Superabsorbent polymer used for saline-alkali soil water retention

Enhancing the water retention capacity of soil is an effective measure to curb soil salinization. Superabsorbent polymer (SAP) with a strong absorbing water ability is particularly suitable as a water-retaining agent in agriculture. However, their limited salt tolerance restricts their applicability in saline-alkali soil. Hence, this research aimed to develop a salt-tolerant superabsorbent polymer (ST-SAP) that can be utilized in saline-alkali soil. ST-SAP, prepared by using 2-acrylamide-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA) and acrylamide (AM), was evaluated by swelling and reswelling experiments. The salt-tolerant mechanism of ST-SAP was studied by XPS, FT-IR and CT. The water retention capacity of saline-alkali soil, collected from Lop Nur of Xinjiang and containing 18.13 wt% total dissolved salt, was determined to validate the effectiveness of ST-SAP in high-salt soil. The ST-SAP synthesized in this study exhibited excellent swelling capacity (69.04 g/g) under high salt condition. Notably, ST-SAP presented exceptional stability under high salt condition, due to the complexation reaction between Ca2+and its three hydrophilic groups (R-SO3H, R-COOH, R-CONH2). Moreover, when 2 wt% ST-SAP was added to the saline-alkali soil, the water retention time was extended to 28 days, confirming the efficacy of ST-SAP in saline-alkali soil.