Experimental And Theoretical Study On The Separation And Enrichment Of Cobalt And Nickel From Sulphate Solution By Emulsion Liquid Membrane

A large number of industrial wastewater containing heavy metal ions in general, because of the pollution of their own characteristics to the enormous harm the environment and received great attention and concern of society and nation.However, the traditional wastewater treatment technology is expensive, and the process is complicated and the wastewater is difficult to be effectively treated. Therefore, it is imperative to develop a kind of economical and environmentally friendly wastewater treatment technology.Liquid membrane separation technology is a new separation and enrichment technique, due to its separation effect is good, fast mass transfer rate, selectivity and low energy consumptiong,etc, so it was widely using in the study on the treatment of industrial wastewater containing heavy metal ions.Cobalt and nickel ions in sulphate solutions were separated by emulsion liquid membrane method(ELM) in this paper.The ELM system consists of a solvent(n-Heptane), a surfactant(Span80), a carrier(Cyanex272, P272), a kind of film formation additive(liquid paraffin) and an internal phase of sulfuric acid solution.Due to the similarity of cobalt and nickel in physical and chemical properties, the separation process is one of the more difficult process in Hydrometallurgy. At present, the separation methods of cobalt and nickel mainly include chemical precipitation method and solvent extraction method.Chemical precipitation method is mainly applied to cobalt and nickel compounds when there are some differences in the solubility product.However, the chemical precipitation method have some problems,for example the content of nickel in cobalt products is high, the purity of product is low, and it is often needed to be further processed and purified.In comparison, solvent extraction has a certain advantage than chemical precipitation method, more able to meet the demand of industrial needs.In this paper, the separation and treatment of cobalt and nickel by emulsion liquid membrane method.At the same time, the effects of emulsion liquid membrane composition volume ratio, stirring speed, carrier concentration and internal and external volume ratio on the extraction and separation of cobalt and nickel were studied.Through the establishment of mathematical model, the mass transfer mechanism of emulsion liquid membrane is explained in depth, and the change of ion concentration in sulfate solution can be easily understood by mathematical model.The optimal separation conditions for the separation of cobalt and nickel can be investigated through the study of this paper.Under the conditions of φ(P272) =5.0%( V/V),φ(Span 80) =5.0%( V/V), stirring speed of 400 rpm and volume ratio of external phase to internal phase of 20, Stirring time 1200 s,the transfer ratio of the cobalt ion could reach to 98.0 % and that of the nickel ion was only less than 9.0 %. The separation ratio of cobalt to nickel is about 11.0:1.0.so the effective separation of cobalt ion and nickel ion was achieved.When the emulsion liquid membrane was used to separate the nickel.The optimal separation conditions for the separation of nickel can be investigated. Under the conditions of φ(PC88A) =6.0%( V/V),φ(Span 80) =5.0%( V/V), stirring speed of 400 rpm and volume ratio of external phase to internal phase of 16, Stirring time 900 s,the transfer ratio of the nickel ion could reach to 99.98 %,which meet the discharge requirements of industrial waste water.All the technological parameters obtained in this study can be the basis and reference for industrial experiment in the future.