In order to efficiently and rationally develop Zhijin phosphorite and optimize the rare earth enrichment process,the solvent extraction method was used to remove iron from 4-stage hydrochloric acid leaching solution of Zhijin phosphorite,and then the rare earth elements in the extract solution were enriched by the solvent extraction method.The effects of O/A,extraction time,P204 concentration and extraction times on the extraction rate of rare earth were studied.The results show that when 15 mL N235+(1~5)mL isooctanol+(34~30)mL sulfonated kerosene is used as the iron extraction agent,the content of isooctanol and sulfonated kerosene has little effect on the iron extraction effect,and the iron extraction rate is close to 100%.The optimized extraction conditions of rare earth are O/A of 3∶1,P204 concentration of 1.5 mol/L and extraction time of 15 min.Under the optimized conditions,the extraction rate of rare earth reaches 82.24%after four times of extraction.

The reduction roasting technology was used to reduce the iron minerals in a mixed rare earth concentrate from Inner Mongolia to elemental metals,and then the magnetic separation technology was used for high efficient separation and enrichment of iron,rare earth,niobium and other elements.The effects of reduction temperature,roasting time and carbon content on the reduction roasting were investigated by single factor experiments,as well as the enrichment and recovery of rare earth and niobium at different roasting temperatures.Under the optimized conditions of roasting temperature of 1175℃,roasting time of 90 min and C/O ratio of 1.5,the iron metallization rate reaches 92.52%,the iron grade and recovery rate in magnetic materials are 89.71%and 92.12%,the niobium grade and recovery rate in non-magnetic materia-ls are 3.85%and 87.92%,and the rare earth grade and recovery rate are 7.15%and 88.23%,respectively.

The resource characteristics and recovery process status of vanadium in stone coal were reviewed.Focusing on the recovery process of vanadium in stone coal by hydrometallurgical acid leaching,and combined with the control factors and kinetics of vanadium leaching reaction process under different process conditions,the influences of vanadium occurrence state,leaching aid and leaching process on the vanadium recovery process by hydrometallurgical acid leaching were analyzed.The promotion effect of fluorine-containing leaching aid,oxidant and their compound on the hydrometallurgical leaching of vanadium was expounded.Based on the occurrence state of vanadium in stone coal,it is pointed out that the development of environmentally friendly and high-efficiency leaching aid and the in-depth analysis of its leaching kinetics to improve the leaching and recovery efficiency of vanadium,and the development of the recovery and recycling technology of leaching waste liquid and slag are the focus of future research and the key to realize the high-efficiency and clean recovery of vanadium in stone coal.

The electrochemical performance was studied of Cu(Ⅰ)ions in CuCl-containing choline chloride-urea(ChCl-Urea)deep eutectic solvent as the electrolyte.The results show that the conductivity of ChCl-Urea-CuCl electrolyte increases with the increase of temperature,but increases at first and then decreases with the increase of CuCl concentration.The variation of its viscosity is opposite to its conductivity.In addition,the reduction reaction of Cu(Ⅰ)ions in ChCl-Urea-CuCl electrolyte is quasi-reversible and controlled by diffusion.The diffusion coefficient of Cu(Ⅰ)ions increases with the increase of temperature,but increases firstly and then decreases with the increase of CuCl concentration,which is mainly related to the existence form of Cu(Ⅰ)ions in ChCl-Urea deep eutectic solvent.

The process of recovering valuable metals such as copper and zinc from heavy metal-containing sludge by oxygen-enriched side-blown molten pool smelting is introduced from the aspects of process selection and design,main equipment selection and main technical indicators,to provide a reference for the comprehensive utilization of heavy metal-containing sludge.

The dissolution equilibrium of Y2O3 and its solubility variation laws with temperature and NaF/AlF3 molar ratio were studied with isothermal saturation method in NaF-AlF3-LiF molten salt system at 995~1115℃.The first-order regression equation of solubility with temperature and NaF/AlF3 molar ratio was established.The results show that the dissolution equilibrium time of Y2O3 in NaF-AlF3-LiF molten salt system is not less than 40 min at 995~1115℃.Meanwhile,the solubility of Y2O3 in the system increases both with the increase of temperature and NaF/AlF3 molar ratio.The fitness of the regression equation of Y2O3 solubility exceeds 90%under the conditions of 995~1115℃temperature and 2.3~2.9 NaF/AlF3 molar ratio.

