Kinetics Of Peroxide Decomposition Research Articles

Hydrogen peroxide decomposition kinetics in aquaculture water

Hydrogen peroxide (HP) is used in aquaculture systems where preventive or curative water treatments occasionally are required. Use of chemical agents can be challenging in recirculating aquaculture systems (RAS) due to extended water retention time and because the agents must not damage the fish reared or the nitrifying bacteria in the biofilters at concentrations required to eliminating pathogens. This calls for quantitative insight into the fate of the disinfectant residuals during water treatment. This paper presents a kinetic model that describes the HP decomposition in aquaculture water facilitated by microbial enzyme activity. The model describes how the hydrogen peroxide removal declines and eventually stops at relatively low chemical oxygen demand (COD) concentrations. It is hypothesized that this is due to an enzyme deficit because it is destructed due to the reactive radicals created during the HP decomposition. The model assumes that the enzyme decay is controlled by an inactivation stoichiometry related to the HP decomposition. In order to make the model easily applicable, it is furthermore assumed that the COD is a proxy of the active biomass concentration of the water and thereby the enzyme activity. This was, however, not measured. The model developed successfully described the removal of HP in aquaculture water from three types of RAS and model parameters are estimated. The model and the model parameters provide new information and are valuable tools to improve HP application in RAS by addressing disinfection demand and identify efficient and safe water treatment routines.

Simulation approach to benzoyl peroxide decomposition kinetics by thermal calorimetric technique

To explore the thermal runaway behavior of benzoyl peroxide (BPO) in industrial processes during upsets situations and to compare the difference of values between simulation and experimentation, two calorimeters, differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), were employed to measure thermokinetic data of the thermal decomposition of BPO, and to calculate values of parameters by simulation approach, which were based on kinetic models and the thermal safety software. This study shows the novel finding that benzoyl peroxide (BPO) has an autocatalytic reaction at low temperature. The simulation results showed that the Ea value was 124kJ/mol by VSP2 tests. The Ea value was much closer to Zaman's studies than the Ea values developed by the Kissinger and/or Ozawa methods. The Ea value resulting from the optimal fit approach average was 91.47±17.69kJ/mol also closer to Zaman's studies than values from the Kissinger and Ozawa methods.

High-Temperature Epoxidation of Soybean Oil in Flow—Speeding up Elemental Reactions Wanted and Unwanted

The soybean oil epoxidation reaction is investigated theoretically through kinetic modeling of temperature effects enabled through flow processing under superheated conditions. Different from previous studies on such processing, here a complex reaction network superimposed by multiphase transport is considered; with one elemental step—the hydrogen peroxide decomposition—which can defeat the much boosted product formation. For such a delicate reaction network, the accessibility of accurate and reliable kinetics is absolutely essential, especially when exploring this completely new temperature range. Initially, an overview of the actual kinetic models is given, this gives rise to implications for the study developed here considering high temperature flow processing, heat removal efficiency, hotspot formation, and the effect of different hydrogen peroxide decomposition kinetics. Subsequently an optimized process involving the use of microreactors at different temperatures is proposed for the process manageme...

Batch and Semibatch Partial Oxidation of Starch by Hydrogen Peroxide in the Presence of an Iron Tetrasulfophthalocyanine Catalyst: The Effect of Ultrasound and the Catalyst Addition Policy

Oxidized starch is important for paper coating because of its good mechanical and sizing properties. Traditionally, starch oxidation is performed by different heavy metals as catalysts and chlorites or chlorines as oxidizing agents. In this study, an environmentally friendly method was developed, utilizing iron tetrasulfophthalocyanine as a catalyst only in small amounts and hydrogen peroxide as a clean oxidant. It has been previously shown that the method works well, but analysis of the kinetic data as well as catalyst deactivation was difficult because of the semibatch operation mode. In this study, hydrogen peroxide was employed in a batch mode, allowing more simple analysis methods for determining the degree of substitution, starch degradation, and hydrogen peroxide decomposition kinetics. Additionally, the effect of adding the catalyst continuously into the solution, as well as the influence of ultrasound treatment on starch prior to oxidation, was studied. The batch-mode results showed DSCOOH = 0.73 for 100 anhydroglucose units at 52 °C and pH 10, whereas adding the catalyst continuously increased DSCOOH to 1.62. An increased DSCOOH was obtained with the ultrasound-treated starch, which shows that ultrasound is a promising method for enhancing the reaction performance.

