Data/hora: 15/05/2024 13:12:20

Biblioteca(s): | Embrapa Cerrados.
Data corrente: | 22/10/1999
Data da última atualização: | 22/10/1999
Autoria: | CHARLET, L.
Título: | Adorption of some macronutrient ions on an oxisol: an application of the triple layer model.
Ano de publicação: | 1986
Fonte/Imprenta: | Riverside: University of California, 1986.
Idioma: | Inglês
Notas: | Ph.D. Dissertation.
Conteúdo: | An experimental method was designed to study simultaneously the development of net  proton charge density and the amount of metal or ligand adsorbed on the same Oxisol soil material. The method involved saturation of the soil with LiC104 at high pH (pH 6.0) and ionic strength (500 mol m-3); exchange of Li and C104 for the adsorptive ions of interrest, decrease of the ionic strength while minimizing dispersion, and preparation of a paste which allowed replicate sampling of small quantities of whole soil. Next, a combined titration /adsorption experiment was performed in the pH range 2.5 - 6.0, which minimized undesirable dissolution side-reactions. It was shown for an Oxisol sample suspended in a 1:1 electrolyte solution at 298.15ºK that the point of zero salt effect (PZSE) is equal to the point of zero net proton charge and, therefore, the net proton charge density can be obtained directly from titration curves "restandardized" to the PZSE. A single "average"hydroxyl surface site in the soil was considered and intrinsic protonation or dissociation constants were calculated, together with intrinsic surface complexation constants for Na+,K+, Ca2+, Mg2+, C1- and NO3-, according to the Triple Layer Model. The net proton surface charge developed by the Oxisol sample suspended in an "indifferent" electrolyte solution was found to depend very little on ionic strengrh and to vanish at pH 4.15. The amount of calcium or magnesium adsorbed increased proportionally with pH from pH 2.5 to 5.5. This behavior could be simulated by invoking inner-sphere, monodentate complex formation between the bivalent metal and a deprotonated surface hydroxyl group. The amount of sulfate adsorbed was studied as well but could not be simulated by a model involving a single site and a single adsorption mechanism. The amount adsorbed exhibited an exponential, ionic strength-dependent decrease with pH up to pH 4.0. Above pH 4.0, the decresase in adsorption was linear with pH and ionic strength-dependent. Either defferent kinds of surface sites are inolved or different surface complexation mechanisms are involved, depending on pH.
Palavras-Chave: | Modelo; Oxissols.
Thesagro: | Absorção; Íon; Macroelemento; Nutriente; Química do Solo; Solo.
Thesaurus Nal: | adsorption; ions; models; Oxisols; soil; soil chemistry.
Categoria do assunto: | --
Registro original: | Embrapa Cerrados (CPAC)
Exemplares: | CPAC - (15925-1) - ADD - TS - -- - T027/86 - CHA - T027/86 - DIS