China is a large country of tungsten industry, but there is a lack of effective industrialized treatment methods for tungsten slag.With the extensive exploitation of tungsten ore, the traditional landfill method is no longer suitable for the treatment of existing tungsten slag, resulting in the continuous accumulation of tungsten slag.At the same time, heavy metals in tungsten slag have caused serious environmental pollution.In view of these problems, many scholars are committed to solving the problem of tungsten slag accumulation and have carried out a lot of research to comprehensively recover and utilize the va-luable metals in tungsten slag.This paper summarizes the research progress on the recovery and utilization technology of tungsten slag at home and abroad in recent years, which is mainly divided into the recovery of valuable metals in tungsten slag and the use of tungsten slag to make special materials.Finally, the deve-lopment trend of tungsten slag recycling is prospected.

Alkaline treatment of spent hydrogenation catalyst has been widely studied and applied for its advantages of mild reaction condition,high metal recovery and simple composition of leaching solution.In order to improve the purity and recovery of molybdenum and vanadium in the products,the separation and recovery of molybdenum and vanadium from alkaline leaching solution are very important.The precipita-tion recovery process of molybdenum and vanadium in alkaline solution was studied in detail,and the effects of the precipitant dosage and pH value on the precipitation rate of molybdenum and vanadium in alkaline solution were investigated by thermodynamic calculation and condition experiments.The experimental results show that the pH value and the amount of precipitants have a great influence on the precipitation rates of molybdenum and vanadium,and the influence law is roughly consistent with the theoretical calculation result.Under the optimal reaction conditions,the precipitation rates of molybdenum and vanadium can reach 93%and 94%,respectively.NH₄Cl and BaCl₂ are used to separate Mo-V alkaline mixed solution by step-by-step precipitation,and 93.6%vanadium and 92.4%molybdenum can be respectively recovered by one-step precipitation separation.However,there is co-precipitation phenomenon of molybdenum and vanadium.After multiple dissolution and precipitation separation,the products with high purity can be obtained.

The fluorine removal effects from ammonium molybdate solution by different magnesium salts and aluminum salts such as magnesium sulfate, active magnesium oxide, active alumina and aluminum sulfate were compared.And active magnesium oxide is determined to be the reagent for removing fluoride ions from ammonium molybdate solution.The effects of reaction temperature, addition amount of magnesium oxide, reaction time and solution pH on fluorine removal by active magnesium oxide were emphatically investigated.The results show that the fluorine content in ammonium molybdate solution can be reduced by more than 90% under the conditions as follows: solution pH of 7~7.5,reaction temperature of 60 ℃,magnesium oxide addition amount of 2.5 times the fluorine content, and stirring reaction time of 1 h.

With the development of localization of foreign technology,China has already obtained a relatively stable tantalum-niobium hydrometallurgy process.However,there is still plenty of scope for improving the treatment,reduction and resource utilization of“three wastes”in China.This paper briefly describes the development of waste gas,wastewater and waste residue treatment technology in tantalum-niobium hydrometallurgy industry,and discusses how tantalum-niobium hydrometallurgy industry can do well in inspection work of ecological environmental protection under the background of severe environmental protection supervision.Finally,the future research focus on environmental protection in the industry is prospected.

The recycling of spent lithium-ion batteries has double benefits of resource and environment.The coupling system of tartaric acid and glucose leaching and sodium carbonate precipitation regeneration was adopted to realize the recycling and reusing of spent LiNi_0.5Co_0.2Mn_0.3O₂ternary cathode material.Based on the single factor experimental design,the effects of glucose concentration,tartaric acid concentration,stirring rate,leaching time and leaching temperature on the leaching rate of each metal element were investigated.The results show that under the optimal leaching conditions of glucose concentration of 1.25 mol/L,tartaric acid concentration of 2 mol/L,stirring rate of 400 r/min,leaching time of 60 min and leaching temperature of 80℃,the leaching rates of Li,Ni,Co and Mn are 98.88%,98.24%,97.11%and 96.85%,respectively.The regenerated cathode material prepared by sodium carbonate precipitation and high temperature sintering has relatively excellent electrochemical performance.

