Chemical grafting N-GOQD of polyamide reverse osmosis membrane with improved chlorine resistance, water flux and NaCl rejection

Poor chlorine resistance shortens service life of polyamide (PA) reverse osmosis membrane. Here, nitrogen-doped graphene oxide quantum dots (N-GOQDs) were firstly applied to graft on PA membrane surface. Most grafting experiments are often accompanied by a decrease in water flux. In this study, the flux of the grafted membrane can be increased compared with commercial pristine membranes. Also, all modified membranes show better chlorine resistance than pristine ones. Specifically, N-GOQDs are integrated onto polyamide membranes through grafting method. Comprehensive regulation of chlorine resistance and desalination performance can be achieved by changing grafting conditions. For example, under the conditions of 12 h grafting time and 0.002 mg/mL of N-GOQD solution, water flux, NaCl rejection, and chlorine resistance of the modified membrane are improved by 11.1%, 2.3% and 32.8% after 280 h chlorine soaking respectively. FTIR analyses show that hydrogen bonded C=O groups can be observed in the N-GOQD grafted membrane after chlorine tests, but they are destroyed and weakened in pristine membranes, which indicates that the modified membrane has better resistance to reactive chlorine.