Initial Peroxide Concentration Research Articles

Fenton-like oxidation of Reactive Black 5 using rice husk ash based catalyst

Fenton-like oxidation of Reactive Black 5 dye was carried out using iron(III) impregnated on rice husk ash as heterogeneous catalyst. The catalyst was prepared by wet impregnation method and characterized. The effectiveness of this catalyst in degradation and decolorization of the dye, as well as the influence of reaction parameters on the catalytic activity was discussed. The effects of pH, the initial hydrogen peroxide concentration, the catalyst loading, and the temperature on the oxidative degradation and decolorization of Reactive Black 5 have been assessed. The best degradation efficiency (59.71%) and decolorization efficiency (89.18%) was obtained at temperature=30°C, pH=3, [H2O2]0=4mM, catalyst loading=0.5g/L for initial dye concentration of 100mg/L.

Discoloration of Methyl Orange in the Presence of Schorl and H2O2: Kinetics and Mechanism

Kinetics and mechanism on discoloration of an azo dye, methyl orange (MO), by heterogeneous Fenton-like reaction using natural schorl as catalyst were investigated in this study. Among the three kinetic models (the first-order, the second-order, and the Behnajady–Modirshahla–Ghanbery (BMG)), the BMG kinetic model was the best one to describe MO discoloration at different reaction conditions, due to its highest determination coefficients. The BMG model parameter, 1/m, increased with initial hydrogen peroxide (H2O2) concentration, and schorl dosage and reaction temperature increased while the pH solution decreased. The phenomenon indicated that the initial MO discoloration rate increased with the ascending of the initial H2O2 concentration, schorl dosage, and reaction temperature and the descending of the pH solution. Meanwhile, another BMG parameter, 1/b, except for the one at pH = 5, were all around 1, implying that the schorl-catalyzed Fenton-like reaction had high capacity for MO discoloration. The possible reason for these phenomena was interpreted from the point of view of OH generation and Fe dissolution. Generally speaking, the amount of hydroxyl radicals increased with initial H2O2 concentration, increased schorl dosage and reaction temperature, and decreased pH solution, playing an important role in the change of 1/m values. The concentration of soluble iron ions at all adopted experimental conditions ranged from 0.23 to 1.14 mg/L, much lower than the European Union directive (2 mg/L), which demonstrated that natural schorl would be a promising heterogeneous catalyst for the Fenton-like reaction. Finally, a possible mechanism for this process was put forward.

Enhanced mineralization of atrazine by means of photodegradation processes using solar energy at pilot plant scale

Abstract Atrazine is a highly persistent and carcinogenic compound used as herbicide around the world. This compound has been banned in USA and some European countries but in Mexico it is still widely used in the agriculture. In order to achieve a high mineralization of atrazine, present as active compound in the Gesaprim commercial herbicide, detoxification studies in two-compound parabolic solar reactors by means of photo-Fenton process followed by TiO 2 photocatalysis was carried out. The atrazine contents in the Gesaprim solutions tested were 35 mg L −1 (19.0 mg L −1 of TOC) and 20 mg L −1 (9.5 mg L −1 of TOC). [H 2 O 2 ] 0 /COD 0 ratios of 1, 3 and 5 (1.5 × 10 −3 , 4.5 × 10 −3 and 7.5 × 10 −3 mol L −1 H 2 O 2 , respectively) were evaluated in combination with 5 mg L −1 and 10 mg L −1 Fe 2+ at pH 2.8 in the photo-Fenton oxidation; whereas, in the photocatalytic process, the influence of the pH (4.8, 7.0 and 11.0) and type of TiO 2 (Degussa P25 and HB) were studied with TiO 2 content of 200 mg L −1 . The study showed that photo-Fenton process followed by TiO 2 photocatalysis produce a 72% of mineralization (for an initial TOC of 19 mg L −1 ) and decrease above 90% of toxicity in compliance with NMX-AA-110-1995-SCFI1 Mexican Norm. In order to established a minimum amount of chemical reagents these photodegradation processes were carried out with special emphasis on the optimization of experimental parameters such as concentrations of photocatalyst and oxidant. Atrazine mineralization was influenced by the pH of the solution, the initial concentration of hydrogen peroxide and iron ions.

