Preparation of low-oxygen titanium powder by magnesiothermic reduction of TiO2 assisted by MgCl_(2)−HoCl_(3) molten salt

To reduce the production cost of titanium,a new method for direct preparation of low-oxygen titanium powder by the magnesiothermic reduction of TiO_(2) with the assistance of a MgCl_(2)−HoCl_(3) molten salt was proposed.Thermodynamic calculations showed that the magnesiothermic reduction of TiO_(2) was feasible.However,hindrance of the reduction reaction by the reduction by-product of MgO resulted in a considerably high O concentration in the titanium powder.The addition of HoCl_(3) to the system significantly reduces the activity of MgO to produce low-oxygen titanium powder.Thermochemical deoxidation and reduction experiments were conducted with MgCl_(2)−HoCl_(3) molten salt in the temperature range of 1023−1273 K.The results showed that titanium powder with oxygen concentration(mass fraction)below 5.00×10^(-4) can be prepared at the Mg−MgCl_(2)−HoOCl−HoCl_(3) equilibrium.

Separation of arsenic and antimony from dust with high content of arsenic by a selective sulfidation roasting process using sulfur

The separation of arsenic and antimony from dust with high content of arsenic was conducted via a selective sulfidation roasting process.The factors such as roasting temperature,roasting time,sulfur content and nitrogen flow rate were investigated using XRD,EPMA and SEM-EDS.In a certain range,the sulfur addition has an active effect on the arsenic volatilization because the solid solution phase（（Sb,As）2O3）in the dust can be destroyed after the Sb component in it being vulcanized to Sb2S3 and this generated As2O3 continues to volatile.In addition,an amorphization reaction between As2O（3 ）and Sb2O（3 ）is hindered through the sulfidation of Sb2O3,which is also beneficial to increasing arsenic volatilization rate.The results show that volatilization rates of arsenic and antimony reach 95.36%and only 9.07%,respectively,under the optimum condition of roasting temperature of 350℃,roasting time of 90 min,sulfur content of 22%and N2 flow rate of 70 m L/min.In addition,the antimony in the residues can be reclaimed through a reverberatory process.

Selective recovery of zinc from zinc oxide dust using choline chloride based deep eutectic solvents

Deep eutectic solvents(DESs) are a kind of potential lixiviant for selective metal processing due to their versatile complexation properties. In this study, we investigated the recovery of zinc from zinc oxide dust using choline chloride-ureaethylene glycol(ChCl-urea-EG) DESs. The zinc extraction efficiency can be up to 85.2% when the slurry concentration is 50 g/L, leaching temperature is 80 °C and stirring speed is 600 r/min. The leaching process is controlled by the diffusion and the corresponding activation energy is 32.1 k J/mol. The resultant solution was directly used for the electrodeposition of zinc. The pure zinc deposit is obtained with a current efficiency of 82.6%. Furthermore, the ChCl-urea-EG DESs can be recycled. This approach is shown to be promising for the recycling of zinc from the zinc-containing dust.

Effect of cooling ways on properties of Al/Pb-0.2%Ag rolled alloy for zinc electrowinning

In order to study the new anode materials for zinc electrowinning,Al/Pb?0.2%Ag rolled alloy was produced by composite casting and hot rolling.Then the effect of cooling ways on properties of Al/Pb?0.2%Ag rolled alloy was investigated.As the results of metallographic test indicated,with the increasing of cooling intensity,both Vickers hardness and yield strength of Al/Pb?0.2%Ag rolled alloy increase.Furthermore,the Al/Pb?0.2%Ag rolled alloy,cooled by ice salt,presents the finest grain size and shows the lowest oxygen evolution potential(1.5902V),while that of alloy cooled by water and air are1.6143V and1.6288V,respectively.However,the corrosion current density and corrosion rate of the Al/Pb?0.2%Ag rolled alloy,cooled by ice salt,are the highest.This can be attributed to its largest specific surface area,which promotes the contact between the anode and electrolyte.

φ-pH diagram of As-N-Na-H_2O system for arsenic removal during alkaline pressure oxidation leaching of lead anode slime

In order to illustrate the thermodynamic characteristics of arsenic during alkaline pressure oxidation leaching process oflead anode slime(NaNO3as oxidant;NaOH as alkaline reagent),theφ-pH diagrams of As-Na-H2O,N-H2O,As-N-Na-H2Osystems at ionic mass concentration of0.1mol/kg and temperatures of298,373,423and473K were established according tothermodynamic calculation.The results show that the existence forms of arsenic are associated with pH value,which mainly exists inthe forms of H3AsO4,24H AsO-,24HAsO-,H2AsO2-and As2O3in lower pH region,while it mainly exists in the form of3AsO4-when pH>11.14.High alkali concentration and high temperature are advantageous to the arsenic leaching.The alkaline pressureoxidation leaching experiments display that the tendency of arsenic leaching rate confirms the thermodynamic analysis resultsobtained from theφ-pH diagrams of As-N-Na-H2O system,and the highest leaching rate of arsenic reaches95.85%at453K.

Carbothermal reduction-chlorination-disproportionation of alumina in vacuum

The carbothermal reduction-chlorination-disproportionation of alumina in vacuum was investigated by XRD and thermodynamic analysis. The experiments on alumina and graphite at 1643-1843 K in vacuum were carried out. The results demonstrate that AlCl3（g） reacts with Al2O（g） or Al（g） generated from the carbothermal reduction of alumina to form AlCl（g）, and the AlCl（g） disproportionates to aluminum and AlCl3（g） at a lower temperature and the reaction rate of AlCl（g） reaches 90% at 980 K and 100 Pa. The aluminum can absorb CO to catalyze its disproportionation to C and CO2, and react backward with CO to form Al4C3, Al2O3, C and CO2, resulting in the aluminum product containing C, Al4C3 and Al2O3. The impurities in the aluminum product decrease as the AlCl（g） disproportionation temperature decreases. AlCl3 condenses at a temperature approximated to the room temperature.

