Investigating the microstructures and surface features of seawater RO membranes and the dependencies of fouling resistance performances

Abstract

The structures and surface features of four commercial seawater reverse osmosis (RO) membranes (SW22, SW30, SWC1, and TM810) in nano- and micro-scales were thoroughly investigated by using various characterization techniques. The experimental results show that among the four membranes, only SW22 and SW30 membranes were modified with hydrophilic coatings. The presence of these coatings makes the RO membranes exhibit different contact angles and zeta potentials. It was observed that the middle part of separation layer should play a key role for the desalting process, which provides important direct evidences for the previous reports on the desalination mechanism and back-surface structures of separation layer. Furthermore, the membrane fouling-resistance performances were comprehensively studied in 32,000ppm of NaCl aqueous solutions containing different foulants. Their dependencies on surface features of RO membranes were also proposed based on the experimental results. It was revealed that SW22 membrane possesses superior fouling resistance to humic acid, and SWC1 membrane can strongly resist the fouling from bovine serum album and silica colloids. The functional groups, surface charge properties, and roughnesses are closely related to the anti-fouling properties. It was also found that the fouling mechanism of silica colloids is significantly different from those of humic acid and bovine serum album.