Thin film nanocomposite nanofiltration membranes from amine functionalized-boron nitride/polypiperazine amide with enhanced flux and fouling resistance

Abstract

Thin film composite (TFC) nanofiltration (NF) membranes typically used for drinking water treatment applications are susceptible to fouling by natural organic matter (NOM) which adversely affects the permeation and separation efficacy. Here, new thin film nanocomposite (TFN) NF membranes were fabricated through the incorporation of amine functionalized-boron nitride, BN(NH₂), nanosheets within the polypiperazine amide (PPA) active layer during the interfacial polymerization (IP) process to improve the fouling resistance of membranes. Physical and chemical characterization investigations confirmed the successful embedment of nanosheets within the PPA network and revealed changes in the membrane surface morphology and chemistry as a result of BN(NH₂) addition. Accordingly, the membrane containing 0.004 wt% of BN(NH₂) nanosheets (PPA-BN-4) exhibited a more negatively charged and hydrophilic surface compared with a bare PPA membrane, both prepared under similar experimental conditions. These characteristics correlated well with 13.4% enhancement in permeation of the PPA-BN-4 membrane without significantly compromising the NOM rejection in terms of ultraviolet absorbance at 254 nm (UV₂₅₄) and dissolved organic carbon (DOC). The normalized flux also retained a very high value at 0.97 during the filtration of moderately-concentrated humic acid (HA) solutions which confirms the excellent fouling resistance behaviour of the PPA-BN-4 membrane. The highly reproducible results achieved in this study indicate the great potential of BN(NH₂) TFN membranes in practical drinking water treatment applications.