Poly (vinyl alcohol-co-ethylene) (EVOH) modified polymer inclusion membrane in heavy rare earths separation with advanced hydrophilicity and separation property

Efficient separation of adjacent rare earths is an interesting and challenging job for membrane separation scientists. In this article, a novel polymer inclusion membrane (PIM) incorporating the hydrophilic additive random copolymer poly (vinyl alcohol -co-ethylene) (EVOH) was synthesized. Due to the polarity of P = O and P-OH groups in Cyanex272 and hydrophilicity of -OH groups in EVOH, the membranes exhibited much smaller water contact angles than pure PVDF membranes. And FT-IR results indicated that the addition of EVOH made no difference on the coordination between P = O, P-OH in Cyanex272 and Lu3+. SEM and AFM results indicated that the addition of appropriate amount of EVOH could generate more and larger surface pores and internal channels. Optimum membrane compositions and permeation conditions were fixed via static adsorption and dynamics permeation experiments. Separation factor was calculated as high as 3.78, which was much higher than previous studies no matter in solvent extraction or membrane separation. It is worth noting that it's the first time an obvious carrier's leakage was observed via characterizations which implied Cyanex272 may be not a perfect carrier in terms of PIM's stability. All these results proved that this novel PIM with EVOH serving as hydrophilic additive could be further testified in heavy rare earths separation and purification process.