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Sorption of Dyes on Cellulose II: Effect of Alkali Treatment of Fibre and Dye Structure

Goswami, Parikshit, Blackburn, Richard S., Taylor, Jim and White, Patrick (2011) Sorption of Dyes on Cellulose II: Effect of Alkali Treatment of Fibre and Dye Structure. Cellulose, 18 (4). pp. 1063-1072. ISSN 0969-0239

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Abstract

Cellulose is a linear 1,4-β-glucan polymer where the units are able to form highly ordered structures, as a result of extensive interaction through intra- and intermolecular hydrogen bonding of the three hydroxyl groups in each cellulose unit. Alkali has a substantial influence on morphological, molecular and supramolecular properties of cellulose II polymer fibres causing changes in crystallinity. Lyocell fibres pre-treated with 0.0, 2.0, and 4.0 mol dm−3 aqueous NaOH solution were dyed with hydrolyzed reactive dyes that had different molecular shapes and sizes. Overall exhaustion (qe), value of K, and −ΔG increased for lyocell samples pre-treated with aqueous NaOH solution in the following order: 2.0 > 4.0 > 0.0 mol dm−3 NaOH. The same trends were observed for colour strength (K/S) values of the dyeings. Pre-treatment of lyocell with 2.0 mol dm−3 NaOH creates the substrate that achieves the most thermodynamically favourable system for sorption of hydrolyzed reactive dyes, as at this concentration crystallinity decreases (with respect to 0.0 mol dm−3 NaOH treated lyocell) to afford higher sorption; however, at higher alkali concentrations the macro-sorbent forms a compacted unit that limits diffusion within the sorbent interior. Molecular size of the sorbate dye has a significant effect on the sorption process: for the largest dye structure the sorption isotherm is most closely correlated to a Langmuir isotherm; as the size of the dye decreases correlation to a Langmuir isotherm is observed, but with good correlation to the Freundlich isotherm; as the size of the dye is decreased further sorption is more typical of a Freundlich isotherm.

Item Type: Article
Uncontrolled Keywords: Freundlich isotherm; Langmuir isotherm; Adsorption; Polysaccharides; Lyocell; Sodium hydroxide; Hydrolyzed reactive dye
Subjects: Q Science > QD Chemistry
Q Science > QH Natural history > QH301 Biology
Schools: School of Art, Design and Architecture
Related URLs:
Depositing User: Jonathan Cook
Date Deposited: 06 Sep 2017 15:03
Last Modified: 07 Sep 2017 09:51
URI: http://eprints.hud.ac.uk/id/eprint/33143

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