Preparation and characterization of PPO/PS porous membrane for desalination via direct contact membrane distillation (DCMD)

Abstract

The non-solvent induced phase separation (NIPS) method was used to prepare novel polyphenylene oxide and polystyrene blend (PPO/PS) flat-sheet porous membranes. The performance of prepared samples was studied in a direct contact membrane distillation (DCMD) experimental set-up. The prepared membranes were characterized using field emission scanning electron microscopy (FESEM), attenuated total reflection Fourier transform infrared (ATR-FTIR), atomic force microscopy (AFM), and zeta potential. A number of other properties, such as porosity, contact angle, and liquid entry pressure (LEP), were measured. Permeate flux has also been evaluated at different feed concentrations (0, 3500, and 35000 ppm NaCl) and temperatures (0, 60, and 80 °C). According to the results, by increasing feed temperature from 40 to 80 °C and maintaining permeate temperature constant at 22 °C, the permeate flux was increased from 5.53 to 31.36 kg/m2h. Altering the feed concentration from 0 to 35000 ppm has resulted in a reduction of permeate flux from 31.36 to 27.87 kg/m2h. In all DCMD tests, high rejection was observed (99.9%). Moreover, the anti-fouling and anti-scaling properties of the prepared membrane were investigated. Anti-scaling properties were examined by adding CaCl2 and Na2SO4 to the feed solution; the permeate flux did not change significantly and rejection was maintained above 99.8%. Humic acid (HA) in feed solution led to fouling, resulting in a 20% reduction in flux, but the rejection was maintained above 99.4%. Furthermore, SDS and CTAB surfactants (below CMC) as foulant agents were added to feed and due to the wetting phenomenon, the rejection dropped to 99.11 and 99.28%, respectively, while permeate flux decreased very slightly after 4 h operation.