A large amount of solid waste produced by PDC cylindrical processing and grinding contains Co.After mechanical activation treatment with sodium persulfate solid powder, the above Co can be recovered by water immersion-neutralization precipitation.The effects of ball-to-material ratio, ball milling time, ball milling speed and oxidant dosage on Co leaching rate were studied.The results show that the recovery rate of Co in the PDC cylindrical processing waste increases with the increase of ball-to-material ratio, ball milling speed and ball milling time, but decreases with the increase of oxidant dosage.The optimized mechanical activation process parameters are as follows: The ball-to-material ratio is 42.9,the amount of oxidant(sodium persulfate) is 1 g, the amount of PDC cylindrical processing waste is 1 g, the ball milling speed is 300 r/min and the ball milling time is 360 min.Under the optimized process parameters, the recovery rate of Co in PDC cylindrical processing waste can reach 99.32%.The method has the advantages of short process, high efficiency and low water consumption.

Using lanthanum nitrate hexahydrate,magnesium nitrate hexahydrate and boric acid as the raw materials and glycine as the combustion agent,LaMgB₅O₁₀ luminescent matrix material was prepared by microwave-assisted combustion method.The grain size,morphology,chemical element composition and valence state of the product were analyzed by XRD,SEM and XPS.The experimental results show that the prepared luminescent matrix material LaMgB₅O₁₀ has the best crystal structure when the molar ratio of La(NO₃)₃·6 H₂O,Mg(NO₃)₂·6 H₂O and H₃BO₃is 1∶1∶6,the microwave power is 550 W,the crystallization temperature is 600℃and the crystallization time is 4 h.

In order to improve the cycle stability of the anode materials of Ni/MH battery,the vanadium-based hydrogen storage alloys of V₂Ti_0.5Cr_0.5NiCe_x(x=0~0.10)were prepared by vacuum arc-melting.The effect of adding different contents of rare earth Ce on the microstructure and electrochemical properties of hydrogen storage alloys was analyzed.The results show that all of V₂Ti_0.5Cr_0.5NiCe_x(x=0~0.10)alloys are mainly composed of vanadium-based solid solution main phase with BCC structure and TiNi se-condary phase.As the addition amount of Ce in hydrogen storage alloys increases,the discharge capacity of the prepared alloys as the anode materials of Ni/MH battery firstly increases and then decreases.The alloy electrode has the best comprehensive electrochemical properties at x=0.08:Its maximum discharge capacity reaches 409 mA·h/g,and the capacity retention rate is 87.2%after 100 cycles of charge and discharge.

(Ti, Nb)(C,N) solid solution powder was used for preparing(Ti, Nb)(C,N)-based cermets at different nitrogen partial pressures.At the same time, Ti(C,N)-based cermets were considered as the control group.The effects of different nitrogen partial pressures during sintering on microstructure and mechanical properties of the cermets were studied by a scanning electron microscope with an energy spectrum analyzer and a Vickers hardness tester, combined with thermodynamic calculation.The results show that compared with Ti(C,N)-based cermets prepared with the same sintering process,(Ti, Nb)(C,N)-based cermets have finer grains, and only a few grains have special weak core-rim structure.There is a binder phase Ni-rich gradient layer on the surface of vacuum-sintered(Ti, Nb)(C,N)-based cermets.As the nitrogen partial pressure during sintering increases, the hard phase in the surface layer of(Ti, Nb)(C,N)-based cermets abnormally grows up.The formation of the gradient structure of(Ti, Nb)(C,N)-based cermets is due to the difference in N activity between the surface and the core of the material sintered at different nitrogen partial pressures, and different diffusion direction and rate of Ti, Nb and other atoms, attributed to thermodynamic coupling.

Embedding metal cations in the layered structure of vanadium oxides can significantly improve the electrochemical performance of the vanadate materials.According to the types of pre-embedded metal cations, the synthesized vanadates are mainly divided into alkali metal vanadates, transition metal vanadates and alkaline-earth metal vanadates.The latest research progress of these vanadate electrode materials is reviewed in this article, including preparation process, reaction mechanism, electrochemical performance, performance optimization methods and so on.Finally, the future research direction of vanadate electrode materials is prospected.