Importance of the Operating Conditions on the Photothermal Effect in Solar Pervaporation Desalination

This study evaluated the potential of photothermal carbon black (CB) coatings to use direct solar light as an energy source for pervaporation desalination. We used simulated sunlight to irradiate the CB-coated membrane and measured water flux and salt rejection. The feed was recirculated at a rate of 1 mL/s to replicate the industrial recirculation condition. We observed no statistically significant difference in water fluxes of the CB-coated membranes tested with and without a simulated sunlight irradiation of 0.8 sun intensity (0.82 ± 0.34 and 0.79 ± 0.16 kg/(h m2), respectively). Furthermore, the average permeances of the uncoated and coated membranes were similar. The results indicate that with rapid recirculating large volume feed photothermal heating from CB coatings is insufficient to increase the pervaporation flux of water because the heat generated by the CB heating on the surface of the membrane is largely dissipated into the bulk of the recirculating feed.