| At present,high-grade nickel ore resources which can be economically utilized are in serious shortage in China.The low-grade polymetallic nickel sulphide concentrate need to be efficiently used.In a long time,the related basic research on the utilization of non-traditional nickel ore resources is insufficient in China.There is a lack of efficient separation and extraction techniques for the low-grade polymetallic nickel sulphide concentrate.It has become the development direction for nickel production to solve the technical difficulties in the combination of pyrometallurgy process and hydrometallurgy process.It is important to develop new metallurgical methods and technologies in a clean and efficient way.Developing the basic theoretical research in the extraction of valuable metals,especially for the research on mineral phase transformation in mineral reconstitution process,is of great significance.In recent years,the basic research and application for ionic liquids has made rapid progress.The ionic liquids have many excellent properties which provide a good opportunity for electrochemical metallurgy and material preparation process.It is possible to transform the traditional process of refractory minerals relying on high temperature/wet separation by using ionic liquids.By adding the chlorinating agent,Chlorination metallurgy can convert the metal to be extracted into chloride by phase reconstitution.Moreover,metal chlorides can be effectively separated,concentrated,extracted and refined in ionic liquids.Therefore,selective chlorination is carried out to achieve phase reconstitution to chloride for multi-metal polymetallic.Combined the selective dissolution of chlorinated mineral components with electrochemical controlled electrolysis/electrodeposition by specific ionic liquid is a new integrated technology route.The new integrated technology route will have the potential to achieve separation and purification of complex minerals with low temperature,high efficiency and short process.This article mainly discusses the selective chlorination and reconstitution process of various nickel sulfide ore such as heazelwoodite,low-grade nickel matte and nickel concentrate.The element migration behavior and ore transformation law in the chlorination and reconstitution process of complex polymetallic nickel sulphide ore are discussed.The mechanism of reconstitution process of the complex polysulfide nickel sulphide ore was revealed.And a variety of thermodynamic function equations during the process of mineral reconstitution have been established.The chlorination roasting-water leaching process for different nickel ores was systematically studied.The factors for affecting the leaching and enrichment of valuable elements in different processes were discussed.A variety of technical prototype for the enrichment of valence elements were obtained.Based on these results,the selective chloride phase reconstitution and the ionic liquid electrochemical extraction process were combined to propose and demonstrate for selective chlorination of nickel sulfide ore.A new integrated technology route has been proposed for the separation and extraction of complex nickel sulfide ore.The conclusions are following:?1?Thermodynamic analysis of sulphide ore during the chlorination reconstruction process showed that:the main sufides of Ni,Cu and Fe can react with KCl and Cl2,the trend of chlorides for direct reaction with KCl are:FeSx>NiSx>CuSx.The oxides of Ni,Co and Cu can react directly with Cl2 to form chlorides,however,the oxide of Fe can not react with Cl2.Therefore,selective chlorination can be achieved by controlling the experimental conditions.Increasing the temperature is not conducive to the chloridization for nickel sulfide ore.?2?The results of chloride roast show that:the roasting effect is not good for chloridizing roasting of heazlewoodite.The leaching rate of each valuable component was the highest when the low-grade nickel matte was calcined at 450? for 45 min.The leaching rate of Ni,Co,Cu and Fe are 99.86%,95.86%,97.94%and 0.88%,respectively.The leaching rate of each valuable component was the highest when the nickel concentrate was calcined at 400? for 45 min.The leaching rate of Ni,Co,Cu and Fe are 97.23%,98.34%,98.25%and 3.1%,respectively.The results showed that the effect of selective chlorination is obvious.?3?The study on chlorination and reconstitution mechanism of complex polymetallic minerals shows that:the decomposition of KCl is mainly oxidative decomposition,the decomposition is difficult to proceed without SO2.During the heazlewoodite/KCl roasting process,the oxidative decomposition of Ni3S2 will first happen.KCl will decompose to Cl2 under the action of SO2 and O2.Cl2 will react with minerals to form NiCl2,and NiCl2 gradually transforms into K2Ni2?SO4?3.During the roasting process for low-grade nickel matte and KCl,Fe in pentlandite is preferentially oxidized to Fe3O4,NiS and SO2.KCl will decompose to Cl2 under the action of SO2and O2.Cl2 will react with minerals to form NiCl2,and NiCl2 gradually transforms into K2Ni2?SO4?3.In the roasting process of nickel concentrate and KCl,the Fe2O3 and SO2will form from the preferential oxidation of pyrrhotite and pyrite in concentrates.Above500?,Mg in the mineral also can react to produce K2Mg2?SO4?3.Above 700?,Ni and Fe will form a solid solution?NiFe2O4?,and the phases in minerals are K2Mg2?SO4?3?K2Ni2?SO4?3?K2SO4?NiFe2O4 and NiO.No matter which kind of the three mineral,due to the formation of gas,the mineral surface will first dissociate and produce a large number of pores in the roasting process.As the temperature rises,the pores gradually close and the minerals will be sinter.?4?Two different isothermal thermal analysis methods,FWO and Kissinger,were used to study the kinetics of the reconstitution of hexahedrite,low-grade nickel matte and nickel concentrate.The results show that,during the reconstitution of the hexahedrite,the activation energy in different stages are 170.79 kJ/mol,669.09 kJ/mol and 189.57 kJ/mol.During the reconstitution of the low-grade nickel matte,the activation energy in different stages are 164.18 kJ/mol,164.65 kJ/mol and 255.78kJ/mol.The activation energy for the reconstitution of nickel concentrate is 105.25kJ/mol.In the study,a series of rate equations have been calculated.?5?The study on the extraction of metallic nickel by chlorination reconstitution-ionic liquid electrodeposition shows that the deposition process of Ni is controlled by diffusion.The diffusion coefficient of Ni2+is 2.4×10-7cm2/s.The deposition of metallic Ni tends to grow in clusters,and the agglomeration of metallic Ni particles is apparent as the cathode deposition potential increases.In the electrodeposition process,the initial process of electrocrystallization of metallic Ni on the Pt electrode follows the diffusion-controlled three-dimensional transient nucleation growth mode.The study on the electrodeposition preparation of Cu-Ni alloys show that,electrodeposited Ni-Cu alloy coating is a solid solution alloy phase,and different compositions of copper-nickel alloys can be obtained by controlling different potentials.The initial electrocrystallization process of Ni-Cu alloy on Pt electrode follows diffusion controlled instantaneous nucleation three-dimensional growth mode.What's more,Cu,Ni and CuNi alloy were successfully prepared by direct electrolysis from chalcocite,heazlewoodite and high-grade nickel matte in CaCl2-NaCl molten salt.The results prove that it has a very strong application prospect for the preparation of metal/alloy from sulfide minerals in molten salt electrolysis process. |
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