous ruthenium hydroxide,which is mixed with ammonium chloride.SEM results showed that the ruthenium hydroxide obtained by hydrothermal synthesis was nanoparticles.According to the results of the orthogonal experiment,the optimal process conditions are:the reaction temperature is140℃,the reaction time is 8h,and the ratio of reactants is 1:3.The primary and secondary order of the factors of the hydrothermal synthesis reaction are:reaction time,ratio of reactants,and reaction temperature.In the reaction system,the hydrolysis of ruthenium is a third-order reaction,and the hydrolysis of urea is a first-order reaction.The hydrolysis activation energy of urea is 9.408 k J/mol,and the pre-exponential factor k₀of the reaction rate equation is 0.1547.The hydrolysis activation energy of ruthenium is 5.953 k J/mol,and the pre-exponential factor k₀is67.9906.The morphology of the product was analyzed by means of SEM and TEM,and the particle size of the product was obtained between 30-50 nm,which belonged to nano-scale particles.The calcined product was characterized and analyzed by XPS and XRD,the composition of the product was explored,and it was determined that the final product obtained by calcination was Ru O₂.The product was tested by TG-DTA,and the change stage of the product during the calcination process was obtained.The first stage was from 204℃to 312℃,and the product quality decreased by 20%.The reason for this change is the NH₄Cl doped in the product.Thermal decomposition.The second stage is from 353℃to 436℃,and the product quality is reduced by 5%,because the bound water in the product is removed by heating,and the product is converted into Ru O₂.