Generation Of Manganese Research Articles

Modeling the Kinetics of Contaminants Oxidation and the Generation of Manganese(III) in the Permanganate/Bisulfite Process.

Permanganate can be activated by bisulfite to generate soluble Mn(III) (noncomplexed with ligands other than H2O and OH(-)) which oxidizes organic contaminants at extraordinarily high rates. However, the generation of Mn(III) in the permanganate/bisulfite (PM/BS) process and the reactivity of Mn(III) toward emerging contaminants have never been quantified. In this work, Mn(III) generated in the PM/BS process was shown to absorb at 230-290 nm for the first time and disproportionated more easily at higher pH, and thus, the utilization rate of Mn(III) for decomposing organic contaminant was low under alkaline conditions. A Mn(III) generation and utilization model was developed to get the second-order reaction rate parameters of benzene oxidation by soluble Mn(III), and then, benzene was chosen as the reference probe to build a competition kinetics method, which was employed to obtain the second-order rate constants of organic contaminants oxidation by soluble Mn(III). The results revealed that the second-order rate constants of aniline and bisphenol A oxidation by soluble Mn(III) were in the range of 10(5)-10(6) M(-1) s(-1). With the presence of soluble Mn(III) at micromolar concentration, contaminants could be oxidized with the observed rates several orders of magnitude higher than those by common oxidation processes, implying the great potential application of the PM/BS process in water and wastewater treatment.

Generation of manganese-(III) versus -(IV) complexes with a conjugated ONS donor set: controlling effect of ligand substituents †

Manganese(IV) complexes, [MnL 2 ] [H 2 L = MeC(OH)CHCMeNN C(SH)SR (R = Me 1a or CH 2 Ph 1b)] and manganese(III) complexes, [Mn(O 2 CMe)L] 1c or [Mn(acac)L] 1d [acac = acetylacetonate; H 2 L = PhCH(OH)CPhNNC(SH)SCH 2 Ph] have been synthesized and characterized. The Schiff-base ligands which are derived from an aliphatic carbonyl function, favour the facile oxidation of manganese-(II) to -(IV) under ambient conditions. The structure determination of 1a showed that the molecule is octahedral with the two equivalent tridentate ligands spanned meridionally. The EPR spectrum of 1a with a strong but structured signal at g ≈ 4.0 and a weak one at g ≈ 2.0 implies a large zero-field splitting, but the spectral profile differed from an ideal axial form. All the complexes exhibited reversible or quasi-reversible Mn IV –Mn III redox couples in their cyclic voltammograms at potentials commensurate with the nature of the substituents in the appropriate ligands. A reasonable basis is suggested by which one may predict whether a particular ligand will stabilize manganese-(II), -(III) or -(IV) in an aerobic medium.

Electrochemical generation of manganese (III) at glassy carbon electrode in acetic acid

Conditions were established for the electrochemical generation of manganese(III) at glassy carbon in acetic acid. In the oxidation of manganese-(II) in potassium acetate supporting electrolyte high current efficiencies were achieved in a wide range of current densities at the working electrode, whereas in the presence of sodium perchlorate a successful generation of manganese(III) could be performed only at low current densities. With increasing content of water in the anolyte the amount of generated manganese (III) was abruptly decreased and its stability in the solution was diminished. Procedures are given for a successful coulometric titration of reducing substances with anodically generated manganese (III); biamperometric, potentiometric and bipotentiometric methods for the location of the end-point were employed. The error of the determinations did not exceed ± 2%.

The application of strongly oxidizing agents in flow injection analysis : Part 2. Manganese(III)

The application of manganese(III) as a powerful oxidizing agent in flow injction analysis is described. Manganese(III) is generated electrochemically in the flowing system at a working electrode consisting of a packed bed of gold powder. Spectrophotometric detection is used at 490 nm, where manganese(III) in sulphuric acid solution absorbs strongly. Undr the experimental conditions, the generation of manganese(III) can be accompanied by generation of manganese(IV) and permanganate; manganese(III) alone can be generated by a proper selection of the generating current and the flow rate. Results are presented for the determinatin of various organic and inorganic substances by means of manganese(III), usually at concentrations in the 10 −4—10 − mol l −1 range. Unlike permanganate and manganese(IV), manganese(III) does not react with chloride, so that oxidizable compounds can be determined in the presence of large amounts of this species.

Electrochemical generation of manganese(III) and behaviour of the generated oxidant in acetic acid in the presence of perchlorate ions

Research was carried out to determine conditions for the anodic generation of manganese(III) with high current efficiency in solutions of sodium perchlorate in acetic acid, and to examine the behaviour of the oxidant thus generated. The effects of water and acetic anhydride on current efficiency in the generation of the oxidant was also examined. The formal redox potential of the Mn(III)/ Mn(II) system is decreased with increasing concentrations of sodium acetate in the solution. The effect of sodium perchlorate and perchloric acid concentrations is the reverse. Procedures for coulometric titrations of a number of substances with the generated oxidant were developed, end point being detected using biamperometric and potentiometric methods. Perchloric acid accelerates the oxidation of certain substances with manganese(III) in acetic acid and increases the sensitivity of end-point detection using the potentiometric method.