Destruction of phenol aqueous solution by photocatalysis or direct photolysis

The photodegradation of phenol has been investigated under a high-pressure mercury lamp with a kind of jacket (glass or quartz) depending on used UV light range and a variety of experimental conditions: UV (lambda > 200 nm) with oxygen or with TiO2 and oxygen or with N2; UV (lambda > 330 nm) with oxygen or with TiO2 and oxygen or with N2. Photocatalysis and direct photolysis of phenol have different reaction pathways. Direct photolysis of phenol yielded a brown-yellow complex organic polymer in both aerobic and anaerobic environments. The polymer cannot be mineralized in an anaerobic environment. The effects of catalyst amount and oxygen concentration in the reaction atmosphere on the destruction of phenol were studied. The results prove that an appropriate catalyst amount can avoid direct photolysis and increase the mineralization rate of phenol.     

超声-过氧化氢-氧化铜组合技术催化氧化水中苯酚

研究了超声-H2O2-CuO组合技术对苯酚的降解效果。考察了苯酚初始浓度、溶液温度及鼓入空气对苯酚去除率的影响。实验结果表明，与未鼓入空气时相比，连续鼓气时苯酚的降解效果较好；初始浓度低，苯酚去除率高；溶液温度从20％上升到55％时，苯酚去除率随温度升高而增大，温度对该过程的影响主要表现为对催化剂的影响而不是对超声作用的影响。高效液相色谱分析表明，苯酚降解的中间产物主要为对苯二酚、邻苯二酚及其他有机小分子物质，最终产物为草酸、二氧化碳和水。     

超声-过氧化氢-氧化铜组合技术催化氧化水中苯酚

研究了超声-H2O2-CuO组合技术对苯酚的降解效果。考察了苯酚初始浓度、溶液温度及鼓入空气对苯酚去除率的影响。实验结果表明,与未鼓入空气时相比,连续鼓气时苯酚的降解效果较好;初始浓度低,苯酚去除率高;溶液温度从20℃上升到55℃时,苯酚去除率随温度升高而增大,温度对该过程的影响主要表现为对催化剂的影响而不是对超声作用的影响。高效液相色谱分析表明,苯酚降解的中间产物主要为对苯二酚、邻苯二酚及其他有机小分子物质,最终产物为草酸、二氧化碳和水。     

The influence of pH on the degradation of phenol and chlorophenols by potassium ferrate

This paper presents information concerning the influence of solution pH on the aqueous reaction between potassium ferrate and phenol and three chlorinated phenols: 4-chlorophenol (CP), 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP). The redox potential and aqueous stability of the ferrate ion, and the reactivity of dissociating compounds, are known to be pH dependent. Laboratory tests have been undertaken over a wide range of pH (5.8-11) and reactant concentrations (ferrate:compound molar ratios of 1:1 to 8:1). The reactivity of trichloroethylene was also investigated as a reference compound owing to its non-dissociating nature. The extent of compound degradation by ferrate was found to be highly pH dependent, and the optimal pH (maximum degradation) decreased in the order: phenol/CP, DCP, TCP; at the optimal pH the degree of degradation of these compounds was similar. The results indicate that for the group of phenol and chlorophenols studied, the presence of an increasing number of chlorine substituent atoms corresponds to an increasing reactivity of the undissociated compound, and a decreasing reactivity of the dissociated compound.     

高铁酸钾降解苯酚的机制研究

借助高效液相色谱(HPLC),通过标准物比对法和添加标准物法,研究了高铁酸钾降解苯酚的开环产物.结果表明,高铁酸钾降解苯酚的主要稳定的中间产物有顺丁烯二酸、反丁烯二酸、草酸和甲酸.并据此推导出苯酚被高铁酸钾氧化降解的可能途径.     

Formation of nitrophenols upon UV irradiation of phenol and nitrate in aqueous solutions and in TiO2 aqueous suspensions.

The formation of nitrophenols was studied as a consequence of ultra violet (UV) irradiation of aqueous solutions of phenol and nitrate in the range of pH 1-12. The study was performed both in homogeneous phase and in the presence of water-suspended TiO2. The effects of pH, dissolved oxygen and 2-propanol as .OH scavenger have been evaluated. A reaction mechanism is proposed, based on the experimental results.     

