Chitosan-cyanuric chloride intermediary as a source to incorporate molecules-Thermodynamic data of copper/biopolymer interactions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The reaction of a chitosan-cyanuric chloride (ChC) intermediate with ethylenediamine (d) and diethylenetriamine (t) molecule; yielded the new biopolymers; ChCd and ChCt, which were characterized by elemental analysis, thermogravimetry, X-ray diffractometry, scanning electron microscopy and infrared and C(13) nuclear magnetic resonance spectroscopies. The precursor chitosan (Ch) and all derivatives adsorb copper from aqueous solution at 298 +/- 1 K, determined using a batchwise procedure. The results were fitted to a modified Langmuir equation. The ability to adsorb copper is dependent on the availability of the basic nitrogen atoms attached to the pendant biopolymer chains in the order ChCt > ChCd > ChC > Ch, as given by the values 2.84 +/- 0.03, 2.62 +/- 0.05, 2.55 +/- 0.04 and 2.09 +/- 0.03 mol g(-1), respectively. The same interactive process was also followed through calorimetric titration at 298.15 +/- 0.20K. The net thermal effects were also adjusted to a modified Langmuir equation to give the thermodynamic data at the solid/liquid interface. The exothermic enthalpic values were -28.98 +/- 0.05, -32.77 +/- 0.04. -60.60 +/- 0.03 and -56.41 +/- 0.05 kJ mol(-1) for the biopolymers Ch, ChC, ChCd and ChCt, respectively. The spontaneity of the systems is shown by the negative Delta G values, -21.1 +/- 0.1.-22.1 +/- 0.1, -22.1 +/- 0.1 and 23.4 +/- 0.1 kJ mol(-1) for the same sequence. The negative entropic values -26 +/- 1, -36 +/- 1, -129 +/- 1 and -111 +/- 1 J mol(-1) K(-1) indicate an ordering of solvent as complexation Occurred. The thermodynamic data demonstrate the capability of these biopolymers for cation removal from aqueous solutions, being new derivative biomaterials that May act as useful agents to renew an ecosystem. (C) 2008 Published by Elsevier B.V.483416712128Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

The effectiveness of the protected amino group on crosslinked chitosans for copper removal and the thermodynamics of interaction at the solid/liquid interface

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)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). CIN 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 (13)CNMR, 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. (C) 2009 Elsevier Ltd. All rights reserved.774760766Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP