Fabrication and characterization of okara derived highly water absorbent hydrogel

Abstract

Okara is a fiber rich waste from soybean industry that can be a potential material to make hydrogel. In this study, okara cellulose based hydrogel with high water swelling was fabricated. First, cellulose was extracted from okara using alkaline treatment of 5% (w/v) NaOH solution. The okara cellulose was crosslinked with polyvinyl alcohol (PVA) forming hydrogel using glutaraldehyde as the crosslinking agent. However, the PVA/okara hydrogel had a low water swelling of 19 g/g. Alternatively, another method using carboxymethyl cellulose (CMC) was attempted due to its high hydrophilicity. CMC and okara cellulose were crosslinked by epichlorohydrin as the crosslinking agent. The water swelling of CMC/okara hydrogel reached 390 g/g which is higher than the previous studies of okara hydrogels. The swelling increased with more swelling cycles and remained effective until the fifth cycle. In KNO₃ and NH₄NO₃ solutions (0.05 ⎯ 0.1M), the swelling was significantly reduced by 75-85%. The hydrogel was characterized by scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). With high swelling ability, the CMC/okara hydrogel can be applied as a soil conditioner to retain water near the roots in dry areas.

Date of Award	2023
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Xijun HU (Supervisor)