Oxidative Degradation of Oxalic Acid in Aqueous Medium Using Manganese Oxide as Catalyst at Ambient Temperature and Pressure (original) (raw)
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Applied Catalysis A-general, 1996
Heterogeneous catalysis by MnO 2 of oxalic acid ozonation in aqueous solution has been investigated in the pH range 3.2-7.0. The influence of catalyst load and reaction temperature upon rate development of the ozonation process has also been examined. The observed dependence of system reactivity on pH and the results obtained by ozonation experiments with MnO 2 catalysts of different pHzm values agree with a reaction mechanism involving the formation of a surface Mnoxalic acid complex.
A Kinetic Study of the Reduction of Colloidal Manganese Dioxide by Oxalic Acid
Journal of Colloid and Interface Science, 1996
or reaction products in most permanganate oxidations (11, A kinetic study of the reaction between colloidal manganese 12), being actively involved in the mechanism as autocatadioxide and oxalic acid in aqueous acetate media (pH 4.3-5.1) is lysts in many cases (13, 14). reported. The reaction is autocatalytic and, in order to determine On the other hand, although the kinetic aspects of the the rate constants k 1 and k 2 corresponding, respectively, to the manganese-oxalate reacting systems have gained new internoncatalytic and autocatalytic reaction pathways, the Mn(III) est in the last decade due to their involvement in some oscilformed as an intermediate was stabilized by addition of sodium lating reactions (15-20), the reduction of colloidal mangapyrophosphate. Joint iodimetric and spectrophotometric studies nese dioxide by oxalic acid has received much little attention indicated that the reduction of colloidal manganese dioxide follows (21-23) than its relative, the permanganate-oxalate reacthe sequence tion (24, 25). We have now undertaken a kinetic study of the reaction between colloidal manganese dioxide (in the form of a perfectly transparent, aqueous sol) and oxalic acid and found that it is in fact an autocatalytic reaction, whose Mn(IV) r R Mn(II) Mn(IV) Mn(III) r R Mn(II), where R stands for the reductant. Both reaction pathways exhibit stoichiometry may be written as acid catalysis, and the activation energies associated to k 1 and k 2 are 74.7 { 0.9 and 44.6 { 0.6 kJ mol 01 , respectively. The reaction
Journal of Physics: Conference Series
Birnessite-type manganese oxide is multifunction material that has been used in various application and the characteristic depends heavily upon its preparation method. In this study, birnessite-type manganese oxide was synthesized using the reaction between KMnO 4 (oxidant) and two different reducing agents i.e., citric acid and oxalic acid via a solvent-free method. The characterization of the birnessite was carried out using X-Ray Diffraction (XRD), Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX), and Surface Area Analyzer (SAA). Birnessite from this variation of reducing agents showed different levels of crystallinity, diverse morphology, crystal size, and surface area. The birnessite-type was then applied as a catalyst for the degradation of Palm Oil Mill Effluent (POME) with hydrogen peroxide (H 2 O 2) as an oxidant to reduce the concentrations of Chemical Oxygen Demand (COD). The maximum reduction in COD concentration was obtained using the catalyst concentration of 400 and 800 mg/L for reducing agent of assynthesized catalyst citric acid and oxalic acid. Birnessite-type manganese oxide shows potential as a catalyst in the degradation of POME with citric acid as reducing agents showed better degradation in reducing COD values.
Hydrometallurgy, 2001
Leaching studies of low-grade Joda manganese ore containing 24.7% Mn and 28.4% Fe were carried out at high temperature and atmospheric pressure using oxalic acid as reductant in sulphuric acid medium. The experiments were designed according to 2 4 full factorial design, and regression equations for extraction of manganese, iron and aluminum were determined from the data. All the significant main and interaction effects on extraction of Mn, Fe and Al have positive effect, except oxalic acid concentration and time interaction for extraction of Al. Oxalic acid concentration has strongest effect on extraction of Mn, whereas temperature and time have strongest effect on extraction of Fe and Al, respectively. 98.4% Mn and 8.7% Fe were extracted from À 150 + 105 mm ore with 30.6 g/l oxalic acid, 0.543 M sulphuric acid concentration at 85°C in 105 min. D 2001 Published by Elsevier Science B.V.
Comparison between MnO2, TiO2 and CoO for the Ozonation of oxalic acid
International Journal of Innovation and Applied Studies, 2014
Advanced oxidation, is the main of research in ozone fields for many years. Ozone generations and uses as an oxidant and also the use of heterogeneous reactor were improve the de development of catalytic ozonation axes. The object of our project is the application of catalytic ozonation for some refractor molecules. Oxalic acid was chosen as a model of refractor molecules. In fact, it is the final product of the degradation by ozone of many organic molecules in aqueous solution. Ozonation have a significant effect on the mineralization of water charged with oxalic acid. In our experiences, the dioxide of manganese and titan and the oxide of cobalt were used as homogenous catalysts. Experiences of ozonation have been done in ambient conditions in a gas-liquid reactor with a capacity of 2 liters. Studies of ozone concentration, type and mass of catalysts and oxalic acid concentration have been done. With 1mmol/l of oxalic acid solution and 43mg/l of ozone, we obtained 50% of maximal oxidation report after 20min. the addition of 1g of MnO2 to the solution in the reactor changed the same report to 85% after 5min. a comparison between MnO2, TiO2 and CoO was done and results prove that the oxide of cobalt is more efficient than the two other catalyst. However, with the same mass added to the reactor 500 mg for each catalyst, the rate of conversion obtained with MnO2 and CoO was nearly 95% and 90% with TiO2 but the kinetic of CoO is faster than the two other catalysts.
