Sulfonated Reverse Osmosis Membrane with Simultaneous Mitigation of Silica Scaling and Organic Fouling

Inorganic scaling and organic fouling remain limiting factors for the further application of reverse osmosis (RO) membranes. Herein, a novel monomer, 2,2′-benzidinedisulfonic acid (BDSA), was selected as a comonomer with m-phenylenediamine (MPD) to fabricate RO membranes. Compared with the polyamide (PA) composite membrane, the as-prepared PA-BDSA composite membrane exhibited enhanced surface hydrophilicity and a smoother, more negative charge (zeta potential of −44.4 mV at pH 7). During the 24 h antiscaling experiment with a saturated silica solution (SiO2 concentration of 168 ppm), the water flux decline rate of the PA-BDSA-0.2 membrane was only 18%, which was 10% lower than that of the PA membrane (28%). During antifouling and scaling-fouling experiments, the PA-BDSA membranes also displayed less flux loss than the PA membrane, indicating its simultaneous alleviation of organic fouling and silica scaling. The analysis of the fouling layer revealed that compared to the PA membrane, fewer contaminants adhered to the PA-BDSA membrane surface. Furthermore, the interactions between silica and organic foulants were investigated, and the synergy of sodium alginate (SA) and silica aggravated fouling and scaling processes, resulting in a more serious flux decline rate. This research reveals a simple and practical method for the preparation of RO membranes to mitigate membrane scaling and fouling.