Solar interfacial evaporation is considered a sustainable strategy for seawater desalination and wastewater treatment, yet salt fouling on evaporator surfaces remains a critical challenge that limits long-term performance. Continuous salt harvesting is therefore essential to sustain purified water production while enabling simultaneous salt collection. Here, we design an evaporator (PPy@MS-Filter paper, PMF) that achieves the spatial decoupling of water evaporation and salt crystallization by integrating a photothermal evaporation zone with a detachable salt-collection zone. The in situ polymerization of polypyrrole on a melamine sponge (PPy@MS) was designed for efficient water evaporation, and a superhydrophilic filter paper was wrapped around its upper edge to facilitate salt collection. Owing to the synergistic effects of a strong wettability-induced capillary pressure gradient and an evaporation-induced temperature gradient established between PPy@MS and filter paper, directional liquid and ion transport occurs from the central evaporation zone toward the peripheral filter paper, thereby enabling edge-preferential salt crystallization without compromising the photothermal efficiency of the evaporation interface. Consequently, this PMF evaporator maintains stable evaporation at 3.34 kg m–2 h–1 in 20 wt % brine, together with up to 314 g m–2 h–1 salt collection rate under 1 kW m–3. The replaceable filter paper enables prolonged operation for over 80 h while sustaining efficient salt harvesting. This modular strategy effectively mitigates salt fouling and advances solar desalination toward integrated freshwater production and salt resource utilization.
Cai et al. (Tue,) studied this question.