Optimization of composite atmospheric hygroscopic gel preparation and its application in ecological restoration in arid-semi-arid regions

Water scarcity in arid and semi-arid regions is a critical constraint on the effectiveness of ecological restoration efforts. Adsorptive atmospheric water harvesting (AWH) technologies have emerged as promising tools to alleviate plant water stress in such environments; however, their application in ecological restoration remains underexplored. This study co-polymerized NIPAM and AM to form a new composite gel and loaded it with hygroscopic salts to test the effects of gel ratios on the water absorption and release properties, as well as the performance under different temperature, humidity and light conditions, and water production in the field. The results show that the composite gel with NIPAM∶AM mass ratio of 1∶1.5 had the optimal balance between water adsorption and water release, with the dissolution rate reached 24.7 g/g, while 75.3% of water release could be realized, which was 31.3% more than the water production of the PNIPAM gel. Under the condition of temperature 20 °C and relative humidity (RH) 50%, the composite gel loaded with hygroscopic salt CaCl₂∶LiCl molar ratio of 1∶7 has the highest hygroscopicity, which is 1.14 times that of the loaded pure LiCl gel, and can be hygroscopic under the condition of 30%−100% RH. The above optimized composite hygroscopic gel was applied to the ecological restoration project of mines in arid-semi-arid areas. The average daily water yield in summer was about 0.74 g/g, which could make up for the shortfall of the ecological water demand of plants based on Penman's formula when the dosage was in the range of 14.1−17.6 g. The results confirm the feasibility of the application.