Abstract
Lignocellulose based nanomaterials are emerging green biosolids commonly obtained from wood pulp. Alternative feedstocks, such as as unavoidable food waste, are interesting resources for nano/microfibers. This research reports the production and characterization of microfibrillated lignocellulose (MFLC) from cassava peel (CP) and almond hull (AH) via acid-free microwave-assisted hydrothermal treatment (MHT) at different temperatures (120–220 °C). During processing, the structural changes were tracked by ATR-IR, TGA, XRD, 13C CPMAS NMR, zeta potential, HPLC, elemental analysis (CHN; carbon, hydrogen and nitrogen), TEM and SEM analyses. The microwave processing temperature and nature of feedstock exerted a significant influence on the yields and properties of the MFLCs produced. The MFLC yields from CP and AH shifted by 15–49% and 31–73%, respectively. Increasing the MHT temperature substantially affected the crystallinity index (13–66% for CP and 36–62% for AH) and thermal stability (300–374 °C for CP and 300–364 °C for AH) of the MFLCs produced. This suggested that the MFLC from CP is more fragile and brittle than that produced from AH. These phenomena influenced the gelation capabilities of the fibers. AH MFLC pretreated with ethanol at low temperature gave better film-forming capabilities, while untreated and heptane pretreated materials formed stable hydrogels at solid concentration (2% w/v). At high processing temperatures, the microfibrils were separated into elementary fibers, regardless of pretreatment or feedstock type. Given these data, this work demonstrates that the acid-free MHT processing of CP and AH is a facile method for producing MFLC with potential applications, including adsorption, packaging and the production of nanocomposites and personal care rheology modifiers.Graphic abstract
Highlights
Inefficiencies in the food system from farm to fork generates approximately 1.3 billion tonnes per year of food waste (Matharu et al 2016a)
The %C and %H content is comparable for both feedstocks, but there is a significant difference in their %N content; cassava peel (CP) contains significantly more N than almond hull (AH)
The compositional analysis of almond hulls is in very good agreement with the results reported by others (Gonzalez et al 2005; Aktas et al 2015; Remon et al 2020)
Summary
Inefficiencies in the food system from farm to fork generates approximately 1.3 billion tonnes per year of food waste (both avoidable and unavoidable) (Matharu et al 2016a). Unavoidable food supply chain wastes generated because of primary and secondary processing are recognized as a potential, abundant and natural source of biobased chemicals, materials and bioenergy. Global almond crops contribute to the production of 1.4 million tonnes of biomass per year which include shells, hulls, pruning wastes, leaves, skins, and inedible kernels (Holtman et al 2015). During the processing of almonds, the kernel, shell and hull account for 15%, 33% and 52%, respectively, of the waste (FerrandezVillena et al 2019). Both by-products, cassava peel and almond hull, are unavoidable and have the potential to be renewable materials for nanocellulose production
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