3D electrospray printing PEI-TMC nanofiltration membrane for efficient and long-term stable separation of Mg2+/Li+

The active layer of the thin film composite (TFC) nanofiltration membrane prepared by traditional interfacial polymerization (IP) was usually a non-homogeneous state with dense in the middle and loose on both sides. Such structure would reduce the stability of membrane in operation. In this paper, a novel electrospray polymerization nanofiltration (EPNF) membrane was fabricated for efficient and long-term stable separation for Mg 2+ /Li + by multiple scan 3D electrospray printing technique. The active layer consisted of two homogeneous separation layers, the piperazine-trimesoyl chloride (PIP-TMC) inner layer and polyethyleneimine based (PEI-TMC) outer layer. With a fixed scan of inner layer, the effect of scan number of PEI-TMC outer layer on the performance of EPNF membrane was analyzed detailly from chemical structure and ion separation performance. Under the synergistic effect of electrostatic repulsion and pore size screening, the EPNF membrane achieved a Mg 2+ /Li + separation factor of 36.28 and only 1.5 % performance loss in the operation of 150 h. The electrospray polymerization process presented unique advantages in preparing TFC nanofiltration membranes with long-term separation stability.