Nanocomposite hydrogels based on nanocellulose for applications in agriculture

Abstract

This thesis aimed to study the potential use of the nanocellulose obtained fromagroindustrial wastes to develop nanocomposite hydrogels. In the first part of the work,cellulose nanocrystals (CNC) were obtained from cotton linter fibers. Next, gelatinsingle-membrane and gelatin-alginate double-membrane hydrogels reinforced withCNC were prepared. Compared to the neat gelatin single-membrane, the compressivemodulus of the nanocomposite with 5 wt.% CNC was enhanced by 288% and,meanwhile, the nutrient loading capacity was increased by 155%. Compared withgelatin-based hydrogels reinforced with nanocellulose, the double-membranehydrogels showed a slow-release property and better water retention capacity. In thesecond part of the work, cellulose nanofibrils (CNF) were obtained from coconut huskfibers. High-purity CNF and lignin were isolated from coconut fibers through a multistep treatment process that combined steam explosion, organosolv pretreatment,bleaching, and TEMPO-mediated oxidation. The previous steam explosionpretreatment increased the lignin recovery from 45% to 73%. Next, CNF isolated fromsteam-exploded coconut fibers were used to prepare nanocomposite hydrogels.Poly(N,N-dimethylacrylamide) (PDMA) was used as a matrix material for fabricatingnovel nanocomposite hydrogels reinforced with CNF by a facile synthesis method. Thecompression modulus of the nanocomposite hydrogels was significantly higher thanthose of the pure PDMA hydrogels. The water-retention and NPK release studiesindicated that the addition of CNF considerably improved its water-retention capacitybut reduced the nutrient loading capacity of the hydrogel. All the prepared hydrogelsshowed a significantly improved mechanical performance. Our study provides facileand green routes to produce nanocomposite hydrogels with tunable properties forpotential agriculture applications.