Low fouling/scaling double network thin film composite nanofiltration membranes with improved desalination performance

Conventional poly(piperazineamide) [poly(PIP)] thin film composite (TFC) nanofiltration (NF) membranes undergo severe fouling/scaling and -show low barrier towards heavy metal ions and organic solutes. Herein, we report the preparation of double network (DN) TFC NF membranes to address these issues. In situ interfacial polymerization between PIP + poly(2-dimethyl aminoethyl)methacrylate (PDMA) and trimesoyl chloride+activated dihalide provides DN-TFC NF membranes. Formation of DN leads to the lowering of negative charge and narrowing down the pore size distribution of the membranes. PEGylated DN-TFC membranes have been prepared using copolymers of PEG and PDMA to demonstrate the adaptability of this chemistry and to increase the antifouling property. The DN-TFC membranes show water permeance of 7.9–8 L m−2 h−1 bar−1 and higher rejection of MgCl2 (90–94 %), Co2+ (96–98 %) and bisphenol A (91–94 %) as compared to that of the pristine (74 %, 70 % and 80 %) and the reported negatively charged (9–83 %, 60 % and 48–97.6 %) NF membranes. DN-TFC membranes show Na2SO4 rejection of ∼98 %, close to the reported membranes (98–99 %). The fouling and scaling resistant behaviors of the DN-TFC membranes (Flux recovery ratio = 90–94 % and 93–95 %) are greatly enhanced as compared to that of the pristine membrane (∼82 % and 76 %). DN-TFC membranes show great promises for the purification of water.