Iron-clay as a reusable heterogeneous Fenton-like catalyst for decolorization of Acid Green 25

Decolorization of Acid Green 25 (AG25) was achieved by using Fe-Ipoh clay (Fe-IC) as catalyst on Fenton-like process. The catalyst was prepared by impregnation method and was characterized.The effect of various parameters such as catalyst calcination temperature and duration of time, pH, initial concentration of hydrogen peroxide (H2O2) and AG25, catalyst dosage, and reaction temperature was studied. The best performance of AG25 decolorization was found to be 95% after 2 h of reaction by using 1.25 g/L catalyst dosage of Fe-IC calcined at 500°C for 6 h and 6.7mM of H2O2 at pH 3. Besides, the developed catalyst also indicated an advantage of low iron leaching and ability for reuse up to three runs, with slightly reduced decolorization of AG25 from 95 to 93% at the same reaction time.

Development of MWD and branching during peroxide modification of High-Density Polyethylene by SEC-MALS and Monte Carlo simulation

During the reactive processing of HD Polyethylene molecules are known to form branched structures, eventually resulting in a MFI decrease. This phenomenon was studied by experiments in a twin-screw extruder and measurement of the MWD by SEC-MALS. A Monte Carlo simulation model has been setup to calculate the MWD and branching distribution. The model includes both branching and random scission. Branch points are assumed to be created by coupling of vinyl ends of linear PE to secondary radical sites on PE backbones, yielding tertiary radical sites that undergo termination by disproportionation. This mechanism was recently proposed by Camara et al. [1]. Comparing the computed MWD to SEC-MALS data allowed determining the kinetic coefficients of the branching and scission reactions. Random scission turns out to be weak but still significant to prevent the formation of an extended MWD tail. For the found parameters perfect agreement was found between measured and computed MWD for various initial peroxide concentrations. These findings contribute to a better fundamental understanding of the simultaneous branching and scission during PE modification. It forms a firm support of the vinyl end to secondary radical coupling branching mechanism. Furthermore, it is shown that the MC simulations provide explicit branching topologies as a basis for predicting, for instance, complex rheological behavior of the modified polymer melt (Read et al. [2]).

The influence of hydrogen peroxide initiator concentration on the structure of eucalyptus lignosulfonate

In order to improve lignin-based materials’ utilization, the grafting mechanism of lignin was studied by investigating hydrogen peroxide (H2O2) initiator's effect on the structure of eucalyptus lignosulfonate calcium (HLS). HLS was treated by low content of H2O2 (H2O2/HLSwt=1%, 2%, 4%) under various reaction temperature and time. Changes in HLS structure were investigated by difference UV, UV, FTIR, 1H NMR, GPC and intrinsic viscosity. The results showed that though phenolic hydroxyl group (Ph-OH) of HLS was not oxidated to the quinoid structure, its content still decreased after treated by H2O2 initiator. Meanwhile, the new aryl–alkyl ether structures and increased average molecular weight were observed. A radical coupling mechanism for the decreasing Ph-OH group's content was proposed, which radicals may terminate between phenoxy and benzyl radicals. In addition, the cleavage of methoxyl-aryl ether made a decline in the content of syringyl units, while that of guaiacyl, p-hydroxyphenyl units and free aromatic C-5 hydrogen increased when HLS reacted with H2O2.

Mineralization and efficiency in the homogeneous Fenton Orange G oxidation

This study focuses on the homogeneous Fenton oxidation of the synthetic azo-dye Orange G as a model compound. The impact of initial TOC, hydrogen peroxide and catalyst concentrations and of temperature on mineralization and efficiency in the use of hydrogen peroxide is addressed. Dissolved oxygen concentration is monitored as an indication of the efficient use of H2O2 in the process. A two-stage lumped kinetic model is proposed to address the effect of initial TOC, catalyst and oxidant concentrations and temperature on total organic carbon consumption. Temperature increase and dosification of the oxidant are evaluated and compared as process intensification strategies.

