Characterization of kraft pulp delignification using sodium dithionite as bleaching agent. Issue 6 (2nd June 2020)

• Record Type: Journal Article
• Authors: Krishnan, Jishnu; Sunil Kumar, Susmith; Krishna Prasad, R.
• Is Part Of: Chemical engineering communications. Volume 207:Issue 6(2020)
• Page Start: 837
• Page End: 846
• Publication Date: 2020-06-02
• Subjects: Chemical delignification -- kraft pulp -- Sodium dithionite -- FT-Raman spectroscopy -- Scanning electron imaging -- Delignification kinetics; Chemical engineering -- Periodicals; 660.205
• DOI: 10.1080/00986445.2019.1630391
• Languages: English
• ISSNs: 0098-6445

Abstract

Abstract: The delignification of kraft pulp with sodium dithionite was studied to remove lignin content in the pulp. The sodium dithionite dissolves the chromophoric groups and residual lignin present in the pulp. The increase in dosage of sodium dithionite and reaction temperature of delignification has positive effect on kappa reduction of pulp. X ray diffraction was used to determine the crystallinity index of bleached pulp. The crystallinity increased from 83.3% for unbleached pulp to 86.7% after delignification. Fourier transform infrared spectroscopy shows the reduction in hydrogen bonding in bleached pulp and also the conversion of cellulose I to cellulose II. FT-Raman spectra shows that the fluorescence observed in the spectra of unbleached pulp reduced significantly in comparison to the spectra of bleached pulp resulting in removal of residual lignin and chromophoric groups present in the pulp. Scanning electron imaging shows the smoothening of fiber surface after bleaching. The delignification reaction followed first-order kinetics and activation energy is 33.57kJ/mol.