Valorization of khat (Catha edulis) waste for the production of cellulose fibers and nanocrystals

Abstract

Cellulose fibers (C40 and C80) were extracted from khat (Catha edulis) waste (KW) with chlorine-free process using 40% formic acid/40% acetic acid (C40), and 80% formic acid/80% acetic acid (C80) at the pretreatment stage, followed by further delignification and bleaching stages. Cellulose nanocrystals (CNCs40 and CNCs80) were then isolated from C40 and C80 with sulfuric acid hydrolysis, respectively. Thus, the current study aims to isolate cellulose fibers and CNCs from KW as alternative source. The KW, cellulose fibers, and CNCs were investigated for yield, chemical composition, functionality, crystallinity, morphology, and thermal stability. CNCs were also evaluated for colloidal stability, particle size, and their influence on in vitro diclofenac sodium release from gel formulations preliminarily. The FTIR spectra analysis showed the removal of most hemicellulose and lignin from the cellulose fibers. The XRD results indicated that chemical pretreatments and acid hydrolysis significantly increased the crystallinity of cellulose fibers and CNCs. The cellulose fibers and CNCs exhibited Cellulose Iβ crystalline lattice. TEM analysis revealed formation of needle-shaped nanoscale rods (length: 101.55–162.96 nm; aspect ratio: 12.84–22.73). The hydrodynamic size, polydispersity index, and zeta potential of the CNCS ranged from 222.8–362.8 nm; 0.297–0.461, and -45.7 to -75.3 mV, respectively. CNCs40 exhibited superior properties to CNCs80 in terms of aspect ratio, and colloidal and thermal stability. Gel formulations containing high proportion of CNCs sustained diclofenac sodium release (< 50%/cm2) over 12 h. This study suggests that cellulose fibers and nanocrystals can be successfully obtained from abundant and unexploited source, KW for value-added industrial applications.

Properties and Hydrolysis Behavior of Celluloses of Different Origin

“…It is seen from data in Table 2 that, irrespective of the origin, all the cellulose samples show representative absorption bands of cellulose molecules that match those of commercially available celluloses and cellulose isolated from plant sources [47][48][49].…”

“…The peak near 2901-2918 cm −1 is attributable to stretch vibrations of C-H and CH 2 groups; the vibrations near 1632-1654 cm −1 are due to a bend vibration of absorbed water associated with the hydrophilic nature of cellulosic materials [48]. The IR spectra of the cellulose samples exhibit a well-defined structure of bands near 1430-1435 cm −1 and 1372-1373 cm −1 corresponding to bend vibrations of CH 2 and CH groups [49]. The bands near 1160-1165 cm −1 , 1110-1114 cm −1 , and 1058-1059 cm −1 relate to an asymmetric stretch of the C-O-C bridge of β-glycosidic linkage, a C-O stretch of the pyranose ring skeleton, and a C-O stretch of the cellulose molecule [49].…”

“…The IR spectra of the cellulose samples exhibit a well-defined structure of bands near 1430-1435 cm −1 and 1372-1373 cm −1 corresponding to bend vibrations of CH 2 and CH groups [49]. The bands near 1160-1165 cm −1 , 1110-1114 cm −1 , and 1058-1059 cm −1 relate to an asymmetric stretch of the C-O-C bridge of β-glycosidic linkage, a C-O stretch of the pyranose ring skeleton, and a C-O stretch of the cellulose molecule [49]. The band near 897-899 cm −1 belongs to a C1-H glycosidic deformation with a contribution of the ring vibration and OH bending, typical of β-glycosidic bonds between glucoses in cellulose [49].…”

Magnetic iron‐oxide coffee husk and khat waste biochar nanocomposites for removal of methylene blue from aqueous solution

“…Discarding khat wastes in open dumpsites results in visual pollution, attracts disease-carrying vectors, and creates breeding grounds for pathogens. KLs are sometimes littered on the streets, degrading the environment and potentially blocking drainage systems [34,35].…”

Synthesis of Plant‐Derived Khat Waste for Environmental Application

“…Ethiopia is one of the developing countries having no petroleum reserves and is affected by a lack of foreign currency. Butanol is a key minimal due to important properties such as high energy satisfaction, minimal instability, and geothermal power [1][2][3]. In particular, it can be used uncompromising or in combination with gasoline without the need to modify any current automobiles and is compatible with existing gasoline piping [4,5].…”