Enhanced Interfacial Solar Evaporation Via Janus Polyelectrolyte Hydrogel Fiber Fabric with Rapid Water Transport, Thermal Localization, and Ultra-High Salt Resistance

Abstract

A Janus polyelectrolyte hydrogel-fabric coupled evaporator PCMZ was prepared by coating method, which can stably and efficiently carry out interfacial solar desalination. The evaporator is supported by hydrophobic polystyrene foam (EPS), and the heat loss from the evaporator to the bottom water is reduced. Thin absorbent cotton and fabric were used as water transport channel, and polyvinyl alcohol/chitosan/polyacrylamide/polymethylacryloxyethyl trimethyl ammonium chloride (PVA/CS/PAAM/MTAC) was coated on the surface of the fabric to polymerically crosslink into hydrophilic gel layer. Finally, three-dimensional gel-fabric evaporator PCMZ was prepared by hydrophobic modification with benzaldehyde on the surface of the hydrophilic gel layer. The performance of PCMZ with different heights was tested, and the water transport capacity, thermal management, evaporation rate and the center of gravity in practical application were comprehensively considered. Finally, PCMZ with a height of 3 cm was selected for further experiment. The test results show that the expanded three-dimensional evaporation surface is beneficial to optimize thermal management and reduce heat loss, and the mechanical properties of PCMZ are enhanced. Because of the synergistic effect of these three parts of PCMZ, the overall seawater evaporation efficiency can reach 3.44 kg·m-2·h-1. It can continue working in saline water with a salt content of 15%, and the evaporation efficiency can reach 2.75 kg m-2 h-1. Moreover, PCMZ exhibits excellent mechanical properties due to the toughness of many slender fibers and the hydrogen bonding between polymers in the gel layer, and it can also be stable after ultrasonic, acid and alkali leaching. The results showed that, PCMZ is stable, efficient and easy to manufacture, showing great potential in industrial and agricultural applications.

Keywords: Interfacial Solar Evaporation, Seawater desalination, Janus structure, Salt resistance