Verification of competitive kinetics technique and oxidation kinetics of 2,6-dimethyl-aniline and o-toluidine by Fenton process

The competitive kinetics technique is shown to be a useful and reliable tool for determining rate constants. Regardless of the conditions of the reaction and the operation mode, the intrinsic second-order rate constants of 2,6-dimethyl-aniline and hydroxyl radicals were 1.65 × 10(10), 1.60 × 10(10), and 1.71 × 10(10)M(-1)s(-1) in the absence of SiO(2) under complete-mix conditions, in the presence of SiO(2) under complete-mix conditions, and in a fluidized-bed Fenton reactor with SiO(2) as the media, respectively, demonstrating that the rates are comparable under a variety of reaction conditions. The average intrinsic second-order rate constant of o-toluidine and hydroxyl radicals obtained in a homogeneous system under various conditions was 7.36 × 10(9)M(-1)s(-1), indicating that o-toluidine is less susceptible to hydroxyl radicals than 2,6-dimethyl-anilne. Hydroxyl radicals primarily attacked the amine group rather than the methyl group of the o-toluidine to form o-cresol and 2-nitrotoluene, which sequentially transformed to carboxylic acids including acetic, oxalic, lactic, and maleic acids after the collapse of the benzene ring.     

Chemical oxidation of 2,4-dimethylphenol in soil by heterogeneous Fenton process

Hydrogen peroxide has been used to oxidize a sorbed aromatic contaminant in a loamy sand with 195.9 g kg(-1) of organic carbon by using iron as catalyst at 20 degrees C. The 2,4-dimethylphenol (2,4-DMP) was chosen as pollutant. Because of this soil generates a slightly basic pH in contact to an aqueous phase the solubility of the iron cation was determined in absence and presence of a chelating agent (l-ascorbic acid, l-Asc) and with and without soil. From results, it was found that in presence of soil the iron cation was always adsorbed or precipitaed onto the soil. Therefore, the procedure selected for soil remediation was to add firstly the iron solution used as catalyst and following the hydrogen peroxide solution used as oxidant. As iron cation is sorbed onto the soil before the oxidant reagent is provided a heterogeneous catalytic system results. This modified Fenton runs have been carried out using 0.11 mg(2,4-DMP) g(-1)(soil) and 2.1 mg(Fe) g(-1)(soil). The H(2)O(2)/pollutant weight ratios used were 182 and 364. The results show that H(2)O(2) oxidizes 2,4-DMP producing CO(2) and acetic acid. After 20 min of reaction time a pollutant conversion of 75% and 86% was found, depending on the H(2)O(2) dosage. Moreover, it was found that hydrogen peroxide was heterogeneously decomposed by the soil (due to its organic and/or inorganic components) and its decomposition rate decreases when the iron was previously precipitated-impregnated into the soil.     

有机改性凹凸棒石吸附活性艳蓝KN-R的动力学研究

通过静态吸附实验方法,研究了有机改性凹凸棒石吸附活性艳蓝KN-R的动力学行为。研究结果表明:准二级动力学模型能很好地描述活性艳蓝KN-R在有机改性凹凸棒石上的动力学行为,平衡吸附量q2随着KN-R初始浓度、振荡速度、温度的增加而增加。有机改性凹凸棒石吸附活性艳蓝KN-R主要是外表面吸附,吸附活化能为39.2kJ/mol,说明其为物理吸附、化学吸附综合作用的过程,其速率由化学过程与外扩散共同控制。     

A kinetic study on the degradation of p-nitroaniline by Fenton oxidation process

A detailed kinetic model was developed for the degradation of p-nitroaniline (PNA) by Fenton oxidation. Batch experiments were carried out to investigate the role of pH, hydrogen peroxide and Fe(2+) levels, PNA concentration and the temperature. The kinetic rate constants, k(ap), for PNA degradation at different reaction conditions were determined. The test results show that the decomposition of PNA proceeded rapidly only at pH value of 3.0. Increasing the dosage of H(2)O(2) and Fe(2+) enhanced the k(ap) of PNA degradation. However, higher levels of H(2)O(2) also inhibited the reaction kinetics. The k(ap) of PNA degradation decreased with the increase of initial PNA concentration, but increased with the increase of temperature. Based on the rate constants obtained at different temperatures, the empirical Arrhenius expression of PNA degradation was derived. The derived activation energy for PNA degradation by Fenton oxidation is 53.96 kJ mol(-1).     

