Quantitative measurement of hydroxyl radical(OH) concentration in premixed flat flame by combining laser-induced fluorescence and direct absorption spectroscopy

An accurate and reasonable technique combining direct absorption spectroscopy and laser-induced fluorescence（LIF）methods is developed to quantitatively measure the concentrations of hydroxyl in CH;/air flat laminar flame. In our approach, particular attention is paid to the linear laser-induced fluorescence and absorption processes, and experimental details as well. Through measuring the temperature, LIF signal distribution and integrated absorption, spatially absolute OH concentrations profiles are successfully resolved. These experimental results are then compared with the numerical simulation. It is proved that the good quality of the results implies that this method is suitable for calibrating the OH-PLIF measurement in a practical combustor.

Flow Cytometric Evidence for Hydroxyl Radical-induced Apoptosis in Tobacco Protoplasts

Protoplasts prepared from tobacco (Nicotiana tabacum L., cultivar BY-2) suspension cells have similar morphological characteristics to those in animal cells. The hallmarks of apoptosis such as condensation and peripheral distribution of nuclei, TUNEL positive reaction, and DNA ladders were observed when tobacco protoplasts were treated with the hydroxyl radical generating system (1.0 mmol/L FeSO4/0.5 mmol/L H2O2). In animals, the loss of transmembrane potential (DeltaPsi(m)) and the exposure of phospholipid phosphatidylserine (PS) are believed to be the main apoptosis events. To test whether these significant processes take place in plants, flow cytometry was used to detect annexin V binding and changes in DeltaPsi(m). Results showed that the PS turned out from inner membrane and DeltaPsi(m) gradually decreased during the apoptosis. All these apoptotic characteristics proved that hydroxyl radicals can cause typical programmed cell death (PCD) in tobacco protoplasts and this design can be served as an effective experiment system to explore the mechanism of plant apoptosis.

掺杂BN-OH纳米片的P/PEG@BN-OH同轴纳米纤维的制备及其热性能

为制备高效稳定的相变储热材料,采用同轴静电纺丝技术制备了以聚丙烯腈(PAN)为鞘、聚乙二醇(PEG)与羟基化氮化硼纳米片(BN-OH)为芯的同轴纳米纤维(P/PEG@x BN-OH),并分别通过场发射扫描电子显微镜、透射电子显微镜、差示扫描量热仪、红外热成像仪等手段分析了掺杂不同质量BN-OH纳米片对纤维形貌、热性能、循环稳定性、热能效率及热导率的影响。结果表明:纤维形成了稳定且连续的鞘-芯同轴结构,平均直径介于279~335 nm,而且PEG和BN-OH被包裹在PAN纤维内部,内径大小范围为107~188 nm;P/PEG@x BN-OH纳米纤维显示了优异的相变储热焓值(75~78 J/g)和热稳定性,经100次热循环后PEG无相变渗漏现象;掺杂质量分数为10.0%的BN-OH纳米片可将纤维的热导率提高95%,而且其相变储热和释放率分别提高了67%和154%。

Determination of atmospheric hydroxyl radical by HPLC coupled with electrochemical detection

The hydroxyl radical （·OH） plays a central role in the oxidation and removal of many atmospheric compounds. Measurement of atmospheric ·OH is very difficult because of its high reactivity and low atmospheric abundance. In this article, a simple and highly sensitive method, high performance liquid chromatography coupled with coulometric detection （HPLC-CD）, was developed to determine ·OH indirectly by determining its reaction products with salicylic acid （SAL）, 2,3-dihydroxybenzoic acid （2,3-DHBA）, and 2,5-dihydroxybenzoic acid （2,5-DHBA）. Under the optimum conditions for its determination, 2,3-DHBA and 2,5-DHBA could be well separated and the detection limits for 2,3-DHBA were 3 ×10^-10 mol/L and for 2,5-DHBA were 1.5 ×10^-10 mol/L, which were lower than most previous reports. This method was also applied to measure atmospheric hydroxyl radical levels and demonstrated the feasibility in clean and polluted air.

