Study On Mechanism Of Separation Of Cobalt And Nickel By Microemulsion Membrane Based On Microfluidic Technology

Nickel and cobalt are important strategic metals,and play an important role in the industry.Because of the very similar physical and chemical properties,these two metals are always the symbiotic and associated elements in the deposit,it has significant meaning to separate and recover nickel and cobalt from leachate.To overcome the problems existed in the conventional solvent extraction,the new processes of microemulsion extraction and separation of nickel and cobalt combined with microfluidic technology are introduced in this research.It is concluded that the use of these processes has high extraction efficiency and rapid separation,it is also advantageous to overcome the problems of liquid membrane rupture,swelling,entraining losses and emulsification caused by high shear forces by stirring.Meanwhile,it is conductive to increase the transfer coefficient and contacting area,and achieve a uniform concentration.In this paper,the extraction and separation of Co from Ni sulfate solution by P507 has been studied in two microemulsion systems and two types of micro-channel.Firstly,the extraction and separation of Co from Ni sulfate solution was studied using P507-kerosene-NaOH microemulsion system.The experimental results showed that the extraction rate of cobalt was 90.18%,and co-extraction of nickel was only 10.52%,the separation coefficient between cobalt and nickel was 68 when the volume concentration of extractant P507 was 20%,the concentration of NaOH was 3 mol·l-1,the ratio of microemulsion to water was 1:1,the pH value of water was 5 and the extraction time was 10 min.Secondly,the extraction and separation of Co and Ni from cobalt sulfate and nickel sulfate solution was studied using span80-P507-kerosene-NaOH microemulsion system.The optimized parameters were determinated.The experimental results indicated that the extraction rate of cobalt was 82%,that of nickel only was 4%,the separation coefficient of nickel and cobalt was 90.The separation of cobalt and nickel from sulfate solution by the microemulsion extraction can achieve better separation.The microemulsion system with surfacant span 80 is better for the separation of Co from Ni sulfate solution?Thirdly,the Y-type microfluidic chips have been designed and used for the extraction of Co from aqueous phase to organic phase.The optimum extraction parameters were as follows:0.09mol·l-1 P507,30%saponification rate,0.02ml·min-1 flow rate for each phase.Under the conditions,the extraction rate of cobalt was 99.99%.It was believed that almost all the cobalt in the aqueous phase was extracted into the organic phase,which shows high efficiency in microfluidic extraction.Finally,the extraction and separation of Co and Ni with saponified P507 was implemented in a segmented micro tubular reactor.The effects of the extractant concentration,saponification ratio and flow rate on the extraction efficiency were investigated.From the experimental results we know that under the optimized process parameters,ECo is 81.71%,ENi is 4,3%,?Co/Ni is 99.44.This indicated that the extraction efficiency in microfluidic extraction is obvious higher than that in conventional extraction(?Co/Ni of 68)in parallel.In summary,the combination of microfluidic and microemulsion membrane technology is feasible for the extraction and separation of cobalt from nickel sulfate solution,which provides a new and green prototype of cobalt-nickel extraction.