Omnifarious performance promotion of the TFC NF membrane prepared with hyperbranched polyester intervened interfacial polymerization

It is a grand challenge to achieve the omnifarious performance promotion of the thin film composite (TFC) nanofiltration (NF) membranes due to the mutual influence among membrane permeability, selectivity and antifouling ability. Hereon, a rational strategy denoted as hyperbranched polyester (HPE) intervened interfacial polymerization (IP) was proposed to simultaneously improve various membrane properties. HPE with special molecular structure was mixed into the piperazine (PIP) solution to form a composite aqueous phase, and then a modified selective layer was generated via the IP reaction with the trimesoyl chloride (TMC). In this process, the diffusion rate of PIP monomer was reduced because of the steric hindrance effect brought by HPE and the hydrogen bonding interaction between PIP and HPE. Meanwhile, the primary hydroxyl groups in HPE also participated in the polymerization reaction. The structure and separation performance of the resultant membranes were systematically investigated. The results showed that when the HPE dosage was 1 w/v%, the thickness of the modified selective layer was as low as 8.34 nm. The pure water permeability of the corresponding TFC NF membrane was high to 50.62 L·m-2·h-1·bar-1, while keeping the Na2SO4 rejection over 98%. Moreover, this membrane presented long-term stability and antifouling performance.