Fabrication of thin film composite polyamide membrane for water purification via inkjet printing of aqueous and solvent inks

Abstract

Thin film composite (TFC) polyamide (PA) membranes are typically prepared using the interfacial polymerization (IP) method, which synthesizes the PA layer by soaking in aqueous diamine and organic acyl chloride solutions and allowing the occurrence of amidation. The conventional IP process has been used over several decades in the industrial production of TFC membranes for water purification and excess amounts of monomer solutions are used for PA thin film layer synthesis, generating a lot of chemical wastes. In this work, we first demonstrated the TFC PA membrane fabrication using simple inkjet printing of aqueous and organic inks to effectively prepare a PA layer with no chemical wastes. The organic acyl chloride ink was newly formulated by the combination of dodecane and toluene solvents to allow printability. Precise and uniform depositions of monomer inks via the inkjet printing approach were able to coat a dense and defect-free PA film onto the support membrane using only small volumes of chemicals. After multiple printing numbers of inks, the PA layer was optimized with two printing cycles (30.17 mL m−2) and three printing cycles (8.36 mL m−2) of diamine and triacyl chloride inks, respectively, followed by heat treatment. The inkjet-printed TFC-M2T3-15 membrane exhibited a high salt rejection (95.33 %) which showed higher performance compared to that of the conventional IP-prepared TFC membrane (89.64 %).