Design of In Situ Fenton Oxidation Based on the Integration of Experimental and Numerical Modelling

AbstractCriteria for the design of In-Situ Fenton Oxidation (ISFO) is proposed and applied to the development of a pilot-scale treatment of a former refinery site contaminated by hydrocarbons. The proposed criteria takes in account both the regulatory and technical constraints that typically characterize the application of in situ remediation technologies. The proposed design strategy of the ISFO treatment is based on coupling experimental and numerical modelling of the ISFO treatment in an iterative way. Batch tests are performed first, allowing to select the optimal operating conditions and the data on hydrogen peroxide decomposition kinetics. These data, together with the hydro-geological information collected in the field, are then used for the numerical modelling of the ISFO treatment, which allows to define the pilot plant layout and operating conditions and to evaluate the effective delivery of the oxidant and the hydraulic gradient developed in the field. These data are then used to design column scale tests aimed to evaluate the effective hydrogen peroxide longevity, the process performance and the extent of gas production from hydrogen peroxide decomposition.

Surface and catalytic properties of Cu–Ce–O composite oxides prepared by combustion method

Abstract Surface and catalytic properties of Cu–Ce–O composite materials prepared by solution combustion method have been investigated. The materials are characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR) and electron paramagnetic resonance spectroscopy (EPR). The results of EPR and TPR show finely dispersed Cu2+ species on ceria matrix with low copper content. The Cu2+ species exists in the form of dimers and clusters which are not evident in XRD. In addition CuO is also present as small clusters which grow to larger size at higher Cu content. There is no evidence of CuO forming a solid solution with fluorite CeO2 in combustion method. The Cu2+ species mostly appear on surface rather than in the bulk. Hydrogen peroxide decomposition kinetics has been carried out on Cu–Ce–O composite materials to investigate the effect of crystalline and well-dispersed copper oxide phases on CeO2. From kinetic results, the catalyst materials can be grouped into highly dispersed as well as crystalline CuO phases present on CeO2 matrix. Two parallel compensating lines for dispersed and crystalline CuO phases on CeO2 are observed in ln A versus Ea plot indicating the compensation effect in H2O2 decomposition. This observation is consistent with XRD and EPR results.

Kinetics of hydrogen peroxide decomposition with complexed and ?free? iron catalysts

The hydrogen peroxide decomposition kinetics were investigated for both “free” iron catalyst [Fe(II) and Fe(III)] and complexed iron catalyst [Fe(II) and Fe(III)] complexed with DTPA, EDTA, EGTA, and NTA as ligands (L). A kinetic model for free iron catalyst was derived assuming the formation of a reversible complex (Fe–HO2), followed by an irreversible decomposition and using the pseudo-steady-state hypothesis (PSSH). This resulted in a first-order rate at low H2O2 concentrations and a zero order rate at high H2O2 concentrations. The rate constants were determined using the method of initial rates of hydrogen peroxide decomposition. Complexed iron catalysts extend the region of significant activity to pH 2–10 vs. 2–4 for Fenton's reagent (free iron catalyst). A rate expression for Fe(III) complexes was derived using a mechanism similar to that of free iron, except that a L–Fe–HO2 complex was reversibly formed, and subsequently decayed irreversibly into products. The pH plays a major role in the decomposition rate and was incorporated into the rate law by considering the metal complex specie, that is, EDTA–Fe–H, EDTA–Fe–(H2O), EDTA–Fe–(OH), or EDTA–Fe–(OH)2, as a separate complex with its unique kinetic coefficients. A model was then developed to describe the decomposition of H2O2 from pH 2–10 (initial rates = 1 × 10−4 to 1 × 10−7 M/s). In the neutral pH range (pH 6–9), the complexed iron catalyzed reactions still exhibited significant rates of reaction. At low pH, the Fe(II) was mostly uncomplexed and in the free form. The rate constants for the Fe(III)–L complexes are strongly dependent on the stability constant, KML, for the Fe(III)–L complex. The rates of reaction were in descending order NTA > EGTA > EDTA > DTPA, which are consistent with the respective log KMLs for the Fe(III) complexes. Because the method of initial rates was used, the mechanism does not include the subsequent reactions, which may occur. For the complexed iron systems, the peroxide also attacks the chelating agent and by-product-complexing reactions occur. Accordingly, the model is valid only in the initial stages of reaction for the complexed system. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 24–35, 2000

Mechanistic studies of surface catalyzed H 2O 2 decomposition and contaminant degradation in the presence of sand

This study examined the mechanism and kinetics of surface catalyzed hydrogen peroxide decomposition and degradation of contaminants in the presence of sand collected from an aquifer and a riverbed. Batch experiments were conducted using variable sand concentrations (0.2 to 1.0 g-sand/ml solution) and phenol and quinoline as model contaminants. Inhibition and probe studies were conducted to ascertain the role of several oxygen radicals (e.g. ̇OH, ̇HO 2/O 2 −) on contaminant degradation. Phenol degradation products were consistent with reaction with hydroxyl radical. Concordant with this, phenol degradation was greatly inhibited in the presence of the widely accepted hydroxyl radical scavenger butanol. Additional inhibition studies with superoxide dismutase (SOD) support the conclusion that superoxide anion participates in the formation of hydroxyl radical. It is postulated that the relatively long-lived superoxide anion is capable of leaving the vicinity of the sand surface into bulk solution, where it may react with hydrogen peroxide to form hydroxyl radical and contribute to contaminant degradation. A mechanism is formulated and evaluated which accounts for these observations, as well as hydrogen peroxide decomposition kinetics and the complex decay behavior of phenol and quinoline in the presence of sand.

