To address the technical challenges in the comprehensive development and utilization of Nanling tungsten-tin polymetallic resources,an acid-alkali combined decomposition process was employed to treat low-grade tungsten-tin mixed ore,achieving efficient leaching of tungsten and resourceful enrichment of tin.The influences of various parameters on the decomposition of tungsten minerals and the reaction behavior of cassiterite during the leaching process were investigated.The results demonstrate that the decomposition of the scheelite component in the minerals requires a high concentration of HCl to provide sufficient driving force,while excessively high H_3PO_4 concentration is detrimental to it.The efficient decomposition of wolframite component is achieved using the conventional alkali autoclaving method,with the associated Sn being enriched in the alkali decomposition slag.In the acid leaching process,a mixed acid of 5 mol/L HCl+75 g/L H₃PO₄ is used as the leachant.Under the process conditions of a liquid-to-solid ratio of 2.5∶1,a reaction temperature of 80℃,and a reaction time of 2 h,the W leaching rate is 77.89%and the W content in the slag is 4.58%.In the alkali leaching process,controlling the conditions of a NaOH concentration at 300 g/L,a liquid-to-solid ratio of 1.25∶1,a reaction temperature of 130℃,and a reaction time of 1.5 h,the W leaching rate could reach 99.79%with the W content in the slag only of 0.06%.The complex occurrence state of Sn in the mixed ore causes its slight loss in both acid and alkali leaching systems.The Sn content in the alkali decomposition slag is enriched to 11.21%,which can be used as a medium-grade tin concentrate for resource utilization.

In the acid leaching of scheelite,the decomposition method that tungsten is produced in the form of isopolytungstate provides a new way for scheelite smelting.However,the subsequent recovery of tungsten from the leaching solution of isopolytungstate matters.This paper compared the adsorption behaviors of different anion exchange resins in isopolytungstate solution and determined that the macroporous weak-base anion exchange resin D301 was the optimal resin.The effects of D301 resin dosage,solution pH,adsorption temperature,tungsten concentration,and adsorption time on the resin′s adsorption of tungsten were investigated.The results show that under the conditions of a resin dosage of 5 times the theoretical amount,solution pH of 2~3,adsorption temperature of 40℃,WO₃ concentration of 50~100 g/L,and adsorption time of 240 min,the adsorption rate of D301 resin for tungsten in the isopolytungstate solution exceeds 99.4%.In addition,the desorption behaviors of tungsten loaded resins were also studied.The results show that NaOH serves as the most effective desorption agent for tungsten loaded D301 resin.And under the conditions of a NaOH solution dosage of 20 mL,NaOH concentration of 4 mol/L,desorption temperature of 50℃,and desorption time of 60 min,the tungsten desorption rate reaches 97.94%.

An oxidative leaching process of hydrogen peroxide combined with ammonia was proposed for selective leaching of molybdenum from spent nickel-molybdenum hydrogenation catalysts.The effects of hydrogen peroxide dosage,leaching temperature and leaching time on the leaching rate of molybdenum were studied by experiments,and the leaching residue was characterized by SEM,EDS and XRD.The results show that the leaching rate of molybdenum can reach over 97%under the conditions of a reaction system pH of 8~9 maintained by adding ammonia,hydrogen peroxide dosage of 2.0 times the theoretical amount,leaching temperature of 80℃,leaching time of 120 min,and stirring speed of 250 r/min,while the dissolution rates of aluminum and nickel remain at a low level.

The sources,properties,and treatment measures of three wastes in the hydrometallurgical process of tantalum-niobium concentrate are comprehensively introduced.Among the three wastes,the waste water undergoes refined treatment,with the extraction raffinate containing radioactive substance or heavy metals being treated separately,achieving complete reuse through resource processing without any discharge.Other production wastewater is treated using lime for step-by-step defluorination and desulfation and negative pressure stripping deammoniation for ammonia recycling.The stripping deammoniation effluent is subjected to pH adjustment,flocculent deposition,and deep defluorination before being discharged to meet the standards.All exhaust gases are collected and sent to the purification system for discharge at high altitude after purification.The purification efficiency of pollution factors in process waste gas,dry waste gas and calcined waste gas exceeds 90%,and the boiler flue gas can be directly discharged by using low-nitrogen burners.Low-level radioactive solid waste and hazardous waste are temporarily stored in the radioactive residue storage and hazardous waste storage within the plant respectively,and are regularly entrusted to qualified units for disposal.General industrial solid waste is either comprehensively utilized or undergoes regular sanitary landfill with domestic waste.The process design not only realizes the standard discharge of three wastes but also promotes the efficient recovery and recycling of resources.

In the process of tantalum niobium hydrometallurgy producing tantalum/niobium oxides,the washing of tantalum/niobium hydroxides generates a large amount of alkaline wastewater with high ammonia nitrogen content,which is treated with stripping deammoniation columns by most smelting plants currently.The qualified treated wastewater generally has a temperature higher than 70℃.And a great deal of high-temperature waste flue gas is generated with the calcination of tantalum/niobium hydroxides.The energy storage waste heat recovery technology introduced in this paper utilizes a plate heat exchanger to recover waste heat from the wastewater and a flue gas heat exchanger to recover waste heat from the waste flue gas.The combination of these two heat exchange methods in tantalum/niobium hydrometallurgy could recover waste heat and generate hot pure water above 70℃,effectively saving energy.