Detection of hydroxyl radical in plasma reaction on toluene removal

A new method was introduced to detect the concentration of OH radical in dielectric barrier discharge(DBD)reaction.A film, which was impregnated with salicylic acid,was used to detect OH radical in plasma reaction at room temperature and atmospheric pressure.Salicylic acid reacts with OH radical and produces 2,5-dihydroxybenzoic acid(2,5-DHBA).Then,a high performance liquid chromatography(HPLC)was carried out to detect the concentration of 2,5-DHBA.Therefore,OH radical in nonthermal plasma reaction could be...

Singlet oxygen synergistic surface-adsorbed hydroxyl radicals for phenol degradation in CoP catalytic photo-Fenton

In recent years,there have been numerous studies on Fenton or Fenton-like reactions mediated by nonfree radicals such as singlet oxygen(1O_(2));however,there are few studies on the synergistic effect of 1O_(2) and free radicals on the degradation of organic molecules,such as phenol in Fenton reaction.In this study,a cocatalyst,CoP,commonly used in photocatalysis was synthesized using a simple two-step method,and a CoP/Fe^(2+)/AM1.5 system was constructed by introducing Fe^(2+)and simulated sunlight(AM1.5)irradiation.The newly constructed CoP/Fe^(2+)/AM1.5 system could effectively degrade various organic pollutants,including dyes,phenols,and antibiotics.Radical quenching experiments and electron paramagnetic resonance detection confirmed that there were three reactive oxygen species(ROS)in the CoP/Fe^(2+)/AM1.5 system,including·OH_(ads),·O_(2)^(-),and 1O_(2).Further,combined with the liquid chromatogram of phenol,its intermediate products,and the fluorescence diagram of o-hydroxybenzoic acid,it can be concluded that a synergistic effect exists between 1O_(2) and the surface-adsorbed·OH_(ads) in the CoP/Fe^(2+)/AM1.5 system.The controllable formation of surface 1O_(2) and·OH_(ads) was achieved through the oxidation(Co^(3+))and reduction(Pδ−)centers exposed on the CoP surface,and the synergistic effect between them results in phenol’s hydroxylation,ring-opening,and degradation.The study of this new mechanism provides a new perspective for revealing the surface interface reaction between ROS and organic pollutants.

Photooxidation of hydrochlorofluocarbons and hydrofluorocarbons initiated by OH radicals

Under simulated atmospheric condition, photoomdation for HCFC-22 + H2O2, HCFC-22 + H2O2+O2, HFC-134A + H2O2 and HFC-134A + H2O2+ O2 systems were studied.H2O2 was irradiated by low pressure mercury lamp and produced OH radicals. The OH radicals can initiate photooxidation of HCFC-22 and 134A. The products of photooxidation were determined by a Fourier Transform infrared Spectroscopy with a 20ml long path cell. The products were COF2,CO2, HCI, H2O and HF for HCFC-22 + H2O2 system, HO, CO2, HCI and HF for HCFC-22 +H2O2 +O2 system, HCOF, CF3OOCF3,CO2, H2O and HF for HFC-134A +H2O2 system, HCOF, CO2, H2O, and HF for HFC-134A + H2O2+ O2 system. Based on those results, the mechanisms of photooxidation were suggested.

Hydroxyl radicals-mediated oxidative cleavage of the glycosidic bond in cellobiose by copper catalysts and its application to low-temperature depolymerization of cellulose

As the most abundant source of biomass in nature for sustainable production of fuels and chemicals,efficient depolymerization of cellulose under mild conditions,due to the difficulty in selective cleavage of itsβ-1,4-glycosidic bonds,still remains challenging.Here,we report a novel method for oxidative cleavage of the glycosidic bonds by free radicals.Probed by the cellobiose reaction,it was found that·OH radicals,generated from the decomposition of H2O2 catalyzed by CuSO4 or CuO/SiO2,were efficient for selective conversion of cellobiose to glucose and gluconic acid at a low temperature of 333 K,and their selectivities reached 30.0%and 34.6%,respectively,at 23.4%cellobiose conversion.Other radicals,such as·SO4?,also exhibited high efficacy in the cellobiose reaction.Mechanistic studies suggest that the oxidative cleavage of theβ-1,4-glycosidic bond by the free radicals involve formation of the carbon radical intermediate via abstraction of the H atom dominantly at the C1 position.Following this oxidative mechanism,treatment of microcrystalline cellulose with·OH by impregnation with H2O2 and CuSO4 catalyst at 343 K led to significant enhancement in its hydrolysis efficiency.These results demonstrate the effectiveness of this new method in the oxidative cleavage of glycosidic bonds,and its viability for the efficient depolymerization of cellulose at low temperatures,which can be further improved,for example,by exploring new free radicals and optimizing their reactivity and selectivity.