A kinetic model for the decolorization of C.I. Acid Yellow 23 by Fenton process

The decolorization of azo dye C.I. Acid Yellow 23 (AY23) by Fenton process was investigated. The decolorization rate is strongly dependent on the initial concentrations of the Fe(2+) and H(2)O(2). The optimum operational conditions were obtained at pH 3. A kinetic model has been developed to predict the decolorization of AY23 at different operational conditions by Fenton process. The model allows to simulate the system behavior involving the influence of hydrogen peroxide, Fe(II) and dye concentrations.     

Effect of operational parameters on the decolorization of C.I. Reactive Blue 19 in aqueous solution by ozone-enhanced electrocoagulation

The aim of this paper was to investigate the efficiency of the ozone-enhanced electrocoagulation (EC) process in the decolorization of C.I. Reactive Blue 19 in water using iron electrodes. We determined the effects of various operating parameters such as initial pH, initial dye concentration, current density, salt concentration, temperature, ozone flow rate, and distance between electrodes on decolorization efficiency in a laboratory-scale reactor. Increasing the initial dye concentration decreased the decolorization efficiency, whereas increasing the distance between electrodes increased it. The other operating factors had both positive and negative effects. With an initial pH of 10.0, an initial dye concentration of 100mg/L, current density of 10mA/cm2, salt concentration of 3000mg/L, temperature of 30 degrees C, ozone flow rate of 20mL/min, and distance between electrodes of 3cm, over 96% of the color was removed after 10min. As a consequence, removal of total organic carbon (TOC) was over 80%.     

Comparison of several advanced oxidation processes for the decolorization of Reactive Red 120 azo dye in aqueous solution

In this study UV/TiO2, electro-Fenton (EF), wet-air oxidation (WAO), and UV/electro-Fenton (UV/EF) advanced oxidation processes (AOPs) have been applied to degrade Reactive Red 120 (RR120) dye in aqueous solution. The most efficient method on decolorization and mineralization of RR120 was observed to be WAO process. Photocatalytic degradation of RR120 by UV/TiO2 have been studied at different pH values. At pH 3 photocatalytic degradation kinetics of RR120 successfully fitted to Langmuir-Hinshelwood (L-H) kinetics model. The values of second order degradation rate (k") constant and adsorption constant (K) were determined as 4.525 mg L(-1) min(-1) and 0.387 L mg(-1), respectively. Decolorization efficiency observed in the order of WAO > UV/TiO2 = UV/EF > EF while WAO > UV/TiO2 > UV/EF > EF order was observed in TOC removal (mineralization). For all AOPs, it was found that degradation products in reaction mixture can be disposed safely to environment after 90 min treatment.     

高效液相色谱-串联质谱法快速测定饮料中亮蓝

本文建立了一种高效液相色谱-串联质谱联用快速测定饮料中亮蓝的新方法。使用脱气、调节pH等简单的样品前处理后,利用HPLC-ESI(+)MS/MS对亮蓝二级特征离子m/z735进行定性定量检测,5min内即可完成,方法检出限为0.2μg/kg,加标样品回收率在92.0%-97.8%,相对标准偏差3.5%-5.7%。该方法简便、快速、灵敏度高,抗干扰能力强,适用于饮料中亮蓝的痕量检测。     

Kinetics of 2,6-dimethylaniline oxidation by various Fenton processes

The kinetics of 2,6-dimethylaniline degradation by Fenton process, electro-Fenton process and photoelectro-Fenton process was investigated. This study attempted to eliminate the potential interferences from intermediates by making a kinetics comparison of Fenton, electro-Fenton and photoelectro-Fenton methods through use initial rate techniques during the first 10 min of the reaction. Exactly how the initial concentration of 2,6-dimethylaniline, ferrous ions and hydrogen peroxide affects 2,6-dimethylaniline degradation was also examined. Experimental results indicate that the 2,6-dimethylaniline degradation in the photoelectro-Fenton process is superior to the ordinary Fenton and electro-Fenton processes. Additionally, for 100% removal of 1 mM 2,6-dimethylaniline, the supplementation of 1 mM of ferrous ion, 20 mM of hydrogen peroxide, current density at 15.89 A m⁻² and 12 UVA lamps at pH 2 was necessary. The overall rate equations for 2,6-dimethylaniline degradation by Fenton, electro-Fenton and photoelectro-Fenton processes were proposed as well.     

