Production of oil palm mesocarp fiber-based hydrogel using selected cross-linking acids

Abstract

Over the years, studies showed that hydrogels can be produced through synthetic route to overcome the limitations in obtaining natural-based hydrogels. Biomass resources offer potential alternatives as renewable feedstocks due to their outstanding biodegradability and biocompatibility. Oil palm mesocarp fiber (MF) is the biomass residue obtained after the pressing of palm fruits during palm oil extraction. There is approximately 11 % MF generated from palm fruits after oil extraction. However, the applications of MF are limited. This study aimed to investigate the development of hydrogels from holocellulose MF instead of commonly used cellulose which involving several pretreatment steps, through acid cross-linkers. Holocellulose MF was selected as polymer for chemical cross-linking with two inexpensive and nontoxic hydrophilic organic acids, citric acid and acetic acid for hydrogel production. Comparison study was carried out to evaluate the physicochemical properties, and degree of swelling, as well as gel content in different media for both acids in the production of hydrogel from holocellulose MF. Results indicated that the optimum concentrations of citric acid and acetic acid for gel content and degree of swelling were 5 M and 2 M, respectively. Both optimized hydrogels exhibited comparable profiles in terms of morphology, thermal stability and functional groups, in addition to showing similar degree of swelling profile in different media, i.e., salt solution, acidic, neutral to alkaline, implying their distinctive characteristics. In summary, holocellulose MF is suitable for the production of hydrogel with citric acid and acetic acid as crosslinkers for different desired applications.