By using the method of bisulfate and tungsten ore roasting,arsenic in tungsten ore could be converted into volatile arsenide and absorbed by the alkaline solution,fundamentally changing the easy-dispersion trend of arsenic in the tungsten smelting system and greatly reducing the formation of the arsenic-containing hazardous waste in tungsten smelting.Simultaneously,the tungsten ore is roasted into MnSO₄,Fe₂(SO₄)3+WO₃or CaSO₄+WO₃products,and the next step is to separate tungsten and impurities in the roasted products effectively to obtain relatively pure tungsten compounds.In general,MnSO₄and Fe₂(SO₄)3could be effectively dissolved by cheap sulfuric acid,but whether CaSO₄and WO₃could be dissolved in the same way is unknown.Based on this,the dissolution behavior of CaSO₄-WO₃system in sulfuric acid was systematically studied in this paper.The results show that in the sulfuric acid system,the solubility of CaSO₄is significantly greater than that of WO₃,and their solubility difference varies little with the concentration of sulfuric acid but greatly with temperature.The effective separation of CaSO₄and WO₃can be achieved by controlling certain acidity and temperature.

A method of removing magnesium from mother liquor in the production of water-washed ammonium dimolybdate is proposed,meaning that the magnesium content is reduced by adding ammonium phosphate to the mother liquor to form magnesium ammonium phosphate precipitation.In the experiment,by optimizing the process parameters such as the concentration of Mg²⁺and PO₄^3-in mother liquor,reaction temperature,solution pH and reaction time,the content of magnesium and phosphorus in ammonium dimolybdate products reached the standard.And the method has been successfully applied to the production practice.The study provides an innovative magnesium removal process with simple operation and no impact on the production line for the water-washed ammonium dimolybdate production line.

The molybdenum content in some molybdenum ore in Fujian is only 0.09%,and most molybdenum exists in molybdenites while a small amount of molybdenum exists in the form of molybdenum oxide ore.The gangue minerals mainly consist of easy-sliming silicate minerals and the flotation activity of the molybdenum ore is low,showing that it is the typical refractory molybdenum ore with high mud content and low grade.A novel surface promoter MCS was introduced to effectively enhance the surface activity of the molybdenum ore,thereby improving the molybdenum flotation recovery.The appropriate grinding fineness,MCS dosage,water glass dosage and collector CM dosage for the flotation were determined through condition experiments.The results show that by using the flotation machine,molybdenum concentrates with a Mo grade of 45.75%and Mo recovery of 82.18%can be obtained after one roughing,three scavenging and seven cleaning,but this process is lengthy and the production and operation costs are high.Through the combined flotation column-flotation machine process,the qualified molybdenum concentrates are gained with a Mo grade of 46.01%and Mo recovery of 87.81%after four cleaning.Therefore,it is re-commended as the principle process for the recovery of molybdenum from the molybdenum ore.

The direct saponification of rare earth extraction organic phase with calcium hydroxide powder was studied.The experimental results show that the saponification values of P507 organic phase and naphthenic acid organic phase are 0.55 mol/L and 0.72 mol/L,respectively, with clear appearance and good fluidity through the process of direct saponification by using calcium hydroxide powder.When the calcium saponified organic phase is subject to extraction reaction with rare earth chloride feed liquid, the separation time of P507 organic phase is 40 s with the rare earth load of 0.19 mol/L,and the separation time of naphthenic acid organic phase is 180 s with the rare earth load of 0.19 mol/L.Based on the test data, a centra-lized calcium hydroxide powder direct saponification technology was developed.After years of industrial operation, the results show that calcium hydroxide powder directly saponifies the P507 organic phase and the naphthenic acid organic phase with good fluidity, fast phase separation, little impact on product quality, and no long-term adverse effects on the organic phase.And the saponification cost is only 16.5% of that of liquid alkali.Since the saponifier is a powder, there is no need for emulsion and the saponification reaction with the organic phase directly occurs.Compared with the saponification of liquid alkali, the wastewater greatly reduces and the environmental benefits are quite good.

China is rich in vanadium resources.Vanadium metal is widely used in steel, national defense, aviation and other fields because of its excellent performance.At present, vanadium metal is mainly prepared by metallothermic reduction, followed by refining to obtain high-purity vanadium metal.In this paper, several typical methods of the preparation and refining of crude vanadium are analyzed and summarized, and it is pointed out that the development direction of vanadium preparation is high yield, low cost, low energy consumption, and short process in the future.

