As time develops,the processes for preparing titanium and its alloys have become more and more environmentally friendly.At present,molten salt electrolysis has gained significant attention in the field of preparing titanium and its alloys due to its low energy consumption and low pollution.The article introduces the reduction mechanisms of four methods,including FFC Cambridge process,OS calciothermic reduction method,solid oxygen permeable membrane(SOM)method,and USTB method,which have been the research hotspots of molten salt electrolysis in recent years.Meanwhile,the latest research progress of these methods is summarized to comparatively analyze their merits and demerits,and the future development of molten salt electrolysis is discussed based on the research status.

Aiming at the problems of low lithium recovery efficiency and difficult lithium-sodium separation in the current wet recycling process of spent battery cathode materials,a synergistic extraction system of LIX54/Cyanex923 was proposed for the selective extraction of lithium from lithium-containing sodium sulfate solution.The experimental results show that for the synthetic feed solution containing 0.5 g/L Li and 50 g/L Na,98.72%of lithium in a single contact is extracted by the organic phase consisting of 0.4 mol/L LIX54,0.2 mol/L Cyanex923,and sulfonated kerosene with an O/A ratio of 1∶1 and equilibrium pH of 12.5 at 30℃for 10 min,resulting in a separation factor of lithium from sodium reaching 1578.After three-stage simulated counter-current extraction at an O/A ratio of 1∶5 and equilibrium pH of 12.5,over 99%of lithium is extracted,leaving less than 0.01 g/L Li in raffinate.After two-stage counter-current scrubbing with 1 mol/L HCl at an O/A ratio of 8∶1,nearly 98%sodium is elated,leaving 0.05 g/L Na in the organic phase.After two-stage counter-current scrubbing with 1 mol/L HCl at an O/A ratio of 8∶1,nearly 98%sodium is eluted,leaving 0.05 g/L Na in the organic phase.After scrubbing,the loaded organic phase undergoes two-stage counter-current stripping with 3 mol/L HCl at an O/A ratio of 6∶1.The stripping rate of lithium reaches over 99%and the lithium concentration is enriched up to 16.93 g/L in the strip liquor.The LIX54/Cyanex923 synergistic extraction system can effectively recover lithium from lithium-containing sodium sulfate solution selectively and realize the deep separation of lithium from sodium and the enrichment of lithium at high magnification.

P204 solvent impregnated resins(P204 SIRs)were prepared by using styrene-divinylbenzene macroporous resin(HZ818)as a carrier and bis(2-ethylhexyl)phosphoric acid(P204)as an extractant,and were characterized by scanning electron microscope(SEM),infrared spectrometer(IR),and thermogravimetric analyzer(TG)to investigate the adsorption performance of P204 SIRs for Ga(Ⅲ)in sulfuric acid solution.The results show that the optimal pH value for Ga(Ⅲ)adsorption by P204 SIRs is 1.8.The adsorption equilibrium time of Ga(Ⅲ)at 298 K is approximately 20 h,with a saturation adsorption capacity of 10.9 mg/g,and the kinetic adsorption behavior could be described by a pseudo-second-order kinetic equation as t/Q_t=0.2173+0.0962t.The isothermal adsorption of Ga(Ⅲ)by P204 SIRs follows the Langmuir isothermal adsorption model of C_e/Q_e=0.4482+0.0588C_e,and the fitted saturation adsorption capacity of Ga(Ⅲ)at 298 K is about 17 mg/g.