Removing calcium and magnesium by fluorine precipitation is the most common method to prepare high-purity manganese sulfate solution.However,the introduced fluorine needs a further removal.In this paper,a new technology is proposed to separate and recover fluorine from fluorine-containing manganese sulfate solution,mainly including the two processes of solvent extraction for fluorine and cyclic stripping of fluorine with manganese oxide.Under such conditions,including initial pH of 1.9 for manganese sulfate solution,organic phase composition of 60%TBP+40%sulfonated kerosene,O/A ratio of 2∶1,and extraction time of 3 min,the concentration of fluorine in manganese sulfate solution can be reduced to below 35 mg/L after a five-stage countercurrent extraction at room temperature.And under the optimal stripping conditions of manganese oxide addition of 1.0 times the theoretical amount,O/A ratio of 5∶1,stripping time of 1 h,and temperature of 298 K,the cyclic stripping efficiency of manganese oxide reaches above 98.08%,and the manganese fluoride precipitated in the stripping process can be used for the removal of calcium and magnesium in manganese sulfate solution in return.Compared with the existing fluorine stripping process,this new technology can realize the recycling of fluorine while removing fluorine in depth.

Ni60/WC composite coatings with different Y₂O₃contents were prepared on the surface of H13 steel by laser cladding in-situ generation method,and the macrostructure,microstructure,and microhardness of the coatings were analyzed to find the optimal Y₂O₃addition.And the phase composition,microstructure,microhardness,and wear mechanism of the WC/Ni60 gradient composite coatings with the optimal Y₂O₃addition were also investigated.The results show that the microhardness of the composite coatings presents a trend of increasing at first and then decreasing with the increase of Y₂O₃content.When the Y₂O₃content is 1.5%,the macroscopic quality of the coatings reaches the best with refined grains and the largest microhardness.And when the Y₂O₃content continues to increase,the WC particles in the coatings become larger again while the microhardness decreases.Compared with gradient composite coatings without the addition of rare earth,the thickness of the gradient composite coatings doped with rare earth is reduced,and the morphology and distribution of the microstructure undergo some changes.And the internal enhancement phase particles become finer and more uniform with the angles being blunted,and the microhardness of each layer from top to bottom increases by 49.2 HV_0.5,75.78 HV_0.5,and 72.78 HV_0.5,respectively.The wear loss receives a decrease for different time,and the wear mechanism still consists of adhesive wear,brittle spalling,and abrasive wear.

Using TiO₂,MoO₃,Nb₂O₅,Ta₂O₅,ZrO₂,B₄C and carbon black as raw materials,(Ti,Mo,Nb,Ta,Zr)B₂ high-entropy ceramic powder was prepared by high-energy ball milling and boro/carbothermal reduction method,with the phase composition and microstructure of the reaction products being characte-rized by XRD and SEM.The results show that ball milling time,reduction temperature,and holding time are important factors for the preparation of high-quality(Ti,Mo,Nb,Ta,Zr)B₂ high-entropy ceramic powder.The high-quality(Ti,Mo,Nb,Ta,Zr)B₂ high-entropy ceramic powder can be prepared with particle size of 1~2μm,uniform distribution of elements,and single phase composition under the conditions of ball milling time of 2 h,vacuum carbothermal reduction temperature of 1700℃,and holding time of 2 h.

Ag-Ni-Sc series alloys were prepared by vacuum induction smelting furnace.The corrosion beha-vior of these series of alloys in 0.1 mol/L Na₂S solution and H₂S atmosphere was studied by immersion corrosion and electrochemical tests.And the effects of Sc addition on the corrosion morphology,components of the corrosion products,microstructure,and mechanical properties of Ag-Ni alloys were investigated by SEM,EDS,OM,and hardness tests.The results show that the moderate addition of Sc can reduce the corrosion current of the alloy,improve the sulfuration resistance of the alloy,refine the grains of the alloy,and thus enhance the hardness of the alloy.However,excessive Sc content will lead to excess amount of intermetallic compounds and grain boundary segregation in the alloy microstructure,deteriorating the hardness and sulfuration resistance of the alloy.Taking all factors into consideration,the optimum addition of Sc in Ag-Ni alloys is 0.15%.

Five Mg-xLa alloys with different La contents were prepared by casting method.The effects of La content on the microstructure and corrosion resistance of Mg-xLa alloys were systematically investigated by optical microscope,scanning electron microscope,X-ray diffractometer,microhardness tester and electrochemical workstation.The results show that Mg₁₂La is the only second phase in the Mg-xLa alloys.With the increase of La content,the magnesium alloy grains are gradually refined at first,and the subsequent grain size difference is small.The grain size of Mg-3La alloy is the finest,and its size distribution is also more uniform compared with other alloys.As the content of La increases,the microhardness of the Ma-xLa alloys increases firstly and then decreases slightly,and reaches the maximum value when the La content is 3%.In a 3.5%NaCl solution at 25℃,the corrosion rate of the Mg-La alloy with high La con-tent is significantly lower than that of the Mg-La alloy with low La content.And the corrosion potential of Mg-3La alloy in the 3.5%NaCl solution negatively moves in general with the increase of solution temperature,and its corrosion resistance is the best in the 30℃solution.