Addressing the escalating global scarcity of freshwater resources necessitates effective solutions such as desalination. However, the challenge lies in finding efficient and cost-effective evaporation materials that can be applied on a large scale.
One promising avenue is the use of hydrogels in interfacial solar evaporators. However, conventional hydrogel materials have limitations in achieving the desired trade-off between high evaporation rates, salt resistance, and mechanical durability.
Typically, traditional hydrogels are only suitable for low-salinity brine, falling short of the requirements for long-term evaporation and treatment of industrial high-salinity wastewater. To enhance the salt resistance of hydrogels, researchers have explored constructing interpenetrating 3D macroporous structures.
Nevertheless, the rapid water transport and high water content in these hydrogels can lead to increased conductive heat loss. To address this issue, researchers have proposed designing a Janus structure. While various methods for creating such structures exist, they often lack surface stability and involve complex procedures.
To tackle these challenges, a team of researchers from the School of Chemical Engineering and Technology at Hebei University of Technology in Tianjin, China, introduced hydrophobic fumed nano-silica aerogel (SA) into the hydrogel production process. The remarkable properties of SA, such as its ultra-lightweight nature and super-hydrophobicity, allow it to spontaneously migrate and aggregate to the upper region of the hydrogel during the gelation process, resulting in the formation of a Janus structure.
Lead author Aqiang Chu explained, “We are aware that pore structure regulation can help address the issue of increased heat loss caused by the high salt resistance of the sponge-like hydrogel.” To enhance the overall performance of the hydrogel evaporators, agar (AG) was incorporated.
AG serves the purpose of thickening and stabilizing the bubble structure formed during the foaming process, thereby helping to regulate the pore structure of the hydrogel. Chu further elaborated, “The AG chain possesses a large number of hydroxyl groups, which can simultaneously interact with water to reduce the enthalpy of water evaporation. It forms ether bonds with polyvinyl alcohol, creating a robust cross-linked network that enhances the mechanical properties of the hydrogel.”
Corresponding author Hao Li added, “Considering the low cost and environmental friendliness of the materials used in our Janus dual-network sponge-like hydrogel solar evaporator, it exhibits great potential for practical applications in the field of interfacial solar evaporation.”
By leveraging the unique properties and synergistic effects of hydrophobic fumed nano-silica aerogel and agar, this novel hydrogel-based approach offers a promising solution for addressing the challenges in large-scale interfacial solar evaporation. The researchers’ findings, published in Green Energy & Environment, open up new possibilities for practical and sustainable applications in tackling the global freshwater scarcity crisis.
Source: KeAi Communications