Transformation behavior of ferrous sulfate during hematite precipitation for iron removal

The transformation behavior of ferrous sulfate was examined during hematite precipitation for iron removal in hydrometallurgical zinc.Specifically,the effects of the method used for oxygen supply(pre-crystallization or pre-oxidation of ferrous sulfate)and temperature(170–190℃)on the redissolution and oxidation–hydrolysis of ferrous sulfate were studied.The precipitation characteristics and phase characterization of the hematite product were investigated.The results showed that the solubility of ferrous sulfate was considerably lower at elevated temperatures.The dissolution behavior of ferrous sulfate crystals was influenced by both the concentrations of free acid and zinc sulfate and the oxydrolysis of ferrous ions.Rapid oxydrolysis of ferrous ions may serve as the dissolution driving force.Hematite precipitation proceeded via the following sequential steps:crystallization,redissolution,oxidation,and precipitation of ferrous sulfate.The dissolution of ferrous sulfate was slow,which helped to maintain a low supersaturation environment,thereby affording the production of high-grade hematite.

Theoretical research on vacuum separation of Au-Ag alloy

To provide an accurate prediction of the product component dependence of temperature and pressure in vacuum distillation and give convenient and efficient guidance for the designing of the process parameters of industrial production, according to the molecular interaction volume model(MIVM), the separation coefficient(β) and vapor-liquid equilibrium composition of Au-Ag alloy at different temperatures are calculated. Combined with the vapor-liquid equilibrium(VLE) theory, the VLE phase diagrams, including the temperature-composition(T-x) and pressure-composition(p-x) diagrams of Au-Ag alloy in vacuum distillation are plotted. The triple points and condensation temperatures of gold and silver vapors are calculated as well. The results show that the β decreases and the contents of gold in vapor phase increase with the distillation temperature increasing. Low pressures have positive effect on the separation of Ag and Au. The difference between the condensation temperatures of gold and silver is about 450 K in the pressure range of 1-10 Pa.

Mechanism of coconut husk activated carbon modified by Mn(NO3)2

To study the mechanism by which activated carbon is modified by HNO3 and Mn(NO3)2,the pore texture and surface chemical characteristics of carbon materials in coconut husk activated carbon(AC)were examined via scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FTIR),and X-ray photoelectron spectroscopy(XPS).After being modified by HNO3,the millipore character of AC became deformed,and the character of the adjacent pores remained consolidated.The surface manganites of Mn/AC-1 presented as block and reticular fiber structures,Mn/AC-2's surface manganites presented as petty mammock crystals,and Mn/AC-3's surface manganites were observed as gauze nanosheets that interlace to fill in the pore canal.Nitric acid modification was shown to enlarge surface pores but decrease the specific surface area of AC.Mn loading can be used to construct a new pore structure that,in turn,increased the total specific surface area as well as the specific surface area and the volume of the millipores.Mn/AC-2's pore structure was optimized at a calcination temperature of 500℃and a loading quantity of 5%.The ash content of AC was considerably reduced after modified by HNO3.The active materials for Mn/AC-1 mainly consisted of Mn3O4,with a few Mn2O3 crystals,whereas Mn/AC-2's materials were mainly Mn3O4 and some MnO crystals.Mn/AC-3 was exclusively composed of Mn3O4.HNO3 activation and Mn loading modification did not considerably affect the functional group species present on the catalyst.Modification conditions using the same loading quantities and higher calcination temperatures decreased the number of O—H and N—H bonds while conversely increasing the number of CC and C—O bonds.On the contrary,the use of a higher loading quantity while maintaining the same calcination temperature increased the number of O—H and N—H bonds.A higher loading quantity is beneficial for increasing Mn^4+species.A higher calcination temperature is beneficial for increasing Mn^3+species.The results can optimize the conditions under which Mn/AC catalyst modification occurs,thus improving the physical and chemical properties of carbon-based sorbents.

Theoretical analysis and experimental verification of thermal decomposition mechanism of CuSe

Experiments on the thermal decomposition of CuSe were carried out by using a thermogravimetric analyzer(TGA)at different heating rates.The kinetic parameters and mechanisms were discussed based on model-free and model-based analyses.The decomposition rate and decomposition behavior of CuSe were investigated by using a vacuum thermogravimetric furnace.The results showed that the R3 model was identified as the most probable mechanism function under the present experimental conditions.The average values of activation energy and the pre-exponential factor were 12.344 J/mol and 0.152 s^(−1),respectively.The actual decomposition rate of CuSe was found to be 0.0030 g/(cm^(2)·min).

Optimization of microwave heating thickness for spent automobile catalyst

A new method was developed to optimize the microwave heating thickness of the spent automobile catalyst in order to improve the uniform distribution of the temperature field. The average penetration depth and the microwave heating thickness of the spent automobile catalyst were calculated by Gauss model and numerical calculation based on dielectric loss tangent and reflection loss. The results showed that the spent automobile catalyst was a medium loss material. The average penetration depth was 1.11 m from room temperature to 800 ℃. The optimum microwave heating thickness of the spent automobile catalyst was about 0.83 m or 0.75 times of the average penetration depth. Industrial application analysis indicated that the optimization of heating thickness could improve the uniform distribution of the temperature field and reduce energy consumption.