Optimizing electron spin resonance detection of hydroxyl radical in water

The parameters affecting the electron spin resonance (ESR) detection of hydroxyl free radical in water are studied and optimized. The hydroxyl radical is generated by the Fenton reaction with iron (II) ammonium sulfate and hydrogen peroxide reacting in a phosphate buffer using N-tert-butyl-alpha-phenylnitron as the spin trap. The concentrations of Fe²⁺, H₂O₂, and phosphate buffer are the parameters studied. The Taguchi method and the orthogonal experiment design were used to evaluate the effects of these parameters on the ESR signal intensity. By the analysis of the signal-to-noise ratio and the analysis of variance, the order of importance of the various parameters on the hydroxyl radical formation is determined for optimal ESR detection of hydroxyl radical. The results will help the development of water purification technologies using hydroxyl free radical as a green oxidant.     

Influence of acidification of CCB (Cu/Cr/B) impregnated wood on fungal copper tolerance

Copper tolerant fungi are known for more than 60 years but the complete mechanisms of copper tolerance by these fungi are still not fully understood. Copper tolerance has previously been linked to oxalic acid excretion by copper tolerant brown rot fungi. The oxalic acid then reacts with copper in the wood to form an insoluble and therefore less toxic copper oxalate. It has been suggested that copper tolerance could be due to lowering of the pH of the medium rather than the low solubility of copper oxalate. In order to elucidate this presumption, copper/chromium/boron (CCB) treated wood specimens were acidified with organic (oxalic, acetic, lactic, formic) and inorganic (sulphuric) acids and exposed to copper tolerant (Antrodia vaillantii, Leucogyrophana pinastri) and copper sensitive (Poria monticola, Gloeophyllum trabeum) brown rot fungal strains according to the mini block procedure. After eight weeks of exposure, the wood specimens were isolated and their mass losses determined. Additionally, electron paramagnetic resonance (EPR) measurements on the exposed specimens were performed. The EPR spectra of the specimens decayed by A. vaillantii were very similar to the EPR spectra of the specimens acidified with oxalic acid. Additionally, acidification of the CCB impregnated specimens made them significantly more susceptible to decay by both the copper tolerant and copper sensitive brown rot fungi.     

Hydroxyl radical concentration profile in photo-Fenton oxidation process: generation and consumption of hydroxyl radicals during the discoloration of azo-dye Orange II

Dynamic behaviors of hydroxyl (OH) radical generation and consumption in photo-Fenton oxidation process were investigated by measuring OH radical concentration during the discoloration of azo-dye Orange II. The effects of operating parameters for photo-Fenton discoloration, i.e. dosages of H₂O₂ and Fe, initial dye concentration, solution pH and UV irradiation, on the generation and consumption of OH radicals playing the main role in advanced oxidation processes were extensively studied. The scavenger probe or trapping technique in which coumarin is scavenger of OH radical was applied to estimate OH radical concentration in the photoreactor during the photo-Fenton discoloration process. The OH radical generation was enhanced with increasing the dosages of Fenton regents, H₂O₂ and Fe. At the initial stage of photo-Fenton discoloration of Orange II, the OH radical concentration rapidly increased (Phase-I) and the OH radical concentration decreased after reaching of OH radical concentration at maximum value (Phase-II). The decrease in OH radical concentration started when the complete discoloration of Orange II was nearly achieved and the H₂O₂ concentration became rather low. The dynamic behavior of OH radical concentration during the discoloration of Orange II was found to be strongly linked with the change in H₂O₂ concentration. The generation of OH radical was maximum at solution pH of 3.0 and decreased with an increase of solution pH. The OH radical generation rate in the Fenton Process was rather slower than that in the photo-Fenton process.     

Selective redox degradation of chlorinated aliphatic compounds by Fenton reaction in pyrite suspension

Selective redox degradation of chlorinated aliphatics by Fenton reaction in pyrite suspension was investigated in a closed system. Carbon tetrachloride (CT) was used as a representative target of perchlorinated alkanes and trichloroethylene (TCE) was used as one of highly chlorinated alkenes. Degradation of CT in Fenton reaction was significantly enhanced by pyrite used as an iron source instead of soluble Fe. Pyrite Fenton showed 93% of CT removal in 140 min, while Fenton reaction with soluble Fe(II) showed 52% and that with Fe(III) 15%. Addition of 2-propanol to the pyrite Fenton system significantly inhibited degradation of TCE (99% to 44% of TCE removal), while degradation of CT was slightly improved by the 2-propanol addition (80-91% of CT removal). The result suggests that, unlike oxidative degradation of TCE by hydroxyl radical in pyrite Fenton system, an oxidation by the hydroxyl radical is not a main degradation mechanism for the degradation of CT in pyrite Fenton system but a reductive dechlorination by superoxide can rather be the one for the CT degradation. The degradation kinetics of CT in the pyrite Fenton system was decelerated (0.13-0.03 min⁻¹), as initial suspension pH decreased from 3 to 2. The formation of superoxide during the CT degradation in the pyrite Fenton system was observed by electron spin resonance spectroscopy. The formation at initial pH 3 was greater than that at initial pH 2, which supported that superoxide was a main reductant for degradation of CT in the pyrite Fenton system.     

Inhibition of BPA degradation by serum as a hydroxyl radical scavenger and an Fe trapping agent in Fenton process

Identification of reactive oxygen species (ROS) that contribute to bisphenol-A (BPA) degradation and monitoring of BPA at various concentrations in human serum under Fenton reaction conditions were carried out using electron spin resonance (ESR) spectrophotometry and high performance liquid chromatography with electrochemical detection (HPLC-ECD). BPA recovery decreased with increasing Fe concentration and time, both with a Fenton reaction using Fe(II), and with a Fenton-like reaction using Fe(III). In these reactions, BPA dose-dependently decreased the intensity of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)-*OH, up to 1 microg/ml BPA, and no change in DMPO-O(2)(?-) intensity was observed. The decrease in BPA recovery was inhibited strongly by addition of serum under Fenton-like reaction conditions, and there was a negative correlation between turbidity and BPA recovery. To clarify the mechanism by which serum inhibits BPA degradation, the relationship between BPA recovery and sample turbidity, and characteristics of the precipitates were investigated using spectrophotometry and X-ray analysis. The precipitate formed in the serum-containing sample consisted of C, S, O, P and Fe. BPA degradation was also inhibited under Fenton-like reaction conditions in phosphate buffered saline (PBS), and a precipitate consisting of O, P, and Fe appeared. Precipitates also appeared in authentic albumin and gamma-globulin when sulfate was added with Fenton reagents. After precipitate removal, both Fe and protein concentrations in the supernatant of the protein solutions with sulfate decreased with increasing Fe addition. We demonstrate here that hydroxyl radical generation from Fenton or Fenton-like reactions can degrade BPA, and that serum strongly inhibits BPA degradation, not only by competing with BPA for hydroxyl radicals, but also by trapping Fe with oxidative components present in the serum.     

Effect of ethylenediamine-N,N′-disuccinic acid on Fenton and photo-Fenton processes using goethite as an iron source: optimization of parameters for bisphenol A degradation

The main disadvantage of using iron mineral in Fenton-like reactions is that the decomposition rate of organic contaminants is slower than in classic Fenton reaction using ferrous ions at acidic pH. In order to overcome these drawbacks of the Fenton process, chelating agents have been used in the investigation of Fenton heterogeneous reaction with some Fe-bearing minerals. In this work, the effect of new iron complexing agent, ethylenediamine-N,N'-disuccinic acid (EDDS), on heterogeneous Fenton and photo-Fenton system using goethite as an iron source was tested at circumneutral pH. Batch experiments including adsorption of EDDS and bisphenol A (BPA) on goethite, H₂O₂ decomposition, dissolved iron measurement, and BPA degradation were conducted. The effects of pH, H₂O₂ concentration, EDDS concentration, and goethite dose were studied, and the production of hydroxyl radical (^?OH) was detected. The addition of EDDS inhibited the heterogeneous Fenton degradation of BPA but also the formation of ^?OH. The presence of EDDS decreases the reactivity of goethite toward H₂O₂ because EDDS adsorbs strongly onto the goethite surface and alters catalytic sites. However, the addition of EDDS can improve the heterogeneous photo-Fenton degradation of BPA through the propagation into homogeneous reaction and formation of photochemically efficient Fe-EDDS complex. The overall effect of EDDS is dependent on the H₂O₂ and EDDS concentrations and pH value. The high performance observed at pH 6.2 could be explained by the ability of O ₂ ^?? to generate Fe(II) species from Fe(III) reduction. Low concentrations of H₂O₂ (0.1 mM) and EDDS (0.1 mM) were required as optimal conditions for complete BPA removal. These findings regarding the capability of EDDS/goethite system to promote heterogeneous photo-Fenton oxidation have important practical implications for water treatment technologies.     

Impact of radical versus non-radical pathway in the Fenton chemistry on the iron redox cycle in clouds

Modeling studies have shown that the Fenton reaction of iron(II) with H2O2 can contribute, in a significant amount, to OH radicals production in cloud droplets. However, the destruction mechanism of hydrogen peroxide by iron(II) is still uncertain. Two reaction pathways for the first step of Fenton chemistry have been advanced: a radical pathway which considers an OH radical production and a non-radical pathway considering ferryl ion production. The aim of this work is to evaluate the impact of these two possible reaction pathways for Fenton chemistry on the iron redox cycle in cloud droplets. For this purpose, the numerical model of multiphase chemistry M2C2 has been applied to a rural chemical scenario representative of continental conditions. This study highlights that the iron redox cycling is driven by Fenton reaction whatever Fenton mechanism is considered. The ferryl ion chemistry becomes significant in the iron redox cycling when this species is considered as an active intermediate in Fenton chemistry and under night time conditions the iron redox chemistry is controlled by the ferryl ion reactivity. The partitioning of iron between its two main oxidation states (+II and +III) in cloud droplets, which is the indicator of the iron oxido-reduction potential, does not change significantly between the two cases. However, for the non-radical case, the ferryl ion concentration is up to four orders of magnitude higher than the OH concentration highlighting its potential role in oxidative capacity of cloud droplets.     

Photo-Fenton-assisted ozonation of p-Coumaric acid in aqueous solution

The degradation of p-Coumaric acid present in olive oil mill wastewater was investigated as a pretreatment stage to obtain more easily biodegradable molecules, with lower toxicity that facilitates subsequent anaerobic digestion. Thus, photo-Fenton-assisted ozonation has been studied and compared with ozonation at alkaline pH and conventional single ultraviolet (UV) and acid ozonation treatments. In the combined process, the overall kinetic rate constant was split into various components: direct oxidation by UV light, direct oxidation by ozone and oxidation by hydroxyl radicals. Molecular and/or radical ozone reaction was studied by conducting the reaction in the presence and absence of tert-butylalcohol at pHs 2, 7 and 9. Ozone oxidation rate increases with pH or by the addition of Fenton reagent and/or UV radiation due to generation of hydroxyl radicals, *OH. Hydrogen peroxide and ferrous ion play a double role during oxidation since at low concentrations they act as initiators of hydroxyl radicals but at high concentrations they act as radical scavengers. Finally, the additional levels of degradation by formation of hydroxyl radicals have been quantified in comparison to the conventional single processes and an equation is proposed for the reaction rate as a function of studied operating variables.     

综合法处理酸性高浓度印染废水的研究

传统Fenton法在处理印染类废水时,因亚铁盐及双氧水的昂贵价格而限制了其实际应用。出于工程应用的考虑,提出了以Fenton法为重心,结合其他污水处理方法的综合方法,从而在达到相同处理效果的同时尽可能降低治污成本。研究表明,通过Fenton、铁碳微电解和中和沉淀吸附等方法的综合运用和优化组合,废水色度降至10倍以下,COD降至300 mg/L以下,去除率达到98%以上,pH调节为7,达到排放标准。     

Fe/C微电解和Fenton氧化联合处理印刷电路板废水

研究了Fe/C微电解和Fenton氧化处理印刷电路板废水的最佳条件和联合工艺的处理效果。结果表明,Fe/C微电解最佳工艺条件为：pH=2,Fe/C质量比为2∶1,投加药剂量为30 g/L,停留时间为30 min;Fenton氧化最佳工艺条件为：pH=3,H2O2投加量为6 mL/L,停留时间为2 h。将2种方法联用并进行中试实验,结果表明,对原水的COD去除率可达80%,而且Fenton反应可利用微电解产生的Fe2＋,节约成本,运行稳定,效果良好。     

Modified Fenton reaction for trichlorophenol dechlorination by enzymatically generated H2O2 and gluconic acid chelate

Glucose oxidase is a well-known enzyme that catalyzes the oxidation of β-d-glucose to produce gluconic acid and hydrogen peroxide. Fenton reaction is a powerful oxidation technology used for the oxidation of groundwater pollutants. For the application of Fenton reaction in groundwater remediation, successful operation of Fenton reaction near neutral pH, and on-site generation of both H₂O₂ and chelate will be beneficial. The focus of this experimental study was to couple the glucose oxidation reaction with chelate-based Fenton reaction. The idea was to use the hydrogen peroxide and chelate gluconic acid generated during glucose oxidation for the dechlorination of 2,4,6-trichlorophenol (TCP) by Fenton reaction. The oxidation of glucose was achieved using the enzyme in free and immobilized forms. The rate of production of hydrogen peroxide was determined for each system, and was used to estimate the time required for complete consumption of glucose during the process, thus avoiding any traces of glucose in the Fenton reaction. In the case of free enzyme reaction, separation of the enzyme was achieved using an ultrafiltration membrane before initiating the Fenton reaction. The oxidation of TCP by Fenton reaction was performed at varying ratios of gluconic acid/Fe, and its effect on the decomposition of TCP and H₂O₂ was studied. TCP degradation was studied both in terms of parent compound degradation and free chloride generation.     

