Preparation of cellulose triacetate forward osmosis membranes for treating esterification wastewater

Cellulose triacetate (CTA) membranes for forward osmosis (FO) were prepared by phase inversion. Effects of the polymer concentrations, solvents (1,4-dioxane, N-methylpyrrolidone, N,N-dimethylformamide), additives (lactic acid and PVP-K30) on the FO membrane performance and gelation kinetics mechanism were explored. The pre-treated esterification wastewater was further treated via the optional membrane under the FO mode, the long-term FO performance and fouling behaviors of CTA membranes are further investigated. Results showed that the CTA membrane cast using 1,4-dioxane as solvent has shown lower water flux but higher salt rejection, whereas the membrane cast using N-methylpyrrolidone or N, N-dimethylformamide as solvent has excellent permeability but poor selectivity. The water flux and reverse salt flux reduced with the increase of CTA concentration. As the lactic acid and PVP-K30 increased, the gelation velocity accelerated, the water flux and reverse salt flux enhanced. Furthermore, the water flux went down significantly by 51.1% in the long-term test. Especially in the early 5 h, the flux declined sharply from 9.56 LMH to about 6.0 LMH, and then the water flux reduced slowly since the membrane fouling become to stability. FO treatment brought about 57.1% of water recovery and favorable pollutants rejection with TOC rejection exceeding 96%.