The adsorption and separation of molybdenum from crude ammonium tungstate solution using ZGA351 macroporous strong base anion exchange resin were studied.The effects of resin type,sulfur content,aging time and temperature and pH of the feed solution,adsorption flow rate and adsorption temperature on the adsorption and separation of molybdenum by the resin were studied.The results show that using 100 mL ZGA351 resin in dynamic adsorption tests,the tungsten loss rate in the feed solution is only 0.54%when the tests are conducted under the optimal conditions of sulfur content of 1.1 times the theoretical amount,aging time at 40℃of 48 h,solution pH of 10.0,adsorption flow rate of 15 mL/h,and adsorption temperature of 40℃.The molybdenum penetration capacity of the resin is 107.77 g/L_(wet resin),which is 3.15 times higher than that of the HBDM-1 resin currently used in industrial production.In addition,the repeated experiments showcase good stability,and the average molybdenum-to-tungsten ratio of pure ammonium tungstate solution obtained after adsorption by ZGA351 resin is 0.88×10^-4,which meets the requirement of molybdenum-to-tungsten ratio of pure ammonium tungstate solution to be less than 2×10^-4for industrial production of APT products.In summary,the separation of molybdenum from crude ammonium tungstate solution by strong base anion exchange resin has the advantages of high molybdenum penetration capacity,low tungsten loss rate,high separation efficiency of tungsten from molybdenum,providing an effective technical reference for industrial applications.

The desorption solution of thiomolybdate-saturated resin(molybdenum desorption solution)was treated by hydrogen peroxide oxidation and sulfuric acid regulation.The effects of the type,dosage and adding method of oxidants,and the temperature and time of reaction on S^2-removal from molybdenum desorption solution were studied.The results show that under the conditions of reaction temperature of 35℃,constant stirring speed of 200 r/min,hydrogen peroxide dosage of 1.0 time the theoretical amount added at once,and reaction time of 20 min,the concentration of S^2-in the molybdenum desorption solution could be reduced to below 0.01 g/L,and no hydrogen sulfide gas or molybdenum trisulfide slag are detected in the acid regulation process.This method provides a reference for the green and efficient treatment of molybdenum desorption solution in ion exchange section.

By analyzing the composition of lepidolite ore and the current status of lithium extraction techno-logy,a innovative technology applying sulfuric acid-sulfate mixed roasting to extract lithium from lepidolite is put forward in this paper.A systematic analysis of a designed process using the innovative technology to extract lithium from lepidolite is conducted from the perspectives of process flow,main equipment,technical index,and pollution control in production process.The technology enables the effective extraction of Li,Rb,and Cs from lepidolite,with their recovery rates of 80.3%,54%,and 61%,respectively.

To solve the problem of poor leaching effeciency in the extraction process of gallium and germanium from zinc powder replacement residues,this study first conducted atmospheric sulfuric acid leaching tests,investigating the influence of sulfuric acid concentration,reaction temperature,liquid-to-solid ratio,and reaction time on the leaching rates of Ga and Ge,and carried out kinetic analysis of the leaching process.Then,the enhanced leaching tests of Ga and Ge from zinc powder replacement residues were conducted by reduction leaching(sequentially using Na₂SO₃ and SO₂ as reducing agents)and sulfation roasting-water leaching.The results show that under the optimum conditions of sulfuric acid concentration of 150 g/L,reaction temperature of 90℃,liquid-to-solid ratio of 5 mL/g,reaction time of 4 h,and stirring speed of 400 r/min,the leaching rates of Ga and Ge by atmospheric sulfuric acid leaching are 68.4%and 61.7%,respectively.The main phases in the acid leaching residue are PbSO₄ and ZnAl₂O₄,and increasing acidity can further dissolve the residual jarosite and lead aluminum sulfate.The atmospheric sulfuric acid leaching processes of Ga and Ge are mainly controlled by internal diffusion with the apparent activation energies of the reactions of 18.06 kJ/mol and 16.02 kJ/mol,respectively.The leaching residue from the first stage of atmospheric sulfuric acid leaching underwent a second-stage reduction enhanced leaching.Using Na₂SO₃ as the reducing agent,Ga and Ge leaching rates reach 89.4%and 70.1%,respectively,under the conditions of 50 g/L H₂SO₄ and 3 g/L Na₂SO₃.And using SO₂ as the reducing agent,Ga and Ge lea-ching rates reach 88.9%and 86.7%,respectively,under the conditions of SO₂ partial pressure of 0.3 MPa,sulfuric acid concentration of 50 g/L,reaction temperature of 110℃,and reaction time of 3 h.The sulfation roasting-water leaching process significantly improves the Ga leaching efficiency from zinc powder replacement residues,while it is unfavorable to the leaching of Ge.Under the optimum conditions of acid residue volume-to-mass ratio of 1/2.5 mg/L,roasting temperature of 300℃,roasting time of 3 h,water leaching temperature of 80℃,liquid-to-solid ratio of 5 mg/L,and leaching time of 2 h,the leaching rate of Ga increases to 89.1%.

