Preparation and properties of super water-retaining agent with sulfonic acid and carboxylic acid groups assisted by ultrasounds

Superabsorbent hydrogels demonstrate positive significance as water-retaining materials in agriculture and gardens. The super water-retaining hydrogel (BASA) based on the bamboo powder with the rich sulfonic acid group and carboxyl group was successfully and efficiently synthesized by ultrasonic wave-assisted and polymerization methods. The preparation process has the advantages of mild conditions and process simplification. The impact of reaction conditions (the ionic strength, pH value, cross-linking agent and initiator content) was systematically studied. Characterization methods such as elemental analysis, FTIR, SEM and TGA indicated that the synthesized super water-retaining agent had excellent water retention properties and good stability. The maximal absorbent capacities in ultrapure water and rainwater reached 1047 g g⁻¹ and 952 g g⁻¹, respectively. The water retention properties of BASA were affected by the water quality and ionic strength of water solution. The swelling process is mainly the hydrogen bonding between the active group and the hydrogen atom of the water molecule and the electrostatic interaction of anionic groups such as sulfonic acid groups, but it also includes the synergistic effect of diffusion process. The outcomes demonstrate that BASA is a powerful water absorption hydrogel for soil water retention agent in the agricultural field.