Peg200-(nh <sub> 4 </ Sub>) <sub> 2 </ Sub> So <sub> 4 </ Sub>-h <sub> 2 </ Sub> O Aqueous Two-phase System On The Molybdenum Substrate Separation And Preconcentration Of Trace Chromium 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. The second type is used in this paper. 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 Cr(VI)from Mo matrix using polyethylene glycol2000(PEG2000)-salt-water aqueous two-phase system were studied. Through continuous explorations and experiments, at last, optimized experiment conditions were decided. The extraction rate of Cr 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, the degree of polymerization of PEG and concentration of polymer, and so on.(2) The distribution behavior of Cr(VI) and DPCO in the polyethylene glycol-ammonium and sulphate 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 degree of polymerization of PEG were analyzed. Mixing separation experiments of Cr(VI) were carried out in different amounts of Mo.(3)Mechanism of extraction was studied basically. The composition of Cr and DPCO in PEG was determinated by molar ratio method and continuous variation method. In some Hcl acidity condition: Cr: DPCO=1: 4. The affection caused by different surfactants to the extraction rate of Cr 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 aqueoustwo-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 Cr and Mo without interference were found for the use of CV and DPCO in PEG phase and salt water phase. Through experiments that used the characteristic factor of aqueous two-phase system to determinate 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=2. 0, 3. 0ml 2. 5g/L DPCO solution, 10ml30% PEG2000 solution, 4g ammonium, 20ml total volume. The system has successfully separated Cr from Mo matrix. More than 98% Cr enrichments in PEG phase and 95% Mo enrichments in salt water phase. The result of this experiment is 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.