The Oxidation Reaction of Tl(I) to Tl(III) by the Peroxodisulfate Ion. I. Kinetics and Mechanism in an Aqueous Solution

Abstract

The oxidation reaction of the thallium(I) ion to the thallium(III) ion by the peroxodisulfate ion has been studied in an aqueous acidic solution. The reaction constituted a chain reaction initiated by the thermal decomposition of the peroxodisulfate ion, the reaction involving no direct reactions between the thallium(I) and peroxodisulfate ions. At thallium(I) ion concentrations larger than 0.004 mol dm−3, the reaction mechanism was assumed to be: S2O82−\oversetk1→2SO4\ewdot; S2O82−+H+\oversetk2→HSO4−+1/2O2+SO3; Tl(I)+SO4\ewdot\oversetk3→Tl(II)+SO42−; S2O82−+Tl(II)\oversetk4→Tl(III)+SO4\ewdot+SO42−; 2Tl(II)\oversetk5\undersetk−5\ightleftharpoonsTl(I)+Tl(III). The rate of the reaction was described as −d[S2O82−]/dt=(k1+k2[H+])[S2O82−]+k4(k1⁄k5)1⁄2[S2O82−]3⁄2. The rate constants at an ionic strength of 0.16 mol dm−3 were determined to be k1=1.99×1019exp[−157 kJ mol−1/RT]s−1, k2=2.75×1012exp[−103 kJ mol−1/RT] dm3 mol−1 s−1, and k4(k1⁄k5)1⁄2=2.81×1013exp[−108 kJ mol−1/RT] dm3⁄2 mol−1⁄2 s−1 in 0.01 mol dm−3 perchloric acid, the k4 value being increased with a decrease in the hydrogen-ion concentration. The ionic strength (μ) dependence was described as logk4(k1⁄k5)1⁄2=−4.17–1.05 μ1⁄2 in 0.01 mol dm−3 perchloric acid at 40 °C. The reaction rate was completely retarded by the addition of 1% acrlyronitrile, 5×10−6 mol dm−3 cerium(III) sulfate, 1×10−3 mol dm−3 cerium(IV) sulfate, or 0.1 mol dm−3 sodium acetate, and it was also remarkably retarded by the addition of 1×10−3 mol dm−3 tetranitromethane. The copper(II) ion and molecular oxygen did not appreciably affect the reaction rate, but the iron (III) ion accelerated it greatly.

A kinetic approach for the mechanism of malachite green‐peroxydisulphate reaction in aqueous solution

“…Using its immense attacking capacity in acidic, neutral, and alkaline conditions, oxidation reactions of the inorganic and organic substrates have been extensively studied and findings have been reviewed by House [l], Wilmarth et al [2], and Wilson [3]. Oxidation of various substrates by peroxydisulphate ion (PDS) is known to occur through several schemes: (i) a two-electron transfer by the direct reaction between the reductant and oxidant [4]; (ii) two successive reaction steps of the one-electron transfer from the reductants [2]; (iii) a reaction initiated by the thermal decomposition of peroxydisulphate, with no direct reaction between the reactants, (i.e., through a reaction between reducing substrate and the sulphate radical ion [5]). Beyond elucidation of oxidation reaction mechanisms, the kinetic data of the reactions involving PDS have been successfully used in designing catalytic rate methods for analysis of trace concentrations of Ag(1) [6,7] Cu(I1) [8], and Au(I1) [9] by using their selective catalytic efficiencies on specific indicator reactions.…”

Silver(I) Catalyzed Photochemical Oxidation of Methylene Blue and Safranine-O by Peroxydisulphate: A Green Chemical Approach

“…Jonnalagadda et al [3] observed the photodegradation of methyl orange in methanolic solution under both UV and visible radiations in the presence of Fe +2 /H 2 O 2 . Oxidation of various substrates by peroxydisulphate ion is known to occur through several schemes: (i) a two-electron transfer by the direct reaction between the reductant and oxidant [4]; (ii) two successive reaction steps of one electron transfer from the reductant [5]; and (iii) a reaction initiated by the thermal decomposition of peroxydisulphate with no direct reaction between the reducing substrate and sulphate ion radical [6]. Here, the silver ion may react with persulfate ion to generate sulphate anion radical, which further reacts with silver ion to give sulphate ions.…”

Kinetics of oxidation of nickel(II) aza macrocycles by peroxydisulphate in aqueous media

“…A pulse radiolytic study of the oxidation of Ni(II) complex with an unsaturated macrocyclic ligand by Br 2 and OHradicals in aqueous solutions 16 has been reported. Many kinetic studies have shown the Ni(II) complex to be smoothly oxidized to the +3 state by a variety of oxidants via an outer-sphere mechanism 17 .…”