Photothermal\nCarbon Black Nanoparticle Coating Increases\nScaling Resistance in Solar Membrane Distillation

Self-heating membranes show promise for off-grid solar\nmembrane\ndistillation (MD). High scaling resistance was indicated in solar\nMD systems when only driven by the self-heating surface due to the\nlow bulk feedwater temperature. However, low temperatures also result\nin low permeate flux compared to conventionally heated MD systems.\nTo identify the trade-off between high flux and scaling resistance,\nwe investigated the effect of an increasing feed temperature (<i>T</i><sub>feed</sub>) on permeate flux and scaling resistance\nin MD. Increasing <i>T</i><sub>feed</sub> between 30 and\n70 °C while maintaining a constant distillate temperature of\n20 °C confirmed that higher <i>T</i><sub>feed</sub> increases permeate flux but also results in an earlier flux decline\ncaused by higher membrane scaling. Similar findings were obtained\nwhen a self-heating layer was used; however, the self-heating layer\nin solar MD also resulted in a lower flux decline despite the high\nfeedwater temperature. This effect is attributed to an increase in\nthe hydrophilicity of the heated layer compared to the pristine membrane,\nwhich is hypothesized to reduce the deposition of scaling precursors\non the surface. These findings indicate benefits beyond flux improvement\nfor self-heating MD membranes when used in challenging waters rich\nin inorganic scaling species.