Super Hygroscopic Hollow Biopolymer Microbeads for Clean Water Production and Atmospheric Water Irrigation

Water scarcity is an important limiting factor for human life and agricultural production in arid regions. Atmospheric water harvesting (AWH) technology, which captures moisture from the surrounding air, demonstrates significant potential for clean water production and soil irrigation. In this research, marine polysaccharide-lignosulfonate hollow hygroscopic microbeads were prepared for incorporating salts (LiCl or CaCl 2 ), generating the lithium chloride/sodium alginate/calcium lignosulfonate/carbon nanotubes (LiCl/SA/CaLS/CNTs) and the calcium chloride/sodium alginate/calcium lignosulfonate (CaCl 2 /SA/CaLS) biopolymer microbeads that effectively harvest moisture. The LiCl/SA/CaLS/CNTs microbeads show a high water uptake value of 11.7 g/g at 90% relative humidity (RH) and rapid adsorption-desorption. More than 99.9% of the adsorbed water could be rapidly released in only 2.5 hours at the solar intensity of 2.0 kW/m 2 in the natural environment. Modification of soil with the CaCl 2 /SA/CaLS microbeads significantly prolonged ryegrass survival for 13 days (compared to the blank control) by atmospheric water irrigation at 26°C and 60% RH. The all-natural composite material is also eco-friendly and non-toxic, promising a feasible and effective sustainable solution to clean water production in water-deficient areas and agricultural irrigation in seasonally arid areas.