Order Reaction Rate Constants Research Articles

Adsorption of methyl iodide on reduced silver‐functionalized silica aerogel: Kinetics and modeling

AbstractThe low concentration methyl iodide (CH3I) adsorption process on reduced silver‐functionalized silica aerogel (Ag0‐Aerogel) was studied. The kinetic data were acquired using a continuous flow adsorption system. Because the corresponding physical process was observed, the shrinking core model (SCM) was modified and applied. An average CH3I pore diffusivity was calculated, the CH3I‐Ag0‐Aerogel reaction was identified as a 1.40 order reaction instead of first order reaction, and the nth order reaction rate constant was determined. This modified SCM significantly increases the accuracy of adsorption behavior prediction at low adsorbate concentration. Modeling results indicate that the overall adsorption process is controlled by the pore diffusion. However, at low adsorbate concentration (ppbv level), the CH3I adsorption is limited to the surface reaction due to the low uptake rate in a predictable time period.

CHEMICAL REACTION KINETICS OF 1,5-BIS (3'-ETHOXY-4'-HYDROXYPHENYL)-1,4–PENTADIENT-3–ONE SYNTHESIS WITH FOOD GRADE RAW MATERIAL

Objective: This research aims to develop the 1,5-bis (3'-ethoxy-4'-hydroxyphenyl)-1,4-pentadient-3-one (EHP) synthesis method from ethyl vanilin with food-grade quality and determines the order reaction and formation reaction rate constant of EHP.
 Methods: Synthesis of the EHP was carried out by reflux the starting material, ethyl vanillin (food grade) of various weights, acetone and hydrochloric acid as catalysts. The reflux results are then condensed for two days at cold temperatures. Determination of the reaction order and reaction rate constants are carried out by the graph method based on the reduction in the concentration of ethyl vanilin, which reacts with acetone each time unit.
 Results: The results showed the formation of EHP, which was synthesized by starting material of ethyl vanilin food grade 4 and 8 grams following pseudo-first-order reaction kinetics with reaction rate constants respectively 0,0116/minute and 0,005/minute. The formation of EHP, which was synthesized by starting material ethyl vanilin food grade 16 and 18 grams following zero-order reaction kinetics with reaction rate constants respectively 0,1451 mg/ml minute and 0,248 mg/ml minute.
 Conclusion: The synthesis of EHP from ethyl vanilin with food-grade quality has been success develop. The order reaction kinetics are different in the different mass of ethyl vanillin used.

Identification of a novel di-C-glycosyl dihydrochalcone and the thermal stability of polyphenols in model ready-to-drink beverage solutions with Cyclopia subternata extract as functional ingredient

Heat processing of ready-to-drink beverages is required to ensure a microbiologically safe product, however, this can result in the loss of bioactive compounds responsible for functionality. The objective of this study was to establish the thermal stability of a novel dihydrochalcone, 3′,5′-di-β-d-glucopyranosyl-3-hydroxyphloretin (2), 3′,5′-di-β-d-glucopyranosylphloretin (3) and other Cyclopia subternata phenolic compounds, in model solutions with or without citric acid and ascorbic acid. The solutions were heated at 93, 121 and 135 °C, relevant to pasteurisation, commercial sterilisation and ultra-high temperature (UHT) pasteurisation, respectively. For most compounds, the acids decreased the second order reaction rate constants, up to 27 times. Compound 2 (46.29 ± 0.53 (g/100 g)−1 h−1), and to a lesser extent compound 3 (5.94 ± 0.01 (g/100 g)−1 h−1) were the most thermo-unstable compounds when treated at 135 °C without added acids. Even though differential effects were observed for compounds at different temperatures and formulations, overall, the phenolic compounds were most stable under UHT pasteurisation conditions.

Degradation of ciprofloxacin using UV-based advanced removal processes: Comparison of persulfate-based advanced oxidation and sulfite-based advanced reduction processes

