Designing High Flux and Antifouling Pa Ro Membrane Based on the Surface Modification with Glycerol and Dimethyldimethoxysilane

Abstract

In recent years, the polyamide (PA) reverse osmosis (RO) membrane is widely used in water treatment, however, membrane fouling remains an issue of concern. To enhance its anti-fouling properties, in this work, the glycerol and dimethyldimethoxysilane (DMDMS) modified PA RO membrane was fabricated by grafting glycerol and self-crossing assisted coating DMDMS on the PA RO membrane surface. The results show that the Si-O-Si network is formed on the DMDMS-PA membrane surface by the hydrolysis and condensation reaction of DMDMS, which could make up for the defects caused by the grafting solvent on the membrane surface and improve the NaCl rejection of the membranes. Ultimately, the DMDMS-PA membrane exhibits an increase in water permeance up to 4.39 LMH/bar and a NaCl rejection rate of 98.84%, respectively. In addition, the introduction of DMDMS containing two methyl groups reduces the membrane surface energy, makes the membrane surface smoother, and effectively lessens the amount of negative charge on the membrane surface. Furthermore, density functional theory (DFT) simulation results also show that the interaction energy between DMDMS on the membrane surface and foulants is weak. Based on these, the DMDMS-PA membranes show excellent and widely applicable anti-fouling performance according to the results of dynamic fouling tests using organic (electropositive and electro negative small molecular, macromolecule) and inorganic model foulants.

Keywords: Organoalkoxysilane, Low surface energy, Anti-fouling performance, Reverse osmosis membrane