Sorption of dyes on cellulose II: Effect of alkali treatment of fibre and dye structure

Parikshit Goswami, Richard S. Blackburn, Jim Taylor, Patrick White

Research output: Contribution to journalArticle

10 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)1063-1072
Number of pages10
JournalCellulose
Volume18
Issue number4
DOIs
Publication statusPublished - Aug 2011
Externally publishedYes

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