Degradation of Phenol by Hydroxyl Radicals on Different Coating Lead Dioxide Electrodes

Lead dioxide electrodes on Ti substrates were prepared by thermal-deposition or electro-deposition. The amount of hydroxyl radicals generated at the electrodes prepared by the above-mentioned two methods was compared with that at the electrodes mingled with Bi or La prepared by electro-deposition. The experimental results indicate that the highest concentration of hydroxyl radicals generated by thermal-deposition, electro-deposition mingled with nothing, electro-deposition mingled with Bi or La was 0.781, 1.048, 1.838 or 2.044 μmol/L, respectively. When phenol was electrolyzed on the four electrodes at a current density of 30 mA/cm2, the removal efficiency of phenol after electrolysis for 1.5 h was 87.30%, 93.55%, 97.95% or 98.70%, TOC removal efficiency after electrolysis for 5 h was 86.76%, 94.26%, 98.53% or 99.60%, respectively. Through the degradation experiments of phenol, the amount of hydroxyl radicals was responsible for the removal efficiency of phenol. The electro-catalytic characteristics were investigated by SEM, the generation amount of hydroxyl radicals, the degradation degree of phenol and the stability and conductivity of the electrodes were also investigated. The experimental results indicate that the four electrodes all show good electro-catalytic characteristics; the electro-catalytic characteristics of the electrode mingled with La were superior to those of the other three ones, and the electrochemical degradation of phenol followed one-step reaction dynamics.

Theoretical Studies on the Reaction Mechanism of Hydroxyl Radical with 1,1,1-Trichloroethane

Ab initio and density functional theory calculations have been carried out to investigate the reaction of hydroxyl radical （OH） and 1,1,1-trichloroethane （CH3CCl3）. The potential energy surface has been given according to the relative energies calculated at the MP2/cc-pVTZ level after the spin projection （PMP2）. Five reaction channels were identified and the intramolecular hydrogen bonding was observed in some transition state structures. The barrier heights and reaction enthalpies calculated for all possible channels show that the hydrogen abstraction channel is predominant kinetically and thermodynamically. The contribution from other channels was predicted to be minor.

Inhibitory Effects of Ginseng Water Extract on Hydroxyl Radical

[Objectives] The aim of this work was to compare the inhibitory effects of different water-soluble extracts of ginseng on hydroxyl radical. [Methods]The water-soluble effective parts of ginseng were extracted by orthogonal test,the hydroxyl radical scavenging rate of each extract was determined by salicylic acid method,and the extraction process of the optimum hydroxyl radical inhibitor was optimized using variance analysis and cluster analysis. [Results] A total of 16 samples were prepared. Among them,the sample No. 12 had the highest hydroxyl radical scavenging rate,and the inhibition rate reached 105. 08% at the concentration of 1 g/L. [Conclusions] Ginseng water extract contained hydroxyl radical scavenger,of which the optimum extraction process was as follows: p H of 8,solid to liquid ratio of 1∶ 10,extraction temperature of 4℃,extraction time of 12 h and extraction times of 3.

Effects of Hydroxyl Radicals on Introduced Organisms of Ship's Ballast Water Based Micro-Gap Discharge

With the physical method of micro-gap gas discharge, OH. radicals were produced by the ionization of O2 in air and H2O in the gaseous state, in order to explore more effective method totreat the ship＇s ballast water. The surface morphology of Al2O3 dielectric layer was analysed using Atomic Force Microscopy （AFM）, where the size of Al2O3 particles was in the range of 2 μm to 5 μm. At the same time, the biochemical effect of hydroxyl radicals on the introduced organisms and the quality of ship＇s ballast water were studied. The results indicate that the main reasons of cell death are lipid peroxide and damage of the antioxidant enzyme system in Catalase （CAT）, Peroxidase （POD） and Superoxide dismutase （SOD）. In addition, the quality of the ballast water was greatly improved.

