New Biochar Hybrid Hydrogel Achieves Record-Breaking Solar Evaporation Efficiency for Low-Cost Desalination

Researchers use agricultural waste to create a hydrogel that purifies water with 95% light absorption. See how biochar is revolutionizing low-cost desalination.

By: AXL Media

Published: Apr 28, 2026, 9:22 AM EDT

Source: Information for this report was sourced from EurekAlert!

Engineering a Solution for Global Water Scarcity

The urgent need for potable water in resource-limited regions has led to a breakthrough in solar-driven interfacial evaporation. A study recently published in the journal Biochar details the development of a hybrid material that integrates biochar into a polyzwitterionic hydrogel network, dramatically outperforming existing purification technologies. By utilizing sunlight to convert saline water into vapor at the surface, this system offers a decentralized and energy-efficient alternative to industrial desalination plants. The innovation achieves a standard-sunlight evaporation rate of 3.57 kilograms per square meter per hour, a figure that represents a substantial leap in performance for hydrogel-based evaporators.

The Role of Biomass in Light Absorption

The integration of biochar, a carbon-rich substance derived from materials such as sorghum straw, serves a vital dual purpose within the hydrogel matrix. Physically, the biochar transforms the naturally transparent hydrogel into a dark, light-trapping medium capable of absorbing over 95 percent of the solar spectrum. This porous structure allows the material to capture energy across a broad wavelength range, converting photons into heat precisely where the evaporation occurs. This localized heating strategy ensures that energy is not wasted on warming the bulk body of water, but is instead focused entirely on the phase change of the surface molecules.

Molecular Modification of Water Enthalpy

Beyond simple heat absorption, the hybrid material alters the fundamental behavior of water molecules at a molecular level. The surface functional groups of the biochar interact with the hydrogen bonds within the hydrogel, creating a higher proportion of intermediate water. This specific state of water requires significantly less energy to vaporize than traditional bulk water, effectively lowering the equivalent evaporation enthalpy to 877.79 joules per gram. By reducing the thermal threshold for evaporation, the system can produce more freshwater using the same amount of solar energy, addressing one of the primary bottlenecks in solar thermal technology.