Artículo
Interaction of catechol and gallic acid with titanium dioxide in aqueous suspensions. 1. Equilibrium studies
Fecha de publicación:
04/2005
Editorial:
American Chemical Society
Revista:
Langmuir
ISSN:
0743-7463
Idioma:
Inglés
Tipo de recurso:
Artículo publicado
Clasificación temática:
Resumen
The adsorption isotherms of catechol (1,2-dihydroxybenzene) and gallic acid (3,4,5-trihydroxybenzoic acid) onto titanium dioxide (Degussa P-25) were measured at various pH values and room temperature using attenuated total reflection Fourier transform infrared (FTIR-ATR) data, processed by singular value decomposition. The affinity is largely pH independent, although the deprotonatation of the carboxylic group in gallic acid might produce a slight increase in the affinity. Catechol was shown to form two complexes, with Langmuir stability constants log K of 4.66 (strong mode) and 3.65 (weak mode). Both complexes have the same spectral signature, and mononuclear and binuclear chelate structures are proposed for them. Gallic acid chemisorbs by complexation through two -OH groups and forms one complex only, log K= 4.70. The third -OH and the pendant carboxylate do not influence much the stability of the surface complex. Comparison with literature data demonstrates that the affinity of 4-chlorocatechol is also similar, whereas 2,3-dihidroxynaphthalene and 4-nitrocatechol form more stable complexes, probably because of the solvation contribution to the overall Gibbs adsorption energy. All quoted constants refer to the surface complexation equilibria written as follows: (≡Ti-OH) 2 + H2L = (≡Ti)2-L + 2H2O, i.e., as electroneutral processes. The FTIR-ATR spectra of the surface complexes are also discussed. © 2005 American Chemical Society.
Palabras clave:
Catechol
,
Gallic Acid
,
Titanium Dioxide
,
Equilibrium
Archivos asociados
Licencia
Identificadores
Colecciones
Articulos(CERELA)
Articulos de CENTRO DE REFERENCIA PARA LACTOBACILOS (I)
Articulos de CENTRO DE REFERENCIA PARA LACTOBACILOS (I)
Citación
Araujo, Paula Zulema; Morando, Pedro Juan; Blesa, Miguel Angel; Interaction of catechol and gallic acid with titanium dioxide in aqueous suspensions. 1. Equilibrium studies; American Chemical Society; Langmuir; 21; 8; 4-2005; 3470-3474
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