Accelerating the extraction of germanium resource from coal fly ash can not only alleviate the contradiction between the shortage of germanium resource and its increasing demand but also broaden the ways of high-value utilization of coal fly ash and improve the added value of products.By reviewing the development status of germanium enrichment and recovery technology from coal fly ash in recent years,the merits and demerits of various methods are analyzed and relevant suggestions are given on the efficient utilization of germanium in coal fly ash.

WC-Al₂O₃composite was prepared by vacuum hot pressing sintering(HPS)method.The effect of metal elements(Cr,Mo,Ti)on the corrosion behavior of WC-Al₂O₃composite in NaCl solution was studied by electrochemical corrosion method,and open circuit potential,electric polarization curve and electrochemical impedance spectroscopy were mainly measured.The experimental results show that Cr and Mo additives can improve the corrosion resistance of WC-Al₂O₃composite,and the enhancement effect of Cr additive is significantly better than that of Mo additive while Ti additive reduces the corrosion resistance of WC-Al₂O₃composite.Based on analysis,oxide film formed on the surface of the Cr-containing composite in the corrosive medium is more complete and denser,thereby effectively reducing the corrosion rate of the composite.

The WC-reinforced Ni60 gradient coating was generated on the surface of H13 steel by laser cladding.The microstructure,phase composition,microhardness and friction&wear properties of the coating were analyzed by metallographic microscope,scanning electron microscope,X-ray diffractometer,microhardness tester and universal friction&wear tester.The results indicate that there are relatively few pores and cracks in WC-reinforced Ni60 gradient coating.The coating and the substrate form a good metallurgical bond.The phases of gradient coating surface are mainly iron-carbon compound(FexC),iron-nickel solid solution((Fe,Ni)₂₃C₆,Ni₄B₃)and ceramic-reinforced phases such as WC,W₂C and Cr₇C₃.The hardness and wear resistance of the die steel surface are significantly improved by the gradient coating.The maximum microhardness of the coating surface is about 4 times of the substrate,and its wear amount is only about 18%of the substrate.The wear mechanism of the coating mainly includes adhesive wear,brittle spalling and abrasive wear,which can prolong the service life of the die and reduce the waste of resources.

Bayan Obo rare earth tailings were pretreated with sulfuric acid and then loaded with 5%manganese acetate by impregnation and roasted by microwave to prepare denitration catalysts.And the effects of sulfuric acid concentration(0 mol/L,0.5 mol/L,1 mol/L,and 3 mol/L)on the denitration performance of the catalysts were investigated.The catalysts were characterized by XRD,NH₃-TPD,H2-TPR,and XPS.The results of denitration activity tests show that the denitration activity of the catalysts at 100~250℃increases at first and then decreases with the increase of sulfuric acid concentration,and reaches the best when the sulfuric acid concentration is 0.5 mol/L.The higher concentration(3 mol/L)of sulfuric acid deteriorates the originally good low-temperature activity of the catalyst.The catalyst treated with 0.5 mol/L sulfuric acid has a wide temperature window with good activity in the range of 150℃to 250℃and the conversion rate of nitrogen oxides reaches 92%at 200℃.The characterization results show that the loaded manganese exists in amorphous state or is highly dispersed on the surface of the rare earth tailings.The concentration of Mn4+on the catalyst surface decreases with the increase of sulfuric acid concentration,and both the ammonia adsorption capacity and redox capacity of the catalysts decrease,thereby reducing the denitration activity.

The continuous cooling in the casting process of rare earth glass-ceramics would change the microstructure of the melt.Through Raman,XRD,and SEM-EDS,samples with different quenching temperatures(1550~1100℃)were analyzed to study the effect of temperature on high-temperature melt structure of La₂O₃-SiO₂-CaO-Al₂O₃-MgO system.The results show that the quenched samples are amorphous at high temperatures and crystalline at relatively low temperatures.After the decomposition of Raman spectra of amorphous quenched samples,it is found that with the temperature decreasing,the Raman peak positions of the basic structural unit of each silicon oxygen/aluminum oxygen tetrahedron have a shift towards the high frequency.The shift of the peak positions of the low-frequency(200~800 cm^-1)structural unit is large while that of the high-frequency(800~1200 cm^-1)structural unit is small,and La₂O₃inhi-bits the peak positions of each structural unit from shifting towards the high frequency.The results of XRD and SEM-EDS show that the addition of La₂O₃reduces the temperature at which CaMg(SiO₃)2crystalline phase is produced in La₂O₃-SiO₂-CaO-Al₂O₃-MgO melt.