Characteristics of cellulose extracted from Josapine pineapple leaf fibre after alkali treatment followed by extensive bleaching

Cellulose, being an abundantly available natural biopolymer, has a high potential to replace synthetic fibre. However, a paucity of knowledge and awareness on the use of cellulose, and agricultural waste base in particular, hampers efforts to harness this highly biodegradable resource to its full potential. This study aimed to extract and characterise cellulose obtained from pineapple (Ananas comosus) leaves of cultivar Josapine. Chemical composition analysis found that the pineapple leaves contain 11.8% lignin and 55.1% holocellulose, of which 32.6% is alpha cellulose. This extracted cellulose is light yellow to pure white in colour. The extraction of cellulose trace amounts of lignin was found to be between 0.4 and 2.8%. SEM micrograph of pineapple leaves shows fibrils 36 µm in diameter while the sample cellulose has defibrillated fibres with an average diameter ranging from 4.28 to 3.12 μm. Viscosity tests show the molecular weight (MW) at 3.8671 × 10⁻⁴ to 1.0560 × 10⁻⁴ and the degree of polymerisation of 447–107, respectively. Characterisation using X-ray diffraction (XRD), Raman and Fourier-transform infrared (FTIR) spectroscopy shows the cellulose samples are cellulose I. As compared to control, XRD data shows considerably higher percentage of crystallinity (82.90–85.41%) in all bleached sample with crystal size ranging from 3.564 to 3.807 nm. In conclusion, the extraction of cellulose from pineapple leaves using 2% NaOH and hypochlorite bleaching retains the original structure of cellulose in the pineapple leaves. The unique properties of cellulose microfibre from Josapine pineapple leaf fibres have great potential for further utilisation in various industries.