가축 사체 매몰지 침출수 처리를 위한 Fenton 산화공정의 최적조건

Outbreak of animal infectious diseases such as foot-and-mouth disease, avian influenza are becoming prevalent worldwide. For prevent the further infection, tremendous numbers of the infected or culled stocks are buried around farm. This burial method can generate a wide range of detrimental components such as leachate, nutrient, salt, and pathogenic bacteria, consequently. In this study, for the stabilization of livestock carcasses leachate, advanced oxidation processes utilizing the Fenton reaction was investigated in lab-scale experiments for the treatment for CODCr of livestock carcass leachate. CODCr reduction by the Fenton oxidation was investigated response surface methodology using the BoxBegnken methods were applied to the experimental results. A central composite design was used to investigate the effects of the independent variables of pH (x1), dosage of FeCl2· 4H2O (x2) and dosage of H2O2 (x3) on the dependent variables CODCr concentration (y1). A 1 M NaOH and H2SO4 was using for pH control, FeCl2·4H2O was used as iron catalyst and NaOH was used for Fenton reaction. The optimal conditions for Fenton oxidation process were determined: pH, dosage of FeCl2·4H2O and dosage of H2O2 were 3, 0.6 g (0.0151 M) and 7 mL(0.259 M), respectively. Statistical results showed the order of significance of the independent variables to be pH > initial concentration of ferrous ion > initial concentration of hydrogen peroxide.

Effective pharmaceutical wastewater degradation by Fenton oxidation with zero-valent iron

The pre-treatment of a pharmaceutical wastewater (PWW) by Fenton oxidation with zero-valent iron (ZVI) and hydrogen peroxide was investigated to improve the degradation of the complex-mixture of organic compounds present in the wastewater. The influence of different crucial parameters such as the initial hydrogen peroxide concentration, the ZVI concentration and the capacity of the ZVI/H2O2 system to treat different organic loading have been evaluated. The optimal conditions for degradation led to TOC reductions of up to 80% in only 1h of treatment. This degree of organic mineralization was reached by using moderate loadings of ZVI and hydrogen peroxide (ZVI/TOC weight and H2O2/TOC molar ratios of 12 and 3.2, respectively). Moreover, the use of waste-metallic iron shavings in terms of TOC removal compared to commercial ZVI powder may be a promising and cheaper development.

Kinetic modelling on CI acid blue-113 dye degradation by acoustic and hydrodynamic cavitations

The objective is to study the effect of certain parameters on the degradation rate of the dye CI acid blue 113 by cavitation processes. Kinetic models have been developed and validated for ultrasonic and hydrodynamic cavitation treatment with hydrogen peroxide to enhance oxidation. The magnitude of effect of the reaction parameters in acoustic cavitation for geometric ratio, pH, ultrasonic density, initial dye concentration and hydrogen peroxide concentration were –0.4370, –1.2455, 0.1140, –0.3741 and 0.2788. In the case of hydrodynamic cavitation, values for initial dye concentration, pH, inlet pressure, power density and hydrogen peroxide concentration were –0.2562, –0.1494, 0.4556, 0.4807 and 0.1681. Finally, the energy efficiencies of the two processes have been compared. Hydrodynamic cavitation was found to be energy efficient than acoustic cavitation.

Chemoenzymatic Epoxidation of α-Pinene Catalyzed by Novozym 435

The synthesis of α-pinene oxide mediated by Novozym 435 (lipase from Candida antarctica) in a three-phase system was studied in this work. Novozyme 435 catalysed the formation of peroxyoctanoic acid directly from octanoic acid and hydrogen peroxide, which was then applied for in situ oxidation of α-pinene. The highest conversion of a-pinene (approximately 80%) was obtained when the reaction was performed at 30°C and initial hydrogen peroxide concentration in the water phase was set to be 30%. The parameters affecting the lipase activity were also investigated，where the peracid generated in organic phase was obvserved to greatly inactivate the enzyme compared to other components in the organic phase.

Hydrothermal Degradation of Congo Red in Hot Compressed Water and its Kinetics

A di-azo dye, Congo Red (CR) was used as a model compound to investigate the degradation mechanism in hot compressed water (HCW). The unique properties of HCW facilitated the degradation efficiency without addition of any organic solvent. The influences of reaction time, temperature, initial dye concentration and amount of hydrogen peroxide (H2O2) on the degradation of CR and the removal of total organic carbon (TOC) from the product solution were investigated. The presence of H2O2 was found to enhance the degradation of CR. The results showed that the degradation yield could reach 99.0% with a solution of 100 ppm CR and 50 mM H2O2 at 150°C at the end of 60 min. Maximum conversion of the total organic carbon was recorded as 62.2%. Moreover, the effect of the presence of several co-existing negative ions such as SO4 2-, Cl-, CO32- were investigated. It was found that the presence of SO42- accelerated evidently the degradation of CR. The other chosen anions (CO32- and Cl-) had an inhibitory effect on the decolorization of CR. Finally, kinetic study was carried out and the order of the reaction was calculated as 0.37.

