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Lenzing, Austria

Goswami P.,University of Leeds | Blackburn R.S.,University of Leeds | Taylor J.,Lenzing Fibers | White P.,Lenzing Fibers
Cellulose | Year: 2011

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. © 2011 Springer Science+Business Media B.V. Source


Siroky J.,University of Leeds | Siroky J.,Christian Doppler Laboratory | Blackburn R.S.,University of Leeds | Bechtold T.,Christian Doppler Laboratory | And 2 more authors.
Cellulose | Year: 2010

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. These physical changes were observed herein using ATR-FTIR spectroscopy, following continuous treatment of the cellulose II fabrics with aqueous sodium hydroxide solution under varying condition parameters. Post-treatment, maxima for total crystallinity index and lateral order index, and minima for hydrogen bond intensity, were observed at concentrations of 3.3 and 4.5 mol dm-3 NaOH, when treated at 25 °C and 40 °C, respectively. Under these treatment conditions, it is proposed that maximum molecular reorganisation occurs in the amorphous and quasi-crystalline phases of the cellulose II polymer. © 2009 Springer Science+Business Media B.V. Source


Siroky J.,University of Leeds | Siroky J.,Christian Doppler Laboratory | Blackburn R.S.,University of Leeds | Bechtold T.,Christian Doppler Laboratory | And 2 more authors.
Carbohydrate Polymers | Year: 2011

To understand the effect of alkali treatment on sorption behaviour of cellulose II fibres, samples were continuously pre-treated using NaOH over a concentration range of 0.0-7.15 mol dm-3, with varying tension; treated substrates were dyed with hydrolysed C. I. Reactive Red 120. Greatest adsorption of dye occurs for cellulose II fibres treated with 2.53 and 3.33 mol dm-3 aqueous NaOH solution. Correlation to sorption isotherms is most closely associated with a Langmuir type isotherm, but correlation to the Freundlich isotherm is still significant, indicating sorption via a combination of Langmuir and Freundlich isotherms. Adsorption energy (ΔG0) increases with increasing NaOH concentration to a maxima between 2.53 and 3.33 mol dm-3 NaOH and then decreases with further increase in NaOH concentration. Equilibrium dye sorption shows good correlation with water sorption as assessed by the reactive structural fraction (RSF) theory. Theoretical monolayer capacity (q0) increases with increasing NaOH concentration to a maxima at 3.33 mol dm-3 NaOH and then decreases with further increase in NaOH concentration; q0 is significantly in excess of the number of available specific sites (-COO-Na +) in the substrate, indicating non-site-specific interactions, more typical of a Freundlich isotherm. Pores in the fibre significantly affected by alkali treatment (<20 diameter) and accessibility of dye (14 ) sorption into those pores account the differences observed herein; maximum qe, q0 and ΔG0 are observed for cellulose II fibre treated with 2.53-3.33 mol dm-3 NaOH as this concentration range affects the greatest increase in accessible pore volume in the fibres. © 2010 Elsevier Ltd. All rights reserved. Source

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