Synthesis, Characterization, and Biodegradability of a Superabsorbent Cellulose-Based Hydrogel Derived from Olive Pomace

In this study, a cellulose-based hydrogel was derived from olive pomace through a three-stage valorization process. In the first stage, cellulose was extracted from de-oiled olive pomace, yielding 9.16%. In the second stage, the extracted cellulose was converted to sodium carboxymethyl cellulose (CMC) via carboxymethylation with monochloroacetic acid (MCA) under alkaline conditions. In the third stage, the synthesized CMC was chemically crosslinked with epichlorohydrin (ECH) in an alkaline medium to produce a biobased hydrogel. The resulting material exhibited an amorphous phase fraction of 80.93% and an exceptional equilibrium swelling ratio of 2616% after approximately 12 days of immersion in distilled water. Thermogravimetric analysis (TGA) revealed that the hydrogel exhibited good thermal stability, with an onset degradation temperature of 236.05 °C, and retained 27.05% of its mass at 600 °C. Furthermore, time-dependent deswelling measurements demonstrated strong water-retention performance, with a cumulative mass loss of only 20.93% after 6.5 h under ambient evaporation conditions. The biodegradability test was systematically assessed via a 28-day soil burial test using two different carrier systems: perforated polyethylene bags and muslin/cheesecloth bags. Following 28 days of soil burial, the hydrogel exhibited gravimetric mass losses of 41.25% and 53.88% in the perforated polyethylene and muslin/cheesecloth carrier systems, respectively. These results indicate that the hydrogel derived from olive pomace is an olive pomace-derived biodegradable water-retention material with significant potential for agricultural soil conditioning, controlled-release fertilizer systems, and other environmental applications.

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