Investigations of bamboo cellulose-based multifunctional hydrogel for integrated water and fertilizer regulation: Experiments and DFT calculations

Superabsorbent hydrogels achieve the functional integration of water storage and fertilizer release through molecular design, offering an innovative pathway for the development of sustainable agricultural materials. Bamboo is a rapidly growing and widely distributed renewable biomass resource, and composite hydrogels with multiple functions can be constructed based on bamboo powder. This study developed a bio-based multifunctional superabsorbent hydrogel (BP-AD) that features both water retention and intelligent fertilizer control functions by grafting bamboo power (BP) with diacetone acrylamide (DAAM) and acrylic acid (AA) through an ultrasonic-assisted green aqueous solution polymerization technique. Characterization of FT-IR, XRD, and TGA confirmed that BP-AD is functionalized with carboxylic acid and amide groups and endows the material with excellent thermal stability. BP-AD exhibited an exceptional water absorbency capacity of 1401.5 g·g⁻¹ in ultrapure water, and its water absorption kinetics followed the pseudo-second-order kinetic model (R²= 0.9991), indicating that chemical adsorption predominates in the moisture capture process. The adsorption of urea by BP-AD conforms to the Freundlich model, suggesting that multiphase multilayer adsorption is the mechanism behind urea adsorption. Density Functional Theory (DFT) calculations indicate that the adsorption of urea by BP-AD can be attributed to hydrogen bonding and electrostatic interactions. The release of urea from BP-AD aligns with both the Korsmeyer-Peppas model and Zero-order kinetic model, and regulated by an ionic strength response mechanism. This research integrates biomass resource conversion with precision modern agriculture by innovatively developing dual-functional hydrogels, offering technical support for sustainable agriculture.