Improving the water absorption properties of bacterial cellulose by in-situ and ex-situ modifications for use in CMC-graft-sodium acrylate superabsorbent

Abstract

Hydroxyl functional groups along the bacterial cellulose (BC) chains serve as sites for BC modification sites. This study focuses on in-situ and ex-situ modifications of BC to enhance its rehydration and equilibrium swelling ratio. In-situ modification of BC was achieved by adding carboxymethyl cellulose (CMC), sodium bicarbonate, and rapeseed oil to the culture medium of Acetobacter xylinum. Following this, BC ex-situ modification was conducted using sodium bicarbonate (5, 10, and 15 wt%) and glycerol (1, 2.5, and 5 v.v⁻¹%) solutions, utilizing the in-situ modified samples as starting materials. The final modified BC (MBC) exhibited an impressive increase of up to 2329.67% in its equilibrium swelling ratio and a 62.69% increase in rehydration compared to the unmodified sample. In the study’s second phase, two superabsorbents were synthesized through the polymerization of partially neutralized acrylic acid on the CMC backbone, both with and without MBC. The swelling ratio of these superabsorbents was investigated, and the amount of sodium acrylate, CMC, aluminum hydroxide (Al(OH)₃, used as an inorganic cross-linker), and ammonium persulfate ((APS, as an initiator) was optimized using the central composite design (CCD) method to achieve a high swelling ratio. The resulting superabsorbents showed swelling ratios of 306 (g water.g⁻¹ dry superabsorbent) and 326 (g water.g⁻¹ dry superabsorbent), without and with MBC, respectively. This study represents one of the first attempts to explore both BC in-situ and ex-situ modifications of BC aimed at improving its rehydration and swelling ratios and its application in superabsorbent.

Graphical Abstract