A study of the distribution of chitosan onto and within a paper sheet using a fluorescent chitosan derivative |
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Authors: | Susana C.M. Fernandes, Carmen S.R. Freire, Armando J.D. Silvestre, Carlos Pascoal Neto, Alessandro Gandini, Jacques Desbri res, Sylvie Blanc, Rute A.S. Ferreira,Luí s D. Carlos |
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Affiliation: | aInstitute of Chemistry, University of Campinas, P.O. Box 6154, 13084-971 Campinas, São Paulo, Brazil |
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Abstract: | Acidic glutaraldehyde (Gh) crosslinked chitosan (ChGhH) when deprotonated the biopolymer (ChGh) presents high content of free amino groups. These modified biopolymers are comparable to epichlorohydrin (Ep) crosslinked (ChEp). C/N molar ratio of 6.1 for chitosan increases to 7.3, 7.5 and 7.1 for ChGhH, ChGh and ChEp. The effectiveness of the carbon-6 hydroxyl group in interconnecting chitosan units was supported by IR and 13CNMR, where Ep promotes increase in crystallinity. Copper uptake gave the order Ch > ChGh > ChGhH > ChEp, as: 1.35 ± 0.06, 1.30 ± 0.05, 1.05 ± 0.07 and 0.96 ± 0.22 mmol g−1, reflecting the availability of nitrogen basic centers in adsorbing. The favorable thermodynamic data of adsorption through calorimetric titration gave exothermic enthalpic values: −28.98 ± 0.05, −6.68 ± 0.04, −6.13 ± 0.07 and −0.65 ± 0.23 kJ mol−1 for Ch, ChGh, ChGhH and ChEp. Free Gibbs energy reflected spontaneity of interactions and, with the exception of chitosan, the entropic values are positive. |
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Keywords: | Chitosan Crosslinking Adsorption Calorimetry |
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