Leaching Behavior Study Of Nickel And Cobalt From Low-Grade Copper-Nickel Sulfide Ore By Microwave-Assisted Iron Chloride Oxidative Pressure Leaching

With the development of new batteries and special alloys,the world’s demand for nickel and cobalt resources continues to increase.However,high-grade and easily processed mineral resources are increasingly scarce and can no longer meet the needs of China’s technological development.Therefore,the efficient utilization of low-grade and difficult-to-process mineral resources has become crucially important.Traditional copper-nickel sulfide ore smelting processes are mainly aimed at preparing a single product,resulting in the waste of a large amount of valuable resources.Pressure oxidation sulfuric acid leaching,as a common process for the enhanced extraction of valuable metals,requires a large amount of acid.Without neutralization treatment,it can cause serious soil and water acidification and corrosion.In addition,sulfuric acid reacts with impurity metals such as iron and aluminum,producing a large amount of sulfuric acid slag.With the scarcity of resources and the increasing environmental protection requirements,the clean and efficient utilization of valuable resources in minerals has become the focus of research.Therefore,this paper takes the low-grade copper-nickel sulfide ore from Jinchuan as the research object to explore the metallurgical behavior of nickel and cobalt during the leaching process under the iron chloride pressure oxidation microwave leaching system.This paper mainly analyzes the thermodynamics,process,microwave leaching mechanism,and kinetics of nickel and cobalt leaching during the iron chloride pressure oxidation microwave leaching of low-grade copper-nickel sulfide ore.The main research work and conclusions are as follows:1.Draw E-p H diagrams of Ni-Fe-S-H₂O and Co-Fe-S-H₂O systems under high temperature conditions.There are stable coexistence regions of Ni²⁺,Co²⁺,and S at different potentials in each system at different temperatures.As the temperature increases,the stable regions remain unchanged,and the corresponding precipitation potentials slightly increase.By comparing them with E-p H diagrams of Ni-S-H₂O and Co-S-H₂O systems,it can be seen that the addition of Fe³⁺increases the eaching area of Ni²⁺and Co²⁺and requires p H correction.2.A study was conducted on the chlorination-iron oxidation-pressure microwave leaching of low-grade copper-nickel sulfide ore,and the results showed that the leaching rate of nickel and cobalt increased with the increase of liquid-solid ratio,leaching temperature,iron chloride concentration,oxygen pressure,leaching time,microwave intensity,and stirring speed.The optimal leaching conditions for nickel and cobalt were liquid-solid ratio of 7:1,leaching temperature of 160℃,iron chloride concentration of 250 g/L,oxygen pressure of 1.6 Mpa,leaching time of 120 min,microwave intensity of 1400 W,and stirring speed of 400 r/min,with the leaching rates of nickel and cobalt reaching 98.5%and 98%,respectively.The leaching residues under microwave and traditional electric heating conditions were characterized under the same experimental conditions.It was found that the leaching residues under microwave heating conditions had smaller particle sizes,higher specific surface area,and higher nickel and cobalt leaching rates.Additionally,cracks were observed in the leaching residues under microwave heating conditions,indicating that the selective heating characteristics of microwave conditions had a significant promoting effect on the leaching of low-grade copper-nickel sulfide ore.3.The kinetics of nickel and cobalt leaching in the low-grade copper-nickel sulfide ore using the"liquid-solid phase leaching reaction model with a solid product layer"under the conditions of ferric chloride-oxygen pressure acid leaching and microwave were studied.The results show that the leaching rates of nickel and cobalt increase with an increase in temperature,ferric chloride concentration,and oxygen partial pressure,and decrease with a decrease in particle size.The activation energies of nickel and cobalt leaching are 40.99k J/mol and 33.92 k J/mol,respectively.The leaching rate of both nickel and cobalt is controlled by interfacial chemical reaction.Finally,the kinetic equation for nickel and cobalt leaching in the process of ferric chloride-oxygen pressure acid leaching and microwave on low-grade copper-nickel sulfide ore was established based on the reaction order of ferric chloride concentration and oxygen partial pressure and activation energy.