Enhancing the flux and salt rejection of thin-film composite nanofiltration membranes prepared on plasma-treated polyethylene using PVA/TS-1 composite

Abstract

The high hydrophobicity of polyethylene (PE) film restricts its application as a thin-film composite (TFC) support layer. Therefore, in this study, oxygen plasma treatment was used to generate hydrophilic groups on PE and facilitate the formation of the TFC membrane. The difference in the performance of the plasma treated-PE (P-PE) membrane compared to untreated-PE indicated the significant effect of plasma pretreatment. In the following, to enhance the hydrophilicity of the P-PE membrane, titanium silicate-1 (TS-1) was synthesized as a zeotype through the hydrothermal method and added to the aqueous solution of the interfacial polymerization process. Due to the decrease in the agglomeration of TS-1 in the membrane matrix, PVA/TS-1 composites with distinct concentrations of polymer were prepared and applied for modifying membrane properties. Membranes were characterized by FESEM, ATR-FTIR, AFM, zeta potential, and water contact angle analyses. Permeability, rejection of monovalent and divalent salts, and antifouling ability of the fabricated nanofiltration membranes were studied and the optimal polymer concentration was determined. Comparison of P-PE-TFC 0.1 membrane with P-PE showed an increase of ~42% in pure water flux. Also, the rejection of Na2SO4, MgSO4, MgCl2, and NaCl salts were 90.28%, 81.77%, 74.79%, and 70.94% for P-PE-TFC 0.1 membrane, respectively, which showed a notable improvement compared to the P-PE membrane. Evaluation of antifouling ability showed that P-PE-TFC 0.1 membrane had a higher resistance to fouling compared to other membranes. Flux recovery ratio of this membrane after three cycles of bovine serum albumin (BSA) filtration was higher than other membranes resulting from the reduced roughness due to the combined effect of PVA and TS-1.