Selective separation of low concentration rare earths via coordination-induced ion imprinted electrospun membranes

How to efficiently utilize the low-concentration rare earth wastewater has become an urgent demand for the sustainable mining and resource utilization of ion-type rare earth minerals in China. Herein, we developed Y ion-imprinted electrospun membranes (Y-IIEMs) for the selectively separation of neighboring heavy rare earth ion Y(III) from Ho(III) and Er(III) by applying high efficient ligand-inducing and aqueous phase ion-imprinting. Cyanex272 was applied as carrier in membrane matrix and also as high-efficient ionic ligand in imprinted layer. Thermal stability of Cyanex272 was greatly improved after pDA bionic adhesion and sol-gel aqueous phase imprinting. Water contact angle of Y-IIEMs was only 23.2° which was probably a combination result from all the polar groups PO and P–OH from Cyanex 272 ligand, the imino groups from pDA layer and the silicon hydroxyls from sol-gel imprinting. And the calculated static adsorption imprinting factor of Y(III) was more than 7 indicating that valid recognition sites were successfully formed. The separation factors β(Y/Ho) and β(Y/Er) in dynamic permeation process increased significantly from 1.24 and 0.85 for non-imprinting to 2.01 and 1.77 for imprinting membranes. After 8 cycles of dynamic permeation, Y-IIEMs’ flux decreased only 13.8%, which implied good stability and reuse performance.