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Phenolic Pollutant Uptake Properties of Molecular Templated Polymers Containing β-Cyclodextrin B

Danquah, Michael K., Aruei, Riak C., Wilson, Lee D.
The Journal of physical chemistry 2018 v.122 no.17 pp. 4748-4757
adsorption, beta-cyclodextrin, crosslinking, epichlorohydrins, models, nuclear magnetic resonance spectroscopy, p-nitrophenol, phenol, phenolphthaleins, pollutants, polymers, scanning electron microscopy, thermogravimetry, toluene
Templated (T) and nontemplated (NT) cross-linked materials containing β-cyclodextrin (β-CD) and epichlorohydrin (EPH) were prepared at variable β-CD–EPH ratios (1:15, 1:20, and 1:25) in the presence and absence of a molecular template (toluene). The structural characterization of the materials was carried out using spectroscopy (Fourier transform infrared, solids ¹³C NMR, and scanning electron microscopy) and thermogravimetric analysis. The adsorption properties were studied with phenol-based adsorbates (2,4,6-trinitrophenol (TNP) and p-nitrophenol (PNP)) at equilibrium and dynamic conditions. The monolayer adsorption capacity (Qₘ) varied for the T-polymer/TNP systems (Qₘ = 0.10–0.95 mmol/g) and NT-polymer/TNP systems (Qₘ = 0.23–0.83 mmol/g). The range of Qₘ values for the T-polymer/PNP systems (0.26–0.62 mmol/g) exceeded that of the NT-polymer/PNP systems (0.23–0.40 mmol/g). The kinetic uptake profiles for the polymers and phenolphthalein were reliably described by the pseudo-first-order model. The β-CD inclusion site accessibility for the polymers varied from 15 to 20%, according to the level of cross-linking, where the accessibility of the T-polymers exceeded that of the NT-polymers. The structural characterization and phenol adsorption properties provide complementary support for the role of tunable polymer morphology in adsorption processes. The role of two-site binding was demonstrated for linear and globular polymer materials according to their unique adsorption properties with phenols of variable size and hydrophile–lipophile character.