An ultra-antifouling polyethersulfone membrane embedded with cellulose nanocrystals for improved dye and salt removal from water

Cellulose nano-crystals (CNCs) were introduced into a polymeric membrane matrix to prepare CNC/polyethersulfone (PES) nano-enhanced membranes. The CNC suspension in N,N-dimethylacetamide was prepared by acidic hydrolysis of microcrystalline cellulose followed by solvent exchange. Various mass ratios of the suspension were employed to prepare a casting solution containing 20 wt% PES and 1 wt% polyvinylpyrrolidone (PVP). Distilled water was applied as coagulant. The pure effect of CNCs on the membrane morphology was also monitored by fabrication of a control membrane without pore former (PVP). The membranes were characterized using dye and salt removal, antifouling tests, scanning electron microscopy, atomic force microscopy, and hydrophilicity determination. It was found that presence of CNCs led to thin, but dense skin-layer and significant higher hydrophilicity, as well as higher water flux. CNCs at 0.8 to 1.2 wt% in dope solution showed twofold higher water permeability, complete whey proteins filtration, around 30% higher bivalent salt rejection, 20% higher acid orange 7 removal, and surprisingly, complete flux recovery compared to neat PES membrane. Mixing CNCs into the casting solution in the absence of pore former resulted in a very thin skin layer (0.15 µm) that did not allow the membrane to be used in the nanofiltration area.