As desalination capacity expands, so does the volume of concentrated brine left behind. That waste stream can carry not only high salt loads but also residual treatment chemicals, heavy metals, and other pollutants, creating serious ecological and disposal challenges. Solar-driven interfacial evaporation (SDIE) has emerged as a promising low-carbon strategy because it localizes heat at the water surface and can both recover freshwater and further concentrate brine. Yet sunlight is inherently intermittent, and existing phase change materials (PCMs) often suffer from high transition temperatures, leakage, and poor durability under hypersaline conditions. Due to these challenges, there is a need to carry out in-depth research on continuous, salt-resistant solar desalination systems for hypersaline brine.
Researchers from Ocean University of China and Huzhou University developed the evaporator and reported (DOI: 10.1016/j.ese.2026.100696) the work in a paper accepted on April 2, 2026, for Environmental Science and Ecotechnology. Their device, named PPy-CS/PF@DDA, is built by confining dodecylamine inside a polypyrrole-coated chitosan/phenolic resin foam. In this design, polypyrrole captures sunlight, the porous foam moves water efficiently, and dodecylamine stores thermal energy at relatively low temperature. Together, those features allow the system to continue producing vapor under fluctuating light rather than stopping as soon as solar input weakens.
The performance numbers give the story its punch. The PPy-CS/PF@DDA evaporator reached an evaporation rate of 1.862 kg m⁻² h⁻¹ under one sun and still maintained 0.684 kg m⁻² h⁻¹ after the light source was removed, showing that stored heat was still doing useful work. In 20 wt% sodium chloride (NaCl), it retained a high evaporation rate of 1.763 kg m⁻² h⁻¹ without salt accumulation. The material also remained stable through repeated light-dark cycling. Beyond desalination, it reduced major seawater ions by two to three orders of magnitude to levels compliant with World Health Organization drinking water standards, sharply lowered heavy metal concentrations in model wastewater, and separated clean water from methyl orange solution without carrying over the dye.
“This work suggests a future in which solar desalination is not limited to bright, steady sunshine,” the findings indicate. “By integrating heat capture, heat storage, and salt resistance into one lightweight evaporator, the system moves closer to real continuous operation in harsh brine conditions.” That is the real advance here: not just faster evaporation at noon, but steadier performance across changing light conditions, where many laboratory systems begin to falter.
The outdoor test made that promise tangible. Using natural sunlight on an outdoor platform at Ocean University of China, the system produced 9.229 kg m⁻² of freshwater over 10 hours, with peak evaporation between 11:00 and 13:00. The authors also report a low material cost of $0.54 m⁻² and a straightforward fabrication process, suggesting real scale-up potential. That could make the foam useful not only for seawater desalination, but also for zero-liquid-discharge treatment, brine concentration, and wastewater purification in places where reliable clean water is needed and sunlight is abundant but variable.
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References
DOI
10.1016/j.ese.2026.100696
Original Source URL
https://doi.org/10.1016/j.ese.2026.100696
Funding information
This work was supported by the National Natural Science Foundation of China (No. 22378374) and the National Natural Science Foundation of Shandong Province (No. ZR2024MB086).
About Environmental Science and Ecotechnology
Environmental Science and Ecotechnology (ISSN 2666-4984) is an international, peer-reviewed, and open-access journal published by Elsevier. The journal publishes significant views and research across the full spectrum of ecology and environmental sciences, such as climate change, sustainability, biodiversity conservation, environment & health, green catalysis/processing for pollution control, and AI-driven environmental engineering. The latest impact factor of ESE is 14.3, according to the Journal Citation ReportsTM 2024.