Rapid preparation of Tannic acid (TA) based zwitterionic nanofiltration membrane via a multiple layer-by-layer (mLBL) assembly strategy for enhanced antifouling performance

Tannic acid (TA) is a promising material to prepare nanofiltration membranes due to its multiple interaction abilities with metal ions and zwitterionic polymer via coordination interaction and electrostatic interaction, respectively. Herein, we proposed a multiple layer-by-layer (mLBL) assembly strategy using three assembly materials for the rapid preparation of TA based zwitterionic nanofiltration membranes with enhanced antifouling performance, which was compared with the non-zwitterionic nanofiltration membranes prepared via the conventional layer-by-layer (cLBL) assembly. Among a series of transition metal ions, Fe3+ was chosen to prepare nanofiltration membranes. The ATR-FTIR and XPS analysis revealed the TA/Fe3+ layer was formed and the poly(sulfobetaine methacrylate) (PSBMA) polymer was successfully assembled on membrane surface. The prepared zwitterionic nanofiltration membranes showed enhanced hydrophilicity, roughness and zeta potential than the non-zwitterionic nanofiltration membranes. The influence of TA/Fe3+ bilayer number and PSBMA concentration on membrane performance was systematically studied and the rejection properties of the prepared membranes for dyes and salts were also investigated. Under the optimum preparation condition, the zwitterionic (TA/Fe3+)(1.5)/PSBMA membrane showed water permeability of 40.36 LMH/bar with rose bengal (RB) rejection more than 98% and Na2SO4 rejection about 60%. Because of the introduction of the PSBMA polymer, the zwitterionic (TA/Fe3+)(1.5)/PSBMA membrane showed better antifouling performance than non-zwitterionic (TA/Fe3+)(2.5) membrane with similar rejection properties.