Effect of ZnO morphology on GO-ZnO modified polyamide reverse osmosis membranes for desalination

In this investigation, the effect of embedding nanocomposite with different morphology in a polymer-based reverse osmosis (RO) membrane was studied. Thin-film-nanocomposite (TFN) RO membrane was prepared with graphene oxide (GO) and amino-functionalized zinc oxide (ZnO) having different morphologies, i.e. spherical (ZnO-S), flower (ZnO-F) and rod (ZnO-R) shaped nanostructure. The surface properties of the fabricated TFN-RO membrane were investigated using SEM, TEM, XRD, FTIR, AFM, XPS and contact angle measurement. The membrane performance was evaluated using a cross-flow filtration set-up at 25 °C and 20 bar pressure for 2000 mg/L NaCl solution. The experimental results indicated that 0.02 wt% GO-ZnO composite membranes (regardless of their shape) exhibited enhanced hydrophilicity, flux, and permeability. A comparison of different GO-ZnO morphology highlighted that the GO-ZnO-S TFN-RO membrane exhibited superior performance due to the smaller size of ZnO-S, which effectively prevented GO nanosheets from stacking together. The modified membrane with an optimum GO-ZnO-S concentration of 0.02 wt% showed higher solute water flux (31.42 L/m2·h) compared to the pristine TFC membrane (14.28 L/m2·h) with a good salt rejection. Moreover, the modified membranes were found to be chlorine resistant and showed better anti-fouling performance compared to the pristine membrane.