Synthesis and characterization of carboxymethyl chitosan superabsorbent hydrogels reinforced with sugarcane bagasse cellulose nanofibers

Carboxymethyl chitosan (CMCS) nanocomposites reinforced by different percentages of cellulose nanofibers (CNFs) were prepared using glutaraldehyde, as a chemical cross-linker, in the form of chemically cross-linked superabsorbent hydrogels (SAHs). CNFs were isolated from sugarcane bagasse fibers through the combination of chemo-mechanical pretreatments. The swelling behaviors of the resultant SAHs were studied in water, different pHs, and various salt solutions. The absorption kinetics of the as-prepared SAHs at different CNFs percentages was also investigated. SEM images showed that the addition of nanofibers into the hydrogel matrix increased the averaged-dimension of porous. The swelling capacity of SAH in water at 7 wt% CNFs was found to be 277 g(water)/g(absorbent), which was measured to be 193 g(water)/g(absorbent) for the unreinforced SAH indicating 43% enhancement. Based on the kinetics study, the more swelling capacity the SAHs had, the less requisite time they required to reach the equilibrium swelling. Moreover, although the swelling of SAHs in salt solutions significantly decreased, adding CNFs somewhat ameliorated their absorption capacity. On average, the hydrogel swelling increased about 47% at all pHs after incorporation of 7 wt% CNFs.