Graphical abstract showing the outcomes of wet grinding of untreated banana fibresiii Highlights:• 95% reduction in fibre diameter and high crystallinity (76 -80%) were obtained.• High degree of fibrillation was obtained at a relatively low power consumption.• Gap distance is more important than the number of passes during wet grinding.• Gap distance affects fibre diameter reduction, crystallinity and degree of fibrillation.• The grinding process has decreased lignin and hemicellulose contents by 37%.
This study aims to explore the use of wood ash, a common waste, as an alternative and eco-friendly pulping agent. The first and most important singularity of the study is that wood ash solution, though mild in nature, has proven to be an effective pulping agent (in comparison with the common pulping solution, sodium hydroxide): comparable lignin (45%) and hemicellulose (50%) removal, high crystallinity (72–77%) and high pulp yield (70%) were obtained. Another particularity of this study is that the reported advanced aspects of pulped banana fibres, notably the chemical functionality, crystallinity and crystallite size have been correlated with the chemical composition of the wood ash used: calcium pectinate was formed on the pulped fibre surface. It apparently played a role in enhancing the fibre crystallinity. Moreover, another specialness of this study is that non-conventional factors, which would have significant bearing during industrial scale processing, such as liquor ratio, fibre input size and duration have been investigated—the latter has shown that to attain maximum delignification, small fibre input size at a high liquor ratio of 40 for an extended period of 2 h are necessary. Finally, the pulped banana fibres (which were intended to be used for membrane fabrication for use in water purification system) have depicted their applicability in the fabrication of ultrafiltration membranes by virtue of their aspect ratio, semi-hydrophilicity (due to presence of residual lignin) and projected high mechanical strength (due to high crystallinity and low crystallite size).
Graphical Abstract
Graphical abstract showing outcomes when pulping with wood ash solution.
This study describes an investigation of the evolution of the mechanical and chemical properties of maize stem fibres with the growth stages of the plant, and how the tensile strength is influenced by the presence of nodes along the fibre length. Furthermore the variation of the tensile strength and chemical functional groups among four common maize varieties were determined. In this context, the fibres were characterised by performing tensile test, density & linear density tests, Fourier Transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), Thermo-gravimetric analysis (TGA) and surface morphology (SEM image analysis). The fibres were all extracted manually, and in some cases preceded by a water retting process for ten days. The thermal analysis, FTIR and x-ray results showed that in general the fibres from the different maize varieties and from the different growth stages are semi-crystalline in nature. The SEM micrographs revealed the presence of equi-spaced nodes along the fibre length, which are believed to be due to the growth stresses induced in the plant stem. The inter-node distance varied in relation to the growth stage of the plant, and yielded a good correlation (coefficient of 0.91) with the tensile strength of the fibres. Finally a better fibre yield was obtained from the stem at the senescence stage of the maize plant.
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