The delignification and bleaching of non-wood fibres with peroxymonosulphate. Part 3. Sisal

The effect of peroxyraonosulphate (oxone™) as an acting agent in the delignification of sisal and jute has been studied. Conditions were varied in the following ranges: Oxone™ 0-200 g/L and temperature 30-100°. Delignification was followed by extraction with 1 M NaOH. The residues were analyzed, both before and after alkali extraction for lignin and residual sugar composition and their diffuse reflectance Fourier-transform infrared (DRFIT) spectra were acquired.Treatment in the absence of Oxone™ (acid alone) removed some pectic-linked lignin fragments. The presence of Oxone™, however, resulted in a net removal of glucuronoxylan and rhamnogalacturonan II. At moderate Oxone™ concentration and temperature, e.g.. 50 g/L, 700, residual lignin contents were reduced significantly (80%). This was confirmed by DRFIT spectroscopy. Alkali extraction of Oxone™ treated residues reduced, without exception, the residual lignin contents, some to as low as 98% of the original level. The removal of non-cellulosic polysaccharides, with the exception of glucomannan, was directly related to temperature and Oxone™ concentration. Evidence was found, suggesting that at least portions of the arabinose and galactose residues were linked to lignin. The bleaching ability exhibited a direct relationship to temperature and Oxone™ concentration, and acceptable levels of brightness were achieved at moderate temperature (700) and Oxone™ concentration (5 g/L).