A Study Of Separating Iron, Zinc And Manganese In Mixed Sulphate Solution By Solvent Extraction

In this paper, a new process of separating iron(â…¢), zinc(â…¡) and manganese(â…¡) in mixed sulphate solution was developed. The separation of iron(â…¢) from sulphate solutions has been firstly investigated using a mixed solvent system consisting of tertiary amine (N₂₃₅) and tributyl phosphate (TBP). Then, zinc(â…¡) was extracted with di(-2-ethyIhexyl)phosphoric acid(P₂₀₄) from the raffinate in order to separate zinc and manganese.In the experiment of iron(â…¢) extraction, the effect of extraction systems, concentration of N₂₃₅ and initial pH value on the extraction of iron(â…¢), as well as the effect of O/A ratio, concentration of sulfuric acid and equilibrium pH on the stripping of iron(â…¢) in loaded organic phase were studied. The results demonstrated that N₂₃₅— TBP system had a synergistic effect on the extraction of iron(â…¢); By adding TBP in N₂₃₅, the demixing of loaded organic phase can be prevented and the stripping ratio of iron(â…¢) increased. At O/A ratio 1.5, initial pH 0.66, contact time 5min, the extration ratio of iron(â…¢), zinc(â…¡) and manganese(â…¡) are 87.24%, 1.23% and 0.29% respectively for a solution containing 12.73 g·L^-1 iron(â…¢), 24.01 g·L^-1 zinc(â…¡) and 40.02 g·L^-1 manganese(â…¡). The separation coefficient of iron and zinc(β_Fe/Zn) reaches 549, thus iron(â…¢) and zinc(â…¡) can be separated. Initial pH value and concentration of N₂₃₅ had remarkable influences on iron(â…¢) extraction, there was a maximum on the extraction curve, which moved towards the direction of low pH value with increasing concentration of N₂₃₅. Further more, the stripping results indicates that with a dilute sulphuric acid (0.4 mol·L^-1), iron(â…¢) stripping ratio can reach 96 percent controlling equilium pH less than 0.8. At O/A ratio 1:1, iron(â…¢) in loaded organic phase can be easily and completely stripped by a dilute sulphuric acid (0.4 mol·L^-1) after a two-stage stripping. The zinc and manganese in organic phase being extracted need further stripping.With the methods of slope analysis and equimolar series, the formation of iron(â…¢) extracted into the tertiary amine sulfate solution is confirmed:[(R₃NH)₂Fe(OH)(SO₄)₂]·TBPZinc(II) and manganese(II) in raffinate can be separated with P204. The saponification of P204 can inhance the extraction of zinc. With P204 concentration 40%, saponification degree 40%, O/A ratio 1.5:1 and equilibrium pH less than 1.9, the extraction ratio of zinc(II) and manganese(II) were 90.76% and 9.67% respectively and the separation coefficient of zinc and manganese(/?zn/Mn) was 91.75. As a result, zinc(II) and manganese(II) can be separated preferablely. Further more, the stripping results indicated that at O/A ratio 2:1, zinc in loaded organic phase could be easily and completely stripped by a dilute sulphuric acid (1.0 mol-IT1) after a two-stage stripping. Zinc(II) in organic phase was less than 0.5gL-1 and the whole stipping ratio of zinc was 97.19%.In this study, a whole-extractive process for the separation of iron(III), zmc(II) and manganese(II) is discribed. It has no such complex problems, as precipitation, clarification, leaching and scruff pollution camparing with the method of traditional chemistry precipitation. In this process, the separation of iron(III), zinc(II) and manganese(II) is deeply; the needed equipment is simple; the process is short and it is beneficial to successive operation. The proposed method is prior to and provide a bright future for the existing study of separation iron(III), zinc(II) and manganese(II) by solvent extraction.