Separation And Preconcentration Of Trace Nickel And Trace Amounts Of Cobalt Study

Aqueous two-phase system is a new kind of extraction separation system quickly developed in recently years. It mainly includes two types: polymer/polymer,polymer/salt. This article is not the first kind of type and the second type, This article is other one kind of type extraction separation system: alcohol/salt.Aqueous two-phase extraction is a technique which is used special extraction method and based on the principle that soluble polymer solution can separate two phase in the presence of inorganic salt and the difference of the distribution ratio of matter.The separation and concentration of Co( II) and Ni using alcohol-salt-water aqueous two-phase system were studied. Through continuous explorations and experiments, at last, optimized experiment conditions were decided. The extraction rate of Co surpassed 96%, specifying finished work as follows:(1) There are many factors affecting the phase separation,such as the kind and concentration of inorganic, acidity, and concentration of alcohol, and so on.(2) The distribution behavior of Co(II) and NRS in the alcohol-ammonium and sulphate-water aqueous biphasic system has been investigated. The factors which affect extraction such as acidity, the amounts of extractant and salt, range of phase ratio and the concentration of alcohol were analyzed. Mixing separation experiments of Co( II) were carried out in different amounts of Ni.(3) Mechanism of extraction was studied basically. The composition of Co and NRS was determinated by molar ratio method and continuous variation method. In some acidity condition: Co:NRS=1:3. The affection caused by different surfactants to the extraction rate of Co in two-phase system was investigated. Mechanisms of extraction in aqueous two-phase system was studied on the basis of the experiment results and theoretical analysis. It was believed that metal ion extraction in aqueous two-phase system is the result of complexation reaction,electrostatic effect and hydrogen bonding and hydrophobic bonding.(4) In the ionic determination,the effective spectrophotometry to Co and Ni without interference were found for the use of NRS and DMG in alcohol phase and salt water phase. Through experiments that used the characteristic factor of aqueous two-phase system todeterminate metal ion in upper phase without back extraction, many factors which affect determination were studied, The optimized conditions were decided.Optimized separation conditions were decided through many experiments. It is pH=5.7, 1.5ml NRS solution,6m195% alcohol solution, 9g ammonium and sulphate, 20ml total volume. The system has successfully separated Co from Ni minim. More than 96% Co enrichments in alcohol phase and 93% Ni enrichments in salt water phase. The result of this experimentis satisfactory. Compared with traditional extraction methods, aqueous two-phase extraction has many advantages, such as high extractability, simple operation, low price, low pollution to environment. Therefore, it is a vast useful separation technology.