The Collapse Intensity of Cavities and the Concentration of Free Hydroxyl Radical Released in Cavitation Flow

Enhancing the chemical reaction processes by means of the energy released in the collapse of micro bubbles or cavities in the cavitation flow is a new research area. In the previous work, a new approach of measuring concentration of free hydroxyl radicals induced in cavitation flow by using methylene blue as the indicator was developed and used to study concentration of free radical induced in Venturi cavitation flow under various experimental conditions. In the present research, the radial evolution of a cavity bubble and the corresponding collapse pressure in sonic cavitation field are obtained by solving three different bubble dynamics equations： Rayleigh equation, Rayleigh-Plesset equation and Gilmore equation. By comparing with the experimental data on the radial evolution of a cavity bubble in the literature, it is found that the predicted results by the Gilmore equation, which takes account of the compressibility of fluid in addition to the viscosity and interfacial tension, agree with the experimental ones better than those by other two equations. Moreover, the theoretically predicted collapse pressures are consistent with the concentration of the free hydroxyl radical induced in the experimental venture. Thus, the concentration of the liberated free hydroxyl radical not only influences the reaction rate but also is used as an available parameter for measuring collapse intensity of cavities.

Glow Discharge Induced Hydroxyl Radical Degradation of 2-Naphthylamine

In an aqueous solution, normal electrolysis at high voltages switches over spontaneously to glow discharge electrolysis and gives rise to hydroxyl radical, hydrogen peroxide, and aqueous electron, as well as several other active species. Hydroxyl radical directly attacks organic contaminants to make them oxidized. In the present paper, 2-naphthylamine is eventually degraded into hydrogen carbonate and carbon dioxide. The degradation process is analyzed by using an Ultraviolet (UV) absorption spectrum, high-performance liquid chromatography (HPLC) and chemical oxygen demand (COD). It is demonstrated that 2-naphthylamine (co =30 mg·1-1) is completely converted within 2h at 30℃ and 600 V by glow discharge electrolysis, and the degradation is strongly dependent upon the presence of ferrous ions. COD is ascended in the absence of ferrous ions and descended in the presence of them.

绿脱石结构Fe(Ⅲ)还原程度对氧化过程·OH形成及有机质矿化的影响

土壤和沉积物有氧-无氧界面黏土矿物结构Fe(Ⅱ)氧化产生的羟自由基(·OH)在有机物质转化过程中具有重要作用。土壤和沉积物黏土矿物结构Fe(Ⅲ)的还原程度会随环境条件变化而不同,然而,关于含铁黏土矿物还原程度[Fe(Ⅱ)/Fe总]对氧化过程中·OH的形成及有机质矿化的影响尚不明确。本研究以富铁绿脱石为黏土矿代表,研究了不同还原程度绿脱石[Fe(Ⅱ)/Fe总:15%、22%、39%和56%]有氧氧化产生·OH的机制及该过程对溶解性有机质(DOM)转化的差异。结果表明,当不同还原程度绿脱石的悬浊液体系中结构Fe(Ⅱ)浓度为2.2 mmol·L^(-1)时,随着还原程度从15%增加到56%,其氧化120 min后·OH的累积浓度从13.6μmol·L^(-1)增加到27.1μmol·L^(-1),单位O_(2)转化为·OH的效率从3.3%提高到5.9%。傅里叶变换红外光谱(FTIR)、氮蓝四唑(NBT)猝灭实验和2,2′-联吡啶(BPY)钝化边缘反应位点的结果证明了还原程度为15%的绿脱石主要存在二八面体Fe(Ⅱ)[Al-Fe(Ⅱ)],并在边缘位点活化O2产生·OH;而还原程度为56%的绿脱石除二八面体Fe(Ⅱ)外,还存在高活性三八面体[Fe(Ⅱ)-Fe(Ⅱ)-Fe(Ⅱ)],底面位点和边缘位点均可活化O_(2)产生·OH,并且O2在底面位点还原形成·OH效率更高。氧化过程中·OH矿化溶解性有机质(DOM)形成CO_(2)的含量随绿脱石的还原程度的升高而升高。因此,与低还原程度绿脱石(15%)相比,高还原程度的绿脱石(56%)存在高活性三八面体并能从底面位点形成·OH从而提高了·OH生成的效率并进一步促进了DOM的矿化。

Treating ballast water with hydroxyl radical on introduced organisms

With physical method of micro-gap gas discharge, a large amount of hydroxyl radical can be produced in 20t/h pilot-scale system using the ionization of 02 and H2O. In this paper, the effect of biochemistry of hydroxyl radicals on introduced organisms in ballast water was experimentally investigated. The results indicate that the contents of chlorophyl-a, chlorophyl-b, chlorophyl-c and carotenoid are decreased by 35%-4% within 8.0s and further to the lowest limit of test 5 minutes. In addition, the main reasons of cell death are the lipid peroxidation, the strong destruction to the monose, amylose, protein, DNA and RNA of cell, and damage in CAT, POD and SOD of antioxidant enzyme system.