CuAPO-5分子筛催化氧化水溶液中苯酚的性能

以水热晶化法合成了铜磷铝分子筛CuAPO-5,并用XRD、SEM,FT-IR,UV-Vis等对样品进行了表征,结果表明Cu²⁺进入到了AlPO₄-5分子筛骨架中。研究了以CuAPO-5为催化剂, H₂O₂为氧化剂对水溶液中苯酚的催化氧化性能。在苯酚初始浓度200 mg/L 、H₂O₂添加量1 200 mg/L、pH值5.0、处理温度80 ℃时,处理240 min时苯酚去除率达到100％,TOC去除率达81.76％,析出到溶液中Cu²⁺浓度仅为0.527 mg/L。温度从40 ℃上升到80 ℃时,苯酚的去除率及TOC去除率明显增大,表明温度对催化剂的活性影响显著,相比于均相催化剂骨架Cu催化过氧化氢分解需要更多的能量。重复性实验表明,催化剂性能稳定。     

Wet air oxidation of nitrobenzene enhanced by phenol

Simultaneous nitrobenzene and phenol wet air oxidation was investigated in a stainless autoclave at temperature range of 180-220 degrees C and 1.0 MPa oxygen partial pressure. Compared with the single oxidation of nitrobenzene under the same conditions, the presence of phenol in the reaction media greatly improved the removal efficiency of nitrobenzene. The effect of temperature on the reaction was studied. Phenol was considered as a type of initiator in the nitrobenzene oxidation.     

Contribution of free radicals to chlorophenols decomposition by several advanced oxidation processes

The chemical decomposition of aqueous solutions of various chlorophenols (4-chlorophenol (4-CP), 2,4-dichlorophenol (2-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP)), which are environmental priority pollutants, is studied by means of single oxidants (hydrogen peroxide, UV radiation, Fenton's reagent and ozone at pH 2 and 9), and by the Advanced Oxidation Processes (AOPs) constituted by combinations of these oxidants (UV/H2O2 UV/Fenton's reagent and O3/UV). For all these reactions the degradation rates are evaluated by determining their first-order rate constants and the half-life times. Ozone is more reactive with higher substituted CPs while OH* radicals react faster with those chlorophenols having lower number of chlorine atoms. The improvement in the decomposition levels reached by the combined processes, due to the generation of the very reactive hydroxyl radicals. in relation to the single oxidants is clearly demonstrated and evaluated by kinetic modeling.     

Nitrate and natural organic matter in aqueous solutions irradiated by simulated sunlight

By means of simulated sunlight, the influence of natural organic matter (NOM) on the photochemical degradation of halogenated pesticides in the absence and presence of nitrate as a precursor of the highly reactive OH radicals in aqueous solutions and freshwater was investigated. Solutions of dichlorprop or terbutylazine (a) in phosphate-buffered demineralized water containing nitrate and/or NOM and (b) in natural freshwaters were irradiated by a 1000-W Xe short-arc lamp. The collimated beam was filtered using a combination of optical filters (WG 320 and WG 295) to simulate the solar spectrum under summer midday conditions. In the absence of nitrate and NOM, the pesticides were degraded photolytically by simulated sunlight. The degradation rates depended on the absorption spectrum in the UVB range and the quantum yield of the degradation. The photochemical degradation of the pesticides was faster in the presence of nitrate due to the sunlight-induced formation of OH radicals. In the absence of nitrate, low concentrations of NOM of a brownwater lake accelerated the degradation due to the formation of reactive species by NOM. At higher concentrations of NOM, the inner filter effect of NOM lowered the degradation rates. In the presence of 50 mg l−1 nitrate, NOM decreased the degradation rate significantly. In case the natural water samples were used as a matrix for the experiments (nitrate concentrations between 2 mg l−1 and 15 mg l−1, DOC concentrations below 2.3 mg l−1), NOM acted mainly as a radiation filter and as a scavenger of OH radicals. As a consequence, in most freshwater systems, the accelerating effect of NOM by the formation of reactive species is of minor importance compared to the inner filter effect and to radical scavenging.     

CuO / 过硫酸氢钾体系催化氧化苯酚简

本论文通过直接沉淀法制备了CuO催化剂,结合过硫酸氢钾,在常温常压下催化氧化处理苯酚模拟废水。采用电子显微镜（SEM）、X射线粉末衍射（XRD）对催化剂进行了表征,并研究了反应过程中各影响因素对降解效率的影响。实验结果表明,在催化剂用量为0.2 g/L,氧化剂浓度为0.25 g/L,pH值为7,反应时间为60 min的条件下,浓度为50 mg/L的苯酚降解率可达100%,TOC去除率达84%。进一步实验表明,催化剂具有良好的重复使用能力。最后,通过自由基捕捉实验,考察了体系中的自由基种类,并根据实验结果,讨论了CuO/过硫酸氢钾体系的催化降解机理。     

CuO/过硫酸氢钾体系催化氧化苯酚

本论文通过直接沉淀法制备了CuO催化剂,结合过硫酸氢钾,在常温常压下催化氧化处理苯酚模拟废水。采用电子显微镜（SEM）、X射线粉末衍射（XRD）对催化剂进行了表征,并研究了反应过程中各影响因素对降解效率的影响。实验结果表明,在催化剂用量为0.2 g/L,氧化剂浓度为0.25 g/L,pH值为7,反应时间为60 min的条件下,浓度为50 mg/L的苯酚降解率可达100%,TOC去除率达84%。进一步实验表明,催化剂具有良好的重复使用能力。最后,通过自由基捕捉实验,考察了体系中的自由基种类,并根据实验结果,讨论了CuO/过硫酸氢钾体系的催化降解机理。     

Enhanced oxidation of methoxy phenols at micromolar concentration photosensitized by dissolved natural organic material

The rate coefficients for the photosensitized oxidation of various phenols in aqueous solutions containing dissolved natural organic material increased in some cases with decreasing phenol concentration. For 3,4-dimethoxyphenol and 4-methoxyphenol at initial concentration going from 10 to 1.0 μM, the rate coefficients increased by a factor of 5 in a humic acid solution and by a factor of 2 in a fulvic acid solution and a lake water. For 2,4,6-trimethylphenol, 4-methylphenol and phenol at initial concentration going from 15 to 2.5 μM, they increased by a factor < 2 in the humic acid solution and were constant in the fulvic acid solution and the lake water. We suggest that the methoxy phenols, which are known to easily reduce oxidants, readily react with a class of photo-oxidants whose lifetime is expected to be > 100 μs. Thereby the long-lived photo-oxidants seem to be scavenged by the phenols themselves.     

喹禾灵含酚废水混凝氧化效果的试验研究

选用三氯化铁作混凝剂,次氯酸钠作氧化剂,研究了混凝剂和氧化剂的投加量、pH及不同的反应时间对喹禾灵含酚废水处理效果的影响。试验结果表明,混凝剂最佳投加量为8．0g／L,最佳pH为9～10;氧化剂最佳投加量为50mL/L(有效氯为5．2％)．最佳pH为2～3。在最佳条件下,废水经混凝氧化后,其CODc,、对苯二酚、色度的去除率分别达98．12％、97．26％、99．00％。     

炭化百合杆对废水中苯酚的吸附

采用聚乙二醇活化原材料百合杆,分别在300％和600℃对活化后百合杆进行炭化,制得炭化百合杆,用于吸附废水中的苯酚。实验考察了pH值、吸附时间和吸附质初始浓度对苯酚吸附的影响,采用Langmuir、Freundlich和Dubinin．Radushkevich等温式分别对该吸附过程进行描述,并结合实验数据对比了准一级和准二级动力学模型。结果表明：炭化百合杆对苯酚的吸附过程符合Langmuir等温式和准二级动力学模型,计算了热力学参数（△G、△H和△s）,说明该吸附过程为自发进行。碳化百合杆对苯酚具有良好吸附性能。     

Uptake and transformation of phenol and chlorophenols by hairy root cultures of Daucus carota, Ipomoea batatas and Solanum aviculare

Hairy root cultures of Daucus carota L., Ipomoea batatas L. and Solanum aviculare Forst were investigated for their susceptibility to the highly toxic pollutants phenol and chlorophenols and for the involvement of inherent peroxidases in the removal of phenols from liquid media. Roots of D. carota grew normally in medium containing 1000 micromol l(-1) of phenol, whilst normal growth of roots of I. batatas and S. aviculare was only possible at levels up to 500 micromol l(-1). In the presence of chlorophenols, normal root growth was possible only in concentrations not exceeding 50 micromol l(-1), except for I. batatas which was severely affected at all concentrations. Despite the reduction in biomass, the growth of S. aviculare cultures was sustained in medium containing up to 2000 micromol l(-1) of phenol or 2-chlorophenol, and up to 500 micromol l(-1) of 2,6-dichlorophenol. The amounts of phenol removed by the roots within 72 h of treatment were 72.7%, 90.7% and 98.6% of the initial concentration for D. carota, I. batatas and S. aviculare, respectively. For the removal of 2,6-dichlorophenol the values were, respectively, 83.0%, 57.7% and 73.1%. Phenols labelled with 14C were absorbed by the root tissues and condensed with highly polar cellular substances as well as being incorporated into the cell walls or membranes. The results suggest that S. aviculare, an ornamental plant, would be best suited for remediation trials under field conditions.     

