Artículos de revistas
Chitosan metal-crosslinked beads applied for n-alkylmonoamines removal from aqueous solutions - a thermodynamic study
Registro en:
Journal Of Chemical Thermodynamics. Academic Press Ltd- Elsevier Science Ltd, v. 73, n. 197, n. 205, 2014.
0021-9614
1096-3626
WOS:000335846900029
10.1016/j.jct.2013.12.030
Autor
Oliveira, M
Simoni, JA
Airoldi, C
Institución
Resumen
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Chitosan has ability in coordinating divalent cations when immersed in crosslinked beads, after dripping: (i) chitosan gel into a copper solution, (ii) nickel chitosan gel into sodium hydroxide and (iii) chitosan/cobalt gel into sodium tripolyphosphate. The amounts of (1.82; 1.27 and 0.44) mmol . g (1) for copper, nickel and cobalt cations in these well-formed structures were determined, to give nitrogen/metal ratios of 3.52; 2.09 and 8.51, indicating the least effectiveness for cobalt in the coordination. Copper cation is well-adjusted in the coordination model through free amino and hydroxyl electron pairs, while amino and acetamino groups for nickel and cobalt were used. The chitosan-hydrogen bond breaking in bead formation caused decreases in crystallinity to yield amorphous structures for cobalt and nickel. The water mass fraction released during heating depends on the hydration of the cations, with the highest value of 0.20 for cobalt. The quantitative aspects of the interaction among cations on beads and basic n-alkyl-monoamines determined via sorption batch methodology adjusted to the Langmuir isothermal model, with maximum sorption quantities to saturate nickel of (2.50; 2.38; 2.03; 1.79) mmol . g (1) and copper of (2.59; 2.29; 2.28; 1.92) mmol . g (1) for ethyl- propyl-, butyl- and pentylamines, respectively. The interaction energies quantitatively determined from isothermal titration calorimetry (ITC) at the solid/liquid interface resulted in exothermic enthalpic values. These negative enthalpy values combined to the negative Gibbs free energies from the application of the Langmuir isothermal model to the ITC data gave positive entropic values. The entropy changes varied from (48 to 64) J . mol (1) . K (1) for nickel and between (18 and 31) J . mol (1) . K (1) for copper beads. These thermodynamic data strongly suggest that these easily synthesized crosslinked metal beads may be useful and practical designed agents to apply in waste effluent treatments for pollutant removal. (C) 2014 Elsevier Ltd. All rights reserved. 73 SI 197 205 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)