Glycerol/lemon juice/based green superabsorbent hydrogel cross-linked with maleic acid

Abstract

Superabsorbent hydrogels continue to be very important materials due to their applications in several technologies. Unfortunately, most superabsorbent hydrogels currently on the market are acrylate-based products that are non-biodegradable, and, most importantly, some concerns exist about their toxicity for use in agriculture. This study aimed at synthesizing and characterizing biocompatible superabsorbent hydrogel derived from lemon juice. The process involved polymerizing lemon juice (LJ) with glycerol (G) monomers to form polymeric material (HLG-1). HLG-1 was then converted to HLG-2 by crosslinking with maleic acid. Characterization of the hydrogels was done using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), and X-ray diffraction (XRD). The synthesis conditions producing optimal swelling capacity were studied by varying contact time and dosage of both lemon juice and the cross-linker. The FT-IR results showed a peak at 1528 cm-1 and 1591.34 cm-1 associated with –COO- stretching indicating successful polymerization and crosslinking processes. XRD analysis showed conversion from amorphous to crystalline phases upon crosslinking. SEM micrographs showed clear pores with large surface area in HLG-2 compared with the rigid and constricted surface of HLG-1 hydrogel. A maximum swelling capacity of 910% was obtained upon synthesizing hydrogel HLG-2 with lemon juice, glycerol, and maleic acid of a volume ratio of 5.4: 3.75: 3.75 respectively. Crosslinking the hydrogel with maleic acid was found to improve the water absorption capacity of the hydrogel. The superabsorbent hydrogel with such high swelling and water absorption ability has the potential of being applied in arid and semi-arid regions to boost agricultural production.