Electrodeposition Of Sn-Ni-Cu Alloy From Low Nickel Matte In Ionic Liquids

Nickel and copper are important strategic metals and widely used in China.With the exploitation of copper-nickel ore resources,the high-grade copper-nickel sulfide ore resources are in serious shortage.Therefore,how to make efficient and comprehensive utilization of low-grade polymetallic copper-nickel sulfide ore is the key issue.Searching for a new alternative route with high efficiency,cleanness and short process to extract high-value metals from low-grade copper-nickel ore has become the development direction.Based on the mineral phase and elemental composition characteristics of low nickel matte,in this work,an integrated technology for preparing binary alloy and ternary alloy from low nickel matte precursor has been proposed,the technology generally includes a chlorination sintering process and an electrodeposition process in ionic liquids.This work firstly investigated the technological conditions for chlorination sintering process and ionic liquid leaching process with low nickel matte as raw material.Then,further research on the electrodeposition of Ni-Cu binary alloy in ionic liquid from low nickel matte and pure metal chlorides was carried out.Finally,by the addition of the third element Sn,electrodeposition of Sn-Ni-Cu ternary alloy in ionic liquid from low nickel matte was also studied.The main conclusions are drawn as follows:（1）The optimum sintering conditions for chlorination sintering of low nickel matte are:using KCl as chlorinating agent,heating with the furnace,40 wt%KCl addition,sintering at temperature of 450℃ for 45 min.The main phase composition of the sintered product is double sulphate salt（K₂Ni₂（SO₄）₃）,iron oxide（Fe₂O₃）and metal chlorides（NiCl₂,CuCl,KCuCl₃）.The sintered product was dissolved in choline chloride/urea ionic liquid（ChCl/urea）.The leaching rates for Fe、Ni and Cu in ChCl/urea from the sintered low nickel matte were 0.33%,49.17%and 73.28%,respectively.Fe mainly remains in the leaching slag in the form of Fe₂O₃.The loss of Ni and Cu elements is mainly attributed to the low solubility of the double sulphate salt in ChCl/urea.（2）Ni-Cu binary alloy can be obtained by chlorination sintering and electrodeposition in ChCl/urea from nickel matte.At the same conditions,Ni-Cu binary alloy can be also prepared by electrodeposition in ChCl/urea from pure metal chlorides.In the electrodeposition process,the applied potential plays an important role on the compositions,morphologies and properties of the deposits.Moreover,different precursors have similar dissolution behaviors in ChCl/urea,the metal complexes are formed after dissolution and the structure of ChCl/urea is unchanged.The Ni-Cu binary alloys obtained from different precursors show similar electrodeposition processes,similar compositions,morphologies and properties.The largest difference between the two processes is that the current density is higher during the preparation of Ni-Cu binary alloy from pure metal chlorides,which leads to fast reaction in the deposition process,and thus thicker coating with larger particles and higher Ni content can be obtained.Accordingly,the coating has better corrosion resistance.The different observation is mainly due to the presence of some impurities in the electrolyte from low nickel matte.（3）Sn-Ni-Cu ternary alloy can be obtained by electrodeposition from low nickel matte with the addition of SnCl₂ in ionic liquid.The optimum deposition conditions are:deposition at potential of-0.4 V and temperature of 60℃ for 15 min in choline chloride/ethylene glycol ionic liquid（ChCl/EG）,the substrate is foam nickel,the main phase of the prepared Sn-Ni-Cu alloy is CuNi₂Sn₃ and Ni₃Sn₂.The Sn-Ni-Cu alloy prepared on the foam nickel substrate has a three-dimensional porous structure,in which the distribution of Sn,Ni,Cu elements is relatively uniform,which is beneficial to improve the electrochemical performance of the material.The reversible capacity of the Sn-Ni-Cu ternary alloy electrode material prepared by electrodeposition is 533mAh/g after 50 discharge-charge cycles.Meantime,the coulombic efficiency reaches98%,and the structure remains stable after 50 discharge-charge cycles.The Sn-Ni-Cu ternary alloy displays high reversible capacity and excellent cycling performance.The results show that the porous structure and the embedding of higher content of Ni and Cu elements inhibit the volume expansion of Sn and improve the cycling performance of the material,and the three-dimensional porous structure provided by Ni foam also has beneficial to improve the cycling performance.