The L₂₅(5⁶)orthogonal test was used to study the effects of sulfuric acid concentration,liquid-solid ratio,leaching temperature,stirring speed,reaction time and tungsten slag particle size on the tungsten leaching rate in the sulfuric acid leaching process of alkali-decomposed tungsten slag,and the experimental results were analyzed.The results show that the significant factors affecting the tungsten leaching rate are in the descending order of leaching temperature,sulfuric acid concentration,tungsten slag particle size,liquid-solid ratio,stirring speed and reaction time.The optimum conditions for tungsten leaching are leaching temperature 40℃,sulfuric acid concentration 20%,tungsten slag particle size 75~150μm,liquid-solid ratio 20∶1,stirring speed 250 r/min and reaction time 1.5 h.Under the optimum conditions,the tungsten leaching rate can reach 91.63%.This study can provide a reference for optimizing the sulfuric acid leaching process of alkali-decomposed tungsten slag.

The content of Sc2O3in the tailings of Bijigou vanadium-titanium magnetite in Yang County,Shaanxi Province is 97.08 g/t.In order to fully recover the rare earth resources,scandium was leached by direct acid leaching,and the effects of acid type and dosage,aid-leaching agent type and dosage,leaching temperature,leaching liquid-solid ratio,leaching time,and feed fineness on the leaching rate of scandium were systematically studied.The results show that without the addition of aid-leaching agent,the leaching effects of H2SO4,HCl,H2SO4+HF,and HCl+HF on scandium in tailings are very poor,but the leaching rate by HCl is higher than that by H2SO4.Adding 2^#aid-leaching agent in HCl system can significantly increase the leaching rate of scandium.When the tailings are ground to a fineness of-0.075 mm paticles accounting for 80%,the leaching rate of scandium can reach 89.53%under the optimal conditions of 2^#aid-leaching agent dosage of 15%,HCl concentration of 6 mol/L,liquid-solid ratio of 3∶1,leaching temperature of 90℃,and leaching time of 6 h.The direct acid leaching process has a high leaching rate of scandium and is more operatable,which can promote the development of recovering scandium from tailings.

As a rare earth metal,scandium has been widely used in many industries.Recycling scandium from scandium-containing wastes can not only solve the problem of environmental pollution by waste,but also alleviate the serious shortage of scandium supply in China.In this paper,the research progress of scandium recovery from various scandium-containing wastes(red mud,titanium dioxide waste acid,tungsten slag,fly ash)is reviewed,and the development of scandium recovery technology in China is prospected.It is pointed out that high efficiency,low cost and environmental protection are the development direction of the scandium recovery industry.

Vanadium in the precipitated mother liquor from the hydrolytic precipitation process was reco-vered by ion exchange,and the effects of resin type,feed solution pH,temperature and adsorption time on vanadium adsorption were investigated.The kinetics and isothermal adsorption model of vanadium adsorption by D314 resin were studied.The column dynamic adsorption and desorption tests of vanadium were carried out,and the qualified desorption solution was used to dissolve red vanadium.The results show that under the conditions of pH 2.4,temperature 45℃and adsorption time 40 h,the saturated adsorption capacity of D314 resin for V₂O₅is 243 mg/mL.With 5%NaOH+10%NaCl as a desorption agent,the V₂O₅concentration at the peak of desorption solution reaches 67.5 g/L with an enrichment ratio of 23.6 times.The adsorption behavior of vanadium on D314 resin conforms to the pseudo-first-order adsorption kinetic equation,and the isothermal adsorption process conforms to the Langmuir model.The recovery of vana-dium from the precipitated mother liquor by ion exchange shows an adsorption rate of over 95.5%and a desorption rate of over 98.2%.The qualified desorption solution can be used to dissolve red vanadium.The technology is feasible and the process is simple,providing a technical way for vanadium recovery.

With the development of new energy industry,the development and utilization of lithium resources in salt lake brines have attracted more attention.In this context,the technology of extracting li-thium from salt lake brines has also developed rapidly.This paper analyzes the development stage of the technology of extracting lithium from salt lake brines in China and its future development direction by using patent technology life cycle method.The results show that among traditional methods,the membrane method has become mature and the substitution of the old technologies with the new ones is obvious;adsorption and extraction methods are still in the technology growth stage with a number of technological innovations.In recent years,electrochemical lithium extraction technology has developed rapidly for its advantages of high selectivity,low cost,and eco-friendly protection,showing that it is a promising method for lithium extraction from salt lake brines.

