A novel transparent hydrogel made of nanocellulose derived from oil palm residue: evaluation of its water retention and biodegradation properties

Nanocellulose from oil palm empty fruit bunch residue was synthesized using TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl)-mediated oxidation to produce TEMPO-oxidized cellulose nanofibres (TOCNs). Nanocellulose was suspended in water at a concentration of 1% (w/v) and then crosslinked with HCl, citric acid and CaCl2 to as much as 20 mmol g-1 TOCNs to form a hydrogel. The hydrogel's water-retention capacity was analysed along with its morphological, microscopic and biodegradable properties. Hydrogels with HCl crosslinkers are known to have a higher water-retention capacity than others. After 72 h of observation, all hydrogels retained more than 80% of their water. All hydrogels were known to be completely degraded in the soil after 21 days of observation with an abundance of microbes (2.25 x 106 CFU g-1 soil). The use of crosslinkers did not seem to affect the morphology of the hydrogels microscopically, but the freeze-dried results showed that hydrogels with citric acid crosslinkers seemed to be able to maintain a 3D shape in dry conditions compared to others. This research is expected to encourage the use of agricultural residues as a source of nanocellulose that can be applied to the agricultural sector.