Treatment of printed circuit board industrial wastewater by Ferrite process combined with Fenton method

Printed circuit board wastewater typically contains organics and metal ions. The study explored the feasibility of a sequential procedure, FFP (the combination of the Fenton method and the Ferrite process), for treating printed circuit board wastewater, and established the optimum parameters for it. The analytical results showed that the proper pH level was 2 for Fenton oxidation, and the appropriate H₂O₂ dosing type was batch dosing. For the Ferrite process, the suitable Fe/M (Fe is the total dose of Fe²⁺ added to a solution and M is the initial total moles of various metal ions in untreated wastewater) molar ratio was 10 and the sludge met the toxicity characteristic leaching procedure (TCLP) standards. Following FFP treatment, effluent water or sludge easily met Taiwan's standards. Finally, the SEM/EDS test demonstrated that particle sizes of the sludge were approximately 50–80 nm, and the saturation magnetization was 67.5 emu/g.     

Catalytic Reduction of Coomassie Brilliant Blue R-250 by Silver Nanomagnetic Clusters

The research work represents the synthesis of silver nanoparticles(AgNPs)coated on magnetic iron oxide nanoparticles by chemical reduction and co-precipitation method,respectively.AgNPs were coated on magnetic ironoxide nanoparticles to form Ag@Fe3O4.AgNPs were characterized by UV-Visible spectroscopy.The magnetic nanoparticles(MNPs)and magnetic nanoclusters(MNC)were characterized by Fourier transform infra red(FTIR)spectroscopy.Bulk density,moisture content and ash content were also determined.These MNCs were used for the reduction of 4-nitrophenol(4-NP)and coomassie Brilliant Blue R-250(CBBR-250).The parameters such as effect of time,catalyst dosage,concentration of sodium borohydride and concentration of 4-NP and dye were studied.It was found that the catalytic reduction of 4-NP and dye were in 20 minutes by MNCs.Kinetic analysis shows that the pseudo-first-order was found to be linear.It revealed that the use of these MNCs can be considered as a reliable method for the catalytic reduction studies.     

Degradation of malachite green in aqueous solution by Fenton process

In this study, advanced oxidation process utilizing Fenton's reagent was investigated for degradation of malachite green (MG). The effects of different reaction parameters such as the initial MG concentration, initial pH, the initial hydrogen peroxide concentration, the initial ferrous concentration and the reaction temperature on the oxidative degradation of MG have been investigated. The optimal reacting conditions were experimentally found to be pH 3.40, initial hydrogen peroxide concentration=0.50mM and initial ferrous concentration=0.10mM for initial MG concentration of 20mg/L at 30 degrees C. Under optimal conditions, 99.25% degradation efficiency of dye in aqueous solution was achieved after 60 min of reaction.     

Long-term oxidation kinetics of aluminide coatings on alloy steels by low temperature pack cementation process

The long-term oxidation kinetics of the P92 steel and iron aluminide diffusion coating formed on its surface by the pack cementation process have been investigated at 650 °C over a period of more than 7000 h both in 100% steam and in air under normal one atmospheric pressure by intermittent weight measurement at room temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques were used to analyse the oxidised surfaces. For the P92 steel substrate, the scale formed by oxidation is largely magnetite (Fe₃O₄) in steam and haematite (Fe₂O₃) in air. Despite this difference in the type of oxide scales formed, it was found that the long-term oxidation kinetics of the P92 steel substrate in both steam and air can be described by a logarithmic time relationship: Δm _t = k _lln(t/t° + 1); the constants k _l and t° were subsequently determined using a closest fit process for oxidations in steam and air. For the coating, the oxide scale formed in both steam and air was Al₂O₃, which provided the long-term oxidation resistance. It was observed that the long-term oxidation kinetics of the coating in both steam and air can be best described by Δm _t = Δm ₀ + k _c t ^1/3; the rate constant k _c of oxidation in steam and air was then determined by the least squares method. For both the P92 steel substrate and coating, the rate of oxidation is faster in steam than in air at 650 °C particularly in the case of the P92 steel substrate.     

Decolorization of an azo dye Orange G in aqueous solution by Fenton oxidation process: effect of system parameters and kinetic study

To establish cost-efficient operating conditions for potential application of Fenton oxidation process to treat wastewater containing an azo dye Orange G (OG), some important operating parameters such as pH value of solutions, dosages of H(2)O(2) and Fe(2+), temperature, presence/absence of chloride ion and concentration of the dye, which effect on the decolorization of OG in aqueous solution by Fenton oxidation have been investigated systematically. In addition, the decolorization kinetics of OG was also elucidated based on the experimental data. The results showed that a suitable decolorization condition was selected as initial pH 4.0, H(2)O(2) dosage 1.0 x 10(-2)M and molar ratio of [H(2)O(2)]/[Fe(2+)] 286:1. The decolorization of OG enhanced with the increasing of reaction temperature but decreased as a presence of chloride ion. On the given conditions, for 2.21 x 10(-5) to 1.11 x 10(-4)M of OG, the decolorization efficiencies within 60 min were more than 94.6%. The decolorization kinetics of OG by Fenton oxidation process followed the second-order reaction kinetics, and the apparent activation energy E, was detected to be 34.84 kJ mol(-1). The results can provide fundamental knowledge for the treatment of wastewater containing OG and/or other azo dyes by Fenton oxidation process.     