Based on the composition of Ni-6 B-53.3 Mo,Mo2NiB2 based cermets with different content of nano-La2O3 particles(0,0.3%,0.6%,0.9%,1.2%)were prepared by vacuum hot pressing sintering technology,and their microstructure and mechanical properties were studied.The results show that doping La2O3 can improve the solubility of hard phase and Ni based binding phase of Mo2NiB2 based cermets,reduce the grain size and make the distribution of Ni based binding phase more uniform.With the increase of La2O3 content,the bending strength,hardness and compressive strength of Mo2NiB2 based cermets increase first and then decrease.The cermet with 0.6%La2O3 has the maximum bending strength and hardness of 603.55 MPa and 902.1 HV,respectively.The cermet with 0.3%La2O3 has the maximum compressive strength of 550 MPa.However,with the increase of La2O3 content,both the fracture toughness and density of Mo2NiB2 based cermets decrease.

Experimental study was conducted on the reduction of NO,using CO as the reductant and rare earth tailings as the catalyst.The experimental results show that rare earth tailings can effectively catalyze the reduction of NO,and the denitration rate increases as the reaction temperature and the carbon-to-nitrogen ratio increase.The denitration rate of rare earth tailings in the middle and high temperature section is higher than that of the pure substances of CeO2,Fe2O3,Fe2O3/CeO2 and 5 Fe2O3/CeO2.H2-TPR test shows that the reduction peaks of rare earth tailings above 800℃are also higher than those of the four pure substances.XRD analysis shows that the main mineral phases of the rare earth tailings have no change before and after denitration reaction.However,the intensity of characteristic peaks of each mineral phase decreases,and the characteristic peak of bastnaesite disappears.SEM images show that cracks and pores appear in rare earth tailings after denitration reaction.EDS analysis shows that there are overlapping areas of multiple metal elements in a single particle of tailings.XPS analysis shows that the proportions of Fe3+and Ce3+in the tailings increase after denitration reaction.When the reaction temperature is 800℃and the carbon-to-nitrogen ratio is 4∶1,the denitration rate is 98%by rare earth tailings.

TiC/NbC ceramic particles(mass fractions of 50%,33.33%,25%,20%and 16.67%)were added to the iron matrix,and ceramic particle reinforced iron-based composite materials were prepared by spark plasma sintering(SPS).The microscopic morphology of the sintered samples were characterized by scanning electron microscope(SEM)and energy dispersive spectrometer(EDS),and their relative density and mechanical properties were tested.The results show that the iron-based composite material with 16.67%TiC/NbC ceramic particles has the highest relative density of 96.78%,and high Vickers hardness and flexural strength of 300 HV and 400 MPa,and its fracture shows obvious brittle fracture characteristics.SPS rapid sintering technology can make TiC/NbC ceramic particles uniformly dispersed in the iron matrix,and the interface between the reinforcement phase and the iron matrix is well combined.A small amount of TiC/NbC ceramic particles can significantly refine the matrix microstructure and enhance the strength and hardness of the iron-based composite materials.With the further increase of the content of TiC/NbC ceramic particles,their refinement effect on the matrix microstructure is weakened.

Ti(C,N)-based cermets reinforced by different content of carbon fiber(Cf)were prepared by powder metallurgy with Ti(C,N),Mo2C,Co,Ni,WC and Cf as raw materials.Effect of Cf content on the density,hardness and flexural strength of Ti(C,N)-based cermets was studied.The results show that with the gradual increase of Cf content,the density and hardness of Ti(C,N)-based cermets slightly decrease,and the flexural strength increases firstly and then decreases.When the content of carbon fiber is 2%(mass fraction),the Ti(C,N)-based cermet has the most excellent mechanical properties of 66 GPa hardness and 672.6 MPa flexural strength.