Study on the electrochemical behavior of Mg and Al ions in LiCl-KCl melt and preparation of Mg-Al alloy

The electrochemical behavior of Mg^(2+)and Al^(3+)in LiCl-KCl(mass 4:1)melt at 973 K was studied on a Mo electrode systematically by cyclic voltammetry,square wave voltammetry and chronopotentiometry.The results showed that the reductions of Mg^(2+)and Al^(3+)were reversible processes controlled by the rate of the mass transfer.When Mg^(2+)and Al^(3+)coexisted in LiCl-KCl melt,they had no significant effect on the reduction potential of each other.The equilibrium potentials of Mg^(2+)/Mg and Al^(3+)/Al were obtained by open circuit potential method.Their apparent standard potentials were also calculated in this system and the values were-2.52 V vs Cl_(2)/Cl^(−),-1.66 V vs Cl_(2)/Cl^(−),respectively.Correspondingly,the apparent Gibbs free energies of Mg^(2+)/Mg and Al^(3+)/Al were-485.71 kJ/mol^(-1),-480.78 kJ/mol^(-1).Finally,potentiostatic electrolysis was performed on a Mo electrode in LiCl-KCl-MgCl_(2)-AlCl_(3)(the mass ratio of MgCl_(2) to AlCl_(3) was 10:1)melt at different potentials.The components of the deposits were characterized by scanning electron microscope and energy dispersive spectroscopy.The study revealed that the content of Al in the deposit decreased as the overpotential increased and Al tended to segregate at the grain boundaries.

Reaction characteristics of magnesium production under argon flow by silicothermic reduction and numerical simulation of argon entrainment process

In this study, the reaction characteristics of reduction of calcined dolomite with ferrosilicon under argon flow to produce magnesium were studied by conducting experiments Pidgeon pellets were used to study the effect of reduced temperature, argon flow, and reduced time on the conversion of calcined dolomite reduction by ferrosilicon. The results show that the conversion significantly increases with the increase in the reduction temperature and reduction time. The conversion first increases and then decreases with the increase in argon flow. The highest conversion was obtained when the argon flow rate was 3 L·min^(-1), and a nearly spherical shape, nanoscale magnesium powder was obtained. Then the characters of the circulating argon entrainment process were numerically studied by ANSYS Fluent 17. A physical model of multilayer pellet arrangement was established, and a numerical calculation model of chemical reaction, radiation, heat conduction, and convection heat transfer was constructed. This confirms that high-temperature argon can effectively strengthen the heat exchange between pellets, improve the heat transfer efficiency, and facilitate the pellets to react quickly. When the conversion is 80%, the production efficiency increased by about 28.6%. In addition, the magnesium production efficiency showed an increase tendency with the increase of the argon inlet flow rate.

Advances in Molten Salt Synthesis of Non-oxide Materials

The properties of non-oxide materials are continuously revealed,and their applications in the fields of ceramics,energy,and catalysis are increasingly extensive.Regardless of the traditional binary materials or the MAX phases,the preparation methods,which are environmentally friendly,efficient,economical,and easy to scale-up,have always been the focus of attention.Molten salt synthesis has demonstrated unparalleled advantages in achieving non-oxide materials.In addition,with the development of the process in molten salt synthesis,it also shows great potential in scale-up production.In this review,the recent progress of molten salt synthesis in the preparation of binary non-oxide and MAX phase is reviewed,as well as some novel processes.The reaction mechanisms and the influence of synthetic conditions for certain materials are discussed in detail.The paper is finalized with the discussion of the application prospect and future research trends of molten salt synthesis in non-oxide materials.

Sustainable recycling of titanium from TiO_(2) in spent SCR denitration catalyst via molten salt electrolysis

Spent catalyst used for denitration by selective catalytic reduction(spent SCR denitration catalysts) is one of the important urban mines due to the high content of TiO_(2)(~85 wt%) and the massive accumulation amount(over 100,000 tons),therefore,value-added reutilization of titanium in spent SCR catalysts is considerably meaningful.In this paper,a novel method is proposed for converting the titanium oxide in spent SCR denitration catalysts to metallic titanium.Specifically,titanium dioxide(TiO_(2)) was firstly obtained from spent SCR denitration catalysts after removing the impurities by hydrometallurgy process.Then,TiO_(2) is converted to Ti_(2)CO by carbothermic reduction method,and Ti_(2)CO was further purified by oleic acid capture.Finally,by utilizing the as-prepared Ti_(2)CO as the consumable anode in the NaCl-KCl molten salt,high-purity metallic titanium was deposited at cathode,all confirming the feasibility for the conversion of low-grade TiO_(2) in the spent catalysts,from 60 wt% to high-purity metallic Ti(99.5 wt%), furthermore,the energy consumption of this process is 3950 kWh tonne-1 Ti,which is lower than that of most traditional titanium metallurgy methods.The method herein can provide new insights for the value-added recycling of titanium resources in urban mines.

The silicothermic reduction of magnesium in flowing argon and numerical simulation of novel technology

The silicothermic reduction of magnesium was investigated by the non-isothermal thermoanalysis in flowing argon,while the traditional investigations of silicothermic process for magnesium reduction were carried out under vacuum conditions.Firstly,the thermal gravimetric(TG)and derivative thermogravimetric(DTG)characteristic of briquettes prepared with calcined dolomite,ferrosilicon and fluorite were characterized by the thermogravimetric analyzer(TGA)at different heating rates.The intrinsic chemical kinetic mechanism was identified as a formal chemical reaction with the Nth order type which showed apparent activation energy E and reaction order n were 290.168 kJ mol^(-1) and 1.076,respectively.Then,a novel technique of magnesium production without vacuum was put forward and a three-dimensional unsteady numerical model incorporating the chemical reaction,radiation,heat conduction and heat convection was established and simulated,which was verified by Pidgeon process and novel tech no logy.rIhe nu merical results showed that the cycle time of the novel technique could be reduced when the argon temperature was higher than 1343 K and the argon entrance velocity was over 0.05 m s^(-1).And the effect of the argon temperature on reduction degree was much larger than that of entrance velocity.