用分光光度法测定含氨基酸类制品中的氨基酸含量

采用分光光度法对富含氨基酸类成分的制品中氨基酸含量的测定方法进行了研究探讨。试验主要利用氨基酸的氨基与茚三酮水合物反应可生成蓝紫色化合物,该化合物最大吸收峰在570nm波长处,且此吸收峰值的大小与氨基酸释放出的氨基成正比,因此可作为氨基酸定量分析方法。该方法简便、灵敏、快速,重现性良好,平均回收率为98.4%,RSD为1.0%,可用于食品(保健品)的产品检验方法。     

Comparison of disperse and reactive dye removals by chemical coagulation and Fenton oxidation

The composition of wastewater from the dyeing and textile processes is highly variable depending on the dyestuff type and typically has high COD and color. This study examined the decolorization of some of the most commonly used disperse and reactive dyestuffs by combination of chemical coagulation and Fenton oxidation. In addition, performances between Fe3+ coagulation and Fenton oxidation of dye solutions were compared by measuring COD and dye removals, distributions of zeta potential, concentration of suspended solid were investigated. Fenton oxidation in combination with Fe3+ coagulation has shown to effectively remove COD and dye. About 90% of COD and 99% of dye removals were obtained at the optimum conditions. Compared to reactive dyes, disperse dyes have lower solubility, higher suspended solids concentrations and lower SCOD/TCOD ratios. The COD and dye removed per unit Fe3+ coagulant added for disperse dye solutions were higher than those for reactive dye solutions. Therefore, the disperse dye solutions are more easily decolorized by chemical coagulation than reactive dye solutions. Conversely, reactive dye solutions have higher applicability of Fenton oxidation than disperse dye solutions due to their higher solubility, lower suspended solids concentrations and higher SCOD/TCOD ratios. The COD and dye removed per Fe2+ Fenton reagent added for reactive dye solutions are respectively higher than those for disperse dye solutions.     

Kinetic and mechanistic investigations of mesotrione degradation in aqueous medium by Fenton process

In this work, chemical oxidation of mesotrione herbicide by Fenton process in acidic medium (pH 3.5) was investigated. Total disappearance of mesotrione and up to 95% removal of total organic carbon (TOC) were achieved by Fenton's reagent under optimized initial concentrations of hydrogen peroxide (H(2)O(2)) and ferrous iron (Fe(2+)) at pH 3.5. The time-dependent degradation profiles of mesotrione were satisfactorily fitted by first-order kinetics. Competition kinetic model was used to evaluate a rate constant of 8.8(± 0.2) × 10(9)M(-1) s(-1) for the reaction of mesotrione with hydroxyl radicals. Aromatic and aliphatic intermediates of mesotrione oxidation were identified and quantified by high performance liquid chromatography (HPLC). It seems that the degradation of mesotrione by Fenton process begins with the rupture of mesotrione molecule into two moieties: cyclohexane-1,3-dione derivative and 2-nitro-4-methylsulfonylbenzoic acid. Hydroxylation and release of sulfonyl and/or nitro groups from 2-nitro-4-methylsulfonylbenzoic acid lead to the formation of polyhydroxylated benzoic acid derivatives which undergo an oxidative opening of benzene ring into carboxylic acids that end to be transformed into carbon dioxide.     

Comparative study of oxidation of dye-Reactive Black B by different advanced oxidation processes: Fenton, electro-Fenton and photo-Fenton

This study makes a comparison between photo-Fenton and a novel electro-Fenton called Fered-Fenton to study the mineralization of 10,000 mg/L of dye-Reactive Black B (RBB) aqueous solution, which was chosen as the model dye contaminant. Results indicate that the traditional Fenton process only yields 70% mineralization. This result can be improved by using Fered-Fenton to yield 93% mineralization resulting from the action of ferrous ion regenerated on the cathode. Furthermore, photo-Fenton allows a fast and more complete destruction of dye solutions and as a result of the action of ferrous ion regenerated by UV irradiation yields more than 98% mineralization. In all treatments, the RBB is rapidly decayed to some carboxylic acid intermediates. The major intermediates found are formic acid and oxalic acid. This study finds that formic acid can be completely mineralized by photo-Fenton, but its destruction is problematic using the Fenton method. Oxalic acid is much more difficult to treat than other organic acids. It could get further mineralization with the use of the Fered-Fenton process.