Changes of turbidity during the phenol oxidation by photo-Fenton treatment

Turbidity presented by phenol solutions oxidized with Fenton reagent shows the tendency of a first order intermediate kinetics. Thus, turbidity can be considered a representative parameter of the presence of intermediate oxidation species, which are generated along the decomposition of toxic and reluctant contaminants, such as phenol. Moreover, that parameter presents a linear dependence with the catalyst dosage, but is also determined by the initial contaminant load. When analyzing the oxidation mechanism of phenol, it is found that the maximum turbidity occurs when the treatment is carried out at oxidant to phenol molar ratios R?=?4.0. These oxidation conditions correspond to the presence of a reaction mixture mainly composed of dihydroxylated rings, precursors of the muconic acid formation. The oxidation via “para” comprises the formation reactions of charge transfer complexes (quinhydrone), between the para-dihydroxylated intermediates (hydroquinone) and the para-substituted quinones (p-benzoquinone), which are quite unstable and reactive species, quickly decomposed into hydroxyhydroquinones. Working with oxidant ratios up to R?=?6.0, the maximum observed value of turbidity in the oxidized solutions is kept almost constant. It is found that, in these conditions, the pyrogallol formation is maximal, what is generated through the degradation of ortho-species (catechol and ortho-benzoquinone) and meta-substituted (resorcinol). Operating with ratios over R?=?6.0, these intermediates are decomposed into biodegradable acids, generating lower turbidity in the solution. Then, the residual turbidity is a function of the molar ratio of the ferrous ions vs. moles of oxidant utilized in the essays, that lets to estimate the stoichiometric dosage of catalyst as 20 mg/L at pH?=?3.0, whereas operating in stoichiometric conditions, R?=?14.0, the residual turbidity of water results almost null.     

Experimental and statistical validation of SPME-GC-MS analysis of phenol and chlorophenols in raw and treated water

A procedure based on solid-phase microextraction (SPME) and gas chromatography coupled with mass spectrometry (GC-MS) was developed and validated in order to analyse 10 phenols in water samples. The optimised conditions were obtained using polyacrylate fibre (PA), 20ml of sample volume, 10% NaCl, pH 4.0 and direct extraction at 35 degrees C and 1000rpm, for 40min. The linear range and quantification limits for these compounds by SPME-GC-MS were defined. An evaluation of the main uncertainty sources of this method is included, which allows expanded uncertainties in the 9.4-35% range for the majority of the compounds. The main source of uncertainty is associated with matrix effects. The validated method is suitable for monitoring the production and distribution of potable water and was used, in field trials, for the analysis of samples from main intakes of water (surface or underground) and from water supply system of a large area (Lisbon and neighbour municipalities).     

聚铁硅盐掺杂羟基氧化铁类芬顿催化氧化苯酚

为解决非均相类芬顿法催化剂分离回收困难的问题,采用共沉淀法制备了催化剂聚铁硅盐掺杂羟基氧化铁(PFSC-FeOOH)。利用X射线衍射(XRD)、扫描电子显微镜(SEM)以及傅里叶变换红外光谱(FT-IR)等技术手段对催化剂进行了表征。以苯酚为目标污染物,分别考察了催化剂用量、H₂O₂用量、反应温度、苯酚初始浓度和pH对PFSC-FeOOH催化H₂O₂去除苯酚效果的影响,探究了可能的反应机理。结果表明：在反应时间为40 min、pH=4、H₂O₂投加量为297 mmol·L⁻¹、催化剂PFSC-FeOOH投加量为3 g·L⁻¹、反应温度为室温((25±1) ℃)的条件下,苯酚降解率为90.48%;反应符合准一级反应动力学,速率常数为 0.0415 min⁻¹;反应过程中羟基自由基(·OH)起主要作用,苯酚的分子结构被氧化破坏;反应后,催化剂易于沉降分离,沉降速度为0.1 m·min⁻¹。以上研究结果可为实际有机废水的处理提供参考。     

TiO2负载型活性炭电催化氧化苯酚性能研究

以活性炭为载体,采用溶胶凝胶法制备TiO2负载型活性炭,采用电子显微镜(SEM)和X射线衍射(XRD)仪对催化剂进行表征,TiO2负载型活性炭晶体结构牢固,为锐钛矿.在苯酚质量浓度为600mg/L、30 000 mg/L Na2SO4为支持电解质、恒流泵、电流密度30 A/m2、流速0.6 L/h的条件下对模拟废水进行连续处理,研究TiO2负载型活性炭对COD、平均电流效率和电耗的影响.结果表明,填料为TiO2负载型活性炭比填料为活性炭的最终出水COD去除率提高6.45百分点,平均电流效率提高10百分点,电耗下降7.20 kW· h/kg,说明TiO2负载型活性炭有较高的电流利用率且催化活性较高.进一步说明,在一定的浓度范围内,TiO2负载型活性炭能更有效降解苯酚废水.