Thin-film composite polyester nanofiltration membrane with high flux and efficient dye/salts separation fabricated from precise molecular sieving structure of β-cyclodextrin

Abstract The treatment of dye pollutant and salts by nanofiltration membrane technology usually has the difficulty of low permeability and higher pressure in the case of maintaining a high rejection. In this study, high flux polyester membranes of β-cyclodextrin/trimesoyl chloride - multiwalled carbon nanotubes (β-CD/TMC-MWCNTs) were fabricated on a modified multiwalled carbon nanotubes (MWCNTs) substrate via interfacial polymerization (IP) process. The modified MWCNTs substrate was not only beneficial to modulating the permeation and distribution of aqueous phase monomer (β-cyclodextrin, β-CD), but also in favor of the formation of an ultrathin loose selective polyester active layer due to the porous network structure. The optimization experiments about the reaction time and monomer concentrations were conducted. The experimental results showed that the pure water flux of the as-prepared β-CD/TMC-MWCNTs membrane was 179.93 L m-2h-1 bar-1 (at the pressure of 0.1 MPa) when the reaction time of IP process was 5 min. The single dye removal efficiency of β-CD/TMC-MWCNTs membrane was 97.41% for Brilliant Green (BG) and 96.39% for Congo red (CR), respectively. The removal efficiency of dye/salt mixture by the membrane was above 84% for BG and over 98% for CR, respectively. The results indicated that the membrane had the efficient selective separation performance for the dye/salt mixture benefiting from the special molecular sieving architectures with the precisely intrinsic inner cavity of β-CD/TMC-MWCNTs membrane. Furthermore, the reusability, chlorine resistance, and antifouling ability of the β-CD/TMC-MWCNTs membrane was relatively excellent, and the membrane could effectively remove BG (>93%) and CR (>98%) simultaneously for mixed BG/CR dyes in real water body. These results suggested that the as-prepared β-CD/TMC-MWCNTs membrane had the potential of practical application in dye wastewater treatment.