In this study, the degradation of ciprofloxacin (CIP) in wastewater was investigated using UV-based sulfate radical advanced oxidation processes (SR-AOP) and UV-based advanced reduction processes (ARP). More specifically, a comparison of the UV-based persulfate advanced oxidation process (the UV/PS process) and the UV-based sulfite advanced reduction process (the UV/sulfite process) was made. Considering the UV-based SR-AOPs, the UV/PS process was much more efficient than the UV-based peroxymonosulfate advanced oxidation process (the UV/PMS process), with pseudo first order reaction rate constants (kobs) of 0.752 and 0.145 min−1, respectively. For the UV-based ARPs, the UV/sulfite process was the most efficient, compared to the UV/sulfide and the UV/dithionite process (kobs of 0.269, 0.0157 and 0.0329 min−1, respectively). The optimal process parameters for both the UV/PS and the UV/sulfite process were determined and the contribution of the produced reactive species were identified. For the UV/PS process, maximal CIP degradation was found at pH 8, and both OH and SO4− were responsible for CIP degradation. For the UV/sulfite process, H and eaq− were responsible for CIP degradation, with eaq− being the predominant radical at pH 8.5. Although CIP degradation was much faster for the UV/PS process, the UV/sulfite process was determined to be much more efficient in the defluorination of CIP.

Fabrication of electrochemically-modified BiVO4-MoS2-Co3O4composite film for bisphenol A degradation

A new electrochemically-modified BiVO4-MoS2-Co3O4 (represented as E-BiVO4-MoS2-Co3O4) thin film electrode was successfully synthesized for environmental application. MoS2 and Co3O4 were grown on the surface of BiVO4 to obtain BiVO4-MoS2-Co3O4. E-BiVO4-MoS2-Co3O4 film was achieved by further electrochemical treatment of BiVO4-MoS2-Co3O4. The as-prepared E-BiVO4-MoS2-Co3O4 exhibited significantly enhanced photoelectrocatalytic activity. The photocurrent density of E-BiVO4-MoS2-Co3O4 thin film is 6.6 times that of BiVO4 under visible light irradiation. The degradation efficiency of E-BiVO4-MoS2-Co3O4 for bisphenol A pollutant was 81.56% in photoelectrochemical process. The pseudo-first order reaction rate constant of E-BiVO4-MoS2-Co3O4 film is 3.22 times higher than that of BiVO4. And its reaction rate constant in photoelectrocatalytic process is 14.5 times or 2 times that in photocatalytic or electrocatalytic process, respectively. The improved performance of E-BiVO4-MoS2-Co3O4 was attributed to the synergetic effects of the reduction of interfacial charge transfer resistance, the formation of oxygen vacancies and sub-stoichiometric metal oxides and higher separation efficiency of photogenerated electron-hole pairs. E-BiVO4-MoS2-Co3O4 is a promising composite material for pollutants removal.

The influences of hexadecyl trimethyl ammonium bromide on lanthanum titanate photocatalyst for ofloxacin degradation

The use of template to introduce porous structure in titanate is a novel research topic, especially if photocatalytic activity of the material can be improved. The porous lanthanum titanate photocatalyst was synthesized using hexadecyl trimethyl ammonium bromide (HTAB) as the template in a sol–gel route. The addition of HTAB in the precursor could obviously influence the porous structure and surface morphology of the lanthanum titanate samples. All the samples were composed of perovskite La2Ti2O7, and crystallization of La2Ti2O7 was reduced with rising HTAB concentration. There was a slight enlargement in the band gap energy after using HTAB, and the chemical environments of the elements in the porous lanthanum titanate samples did not change. The enhancement in photocatalytic degradation efficiency was achieved on the lanthanum titanate samples obtained using HTAB. The first order reaction rate constants were increased from 0.0131 min−1 of the nonporous sample to 0.0253 min−1 of the porous sample. All the ofloxacin molecules were degraded on the porous lanthanum titanate sample after 120 min of reaction. Decomposition of ofloxacin in photocatalytic process was identified by the reduced absorption intensities of the organic groups in the UV–Vis spectra.

Sol-gel synthesis of suspensible titanium dioxide-hollow glass microsphere composites for photocatalytic degradation of Acid Red 1

Titanium dioxide was supported on hollow glass microspheres (HGM) via a sol-gel route to prepare xTiO2-HGM composites. The growth and aggregation of the anatase TiO2 crystals were restrained after supporting them. A thin layer of TiO2 was coated on the external surface of the hollow glass microspheres when the TiO2 content was not high. The absorption edges of the xTiO2-HGM composites moved to a shorter wavelength region with decreasing TiO2 content. The band gap energy of the TiO2 (3.21 eV) did not apparently change after loading on the hollow glass microspheres. The mesopores in the xTiO2-HGM composites were much larger than the pores in the TiO2 powders, and the pore size distribution in the xTiO2-HGM composites was broadened. The density of the xTiO2-HGM composites could be adjusted by altering the weight content of the TiO2. When the TiO2 content was more than 50% in the composites, the photocatalytic activity of the composites was very close to the activity of the TiO2 powders. The first order reaction rate constants were 0.00938, 0.0103 and 0.0121 min−1 for Acid Red 1 degradation on the 30TiO2-HGM, 50TiO2-HGM and TiO2 powders.

