In this study, surface chemistry, the morphological properties, water retention values, linear viscoelastic properties, crystallinity index, tensile strength and thermal properties of water hyacinth (WH) cellulose were correlated with the degree of mechanical processing under high-pressure homogenisation. An initial low-pressure mechanical shear of WH stems resulted in the ease of chemical extraction of good quality cellulose using mild concentrations of chemical reagents and ambient temperature. Further passes through the homogeniser resulted in an overall improvement in cellulose fibrillation into nanofibrils, and an increase in water retention property and linear viscoelastic properties as the number of passes increased. These improvements are most significant after the first and second pass, resulting in up to 7.5% increase in crystallinity index and 50% increase in the tensile strength of films, when compared with the unprocessed WH cellulose. The thermal stability of the WH cellulose was not adversely affected but remained stable with increasing number of passes. Results suggest a high suitability for this process to generate superior quality cellulose nanofibrils at relatively low energy requirements, ideal for sustainable packaging applications and as a structural component to bioplastic composite formulations.

Homogeneous high aspect ratio cellulose nanofibrils (CNFs) were prepared from Laminaria hyperborea (LH) seaweed cellulose without any initial mechanical, biological or chemical pre-treatments. Fourier-transform infrared spectrophotometry revealed that LH cellulose was of the cellulose Iα allomorph, typical of algal cellulose. Compared with wood derived CNF, significant enhancements in crystallinity, viscoelastic properties, water retention values (WRV) and morphological characteristics were identified with a single pass at 1 wt. % cellulose content through a high-pressure homogeniser. Further mechanical fibrillation did not lead to appreciable improvements in material properties that would justify the added energy consumption, which at a single pass is at least a factor of 10 lower than with wood cellulose processing. Good quality CNFs with little compromise in material properties were also obtainable at 2–3 wt. % cellulose contents as identified from viscoelastic analysis, WRV and morphological analysis. LHCNFs also showed good thermal stability, which in summary presents a multifunctional high value cellulose nanomaterial that can find application in various fields. Graphic abstract

Water hyacinth is an invasive plant that can be converted to high value cellulose nanofibers. This study presents battery separators prepared from water hyacinth cellulose nanofibres (WHCNF) via a freeze-thawing crosslinking method, using polyethylene glycol as a binder. The separators consist of 95 wt.%, 90 wt.%, 85 wt.% and 80 wt.% WHCNF. The thickness, wettability, electrolyte uptake, porosity and thermal stability of the separators are studied and compared with Celgard 2325, a commercial tri-layer separator. Also, tensile tests are carried out and an aluminium-ion cell is made to compare the performance of the different WHCNF separators using Nyquist plots and battery discharge curves. The results show that WHCNF separators have high thermal stability and wettability, making it a promising sustainable alternative material to petroleum-based polymeric commercial separators.

Flexible dielectric materials with environmental-friendly, low-cost and high-energy density characteristics are in increasing demand as the world steps into the new Industrial 4.0 era. In this work, an elastomeric nanocomposite was developed by incorporating two components: cellulose nanofibrils (CNFs) and recycled alum sludge, as the reinforcement phase and to improve the dielectric properties, in a bio-elastomer matrix. CNF and alum sludge were produced by processing waste materials that would otherwise be disposed to landfills. A biodegradable elastomer polydimethylsiloxane was used as the matrix and the nanocomposites were processed by casting the materials in Petri dishes. Nanocellulose extraction and heat treatment of alum sludge were conducted and characterized using various techniques including scanning electron microscopy (SEM), thermogravimetric analysis/derivative thermogravimetric (TGA/DTG) and X-ray diffraction (XRD) analysis. When preparing the nanocomposite samples, various amount of alum sludge was added to examine their impact on the mechanical, thermal and electrical properties. Results have shown that it could be a sustainable practice of reusing such wastes in preparing flexible, lightweight and miniature dielectric materials that can be used for energy storage applications.