In recent years,the declining grade of the mined germanium-containing ores has led to a decrease in the grade of germanium-containing dust,resulting in increased consumption of reagents and environmental pressure in the process of germanium extraction by chlorination distillation.Taking the germanium-containing dust produced by a factory in Lincang,Yunnan,as the research object,germanium from it was enriched through processes of reduction volatilization,cyclic leaching,and neutralizing precipitation.X-ray diffractometer and atomic absorption spectrometer were used to analyze the phase composition and element content of raw materials and products,and the influence of various factors on the germanium enrichment rate during the enrichment process was also investigated.The results show that the optimal process para-meters for industrial production include a roasting temperature of 1100℃,a reductant dosage of 12.5%,a reagent concentration of 20%,a water bath temperature of 80℃,a liquid pH of 3,and a precipitation do-sage of 20 times.Under such optimized conditions,the germanium grade increases from 0.97%to 28.56%after reduction volatilization,cyclic leaching,and neutralization precipitation of the germanium-containing dust,with an enrichment factor reaching 29.4 times and a germanium recovery rate of 96.49%.The extraction of germanium from germanium-containing dust using this process is feasible and offers advantages of high germanium recovery rate,low environmental pollution,short process duration,and low cost.

Based on the incomplete separation of selenium,tellurium,and copper in the selenite reduction section of the comprehensive recovery process for copper anode slime,a new process was proposed of supplementing chloride ions to the chlorinated de-selenium solution and an industrial trial of secondary selenite reduction was conducted while other parameters such as reduction time,temperature,and reductant flow rate remained unchanged.The results show that with the new process,the reduction rate of selenium in primary reduction can reach 99.72%,while the reduction degree of tellurium and copper is significantly inhi-bited.In the secondary reduction,the reduction rate of tellurium can reach 95.30%,while that of copper decreases to 4.71%.The selenium content of crude selenium product increases from 72.04%to 76.77%,the tellurium content decreases from 1.62%to 0.45%,and the copper content decreases from 2.17%to 1.01%.Compared with the original process,the improvement effect of the new process is significant.

To address the challenge of difficult leaching of valuable elements in high silicon cobalt white alloy,by employing sodium chlorate as an oxidant and adding Fe~(3+),one of the composition elements of the high silicon cobalt white alloy,as oxidation transformers in sulfuric acid system,the Co and Cu could be effectively leached from the high silicon cobalt white alloy while the leaching of silicon reduced.An orthogonal test was conducted to study the effects of initial Fe~(3+)concentration,particle size of the high silicon cobalt white alloy,and reaction temperature on leaching efficiency.Optimized process parameters were obtained,and economically favorable process parameters with lower leaching cost were determined according to the actual production demand.The optimized process parameters are as follows:initial Fe~(3+)concentration of 15 g/L,particle size of the high silicon cobalt white alloy less than 0.075 mm,and reaction temperature of 85℃.Among them,the initial Fe~(3+)concentration has the greatest impact on the leaching efficiency.Under the optimized process parameters for 5.5 h,the leaching rates of Co and Cu reach 99.3%and 98.7%,respectively.The economically favorable process parameters are as follows:initial Fe~(3+)concentration of 10 g/L,particle size of the white alloy ranging from 0.075 mm to 0.150 mm,and reaction temperature of 85℃.The leaching rates of Co and Cu after 6.7 h leaching reach 98.9%and 98.5%,respectively.

Nano WC-10Co4Cr coatings were prepared on ZG0Cr13Ni5Mo stainless steel by internal oxygen-propane HVOF spraying,and the effects of spraying distance on the macro/micro structure and slurry erosion resistance of the coatings were investigated by two types of internal guns at 45°and 90°.The phase composition of the coatings was measured by X-ray diffraction(XRD),the microstructure of cross section of the coatings was observed by scanning electron microscope(SEM),and the porosity was analyzed by metallographic microscope.The microhardness of the coatings was measured by Vickers hardness tester while the surface roughness and 3D morphology were characterized using roughness meter and optical profilometer.The slurry erosion resistance of the coatings and stainless steel substrate was compared using slurry erosion tester,and the erosion wear mechanism was analyzed by SEM.The results show that the main phase composition of the coatings prepared by 45°and 90°internal guns consists of WC,W₂C and amorphous CoCr alloy phases,which are not affected by the spraying distance.Short spraying distances result in the formation of pores defects in the coatings and the porosity initially decreases and then increases with the increase of spraying distance.Though the microhardness of the coating prepared by the 90°spray gun receives minimal influence from the spraying distance,the coating microhardness of the 45°spray gun shows a decreasing trend after the spraying distance increases to 150 mm,and the maximum hardness va-lues of the coatings prepared by the two spray guns are 1343.1 HV_0.2and 1275.4 HV_0.2,respectively.For both guns,short spraying distances lead to the formation of raised agglomeration particles on the coating surface,while the roughness decreases with the increasing spraying distance.With the increase of the spraying distance,the erosion resistance of the coatings increases at first and then decreases gradually,and the highest erosion resistance of the coatings prepared by 45°and 90°internal guns is achieved at the spraying distances of 200 mm and 250 mm,respectively,corresponding to 7.03 times and 8.05 times that of the substrate.The slurry erosion wear mechanism of nano WC-10Co4Cr coatings is mainly attributed to fatigue spalling under alternating stress,and that of stainless steel substrate is slurry micro-cutting.