CuO/γ-Al_2O_3类Fenton试剂降解丁基黄药

CuO/γ-Al2O3类Fenton试剂是降解丁基黄药的优良试剂。该试剂与传统的Fenton试剂相比,提高了反应的pH值,可在较高pH（4~5）条件下反应,而传统的Fenton试剂的适宜pH值一般在3以下。采用单因素实验和正交实验相结合的方法研究了pH、催化剂投加量、过氧化氢投加量以及反应时间对丁基黄药降解效果的影响,并对催化剂的使用寿命进行了探讨。研究结果表明,反应的最佳条件为：pH为4~5,催化剂投加量为6 g/L,过氧化氢用量为30 mg/L,反应30min。在此反应条件下,丁基黄药的降解率达98%以上;影响丁基黄药降解效果的因素大小顺序为：pH〉反应时间〉H2O2用量〉催化剂投加量,其中pH对CuO/γ-Al2O3类Fenton试剂降解丁基黄药的影响最为显著。     

The role of ferrous ion in Fenton and photo-Fenton processes for the degradation of phenol

The efficiency of different Fenton-related oxidative processes such as Fenton, solar-Fenton and UV-Fenton were examined using phenol as a model compound in simulated and industrial wastewater. A batch study was conducted to optimize parameters like pH, hydrogen peroxide concentration and ferrous ion concentration governing the Fenton process. At optimum conditions, different Fenton-related processes were compared for the degradation of phenol. Increased degradation and mineralisation efficiency were observed in photo-Fenton processes as compared to conventional Fenton process. The maximum mineralising efficiency for phenol with Fenton, solar and UV-Fenton processes were 41%, 96% and 97% respectively. In Fenton process, carboxylic acids like acetic acid and oxalic acid were formed as end products during the degradation of phenol while in photo-Fenton processes, both these ions were identified during the early stages of phenol degradation and were oxidized almost completely at 120 min of the reaction time. In photo-Fenton processes (solar and UV light) complete degradation were observed with 0.4 mM of Fe2+ catalyst as compared to 0.8 mM of Fe2+ in conventional Fenton process. In Fenton and solar-Fenton processes, an iron reusability study was performed to minimize the amount of iron used in treatment process. The efficacy of Fenton and solar-Fenton processes was applied to effluent from phenol resin-manufacturing unit for the removal and mineralisation of phenol.     

沼渣生物炭基Fenton催化剂的制备及其高效降解吡虫啉农药废水的研究

以废弃物沼渣和含铁剩余污泥为原料,采用一步热解法制备沼渣生物炭基Fenton催化剂(以下简称催化剂),构建了非均相Fenton反应体系处理含吡虫啉模拟废水,考察了H2 O2和催化剂用量对吡虫啉去除率的影响.结果表明,非均相Fenton反应体系中,H2 O2最佳投加量为0.50 g/L,催化剂最佳投加量为1.00 g/L...     

Decomposition of non-ionic surfactant Tergitol TMN-10 by the Fenton process in the presence of iron oxide nanoparticles

The aim of our studies was to determine the efficiency of decomposition of non-ionic surfactant by the Fenton method in the presence of iron nanocompounds and to compare it with the classical Fenton method. The subject of studies was water solutions of non-ionic detergent Tergitol TMN-10 used in textile industry. Water solutions of the surfactant were subjected to treatment by the classical Fenton method and to treatment in the presence of iron nanocompounds. In the samples of liquid solutions containing the surfactant, chemical oxygen demand (COD) and total organic carbon (TOC) were determined. The Fenton process was optimized based on studies of the effect of compounds used in the treatment, doses of iron and nanoiron, hydrogen peroxide and pH of the solution on surfactant decomposition. Iron oxide nanopowder catalyzed the process of detergent decomposition, increasing its efficiency and the degree of mineralization. It was found that the efficiency of the surfactant decomposition in the process with the use of iron nanocompounds was by 10 to 30 % higher than that in the classical method. The amounts of formed deposits were also several times smaller.     

