| Liquid membrane separation include two different technologies:emulsion liquid membrane separation(ELMs) and support liquid membrane separation(SLMs). These two technologies have their own advantages and drawbacks. ELMs is a dispersive process which easy to bring about the problems such as re-emulsion and membrane swelling; SLMs is a non-dispersive process, but the oil liquid membrane phase may lose from the support solid membrane, which resulted immediately in the decrease of the extraction percentage. In order to take advantage of the merits of ELMs and SLMs, in this work, the extraction was performed by emulsion liquid membrane in hollow fiber membrane contactor(HFMc). This new extraction way can overcome the phenomenon mentioned above; meanwhile, the extraction and re-extraction can accomplished in one step.Scandium and Indium are two important rare metals which existing in associated mine, they are extracted from ore lixivium by solvent. In this work, on the basis of our group researches, the scandium and indium extraction using ELM in HFMc were studied, and the process conditions were optimized, the mass transfer properties were also investigated. The main experimental results are listed as below:(1) The W/O emulsion system is consisted of OP-4, P204[Bis(2-ethyl hexyl)phosphoric acid], paraffin oil, kerosene as well as HCl solution. In which OP-4is a nonionic surfactant, P204is an acidic phosphorus extractants, paraffin oil is the membrane enhancer, and kerosene is diluents, HCl solution is the stripping agent. When both the flow rates of emulsion feed aqueous were fixed, the influence factors such as OP-4concentrations, pH values of feed aqueous and HCl solution concentrations were inspected. The experimental results show that when the mass fraction of OP-4is4%and the pH values of feed aqueous changed in the range of1.7to2.0, extraction percentage of scandium is relatively high; on the contrary, the extraction percentage of iron is relatively low. Above pH2.0, reverser esults appeared. The best HCl concentration in stripping phase is3mol·L-1. Under the appropriate conditions, the extraction percentage of scandium reach85%in single pass, the separation factor βsc/Fe=8.02. The mass transfer coefficients were calculate in varies P204saponification degree, HCl concentration in stripping phase and pH values of feed.(2) Extraction of In(Ⅲ) from feed liquid which contains impurities Fe(Ⅲ), Cu(Ⅱ) was carried out using same techniques. In order to determined the optimized technological parameter, the orthogonal experiment was designed, the related factors are respectively as:P204saponification degree (25-80%), P204 concentration (3-7%), HCl concentration in stripping phase (2to5mol·L-1), pH of feed liquid (2to6), OP-4concentration (4%to9%), paraffin concentration (3-7%). The effect of wetting medium of hollow fiber membrane, circulation extraction times of emulsion or feed liquid on the In(Ⅲ) extraction were also studied. Experimental results show that the optimized parameter values for indium extraction and purification are:P204saponification degree is80%,and P204concentration is4%, HCl concentration in stripping phase is4mol·L-1, pH value of feed is4, OP-4concentration is8%, paraffin concentration is5%. Under this conditions, indium extraction percentage is68.3%, the separation factor β(In/Fe) is4.42, β(in/Cu) is356.9. The effect significance of above several factors onextraction of indium is in the order:saponification degree of P204, paraffin concentration, HCl concentration in stripping phase, OP-4concentration, P204concentration. pH of feed liquid. works little on results of extraction. Experiment results also indicated that when fiber membrane was pre-wetted with emulsion, the indium extraction percentage is higher than pre-wetted with feed aqueous. There are little differences after circulation extraction3times of emulsion or feed liquid. When it is applied to extract indium from acid leaching solution, satisfied results are obtained. |
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