Diatomite/polyaniline-BiOCl functionalized hierarchical composite membranes for simultaneous photothermal interface water evaporation and wastewater purification

Interfacial solar water evaporation technology holds great promise for resource recovery and wastewater purification. In this study, diatomite/polyaniline-BiOCl functionalized hierarchical composite membranes (DpM/PANI-BiOCl) with efficient photothermal water evaporation and pollutant degradation performance were synthesized via a simple in situ hydrolysis method. The composite membrane features a three-dimensional porous polyurethane sponge filled with diatomite as the bottom water transport layer, followed by layer-by-layer loading of polyaniline (photothermal layer) and BiOCl (photocatalytic layer). This design enables the efficient synergy of water transport, photothermal conversion and photocatalytic degradation. Under one-sun irradiation, the optimized DpM/PANI-BiOCl functionalized hierarchical composite membrane achieved an evaporation rate of up to 1.11 kg/m 2 /h while removing 95.9 % of rhodamine B (RhB) from bulk water. After 3 cycles of stability testing, its pollutant removal rate remained above 80 %. Furthermore, the composite membrane exhibited excellent photocatalytic performance across different pollutant concentrations, with degradation rates of 90 % for methylene blue (MB) and 91.2 % for methyl orange (MO). These results highlight the importance of the functionalized hierarchical design in facilitating the photocatalytic pollutant degradation and enabling efficient, sustainable clean water extraction from wastewater.