(V,Cr,W)C composite powders were prepared by carbothermal reduction method using Cr₂O₃,WO₃,V₂O₅,and carbon black as raw materials at 1500℃for 2 h.The phase ingredients and microstructure of(V,Cr,W)C composite powders were characterized by XRD and SEM,and the effects of adding method and content of the composite powders on the microstructure and mechanical properties of WC-11Ni cemented carbides were investigated.The results show that the mechanical properties of the alloy are significantly improved by the addition of(V,Cr,W)C composite powders,and its flexural strength,Vickers hardness,and fracture toughness are increased by 19.97%,19.61%,and 12.18%,respectively,compared with those of the specimens without composite powders.The properties of the alloy with(V,Cr,W)C composite powders are better than those with(V,Cr)C composite powders and with WC+Cr₃C₂hybrid powders.In addition,the flexural strength,Vickers hardness,and fracture toughness of the alloy increase at first and then decrease with the increase of the addition of the(V,Cr,W)C composite powders.When the addition of the(V,Cr,W)C composite powders is 0.6%,the flexural strength,Vickers hardness,and fracture toughness of the alloy reach the maximum values of 2835 MPa,1671 MPa,and 15.1 MPa·m^1/2.

The catalyst of molybdenum oxide-loaded monazite was prepared by impregnation method,and tests for its characterization and NH₃-SCR denitration performance were carried out.The results show that the NO conversion rate of the composite catalyst with Mo/Ce molar ratio of 0.3 reaches 75%at the denitration reaction temperature of 400℃.Monazite increases the specific surface area of the catalyst.The loaded metal oxides are uniformly dispersed on the monazite surface,resulting in the coexistence of Ce³⁺/Ce⁴⁺and Mo⁵⁺/Mo⁶⁺and promoting electron transfer to generate oxygen vacancy and unsaturated chemical bonds,which is in favor of the increase of the active site on the monazite surface.Compared with pure monazite,the redox property and the adsorption and activation capacity of NH₃of the composite catalyst have been improved mainly in the high temperature range,with a relatively small improvement in the denitration efficiency in the low temperature section.

The liquidus temperature of ScF₃-LiF molten salt was measured by step cooling curve method.The solubility of Sc₂O₃in ScF₃-LiF molten salt was measured by the isothermal saturation method,and the effects of temperature and ScF₃content were studied.The dissolution mechanism of Sc₂O₃in ScF₃-LiF molten salt was analyzed by X-ray diffraction.The results show that the liquidus temperature of ScF₃-LiF molten salt rises with the increase of ScF₃content,while it decreases with the addition of Sc₂O₃.The dissolution of Sc₂O₃in ScF₃-LiF molten salt is mainly chemical dissolution,the dissolution equilibrium time is about 2 h,and its solubility increases with the increase of temperature and ScF₃content.

Taking X100 pipeline steel as the research object,the test steel with various amounts of Ce was smelted in a vacuum induction furnace under laboratory conditions.The effects of Ce on microstructure and corrosion resistance of X100 pipeline steel were studied by scanning electron microscope,Zeiss metallographic microscope,electrochemical workstation and X-ray diffractometer.The results show that the addition of Ce transforms MnS and Mn-Si-Al-O inclusions in X100 steel into Ce_xO_yand Mn-Si-Al-O-Ce inclusions,and the size increases from about 4μm to about 10μm.Ce has obvious refining effect on the microstructure of X100 test steel,representing that in the range of 0~0.0049%,the microstructure of the test steel is gradually refined with the increase of Ce content.The addition of Ce can also improve the corrosion potential and lower the corrosion current density of the test steel.Under the condition of immersion in 3.5%NaCl solution for 28 d,corrosion current density of the test steel decreases from 4.6347 mA/cm² without Ce addition to 3.7784 mA/cm² with Ce content of 0.0049%,and the test steel with Ce content of 0.0049%shows better corrosion resistance.In addition,the addition of Ce can effectively increase the content ofα-FeOOH and Fe₃O₄in the corrosion product and enhance the protection of the steel matrix,which is conducive to improving the corrosion resistance of the test steel.

The magnetic properties and microstructure of sintered Nd-Fe-B magnets co-doped with Ga,Al,Cu,and Zr were studied,and coercivity of the magnets was regulated by tempering process.The results show that when the first annealing is 900℃×150 min and the second annealing is 500℃×180 min,the magnet coercivity H_cjgreatly increases from 14.33 kOe in the sintered state to 19.86 kOe in the second annealing state,which is a increase of 38.6%;rectangularity H_k/H_cjincreases from 0.86 to 0.97;remanence B_rdecreases slightly from 13.51 kGs in the sintered state to 13.46 kGs in the second annealing state;the distribution of RE-rich phase becomes more continuous and obvious.The research analysis shows that the reason why the coercivity greatly increases is that Ga doped in the sintered Nd-Fe-B magnets containing small amounts of Nd-rich phase and B-poor phase changes the wettability of intergranular phase and reduces Fe content in the RE-rich phase.The study lays a solid theoretical foundation for the industrialization of heavy rare earth-free sintered Nd-Fe-B magnets with high coercivity and high remanence.