Thermodynamic analysis of the hydrogen peroxide decomposition parameters

This paper discusses the estimation of the decomposition parameters of the liquid–gas-steam system, which is produced by the hydrogen peroxide decomposition at isobar conditions. The thermodynamic analysis calculates the two critical concentrations, which mark the phase transitions of the system depending on the initial pressure and hydrogen peroxide concentration.

Photocatalytic degradation of azo dye Reactive Red 15 over synthesized titanium and zinc oxides photocatalysts: a comparative study

Abstract Nanoparticle TiO2 and ZnO were prepared by facile method. The XRD patt ern study shows that there is no obvious diff erence in crystal composition of various shapes of TiO2 and ZnO. The photocatalytic degradation of Reactive Red 15, commonly used as a textile dye, using synthesized titanium and zinc oxides was investigated. The effects of influential parameters such as initial pH, catalyst loading, initial dye concentration and addition of hydrogen peroxide were studied. The degradation efficiency was expressed by the removal of color and chemical oxygen demand (COD). The study reveals that: (1) Both catalysts, under corresponding optimal conditions, can be employed as an effective photocatalyst for the elimination of color and COD from dye wastewater. Also, ZnO is more efficient catalyst than TiO2; (2) Addition of proper amount of hydrogen peroxide improves both the decolorization and the degradation of the dye; (3) The photocatalytic degradation of Reactive Red 15, in the presence of both photocatalysts, obeyed pseudo-first order kinetics. The biodegradability ratio BOD5/COD increases from original zero up to 0.52 and 0.6 within 90 minutes irradiation time using 1 and 0.75 g/L TiO2 and ZnO, respectively.

Method of removal of volatile organic compounds by using wet scrubber coupled with photo-Fenton reaction – Preventing emission of by-products

The photo-Fenton reaction was applied as a novel method for the removal of volatile organic compounds (VOCs) in the gas phase, and its effectiveness was experimentally examined. In conventional VOCs removal methods using a photocatalyst or ozone, VOCs are oxidized in the gas phase. Therefore, incompletely oxidized intermediates, which may have adverse effects on health, are likely to contaminate the treated air. On the other hand, in the VOCs removal method developed in this study, because the VOCs are oxidized in the liquid phase by the photo-Fenton reaction, any incompletely oxidized intermediates produced are confined to the liquid phase. As a result, the contamination of the treated air by these harmful intermediates can be prevented. Using a semi-batch process, it was found that the removal efficiency for toluene in a one-pass test (residence time of 17s) was 61%, for an inlet toluene gas concentration of 930ppbv, an initial iron ion concentration of 20mgL−1, and an initial hydrogen peroxide concentration of 630mgL−1. The removal efficiency was almost constant as long as H2O2 was present in the solution. Proton transfer reaction mass spectrometry analysis confirmed the absence of any incompletely oxidized intermediates in the treated air.

A 3D Simulation Analysis of Reactive Flow in Screw Elements of Closely Intermeshing Twin Screw Extruders

Abstract The peroxide-initiated degradation of polypropylene in conventional screw elements of closely intermeshing twin-screw extruders is analyzed by means of a three-dimensional (3D) simulation approach. The 3D simulations of the reacting flow are implemented under the assumption of steady-state flow conditions, and scale-up considerations are addressed by simulating screw elements of two different size extruders. The effects of the initial peroxide concentration and reference mass throughputs on processing parameters are analyzed in terms of the specified extruder size. In this study, the scaled-up mass throughput is determined under the assumption of constant residence time. For the implemented processing conditions, the final values of the weigh-average molecular weight (Mw) and polidispersity index (PDI) for both the reference and scaled-up screw elements are similar when the flow rate is close to that corresponding to the maximum conveying capacity of the screw elements. For more restricted flow conditions, however, lower values of both the Mw and PDI are obtained for the larger screw element. Additionally, a previously proposed scale-up procedure from one-dimensional (1D) simulations is evaluated by means of a 3D simulation analysis. The results of this evaluation show a good agreement between the trend of the 3D and 1D simulation results.

