Cellulose acetate (CA) flat sheet membranes were fabricated and evaluated in a forward-osmosis process. Effects of CA concentration, coagulation bath temperature, and annealing thermal treatment on both membrane structure and performance were investigated. NaCl rejection of the optimum membrane was determined utilizing a reverse-osmosis setup based on conductivity measurements. Two validated models were obtained by means of response surface methodology based on Box-Behnken design. The optimum operating pressure, temperature, and draw solution concentration were assessed as well.

BACKGROUND: Novel nanocomposite membranes with spatial distribution of nanoparticles (NPs) were fabricated for forward osmosis (FO) applications. In this work, TiO 2 and Al 2 O 3 NPs were used as hydrophilic additives in order to improve the performance and fouling resistance of cellulose acetate (CA) FO membrane. RESULTS: Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) and x-ray diffraction (XRD) analyses confirmed the successful incorporation of the NPs into the synthesized membranes. The specific reverse salt flux (SRSF) of the TiO 2 modified membrane was reduced from 0.88 to 0.56 g L −1 , which was attributed to enhanced hydrophilicity, porosity, and the simultaneously improved water and salt permeability coefficients. After the evaluation of CA membranes with various contents of TiO 2 NPs, Al 2 O 3 NPs were added to the membrane structure as a secondary additive under the optimized content of TiO 2 NPs. Al 2 O 3 NPs have a higher dispersion in the membrane sublayer beneath, which can affect the hydrophilicity and surface charge of the membranes. Al 2 O 3 and TiO 2 modified membranes showed the lowest values of contact angle and zeta potential in neutral pH, which was 56.7°and − 68.4 mV, respectively. This membrane showed a water flux (WF) of 15 L m −2 h −1 and an SRSF of 0.36 g L −1 when using 1 mol L −1 NaCl as a draw solution. The fouling behavior of sodium alginate on the neat and modified membranes was also investigated, and the results showed a reduced fouling propensity and a superior fouling reversibility in the modified membranes. CONCLUSION: Based upon these findings, using low-density hydrophilic NPs in the membrane structure can fabricate membranes with more hydrophilicity, excellent FO performance, and high organic fouling resistance.

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