Abstract

The chromic acid oxidations of dl-mandelic acid (MA) in the presence and absence of bipyridine (bpy) as catalyst have been studied in aqueous micellar media under the kinetic condition, [dl-mandelic acid]T >> [Cr(VI)]T at various temperatures. The unanalyzed path is first order with respect to [H+], [dl-mandelic acid]T and [Cr(VI)]T. The bpy catalyzed path gives zero order dependency on [H+]. This path also shows a first order dependence on [bpy]T. HCrO4- has been found to be kinetically active in the absence of bpy while in the bpy catalyzed path, a Cr(VI)-bpy complex was considered to be the active oxidant. In this path the Cr(VI)-bpy complex undergoes a nucleophilic attack by the mandelic acid to form a ternary complex which subsequently experiences a redox decomposition involving 3e transfer leading to benzoyl radical, CO2 and corresponding Cr(VI)-bpy complex. Benzoyl radical is then oxidized to form benzoic acid. In the unanalyzed path, the Cr(VI)-substrate ester undergoes an acid-catalyzed redox decomposition through 3e-transfer as the rate-determining step. It is striking to note that unanalyzed paths show a first order dependence on [H+] and catalysed path shows zero order dependence on [H+] and boh paths also show a first order dependence on [dl-mandelic acid]T and [Cr(VI)]T.The bpy catalyzed path is first order in [bpy]T. All these patterns remain unaltered in the presence of externally added surfactants. The effects of an anionic surfactant, sodium dodecyl sulphate (SDS), on both the unanalyzed and catalyzed paths were studied.

How to Cite
MANDAL, Jayashree et al. Hexavalent Chromium Removal By MANDELIC ACID In The Presence And Absence Of Surfactants. Global Journal of Science Frontier Research, [S.l.], v. 10, n. 4, sep. 2010. ISSN 2249-4626. Available at: <https://journalofscience.org/index.php/GJSFR/article/view/172>. Date accessed: 20 jan. 2022.