The relevance of the pretreatment on the chemical modification of cellulosic fibers

Abstract

Cationized fibers and other kinds of chemically modified fibers impart many advantages in papermaking, but unfeasibly long reaction times are necessary to attain acceptable degrees of substitution, due to the low reactivity of bleached kraft pulps. In this work, different aqueous pretreatments were tested in order to activate cellulose towards a 60 min-long etherification with a quaternary ammonium reagent. Severe decrystallization treatments, namely alkalization with NaOH 20%, NaOH/urea or FeTNa, conducted to the best reactivity results (substitution from 2 to 10%), but the fiber properties were harshly affected. Pretreatments involving H 3 PO 4 at different concentrations were also performed, with distinct results, from unnoticeable effects at 20% to amorphization and excessive depolymerization at 80%. Finally, aqueous ammonium thiocyanate was tested as activator and had little effect on fibers, although the addition of ammonia resulted in high degrees of substitution, while maintaining the pulps' capability to retain inter-fiber water and cellulose I as the prevalent allomorph.

Thermal properties enhancement of poplar wood by substituting poly(furfuryl alcohol) for the matrix

“…The increased porosity of the structure may present methods for further modification and the preparation of new wood composites with unique properties. In addition, the alkali swells the crystalline structure of the wood cellulose . Table shows that a weight loss of 18.7% was obtained after alkali treatment, indicating the removal of most of the lignin.…”

“…In addition, the alkali swells the crystalline structure of the wood cellulose. [24] Table 1 shows that a weight loss of 18.7% was obtained after alkali treatment, indicating the removal of most of the lignin. When PFA was incorporated, the WPG of the delignified wood sample was higher than that of the undelignified sample, which could be due to the increased porosity and greater amount of polymers generated in the wood voids.…”

Isothermal and Kinetic Investigation of Exploring the Potential of Citric Acid-Treated Trapa natans and Citrullus lanatus Peels for Biosorptive Removal of Brilliant Green Dye from Water

“…Citric acid breaks and decreases the cellulose crystallinity of lignocellulosic biomass, resulting in increased porosity and surface area of TNP and CLP [66]. Total emplacement sites on the biosorbent surface can be increased by providing additional functional groups during the chemical treatment with suitable modifying agents [67,68]. us, the surface of adsorbents favors more electrostatic and hydrogen bonding interactions with the cationic molecules of BGD due to the presence of a lot of negatively active binding sites.…”

Applications of cellulose-based agents for flocculation processes: a bibliometric analysis

“…Secondly, like any other hydroxy polymer, it can be chemically modified towards different functional groups, cationic or anionic, hydrophilic or hydrophobic, etc. (Moral et al 2015;Aguado et al 2019). Thirdly, their glycosidic bonds are chemically stable, but cleavable by many microorganisms, granting cellulose versatility and biodegradability.…”