CTAB modified TiO2 supported on HZSM-5 zeolite for enhanced photocatalytic degradation of azophloxine

A thin layer of titanium dioxide was supported on HZSM-5 zeolite via a sol-gel route. Cetyltrimethyl ammonium bromide (CTAB) was used to improve the porosity of the supported anatase TiO2. The influences of CTAB on the physicochemical properties of TiO2(n)/HZSM-5 composites were examined. The SEM and TEM images proved the loading of TiO2 layer on the surface of HZSM-5 zeolite. The absorption edge of TiO2(n)/HZSM-5 composite prepared using CTAB moved to longer wavelength region, and the bandgap energies of the composites were approximately 3.0 eV. Both the surface area and the pore volume of TiO2(n)/HZSM-5 composites were enlarged after using CTAB. Micropores were produced in the TiO2 layer after removing CTAB during the calcination process. The number of hydroxyl radicals produced under irradiation was in accordance with photocatalytic activity of the composites, and the photoluminescence intensity was also related to photocatalytic activity of the composites. The TiO2(3)/HZSM-5 sample obtained using 3 g CTAB had the maximum activity. The first order reaction rate constants for azophloxine degradation were 0.02823, 0.01842 and 0.01456 min−1 for TiO2(3)/HZSM-5, TiO2(0)/HZSM-5 and TiO2, respectively. The major organic groups in azophloxine molecule were degraded on TiO2(3)/HZSM-5 after 90 min of reaction.

Interaction kinetics of selenium-containing compounds with oxidants

Selenium compounds have been identified as potential oxidant scavengers for biological applications due to the nucleophilicity of Se, and the ease of oxidation of the selenium centre. Previous studies have reported apparent second order rate constants for a number of oxidants (e.g. HOCl, ONOOH) with some selenium species, but these data are limited. Here we provide apparent second order rate constants for reaction of selenols (RSeH), selenides (RSeR′) and diselenides (RSeSeR’) with biologically-relevant oxidants (HOCl, H2O2, other peroxides) as well as overall consumption data for the excited state species singlet oxygen (1O2). Selenols show very high reactivity with HOCl and 1O2, with rate constants > 108 M−1 s−1, whilst selenides and diselenides typically react with rate constants one- (selenides) or two- (diselenides) orders of magnitude slower. Rate constants for reaction of diselenides with H2O2 and other hydroperoxides are much slower, with k for H2O2 being <1 M−1 s−1, and for amino acid and peptide hydroperoxides ~102 M−1 s−1. The rate constants determined for HOCl and 1O2 with these selenium species are greater than, or similar to, rate constants for amino acid side chains on proteins, including the corresponding sulfur-centered species (Cys and Met), suggesting that selenium containing compounds may be effective oxidant scavengers. Some of these reactions may be catalytic in nature due to ready recycling of the oxidized selenium species. These data may aid the development of highly efficacious, and catalytic, oxidant scavengers.

Significant enhancement of photo-Fenton degradation of ofloxacin over Fe-Dis@Sep due to highly dispersed FeC6 with electron deficiency

An efficient strategy for enhancing iron efficiency in heterogeneous Fenton reaction via the pyrolysis of ferrocene chemically modified sepiolite (Sep) was proposed in this study. Highly dispersed FeC6 on sepiolite (Fe-Dis@Sep) was synthesized as an efficient photo-Fenton catalyst for the visible light degradation of ofloxacin (OFX). It exhibits an excellent Fenton activity and stability towards OFX degradation. The pseudo-first order reaction rate constant of Fe-Dis@Sep was 5.1-fold higher than that of the supported catalyst with aggregated iron oxides prepared by traditional impregnation method (Fe-Agg@Sep). Based on TEM images and density functional theory (DFT) calculation, the enhanced Fenton activity of Fe-Dis@Sep was attributed to the unique incorporation of FeC6 on Sep via Si-O-C-Fe bond which not only favor the high dispersion of FeC6 with an electron deficiency but also promote Fe(III) to Fe(II) cycle via the formation of surface Fe-H2O2 complex. OH and O2- were identified as active species for OFX degradation in Fe-Dis@Sep-H2O2-Vis system. 98.7% of F and 97.0% of N in OFX was converted into F− and NO3− with a TOC removal efficiency of 89.35%. The possible degradation pathway of OFX was also proposed according to HPLC-MS results. Finally, the Fenton reaction mechanism over Fe-Dis@Sep was discussed.

