Thin-film composite nanofiltration membranes with improved acid stability prepared from naphthalene-1,3,6-trisulfonylchloride (NTSC) and trimesoyl chloride (TMC)

Thin-film composite (TFC) nanofiltration (NF) membranes with improved acid stability were fabricated through the interfacial polymerization of trimesoyl chloride (TMC) naphthalene-1,3,6-trisulfonylchloride (NTSC), and piperazine (PIP) on a porous polysulfone support membrane by varying the NTSC content in TMC-organic solution. The physico-chemical characteristics of the membranes were analyzed by ATR-FTIR, streaming potential measurement and surface contact angle measurement, the permeation properties were evaluated through cross-flow permeation tests, and the acid stability was investigated through both static acid soaking tests and long-term permeation tests under acidic condition. It was found that, as the NTSC content in TMC-organic solution increased, the membrane surface became more hydrophilic and negatively charged, the pure water permeability and molecular weight cut-off of the formed NF membrane increased from 5.5 to 10.6 l/m2 h bar and about 360 to 660 Da, respectively, while the rejection rate to Na2SO4 firstly increased from 98.2 to 98.7% and then declined to a lower value of 97.8%. After soaking in 8 w/v% H2SO4 for 30 days or filtration with 4.9 w/v% H2SO4 for 60 days, the TFC membranes prepared from TMC and NTSC showed little performance change, while serious performance deterioration occurred with the TFC membrane prepared from TMC.

► TFC NF membranes with improved acid stability were prepared from TMC, NTSC and PIP.
► The incorporation of NTSC resulted in increased pore size and enhanced hydrophilicity.
► The incorporation of NTSC resulted in a more negatively charged membrane surface.
► The membrane possessed good acid stability to 8 w/v% H2SO4 aqueous solution.
► The membrane showed good selectivity and stability in filtration acidic aqueous solution.