Enhancement of sandy soil water retention using superabsorbent carboxymethyl cellulose grafted with polyacrylamide and polyacrylamidomethyl propanesulfonic acid copolymer

Abstract

Abstract To enhance the productivity of sandy soil, considerable efforts have been devoted to improving its water retention capacity, thereby reducing the frequency of irrigation and minimizing water loss through evaporation. The present study aimed to develop carboxymethyl cellulose (CMC)—grafted-(polyacrylamide (PAM)-co-2-acrylamido-2-methylpropanesulfonic acid (PAMPS) superabsorbent hydrogel (SAH) for effective water retentionin sandy soil. Characterization of the grafted copolymer hydrogel was performed using Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The synthesized CMC-g-(PAM-co-PAMPS) SAH exhibited improved thermal stability, demonstrating a half-weight loss at 391 °C compared to 331 °C for the pure CMC biopolymer. The consequence of various grafting conditions on the percentage add-on was systematically optimized. Additionally, factors influencing water uptake behavior, including contact time, pH and temperature of the medium, particle sizes, and total dissolved salts, were investigated. The results indicated that increasing the co-monomer ratio from 3 to 18% significantly raised the % add-on value from 81 to 97.4%. The developed SAH showed an exceptionalwater uptake capacity of 313 g/g within a short duration of 15 min. Furthermore, it demonstrated the ability to reabsorb water over five successive cycles, achieving an efficiency exceeding 70%. The incorporation of the SAH into sandy soil resulted in a reduction of water outflow, with a significant decrease in the flow rate from 0.96 to 0.32 cm/min. The fabricated superabsorbent hydrogel presents a promising approach for enhancing water retention in sandy soil.

Keywords

• Carboxymethyl cellulose
• PAM
• PAMPS
• SAHs
• Grafting
• Water uptake