One‐step hydrothermal synthesis of nitrogen doped reduced graphene oxide‐silver nanocomposites: Catalytic performance

The aim of this study is to efficiently utilize catalytic properties of silver nanoparticles and nitrogen doped graphene and their combined synergistic effect. For this purpose, nitrogen doped reduced graphene oxide‐silver (NrGO‐Ag) nanocomposites were synthesized by a facile, environmentally friendly, one‐pot hydrothermal method for the first time and characterized by UV–Vis, FTIR, XRD, XPS, SEM, and TEM. Catalytic activity of the synthesized nanocomposites was tested against 4‐nitrophenol (4‐NP) and methylene blue (MB) reduction reactions in the presence of NaBH4. Total degradation was achieved in both reactions in 210 and 44 s, and pseudo first order reaction rate constants were calculated as 0.0071 and 0.0322 s−1 for 4‐NP and MB reduction reactions, respectively.

Degradation of Organic Cibacron Navy FN-B Dye by Photocatalysis Process Using ZnS

The photocatalysis process was studied in this research. UV irradiation as the illumination source was investigated to remove the Cibacron Navy FN-B organic dye from simulated wastewater using Zinc Sulfide treated with Hydrogen Peroxide as the catalyst. Four sets of experiments were conducted throughout the work; the effect of pH (4, 6, 8, and 10), ZnS dosage (0.5, 1.0, 1.5, and 2.0 gm), the initial concentration of dye (25, 50, 75, and 100 mg/L), and the concentration of H2O2 (0, 50, 100, 150, and 200 mg/L) on the photocatalysis process was examined. The effect of contact time was studied implicitly within the sets (0, 15, 30, 45, 60, 75, and 90 min). The optimum conditions for the best decolorization of dye were found to be as: pH=6.2 (the normal pH of the dye solution), ZnS=1.5gm, Co=25mg/L and H2O2=200mg/L, the decolorization of Navy dye increased with increasing the contact time with the ZnS. The addition of H2O2 enhanced the decolorization rate by 8%. A mechanism of the Navy dye degradation in the UV photocatalysis system was proposed. The Pseudo first order reaction rate was found to be applicable on the process and the first order reaction rate constant (k) was found to be 0.033 min−1 with a correlation coefficient of 97.3%.

Surface weak acid-base pair of FeOOH/Al2O3 for enhanced peroxymonosulfate activation in degradation of humic substances from water

Three oxides (SiO2, Al2O3 and FeOOH/Al2O3) made of earth-abundant elements (O, Si, Al and Fe) were prepared to activate peroxymonosulfate (PMS). Humic acid (HA) as a representative of humic substances in water was used to evaluate their PMS activation performance. FeOOH/Al2O3 exhibited the highest catalytic activity towards HA degradation with a pseudo-first order reaction rate constant of 0.0204 min−1, but almost no HA was degraded over SiO2. The results of Electron Spin Resonance (ESR) analysis and radical quenching experiments verified that singlet oxygen (1O2) was the sole reactive species for HA degradation. The relationship between surface properties of tested oxides and their PMS activation efficiency was investigated. According to the characterization results of powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), nitrogen adsorption-desorption experiment, temperature programmed desorption of adsorbed CO2 (CO2-TPD) and Pyridine-FTIR spectroscopy, the surface acid-base property was proven to be responsible to excellent PMS activation performance of FeOOH/Al2O3 for 1O2 generation. A dual-reaction-site mechanism was proposed and the contribution of weak Lewis acid site and weak basic site to HA degradation in PMS-FeOOH/Al2O3 system was discussed based on all the experimental results.

