High salt tolerance hydrogel prepared of hydroxyethyl starch and its ability to increase soil water holding capacity and decrease water evaporation

Hydroxyethyl starch (HES) and 2-Acrylamide-2-methyl-1-propanesulfonic acid (AMPS) as raw material, calcium alginate (CA33) was used as the main carrier for regulating and controlling soil water storage, and in situ polymerization with inorganic clay sodium bentonite to prepare a novel type of superabsorbent HES-PAM/bentonite and HES/CA33-PAM/ sodium bentonite composite materials using in-situ polymerization. The prepared hydrogel was characterized by scanning electron microscope (SEM), infrared spectrum (IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The water absorption/release properties of the superabsorbent polymer were explored. The results showed that the new superabsorbent material reached salt equilibrium within 30 min. The water absorption rates in distilled water, tap water, and 0.9 wt% saline solution were 1484, 312, and 121 g/g. The successful inarching of calcium alginate improved the soil's water holding capacity and provided a slow water release, which increased the water absorption rate of the superabsorbent materials in distilled water and saline solution by 25.8% and 10%, respectively. The influence of soil types, particle diameter, and the content of superabsorbent materials on inhibiting soil water evaporation was studied. Therefore, having great application potential in the agricultural production of saline-alkali soils.