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 positioned along the bacterial cellulose (BC) chains provide the BC modification sites. This study reports BC in-situ and ex-situ modifications to increase its rehydration and equilibrium swelling ratio. BC in-situ modification was achieved by carboxymethyl cellulose (CMC), sodium bicarbonate, and rapeseed oil addition to Acetobacter xylinum culture medium. Then, BC ex-situ modification by sodium bicarbonate (5, 10, and 15 wt. %) and glycerol (1, 2.5, and 5 v/v %) solutions were examined using the in-situ modified samples as starting materials. The final modified BC (called MBC) increased up to 2329.67% and 62.69%, respectively, in its equilibrium swelling ratio and rehydration compared to the unmodified sample. In the second phase of this study, two superabsorbents were synthesized through the polymerization of partially neutralized acrylic acid on the CMC backbone with and without MBC. These superabsorbents’ swelling ratio was investigated, and the amount of sodium acrylate, CMC, Aluminium hydroxide (Al(OH)3, as an inorganic cross-linker), and ammonium persulfate ((APS, as an initiator) was optimized using central composite design (CCD) method to achieve high swelling ratio. The resulting superabsorbents showed 306 and 326 (g water/g dry superabsorbent) as a swelling ratio, without and with MBC, respectively. Also, the MBC addition has increased the superabsorbents’ thermal stability. This study is one of the first attempts to investigate both BC in-situ and ex-situ modifications to rehydration and swelling ratio improvement for BC and its superabsorbent.