KINETICS AND MECHANISM OF SURFACE REACTION OF SALICYLATE ON ALUMINA IN COLLOIDAL AQUEOUS SUSPENSION

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dc.contributor.author Wang Z.
dc.contributor.author Ainsworth C.C.
dc.contributor.author Friedrich D.M.
dc.contributor.author Gassman P.L.
dc.contributor.author Joly A.G.
dc.date.accessioned 2021-01-22T08:02:53Z
dc.date.available 2021-01-22T08:02:53Z
dc.date.issued 2000
dc.identifier https://elibrary.ru/item.asp?id=219530
dc.identifier.citation Geochimica et Cosmochimica Acta, 2000, 64, 7, 1159-1172
dc.identifier.issn 0016-7037
dc.identifier.uri https://repository.geologyscience.ru/handle/123456789/23519
dc.description.abstract The reaction kinetics of salicylate with Al(III) in aqueous solution and at the colloidal alumina-water interface was studied by stopped-flow laser fluorescence spectroscopy. Temporal evolution of the fluorescence spectra suggests that formation of a carboxylate monodentate complex was the reaction intermediate that occurs transiently at the beginning of the reaction in aqueous salicylate-Al(III) solution. However, by lowering the pH to 2.0, the formation of such an intermediate can be directly observed as it is the only species formed. The reaction of salicylate with aqueous Al3+ is completed within 10 min at pH 3.3 but is significantly slower at pH 2.0. At both pH the aqueous reaction follows a single pseudo-first order rate law. In alumina suspension the reaction was initially fast but slowed down after ~30 s. Completion of the reaction took up to 12 h, depending on pH and ionic strength. The formation of a carboxylate monodentate surface complex as a transient species is clearly observed in alumina suspensions at near neutral pH. The initial rapid reaction (<30 s), accounting for ~70% of the total reaction, can be best described by elovich rate equation and slower ~30% obeys pseudo-first order kinetics. these results are consistent with a sorption reaction mechanism that is controlled leaving group lability at surface sites (al-oh2+ and Al-OH). The pseudo-first order rate constant varies little with initial salicylate concentration, ionic strength, or pH > 4, suggesting that the slow reaction pathway involves ligand substitution reactions between salicylate and the hydroxyl groups for which the Al-O binding and activation energy are affected by site heterogeneity or site density to a lesser degree than Al-OH2+ sites.
dc.title KINETICS AND MECHANISM OF SURFACE REACTION OF SALICYLATE ON ALUMINA IN COLLOIDAL AQUEOUS SUSPENSION
dc.type Статья


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