Highly permeable and antifouling reverse osmosis membranes with acidified graphitic carbon nitride nanosheets as nanofillers

Abstract

Ultrathin graphitic carbon nitride (gCN) nanosheets, due to their two-dimensional graphene-like structure, regularly distributed triangular nanopores and structural defects on the laminar network, have attracted great research attention in fabricating high-performance water selective membranes. However, the poor dispersity of gCN limited its application in thin film nanocomposite (TFN) membranes. Here, we synthesized acidified graphitic carbon nitride (aCN) with smaller size and higher solubility. Both aCN and gCN were incorporated into a polyamide (PA) selective layer by interfacial polymerization. The aCN embedded TFN membrane (TFN-aCN) possessed supreme reverse osmosis (RO) performance among the prepared membranes. Compared with the reference TFC membrane, the TFN-aCN50 membrane exhibited a 79.3% increase in permeate flux accompanied by a quite high NaCl rejection of 98.6%. Moreover, the introduction of aCN and gCN generated a more hydrophilic and negatively charged membrane surface, and thus resulted in an improved antifouling performance.