Analytica Chimica Acta, 1982
The reduction of permanganate by oxalate in the presence of manganese(II) ion in acidic media is described. All reactions were run at 525 nm and constant ionic strength 1_0 M_ The reaction was found to obey the rate expression-d[MnO ; j/dt = h [Mn'] [C,O ;-] 2 [MnO;] [H" I` = k' [MnC,O,] [MnO;]. The values of k and k' were shown to be 5 .4 x 10' M-' s-' and 8 .2 x 10° M-' s', respectively. Reaction rate methods for the determination of manganese(II) and oxalic acid are reported. The rate of disappearance of permanganate was monitored automatically and related directly to manganese-(II) and oxalic acid concentrations. Manganese(II) in the ranges 1-10 x 10~ M and 1-10 x 10' M and oxalic acid in the range 0-20 mg m1-' can be determined very rapidly with a precision of 1-2% .
Portugaliae Electrochimica Acta, 2018
This paper deals with the theory and kinetics of oxalic acid electrochemical oxidation, in an acidic solution containing sodium chloride, using a manganese dioxide rotating cylinder anode. Voltammetric and galvanostatic electrolysis techniques were used. The voltametric study shows a higher anodic wave corresponding to chlorine oxidation on the MnO2 electrode, prevailing oxalic acid indirect oxidation. Galvanostatic electrolysis studies confirmed that the rate constant is affected by chloride concentration, current density, agitation and temperature. Electrochemical oxidation rate was found to be a pseudo-first order kinetic process. A strongly linear relationship between the rate constant and chloride concentration was observed, while polynomial relations, with respect to current density and temperature, were found. The activation energy was found to be 14.541 kJ/mol, which suggests a diffusion control kinetic step in oxalic acid degradation. The findings of the present research validate that oxalic acid incineration can be successfully carried out on a MnO2 anode, in NaCl presence.
Kinetics of Oxalic Acid Ozonation Promoted by Heterogeneous MnO 2 Catalysis
Industrial & Engineering Chemistry Research, 1997
A kinetic model is developed for the ozonation of oxalic acid catalyzed by solid MnO 2. The rate of ozonation is limited by the adsorption of oxalic acid on the catalyst surface and by the deactivation of a fraction of the active sites, because of an irreversible reaction with ozone. Moreover, the model includes the ozonation of oxalic acid catalyzed by dissolved manganese. This kinetic model allows for a fairly good correlation of the experimental data when the average size of the catalyst particles is smaller than about 10 µm. When larger particles are employed, noticeable mass-transfer limitations are encountered, mainly deriving from the diffusion of both reactants from the liquid bulk to the solid surface (external and internal). The dependence of the rate constant on pH is experimentally determined and explained in terms of the changing chemical structure of the active sites and of the dissociation equilibrium of oxalic acid.
Journal of Electroanalytical Chemistry, 2006
The oxygen reduction reaction (ORR) was studied in KOH electrolyte on different manganese oxides, dispersed on a carbon powder (MnO x /C). The oxides were prepared by different methods, for producing MnO, Mn 3 O 4 and MnO 2 as major phases dispersed on the Vulcan XC-72 carbon. The oxides were characterized by XRD (X-ray diffraction) and in situ XANES (X-ray absorption near edge structure). The electrochemical measurements were made using cyclic voltammetry and steady state polarization curves carried out in an ultrathin layer rotating ring/disk electrode. The results have shown lower activity for the ORR on the MnO x /C species compared to that on Pt/C, but higher activity compared to that of pure Vulcan carbon. Formation of HO À 2 involving 2e À per O 2 molecule is the main path of the ORR in the studied MnO x /C catalysts but, at low overpotentials and rotation rates the number of electrons is raised to 4 due to the occurrence of a HO À 2 disproportionation reaction. Large differences of electrocatalytic activity were seen for the different oxide species, and these were related to the presence of a Mn(IV) phase and the occurrence of a mediation processes involving the reduction of Mn(IV) to Mn(III), followed by the electron transfer of Mn(III) to oxygen.
Colloids and Surfaces A-physicochemical and Engineering Aspects, 2001
The effects of cationic cetyltrimethylammonium bromide (CTAB), anionic sodium dodecyl sulphate (SDS) and non-ionic Triton X-100 (TX-100) surfactant micelles on the kinetics of the oxidation of oxalic acid by chromium(VI) is studied spectrophotometrically in the absence and presence of manganese(II). The reaction follows second-order kinetics with respect to oxalic acid in absence of manganese(II), which shifts to first-order in presence of manganese(II). In the latter case, the reduction of chromium(VI) to chromium(III) occurs in a single-step without passing through chromium(IV) as an intermediate. The reaction is catalysed by CTAB and TX-100 micelles but SDS has no effect. The observed catalyses are explained with the model proposed by Menger and Portnoy. The activation parameters are determined in water and in CTAB. The effect of added inorganic salts (NaCl, NaNO 3 , Na 2 SO 4 and NaBr) on the CTAB catalysed reaction is also reported.