Reactivity of the H2O2/B(OH)3/HO- system in the decomposition of 4-nitrophenyl esters of diethylphosphonic and diethylphosphoric acids

The kinetics of the decomposition of 4-nitrophenyl diethylphosphonate and 4-nitrophenyl diethyl phosphate by the H2O2/B(OH)3/HO– system with wide variation of the pH and the initial concentrations of H2O2 and B(OH)3 (water, 25°C) was studied. Additions of boric acid either weakly accelerate the reaction or retard it, depending on the ratio of the initial concentrations of hydrogen peroxide and boric acid and on the nature of the substrate. The peroxoborate anions (HO)3BOOH–, (HO)2B(OOH) 2 – , and (HO)3BOOB(OH) 3 2– anions generated by this system do not affect the decomposition rate of the substrates. In both substrates linear relationships were found between the observed rate constants k and the concentrations of peroxide anion.

Cyclic organic peroxides thermal decomposition in the presence of CuFe2O4 magnetic nanoparticles

The effect of magnetically recoverable CuFe2O4 nanoparticles on thermal decomposition of acetone and pinacolone cyclic organic diperoxides, and acetone triperoxide was studied. Ethanol, toluene or ethylbenzene were used as reaction solvents, the initial peroxide concentration was ca. 0.02molL−1 and the amount of heterogeneous catalyst added was ca. 0.5mgmL−1. CuFe2O4 nanoparticles, obtained according to the citric acid-aided process, greatly accelerates the thermal decomposition of methyl substituted cyclic peroxide, but in the case of pinacolone diperoxide only slightly catalytic effects can be detected, probably due to the presence of the bulky tert-butyl substituent in the proximity of the OO bond. This heterogeneously catalyzed reaction can be explained by a free radical mechanism which involves the initiation reaction on the catalyst surface. The products detected (ethane, 2,2-dimethylpropane, ethylbenzene, bibenzyl and 2,3-diphenylbutane) can be interpreted in terms of the initial OO bond homolysis catalyzed by copper ferrites to form an iron peroxo radical species which later undergoes CO and CC bond cleavage. The reduction of the reaction temperature in the styrene and methylmethacrylate polymerization processes could be the main application of the results obtained in the present work, where the thermal decomposition of multifunctional cyclic peroxides in the presence of copper ferrites can be reached decreasing the working temperatures.

Free‐radical grafting of trans‐ethylene‐1,2‐dicarboxylic acid onto molten ethylene‐vinyl acetate copolymer

AbstractDistinctive features of free‐radical grafting of trans‐ethylene‐1,2‐dicarboxylic acid (TEDA) onto macromolecules of molten ethylene‐vinyl acetate copolymer (EVA) in the course of reactive extrusion have been investigated along with structure, mechanical characteristics, and high‐elastic properties of molten functionalized products (EVA‐g‐TEDA). It is shown that EVA‐g‐TEDA yield depends on both the peroxide initiator concentration and content of vinyl acetate units in the copolymer molecular structure. At functionalization, acid grafting is accompanied by secondary reactions of macromolecular degradation and crosslinking. With a low‐peroxide initiator concentration (0.1 wt %), degradation prevails; with a higher (0.3 wt %) concentration, crosslinking of macromolecules prevails. It is reported that monomers being grafted attach mostly over secondary carbon atoms in the polymer chain. EVA‐g‐TEDA appears to have a less perfect crystal structure with a lower‐melting temperature and crystallinity as against the starting polymer. The functionalized products display enhanced rigidity and lower deformability in comparison with the initial copolymer. Variations in the swelling ratio and melt strength of EVA‐g‐TEDA depend on the course of competing secondary processes of macromolecular degradation and crosslinking. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Grafting of maleic anhydride onto an ethylene‐propylene‐diene terpolymer and concurrent organoclay nanocomposite preparation in solution and melt

AbstractThe possibility of simultaneous peroxide‐initiated grafting of MAH (maleic anhydride) onto EPDM (ethylene‐propylene‐diene terpolymer) and EPDM/clay nanocomposite synthesis by the solution and melt process is investigated. Montmorillonite organoclay is used. Maleation efficiency is investigated by infrared spectroscopy. Clay exfoliation and the resulting nanocomposite properties are determined by X‐ray diffraction and dynamic mechanical analysis, respectively. Simultaneous grafting and exfoliated nanocomposite synthesis can be carried out in solution and melt. The use of optimal amounts of initiator and MAH is very important. High peroxide initiator concentration causes extensive EPDM crosslinking and scission reactions. High concentration of MAH deteriorates clay exfoliation in melt because of reduced shearing due to MAH addition. The use of low MAH concentration is a straightforward solution if the extent of MAH grafting onto EPDM is not considerably impaired. To overcome this problem, a two step melt compounding process is suggested and tried out. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013