Validation of the rancimat test for the assessment of the relative stability of fish oils

AbstractThe induction periods for the peroxidation of various fish oils at 55–90°C were studied by the Rancimat test. The natural logarithms of the induction periods varied linearly with respect to temperature, with a mean coefficient of −7.5×10−2°C−1, which was significantly different from that reported for vegetable oils. The activation energy for the formation of volatile acids had a mean value of 38.9 kJ/mol and was independent of the fish oil source. Peroxide formation under Rancimat test conditions followed first‐order kinetics. The same kinetics were followed under Schaal Oven test conditions (forced‐air oven, 60°C). On the basis of the results obtained, the Rancimat test appears to be useful in determining the relative stabilities of fish oils without the change in peroxide decomposition kinetics that may occur at elevated temperatures.

An observation of homogeneous and heterogeneous catalysis processes in the decomposition of H 2O 2 over MnO 2 and Mn(OH) 2

The kinetics of peroxide decomposition by manganese dioxide (MnO 2) and manganese hydroxide (Mn(OH) 2) have been studied in alkaline solutions. The activity for peroxide decomposition on Mn(OH) 2 was generally higher than MnO 2 and the kinetics for the decomposition of H 2O 2 were first-order in the case of MnO 2 catalysts, but 1.3-order for Mn(OH) 2 catalysts. It is suggested that H 2O 2 is mainly homogeneously decomposed by Mn 2+ ions (in the form of HMnO 2 ions in concentrated alkaline solutions) dissolved in the solution in the case of Mn(OH) 2. Compared with the results reported for the decomposition of H 2O 2 in the presence of 1 ppm Co − 2 ions, it is concluded that the kinetics of the homogeneous decomposition of H 2O 2 are directly influenced by the concentration of the active species in the solution.

Spinel ferrites as catalysts: A study on catalytic effect of coprecipitated ferrites on hydrogen peroxide decomposition

Some ferrospinels act as catalysts for the decomposition of H2O2, their effectiveness is dependent on the composition of the catalyst. This study is to find the most effective catalyst of stoichiometry MIIFe2IIIO4. A set of ferrites of different composition MIIFe2II04 (MII = Mn, Co, Ni, Cu, Zn, Cd) was synthesized by co-precipitation and characterized by chemical analysis, X-ray diffractometry, and B.E.T. technique. A comparative assessment of the catalytic power of these ferrites from investigations of their influence on the kinetics of H2O2 decomposition in a neutral medium was made. An analysis of the data on specific rate, and the Eyrings activation parameters for the reaction sharply reveal the following: (a) The catalytic power follows the order MnFe2O4 > CoFe2O4 > CuFe2O4 > NiFe2O4 > CdFe2O4 > ZnFe2O4, MnFe2O4 is much more highly effective than the others (50–100 fold). (b) A compensation effect has been noted from the observed linearity with slightly less than unity slope between TΔ≠S0 and Δ≠H0 over the entire series. Key words: Ferrospinels, catalysis, hydrogen peroxide decomposition kinetics.

Homogeneous and Heterogeneous Catalytic Reactions in Cobalt Oxide/Graphite Air Electrodes: I . Chemical Kinetics of Peroxide Decomposition by Co(II) Ions in Alkaline Solutions

This paper considers the role played by dissolved cobaltous ions in concentrated alkaline solutions in the homogeneous decomposition of and its significance to oxygen reduction in alkaline media. Dissolved cobaltous ions, in the form of in concentrated alkaline solutions, show a very high catalytic activity for the decomposition of even at a concentration of 1 ppm. The homogeneous decomposition of peroxide is not a simple first‐order reaction as reported in literature but is a 1.2 order reaction. It is suggested that kinetics of decomposition of in the presence of is controlled by the homogeneous catalytic reaction of the ions, the heterogeneous redox reaction between ions in solution, and the Co3+ ions in the cobalt oxide spinel lattice sites.

The Curing of Silicone Rubber with Benzoyl Peroxide

Abstract Little has been reported about the action of benzoyl peroxide as a vulcanizing agent for silicone rubber. Knowledge of this action seems to be of consider- able importance, since benzoyl peroxide is the most widely used vulcanizing agent at the present time. Apparently no studies of the kinetics of peroxide decomposition in silicones have been undertaken. It is not known quantitatively whether or not the silicones influence the decomposition rate in the way some of the solvents studied by Cass and by Nozaki and Bartlett do. In this paper we report the results of work undertaken to determine the number of cross-links introduced into polydimethylsiloxane by benzoyl peroxide during the normal vulcanizing process. The apparent efficiency of cross-link production has been determined as a function of the concentration of peroxide, the method of vulcanization, and of the filler content of the sample.