Enhanced separation and antifouling performance of reverse osmosis membrane incorporated with carbon nanotubes functionalized by atom transfer radical polymerization

Abstract

In this paper, an approach to obtain mixed-matrix reverse osmosis (RO) membranes with enhanced separation and antifouling performance is described. Atom transfer radical polymerization (ATRP) was first introduced for functionalization of multiwalled carbon nanotubes (MWCNTs) with polyacrylamide (PAAm) structure. Subsequently, MWCNTs were incorporated into polyamide (PA) thin film composite (TFC) membranes by interfacial polymerization. The dispersion of MWCNTs in aqueous solution and compatibility between MWCNTs and polymeric matrix were effectively improved with PAAm. Membrane surface morphology, hydrophilicity and charge properties were characterized by SEM, AFM, static water contact angles and zeta potential measurement. Moreover, the effect of above properties on separation and antifouling performance of membranes was investigated. Results showed that water flux of the optimal membrane incorporated with MWCNTs grafted at 6 h (MM-6h) was 34% higher than that of virgin PA membrane. More importantly, NaCl rejection of MM-6h membrane was 98.9%, which is higher than that of virgin PA membrane and the membrane incorporated with oxidized MWCNTs. In addition, surface modified membranes showed excellent fouling resistance to BSA. The flux recovery of MM-6h membrane was about 97.6% after cleaning, while that of virgin PA membrane was only 79.2%. This work proves that MWCNTs functionalized by ATRP have potential application in simultaneously improving separation and antifouling performance of TFC RO membranes.