Using copper powder and tungsten powder as raw materials,W-Cu alloys were prepared by mechanical alloying and spark plasma sintering.The effects of different sintering temperatures and the additions of Y₂O₃ and Cr additives on the microstructure and physical and mechanical properties of the alloys were analyzed using SEM,XRD,Vickers hardness tester,electron densitometer,and conductivity tester.The experimental results show that as the sintering temperature increases,the distribution of W and Cu phases becomes more uniform,and the density,hardness,and conductivity of the alloys increase.The W-Cu alloy prepared at a sintering temperature of 1100℃exhibits the best comprehensive physical and mechanical properties.With the increase in Y₂O₃ content,the grains of the W-Cu alloys become finer,the hardness increases,while the density and conductivity decrease.In addition,with the increase in Cr content,the conductivity of the W-Cu alloys decreases,but the hardness and density increase slightly and then decrease significantly.The W-Cu-0.5Cr alloy possesses the best comprehensive physical and mechanical properties.Therefore,adding a small amount of additives can effectively improve the microstructure and physical and mechanical properties of the SPS products(W-Cu alloys).

Anhydrous Pr-Nd fluoride powder was prepared by hydrofluoric acid precipitation,and the effects of oxalic acid addition,bottom water acidity,supernatant recycling times and hydrofluoric acid dosage on the formation of hydrated Pr-Nd fluoride crystal and the morphology,particle size,apparent density and impurities of anhydrous Pr-Nd fluoride powder were investigated.The results show that the optimized process conditions are as follows:oxalic acid addition at 6%~10%of the theoretical amount(1.5 times the molar amount of RE³⁺),bottom water acidity of 1.6~2.0 mol/L,supernatant recycling up to 3 times,and hydrofluoric acid dosage at 100%of the theoretical amount(3 times the molar amount of RE³⁺).The anhydrous Pr-Nd fluoride powder prepared under these optimized process conditions has a median particle size D₅₀of 10~30μm and an apparent density of 0.7~0.8 g/cm³.The content of non-rare earth impurities is low,and the yield rate of rare earth reaches 99.81%.

Using the catalyst powder of rare earth tailings activated by sulfuric acid as raw material,a monolithic catalyst was prepared by adding additives and integral extrusion,and then characterized and analyzed by XRD,BET,XPS,and H₂-TPR.In addition,its catalytic denitration reaction activity and N₂ selectivity were tested on a denitration activity test platform to determine the suitable roasting system of the catalyst.The results show that the strip-shaped catalyst roasted at 350℃presents the best catalytic denitration activity and the largest specific surface area.The XPS spectral peak of its Fe2p orbital shifts towards high binding energy,indicating a significant Fe-Ce synergistic effect.At this roasting temperature,a honeycomb-shaped catalyst with a denitration efficiency of 81%and high N₂ selectivity can be prepared,and its mechanical strength meets the national standard for the monolithic catalysts.

To improve the corrosion resistance of low-carbon microalloyed steel in marine environments,the corrosion behavior of the test steel with different cerium(Ce)contents in a marine environment simulated with 3.5%NaCl solution was studied by employing metallographic microscope,SEM,EBSD,and electrochemical analysis.The results show that the microstructure of the test steel mainly consists of ferrite and pearlite.Ce can refine the grains,reduce the size of inclusions,and modify the Al₂O₃,MnS,and Al₂O₃+MnS inclusions in the test steel into MnS+CeAlO₃ and Ce₂O₃.The modified inclusions significantly reduce the stress,thereby decreasing the probability of micropore and crack initiation.Additionally,the addition of Ce can decrease the corrosion current density of the test steel,increase the corrosion potential,reduce the content ofγ-FeOOH in the corrosion products,and increase the content ofα-FeOOH and Fe₃O₄,lowering the reaction activity and enhancing the protective effect of the rust layer on the substrate.Therefore,compared with low-carbon microalloyed steel without Ce addition,the low-carbon microalloyed steel with Ce addition exhibits better seawater corrosion resistance.

Ti₂AlNb alloy was prepared using high-energy ball milling and spark plasma sintering(SPS).The effects of second-sintering temperature on the microstructure and mechanical properties of the alloy were investigated by X-ray diffractometer(XRD),scanning electron microscope(SEM),and universal tensile testing machine.The results show that the Ti₂AlNb alloys prepared at different second-sintering temperatures consist of B2 phase,equiaxedα₂ phase,and acicular O phase.When the second-sintering temperature is within the range of 900~950℃,the acicular O phase is precipitated as the second phase inside the B2 matrix phase,and the equiaxedα₂ phase agglomerates among the B2 matrix phase.And the equiaxedα₂ phase becomes less concentrated in its distribution and gradually decreases in its number in the range of second-sintering temperature from 1000℃to 1100℃.The Ti₂AlNb alloy prepared at the second-sintering temperature of 1000℃possesses good mechanical properties,with a room-temperature tensile strength of 309 MPa and a Vickers hardness of 466.5 HV.

Lithium niobate(LiNbO₃,LN)piezoelectric ceramics were prepared by vacuum hot-pressing sintering at 900℃and 35 MPa for 120 min.The effects of different Al₂O₃ doping amounts on their piezoelectric properties were studied.Through the analysis of phase,density,microstructure,piezoelectric and dielectric properties,it is found that within the range of Al₂O₃ doping amounts of 0.5%~3%(molar fraction),all LN piezoelectric ceramics samples exhibit the same position of main diffraction peaks that are sharp and indicative of a perovskite-type structure.with the increase of Al₂O₃ doping amount,the particle size of LN piezoelectric ceramics gradually decreases while the porosity increases both in size and quantity.In addition,the density and piezoelectric constant d₃₃increase at first and then decrease,reaching their maximum of 4.65 g/cm³ and 11.3 pC/N,respectively,at an Al₂O₃ doping amount of 1%.The above piezoelectric constant is 88.3%higher than that of LN piezoelectric ceramics prepared by laser sintering.At the test frequency of 1 MHz,the relative dielectric constant of LN piezoelectric ceramics increases gradually with the increase of Al₂O₃ doping amount.