Preparation of Itaconic Acid-Modified Guar Gum Composite Hydrogel for Water Retention in Mine Ecological Restoration

To tackle poor water retention in degraded mine soil and the low stability and short water-holding duration of natural polymer hydrogels, an itaconic acid-modified guar gum composite hydrogel (IAGG hydrogel) was developed using guar gum (GG) as the polymer substrate and itaconic acid (IA) as the functional monomer. This study aimed to improve the stability, water-retention duration, and water-absorption performance of GG-based hydrogels through a covalent–dynamic multiple-crosslinking design and to evaluate their potential for mine ecological restoration. The hydrogel network was constructed through IA-related covalent interactions, ECH-mediated ether crosslinking, and borax-mediated dynamic interactions, forming a covalent–dynamic multiple-crosslinked structure. IA-introduced carboxyl groups enhanced hydrophilicity and water retention via hydrogen bonding and ionic hydration, while covalent–dynamic crosslinking synergy improved network stability and wet–dry cycle resistance. Under the optimized preparation conditions, the IAGG hydrogel exhibited a water absorption capacity of 370.7 g/g in deionized water, and the I5G5 hydrogel retained a water absorption capacity of 255.4 g/g after 10 swelling–dehydration cycles. Soil experiments showed that IAGG increased mine soil water-holding capacity from 13.3 to 77.6 g/g, extended retention from 5 to 14 days, and supported the germination and subsequent seedling development of Suaeda salsa. After 4 months of soil burial, the hydrogel exhibited approximately 63% weight loss, indicating substantial structural deterioration under the tested soil-burial conditions. These results demonstrate the potential of IAGG as a water-retention material for mine ecological restoration.