Nanofiltration‐like forward osmosis membranes on in‐situ mussel‐modified polyvinylidene fluoride porous substrate for efficient salt/dye separation

Abstract

Abstract Here, polyvinylidene fluoride (PVDF) membranes were fabricated via non‐solvent induced phase separation (NIPS) using dopamine (DA) and polyethyleneimine (PEI) as the hydrophilic additives, which has a loose surface and somewhat improved hydrophilicity. Then nanofiltration (NF)‐like thin‐film composite forward osmosis (TFC FO) membrane with a loose polyamide (PA) active layer on the blend membrane was synthesized via the interfacial polymerization. The as‐prepared NF‐like TFC FO membrane exhibited a high water flux ( J w ) of 29.98 L m −2 h −1 and a much low specific salt flux ( J s /J w ) of 0.018 g/L, when 0.6 M NaCl was used as draw solution (DS). It had a superior rejection of malachite green (99.6% ± 0.1%) and a low rejection of NaCl (27.4% ± 4.2%), when filtrated malachite green/NaCl mixture solution in active layer‐facing draw solution (AL‐FS) mode. The results provide new insights on the design and preparation of FO membranes of selective separation for dyes from salty water.