The laminated slurry melting method was used to prepare the composite silicide coating on Nb-W alloy,aiming at comprehensively improving the long-range oxidation resistance under static load and thermal shock resistance of the alloy.The results show that the coating has good resistance to high temperature and oxidation,with a static oxidation resistance of over 640 min at 1800℃and thermal shock resistance of over 680 times at 1700℃.It can also withstand the impingement of oxyacetylene flame at 1500℃for 3600 s.After the long-range oxidation test,the coating begins to deplete Si while the Nb content significantly increases due to diffusion.And as the Nb-rich oxides start to appear in the surface layer of the coating,the coating fails.In addition,there still is a mismatch of the thermal expansion coefficient between the coating and the Nb-W alloy,which results in macroscopic cracks in the coating after 680 times of thermal shock tests at 1700℃,thus leading to the failure of the coating.

In order to improve the thermal conductivity and mechanical properties of Al-Si based die casting aluminum alloys,the effects of La and Ce on microstructure,thermal conductivity and mechanical properties of Al-3Si-0.4Cu-1.0Fe die casting aluminum alloy were investigated using metallographic microscope,SEM,EDS,universal electronic tensile testing machine,and laser conductometer.The results indicate that the rare earth elements of La and Ce refine the alloy grains,transformingα-Al grains from dendrite to cellular morphology,and reducing the average secondary dentritic arm spacing.Meanwhile,the two elements also modify the eutectic Si phase to result in a uniform distribution of fine fibrous morphology.When the added contents of La and Ce are both 0.1%,the thermal conductivity,tensile strength and elongation after fracture are 167.62 W/(m·K),201.0 MPa,and 14.56%,respectively.Compared with the sample without rare earth elements,these values are increased by 11.19%,27.38%,and 246.67%.

Rare earth tailings contain a considerable amount of silicon and aluminum species for molecular sieve synthesis,and the difficulty of green synthesis of molecular sieves from natural minerals lies in the mineral activation.In this paper,rare earth tailings,being used as raw materials,were activated in ways of thermal activation,alkali fusion activation,and sub-molten salt activation,respectively,to depolymerize the silica and aluminum species in the highly polymeric state of rare earth tailings into reactive mono-polymeric silica and aluminum species,setting the basis for the synthesis of molecular sieves,thus to realize the se-condary utilization of rare earth tailings.The chemical composition,phase structure,and surface micromorphology of the activated rare earth tailings were analyzed by XRF,XRD,and SEM-EDS characterization to investigate the effects of different activation modes on the activation of rare earth tailings.The results show that the SiO_2 crystal form in the thermally activated rare earth tailings is stable and the activation effect is not obvious;the rare earth tailings could be more completely activated by alkali fusion and sub-molten salt,and alkali fusion activation could realize more efficient activation of rare earth tailings.And at the same time,the increase of alkali fusion activation temperature can promote the activation of rare earth tailings.When the mass ratio of NaOH to rare earth tailings is 3 and the alkali fusion activation temperature is 450℃,the dissolution rates of reactive silica and aluminum species in rare earth tailings are 84.2%and 63%.The results of the study provide a certain theoretical basis for the green synthesis of molecular sieves from natural minerals and the secondary utilization of rare earth tailings resources.