High efficient removal of dyes from aqueous solution through nanofiltration using diethanolamine-modified polyamide thin-film composite membrane

High energy consumption and membrane fouling are the two major obstacles that limit the extensive application of nanofiltration technology in treatment of textile and dyeing wastewaters. In this work, traditional polyamide (PA) thin-film composite (TFC) nanofiltration membrane was modified with diethanolamine (DEA) for improved water permeability and antifouling property in the removal of dyes from aqueous solution. The DEA-modified PA-TFC membrane was fabricated by a facile approach of pouring the DEA-aqueous solution on the surface of the nascent polyamide membrane prepared via interfacial polymerization between trimesoyl chloride and piperazine. The covalent attachment of DEA molecules was found to make membrane surface more hydrophilic and less negatively charged while having no influence on the morphological structure and compactness of the active layer. Compared with the traditional PA-TFC membrane, the steady-state water fluxes of the DEA-modified PA-TFC membrane to dye aqueous solutions of Congo red, methyl blue, sunset yellow and neutral red were higher by more than 37.0%, the flux decline ratios due to membrane fouling were lower by at least 35.0%, while the dye removal remained constant, and furthermore, the dye molecules adsorbed and deposited on membrane surface could be more readily washed off by simple hydraulic washing.