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Wilson L.D.,University of Saskatchewan | Mohamed M.H.,Aquatic Ecosystems Protection Research Division | Berhaut C.L.,National Graduate School of Chemistry, Montpellier
Materials | Year: 2011

Urethane copolymer sorbent materials that incorporate β-cyclodextrin (CD) have been prepared and their sorption properties with chlorinated aromatic compounds (i.e., pentachlorophenol, 2,4-dichlorophenol and 2,4-dichlorophenoxy acetic acid) have been evaluated. The sorption properties of granular activated carbon (GAC) were similarly compared in aqueous solution at variable pH conditions. The sorbents displayed variable BET surface areas as follows: MDI-X copolymers (< 101 m2/g), CDI-X copolymers (< 101 m2/g), and granular activated carbon (GAC ̃103 m2/g). The sorption capacities for the copolymers sorbents are listed in descending order, as follows: GAC > CDI-3 copolymer ≈ MDI-3 copolymer. The sorption capacity for the aromatic adsorbates with each sorbent are listed in descending order, as follows: 2,4-dichlorophenol > 2,4-dichlorophenoxy acetic acid > pentachlorophenol. In general, the differences in the sorption properties of the copolymer sorbents with the chlorinated organics were related to the following factors: (i) surface area of the sorbent; (ii) CD content and accessibility; and (iii) and the chemical nature of the sorbent material. © 2011 by the authors.


Poon L.,University of Saskatchewan | Wilson L.D.,University of Saskatchewan | Headley J.V.,Aquatic Ecosystems Protection Research Division
Journal of Applied Polymer Science | Year: 2013

Polyester copolymers were prepared with β-cyclodextrin (β-CD) and sebacoyl (SCl) or terephthaloyl (TCl) chloride cross linker agents using a simple, one-pot synthesis. Variation of the mole ratios (i.e., 1: 1, 1: 2, 1: 3, 1: 6, and 1: 9) of β-CD to diacid chloride linker units resulted in copolymers with differing solubility and chemical stability in aqueous solution. The sorption properties of copolymers such as 1: 6 and 1: 9 SCl, and 1: 9 TCl materials were investigated because of their relative insolubility and resistance to hydrolysis at pH 4.6. The monolayer sorption capacity (Q m) of the copolymers varied according to the nature of the cross linker and the relative mole ratio of monomers. Qm values obtained from the Sips isotherm model range from 2.7 to 5.2 mmol/g for the sorption of p-nitrophenol at 295 K and approach the value of Qm for a commercially available granular activated carbon sorbent. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 Copyright © 2012 Wiley Periodicals, Inc.


Mohamed M.H.,University of Saskatchewan | Wilson L.D.,University of Saskatchewan | Headley J.V.,Aquatic Ecosystems Protection Research Division
Carbohydrate Polymers | Year: 2010

Aqueous solutions containing insoluble β-cyclodextrin (β-CD) based urethane copolymers were studied in aqueous solutions by measuring the absorbance changes (decolourization) of phenolphthalein (phth) at pH 10.5. The various copolymers were comprised of β-CD and five diisocyanate linkers (1,6-hexamethylene diisocyanate (HDI), 4,4′-dicyclohexyl diisocyanate (CDI), 4,4′-diphenylmethane diisocyanate (MDI), 1,4-phenylene diisocyanate (PDI), and 1,5-naphthalene diisocyanate (NDI)). The copolymers studied were prepared at the β-CD: linker reactant ratios 1:1, 1:2, and 1:3, respectively. The decolourization studies provided estimates of the 1:1 binding constants (K 1) for the monomer β-CD/phth inclusion complex. It was concluded that the values of K 1 for copolymer/phth systems for highly accessible β-CD inclusion sites in copolymer materials closely resembles the K 1 value for the 1:1 β-CD/phth complex. The surface accessibility of the β-CD inclusion binding sites for the copolymers ranged from 1-100%. The observed variability was attributed to steric effects in the annular hydroxyl region of β-CD and the relative accessibility of the micropore sites within the polymer framework as a consequence of the variable cross linking. The Gibbs free energy of complex formation (ΔG°) and site occupancy (θ) of phth adsorbed to the copolymer materials was estimated independently using the Sips isotherm model. The ΔG° values ranged between -27 and -30 kJ mol -1 and are in agreement with the Gibbs free energy for the 1:1 β-CD/phth complexes (∼-27 kJ mol -1). The phth decolourization technique provides a simple, low cost and versatile method for the estimation of the surface accessible inclusion sites of β-CD in CD based urethane copolymer materials. This method is anticipated to have extensive analytical applications in materials research and for the design of functional β-CD based sorbent materials. © 2009 Elsevier Ltd. All rights reserved.


Mohamed M.H.,Aquatic Ecosystems Protection Research Division | Wilson L.D.,University of Saskatchewan | Pratt D.Y.,University of Saskatchewan | Guo R.,University of Saskatchewan | And 2 more authors.
Carbohydrate Polymers | Year: 2012

The accessible inclusion sites of insoluble copolymers containing β-cyclodextrin (β-CD) were studied in aqueous solutions by measuring the absorbance changes (decolourization) of phenolphthalein (phth) at pH 10.5. The various copolymers were reacted at different β-CD:crosslinker mole ratios with five individual types of crosslinker agents (epichlorohydrin (EP), sebacoyl chloride (SCL), terephthaloyl chloride (TCL), glutaraldehyde (GLU), and poly(acrylic) acid (PAA), respectively). The decolourization provided estimates of the 1:1 binding constants (K1) for the β-CD monomer/phth complex. Comparable values of K1 were measured for copolymer/phth complexes with highly accessible β-CD inclusion sites as compared with the 1:1 β-CD/phth complex. The surface accessibility of the β-CD inclusion binding sites for the polymers ranged from ∼10 to 72%. The observed variability of the inclusion sites was attributed to: (i) steric effects in the annular hydroxyl region of β-CD, (ii) the degree of crosslinking of the copolymer and (iii) the accessibility of the micropore sites within the copolymers. The Gibbs free energy (ΔG°) and site occupancy (θ) of phth adsorbed to the copolymer materials was estimated independently using the Sips isotherm model. The ΔG° values ranged between -27.6 and -30.9 kJ mol-1 for the copolymers and are in close agreement with the value for the 1:1 β-CD/phth complexes (ΔG° = -27 kJ mol -1) in aqueous solution. © 2011 Elsevier Ltd. All rights reserved.

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