Determination of hydroxyl radicals with salicylic acid in aqueous nitrate and nitrite solutions

The qualitative and quantitative analyses of reactive oxygen species are essential to determine their steady-state concentration and related reaction mechanisms in environmental aquatic systems. In this study, salicylic acid was employed as an innovative molecular probe of hydroxyl radical(OH) generated in aqueous nitrate and nitrite solutions through photochemical reactions. Kinetic studies showed that the steady-state concentrations of OH in aqueous NO- 3(10 mmol/L, pH=5) and NO- 2(10 mmol/L, pH=5) solutions under ultraviolet irradiation were at a same magnitude, 10 -15 mol/L. Apparent quantum yields of OH at 313 nm were measured as 0.011 and 0.07 for NO- 3 and NO- 2 respectively, all comparable to the results of previous studies.

Numerical analysis of quantitative measurement of hydroxyl radical concentration using laser-induced fluorescence in flame

The aim of the present work is to quantitatively measure the hydroxyl radical concentration by using LIF（laserinduced fluorescence） in flame.The detailed physical models of spectral absorption lineshape broadening,collisional transition and quenching at elevated pressure are built.The fine energy level structure of the OH molecule is illustrated to understand the process with laser-induced fluorescence emission and others in the case without radiation,which include collisional quenching,rotational energy transfer（RET）,and vibrational energy transfer（VET）.Based on these,some numerical results are achieved by simulations in order to evaluate the fluorescence yield at elevated pressure.These results are useful for understanding the real physical processes in OH-LIF technique and finding a way to calibrate the signal for quantitative measurement of OH concentration in a practical combustor.

Optical Emission Spectroscopic Measurement of Hydroxyl Radicals in Air Discharge with Atomized Water

Effects of discharge mode, voltage applied, size of the nozzle discharge electrode and flow rate of water on the generation of hydroxyl radical were investigated in air discharge with atomized water, by using optical emission spectroscopy （OES）. Water was injected into the discharge region through the discharge nozzle electrode, and a large amount of fine water drops, formed and distributed in the discharge region, corona discharge was more effective to generate were observed. It was found that negative DC the hydroxyl radicals in comparison to positive DC corona discharge or negative pulsed discharge. A larger outer diameter of the nozzle electrode or a stronger electric field is beneficial for hydroxyl-radical generation. Moreover, there is a critical value in the flow rate of atomized water against the discharge voltage. Below this critical value, hydroxyl-radical generation increases with the increase in flow rate of the water, while above this value, it decreases. In addition, it is observed that OES from the discharge is mainly in the ultraviolet domain. The results are helpful in the study of the mechanism and application of plasma in pollution-control in either air or water.

Determination of hydroxyl radicals in TiO2/Ti photoelectrocatalytic oxidation system using Fe（phen）3^2＋ spectrophotometry

A new method of determining the cumulate concentration of hydroxyl radicals in the TiO2/Ti photoelectrocatalytic（PEC） oxidation system was established by o-phenanthroline-Fe（Ⅱ）（Fe（phen）3^2＋） spectrophotometry and using anion exchange membrane. Fe （phen）3^2＋ can be oxidized to o-phenanthroline-Fe（Ⅲ）（Fe（phen）3^3＋） by strong oxidization of hydroxyl radicals（·OH）. Then the cumulate concentration of hydroxyl radicals can be calculated through determining the change of the Fe（phen）3^3＋ absorbency at 509 nm. In addition, the research results showed the production rate of hydroxyl radicals was affected obviously by pH of solution, the cumulate concentration of hydroxyl radicals was the largest at nearby the initial pH 6.3 （isoelectric point）, and the change direction of pH after illumination tended to nearby isoelectric point.