Fe(III)–EDDS complex in Fenton and photo-Fenton processes: from the radical formation to the degradation of a target compound

The present work compares the efficiency of homogenous Fenton and photo-Fenton processes in the presence of Fe(III)–EDDS complex under different experimental conditions. 4-tert-Butylphenol (4-t-BP), which is one of the endocrine disrupting chemicals, was used as a model pollutant to investigate the Fenton and photo-Fenton application. The efficiency of homogenous photo-Fenton process was significantly much higher than homogenous Fenton process, which is due to the rapid formation of Fe²⁺ under UV irradiation of the iron complex and the photochemical formation of HO^? from the photolysis of the complex Fe(III)–EDDS. Through the degradation of 4-t-BP, the effect of Fe(III)–EDDS concentration, H₂O₂ concentration, pH, and oxygen was investigated in both processes. Such trend was also correlated with pH calculating the polychromatic Fe²⁺ quantum yield formation at pH 4.0, 6.0, and 8.6. The results showed that at high Fe(III)–EDDS and H₂O₂ concentrations, a negative effect was found. By the way, the Fenton process was found to be enhanced at basic pH. These results can be very useful for the use and optimization of such iron complex in water treatment process as function of different physico-chemical conditions.     

Removal of sorbed polycyclic aromatic hydrocarbons from soil, sludge and sediment samples using the Fenton's reagent process

The use of the Fenton's reagent process has been investigated for the remediation of environmental matrices contaminated by polycyclic aromatic hydrocarbons (PAHs). Laboratory experiments were first conducted in aqueous solutions, to study the kinetics of oxidation and adsorption of PAHs. Benzo[a]pyrene was more rapidly degraded than adsorbed, while only partial oxidation of fluoranthene occurred. In the case of benzo[b]fluoranthene, its adsorption prevented its oxidation. Besides competition effects between PAHs were found, with slower oxidation of mixtures as compared to single PAH solutions. Apparition of some by-products was observed, and a di-hydroxylated derivative of benzo[a]pyrene could be identified under our conditions. Consequently, application to solid environmental matrices (soil, sludge and sediment samples) was performed using large amounts of reagents. The efficiency of the Fenton treatment was dependent on the matrix characteristics (such as its organic carbon content) and the PAH availability (correlated to the date and level of contamination). However, no pH adjustment was required, as well as no iron addition due to the presence of iron oxides in the solid matrices, suggesting the potential application of Fenton-like treatment for the remediation of PAH-contaminated environmental solids.     

Removal of azo dye from water by magnetite adsorption-Fenton oxidation.

The aim of this study is to highlight the possibility of using powder magnetite adsorption-Fenton oxidation as a method for removal of azo dye acid red B (ARB) from water. The adsorption properties of magnetite powder towards ARB were studied. The oxidation of adsorbed ARB and regeneration of magnetite adsorbent at the same time by Fenton reagent (hydrogen peroxide [H2O2] + iron (II) [Fe2+]) in another treatment unit with a smaller volume was also investigated. The efficiency of Fenton oxidation of ARB was compared for the reaction carried out in solution and on magnetite. The magnetic separation method was used to recover magnetite after adsorption or regeneration. The results indicated that the adsorption rate was fast. The capacity was strongly dependent on pH and inorganic anions, and pH 3.8 was optimal for the adsorption of ARB. The adsorption can be described well using the Langmuir model. The oxidation was more efficient for ARB adsorbed on magnetite than in solution. The adsorption capacity of magnetite increased significantly after regeneration, which was the result of an increase in surface area of the adsorbent and change of elemental ratio (oxygen:iron [O:Fe]) on the surface. The maximum adsorption capacity for ARB was 32.4 mg/g adsorbent.     

超声-Fenton法处理偶氮染料橙黄II的研究

以偶氮染料橙黄II为研究对象 ,考察了Fenton反应在超声辐射条件下 ,pH值、H2 O2 浓度、Fe2 + 离子浓度对COD去除率的影响。实验结果表明 ,超声对Fenton试剂处理偶氮染料橙黄II具有强化作用。超声条件下 ,当染料浓度为10 0mg/L、pH为 3.0、Fe2 + 离子浓度为 10mg/L、H2 O2 浓度为 4 0 0mg/L时 ,反应 90min ,COD去除率最高可达 93%。     

UV/Fenton法处理酸性红B研究

采用UV/Fenton高级氧化技术对酸性红B模拟废水进行处理,当进水浓度为400mg/L时,确定了各影响因素的最佳投加量:H2O2投加量为2 mL/L,Fe2 投加量为0.08g/L,最佳pH值为4;并采用一级动力学公式对酸性红B降解速率进行拟合,研究了反应条件对速率常数的影响.最后通过对单独UV法、单独Fenton法和UV/Fenton法3种处理方法效果的比较,发现UV与Fenton试剂具有协同作用.