Supporting B–TiO2 on iM16K glass bubbles to prepare B–TiO2(x%)/iM16K hollow spheres for ofloxacin degradation

B–TiO2(x%)/iM16K hollow spheres were prepared by loading boron-doped TiO2 on iM16K glass bubbles using a sol-gel route. The density of the hollow spheres was controlled by changing the content of B–TiO2 in the composite material to facilitate photocatalyst-water separation after treatment. The loading of B–TiO2 on the surface of iM16K glass bubbles results in a slight shrinkage in anatase TiO2 cell volume and crystallite size. The distribution of the B–TiO2 layer on the surface of the iM16K glass bubbles is proven by EDS (energy dispersive spectrometry) mapping. The band gap energies of B–TiO2, B–TiO2(50%)/iM16K and B–TiO2(20%)/iM16K are 2.83, 2.97 and 3.10 eV. The N2 adsorption-desorption isotherms of B–TiO2(x%)/iM16K and B–TiO2 present the classical type IV isotherm that is subjected to mesoporous material. All the materials with different B–TiO2 contents have a narrow pore size range between 2 and 7 nm, and the porosity in the B–TiO2 layer is higher than the porosity in the B–TiO2 powder. The first order reaction rate constants for photocatalytic degradation of ofloxacin on B–TiO2(20%)/iM16K, B–TiO2(50%)/iM16K and B–TiO2 powder are 0.00861, 0.0233 and 0.0248 min−1, respectively. All the ofloxacin molecules can be almost degraded after 180 min of reaction on both B–TiO2(50%)/iM16K and B–TiO2 powder. UV–Visible and FTIR spectra of the ofloxacin solution during photocatalytic oxidation indicate decomposition of major functional groups in the ofloxacin molecule. Disruption of the C–F bond and the C–N bond results in the formation of F−, NH4+ and NO2− ions.

Ozonation of trace organic compounds in different municipal and industrial wastewaters: Kinetic-based prediction of removal efficiency and ozone dose requirements

For the wide application of ozonation in (industrial and municipal) wastewater treatment, prediction of trace organic compounds (TrOCs) removal and evaluation of energy requirements are essential for its design and operation. In this study, a kinetics approach, based on the correlation between the second order reaction rate constants of TrOCs with ozone and hydroxyl radicals (OH) and the ozone and OH exposure (i.e., ∫[O3]dt and ∫[OH]dt, which are defined as the time integral concentration of O3 and OH for a given reaction time), was validated to predict the elimination efficiency in not only municipal wastewaters but also industrial wastewaters. Two municipal wastewater treatment plant effluents from Belgium (HB-effluent) and China (QG-effluent) and two industrial wastewater treatment plant effluents respectively from a China printing and dyeing factory (PD-effluent) and a China lithium-ion battery factory (LZ-effluent) were used for this purpose. The OH scavenging rate from the major scavengers (namely alkalinity, effluent organic matter (EfOM) and NO2−) and the total OH scavenging rate of each effluent were calculated. The various water matrices and the OH scavenging rates resulted in a difference in the requirement for ozone dose and energy for the same level of TrOCs elimination. For example, for more than 90% atrazine (ATZ) abatement in HB-effluent (with a total OH scavenging rate of 1.9 × 105 s−1) the energy requirement was 12.3 × 10−2 kWh/m3, which was lower than 30.1 × 10−2 kWh/m3 for PD-effluent (with the highest total OH scavenging rate of 4.7 × 105 s−1). Even though the water characteristics of selected wastewater effluents are quite different, the results of measured and predicted TrOCs abatement efficiency demonstrate that the kinetics approach is applicability for the prediction of target TrOCs elimination by ozonation in both municipal and industrial wastewater treatment plant effluents.

Sol–gel synthesis of B-TiO2(20%)/HZSM-5 composite photocatalyst for azophloxine degradation

Photocatalyst in the supported form is more meaningful in large scale wastewater treatment than using powder material. HZSM-5 zeolite was used to support boron-doped anatase TiO2 in a sol–gel route in this work. The supported B-TiO2(20%)/HZSM-5 composite photocatalyst has strong activity on azophloxine degradation. The crystallite size of anatase TiO2 slightly increased from 6.1 to 8.4 nm when calcination temperature rose from 350 to 450 °C. The bandgap energies were around 3.3 eV for the composites calcined between 350 and 600 °C. The adsorption–desorption isotherm of the composites was the type IV isotherm for mesoporous material. The porous structure in the supported B-TiO2 layer was responsible for the variations of both BET surface area and pore volume in the composite. The maximum photocatalytic activity was obtained on the sample calcined at 450 °C. After 30 min of irradiation, 61.8% of the initial azophloxine molecules were degraded on the material. The first order reaction rate constant was 0.06168 min−1. Photocatalytic degradation efficiency was enhanced with increasing B-TiO2 concentration when the B-TiO2 dosage was below 400 mg/L.

