Bioinspired modification of molybdenum disulfide nanosheets to prepare a loose nanofiltration membrane for wastewater treatment

Loose nanofiltration membrane (NFM) is suitable for wastewater treatment especially for dye solution desalination due to its high rejection of dyes and high permeance of salts. In this study, MoS2@PDA was prepared by modifying molybdenum disulfide (MoS2) nanosheets with polydopamine (PDA). Then, the loose nanofiltration membrane was prepared by the deposition of MoS2@PDA on hydrolyzed polyacrylonitrile (HPAN) ultrafiltration membrane with pressure-assisted self-assembly. The morphology and properties of MoS2@PDA and MoS2@PDA NFMs were analyzed by SEM, TEM, TGA, FT-IR, AFM, WCA, XRD, and ζ-potentials. The PDA nanoaggregates on the surface of MoS2 nanosheets interfered with the regular stacking of MoS2 nanosheets parallel to the membrane surface, so the resultant membranes showed irregular loose structure which could provide transmembrane channels along with the impermeable nanosheet surface for molecule diffusion. When the MoS2 loading was 0.116 mg/cm2 and the PDA modification time was 5 h, the pure water flux of MoS2@PDA NFM could reach 204.05 LMH/bar, the rejection of methylene blue was 99 %, and rejection of salts (NaCl, Na2SO4, MgCl2, MgSO4) were less than 12 %. And MoS2@PDA NFM exhibited satisfactory long-term operational stability. This study provides a new strategy for the design of loose nanofiltration membrane with high performance.