Study On The Separation Of Ce³⁺ And Pr³⁺ By The Hollow Fiber Membrane Extraction Technology

Rare earths, the important strategic resources, have special excellent properties and are widely applied in the really high-tech sophisticated equipment and military fields. The store quantities, consumption quantities, production quantities, and export quantities of rare earths both rank first in the world. That is why the development and utilization of rare earth resources become increasingly concerned. Chinese government has fully supported all endeavors to pursue this development, and classed it as part of plan973. The rare earth functional materials are mostly consists of single high-purity elements. Solvent extraction is a kind of commonest method in separating and purifying rare earth, but it still has many disadvantages such as large investment, huge facilities and high cost for operating and maintaining.Hollow fiber membrane separation technology is a new separation technology. It utilizes the differences of penetrability of each component in the mixture to enrich purification separation and promoting reacts through different membrane filtration. Hollow fiber membrane module has high surface areas, high filling density and high reliability, which is very suitable to separation of rare earths. More and more people applied this method in-depth.The factors affect extraction such as the pH and meatal concentration of feed liquid, the concentration and saponification ratio of P507, were analyzed through balance test. Ce3+and Pr3+are separated from HC1solution to obtain single rare earth with P507as extraction agent, kerosene as diluent. PP (polypropylene) hollow fiber membrane module was used to separated Ce3+/Pr3+in the HC1solution on this basis. We studied the effect of P507concentration and saponification rate and feed liquid pH on the separation of Ce3+and Pr3+in the saponated system, and invested the effect of mole ratio of acetic acid and rare earths and mole ratio of rare earths and P507on the separation of Ce3+and Pr3+in the unsaponified system by addition of complexing agent (HAc) to feed liquid. At the same time, some operation parameters were analyzed and optimized, such as flow rate of two phase, co-current and counter-current operation, cascade and circulation operation, and filling factor. The results show saponated P507is not applied especially for the hollow fiber membrane module because of emulsion caused by saponification. The complexing agent in the feed liquid could increase the separation factor of Ce3+and Pr3+efficiency. With increasing the flow ratio of organic phase over aqueous phase, the separation effect of Ce3+and Pr3+significantly increased as a result of the decreasing transfer resistance of organic phase. As the same time, with the increasing of the filling factor of hollow fiber membrane module, the separation effect of Ce3+and Pr3+significantly increased, but excessive filling factor could decrease the separation effect instead. The stripping of rare earths in the modules presented excellent results.Based on double film theory, we investigated the mass transfer in the tube side and the shell side hollow fiber modules. We revised the mass transfer area for the process of rare earths separation combined with the existing mass transfer model of hollow fiber membrane modules. The mass transfer model we corrected results agreed well with experiment results.