Evaluation of process influencing factors, degradation products, toxicity evolution and matrix-related effects during electro-Fenton removal of piroxicam from waters

The degradation kinetics, the operational influencing factors, the determination of short-chain organic by-products, the mineralization degree, the evolution of residual toxicity, as well as the treatment of complex matrices were systematically investigated on removal of piroxicam by Electro-Fenton process (EF), due to its persistence and low removal in water matrices. The second order reaction rate constant between piroxicam and hydroxyl radical (•OH) was determined as (2.19 ± 0.01) × 109 M−1 s−1. It was found that the process was able to almost completely mineralize 0.08 mM piroxicam solution (92% TOC removal) at 6 h treatment. Based on identification of short-chain carboxylic acids, released inorganic ions and the removal of total organic carbon, a schematic proposal of piroxicam degradation by EF treatment was done. The evolution of the acute toxicity of treated piroxicam solution was monitored by Microtox method, showing a significant toxicity reduction at 180 min treatment. Remarkably, piroxicam in simulated urine and hospital wastewater was completely degraded after 120 min of EF treatment. Therefore, the results indicate that the tested EF process constitutes an efficient option for the elimination of piroxicam in aqueous media.

Carbon quantum dots @ Pd-SnS2 nanocomposite: The role of CQDs @ Pd nanoclusters in enhancing photocatalytic reduction of aromatic nitro compounds

2D layered SnS2 is one of the most popular semiconductor photocatalysts. However, its performance on photocatalytic reduction of aromatic nitro compounds is unsatisfactory, due to charge carrier recombination and weak adsorption of active hydrogen from the hydrolysis of NaBH4. Herein, we have prepared CQDs @ Pd nanoclusters with Pd nanoparticles below 5 nm through an in-situ reducing Pd(Ⅱ) with CQDs containing some oxygen-containing groups at first. CQDs @ Pd-SnS2 is achieved through a strong interaction of sulfur ions bonding on nanometric Pd surface. The composite shows a stable and efficient visible-light-driven catalytic reduction of aromatic nitro compounds in H2O and NaBH4. Under 40 min visible light irradiation, the conversion rate of 4-NP attains 99.7% on CQDs @ Pd-SnS2. The first order reaction rate constant is 0.0332 min−1, 586.5, 202.4 and 31.9 times that on SnS2, CQDs-SnS2 and Pd-SnS2 in the condition of 20 mg·L−1 4-NP and excess NaBH4, respectively. The significant enhancement is ascribed to CQDs @ Pd promoting the charge carrier separation on SnS2 and increasing the adsorption of active hydrogen from the hydrolysis of NaBH4.

H2O2 and γ-radiation induced corrosion of 304L stainless steel in aqueous systems

In light-water reactors the water used as neutron moderator and coolant is subjected to a constant radiation field which leads to the formation of a number of oxidizing and reducing species. In this work, the reactivity of the radiolysis product H2O2 towards the 304L alloy, commonly used for structural materials in nuclear power plants, was investigated as well as oxidative dissolution of steel components as a consequence of γ-radiation and chemically added H2O2. The concentration of hydrogen peroxide as a function of time was monitored in the presence of different amounts of steel powder, and the second order reaction rate constant was determined to k2 = (1.8 ± 0.2) × 10−10 m s−1. In the case of catalytic decomposition of hydrogen peroxide, hydroxyl radicals are formed which can be scavenged by methanol. In this reaction formaldehyde is formed, which can be detected spectroscopically. A high yield of formaldehyde was observed, indicating that catalytic decomposition is the main reaction path of H2O2 in the current system. A significant contribution of the homogeneous Fenton reaction to both the reaction rate constant and the formaldehyde formation must however be considered, as Fe(II) will be released from the oxide layer in solution. In the case of γ-irradiation, an increased nickel content in solution compared to background experiments is seen. When the steel is subjected to chemically added hydrogen peroxide on the other hand, the chromium content in solution is increased. This indicates that the different types of exposure will impact different parts of the oxide layer characterized by different composition.

Determination of exothermic batch reactor specific model parameters

An alternative method of determining exothermic reactor model parameters which include first order reaction rate constant is described in this paper. The method is based on known in reactor temperature development and is suitable for processes with changing quality of input substances. This method allows us to evaluate the reaction substances composition change and is also capable of the reaction rate constant (parameters of the Arrhenius equation) determination. Method can be used in exothermic batch or semi- batch reactors running processes based on the first order reaction. An example of such process is given here and the problem is shown on its mathematical model with the help of simulations.