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1.
Degradation of atrazine by modified stepwise-Fenton's processes 总被引:3,自引:0,他引:3
The removal of atrazine (ATZ) by stepwise Fenton's processes (stepwise-FP) was studied and the system models were developed through the examination of reaction kinetics. The study compared the performance of the removal of ATZ by conventional FP with stepwise-FP, where the total dose of H(2)O(2) was split and inputted into the system at different times and/or quantities. The performance of stepwise-FP was found to be better than that of conventional FP. This was probably due to the minimization of the peak concentration of H(2)O(2) in the solution, which reduced the probability that valuable H(2)O(2) and hydroxyl radicals would be consumed in forming weaker radicals. The reaction kinetics of the decay of ATZ in stepwise-FP was found to be a two-stage process; and in each stage, fast decay followed by stagnant decay was observed. Two characterized constants (the initial decay rate and the oxidative capacity) were introduced and were found to be useful in quantifying the stepwise-FP. The models for predicting stepwise-FP with respect to different dosing times and/or asymmetrical doses were developed, and were found to be very useful for evaluating the system performance and/or for process design. 相似文献
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微波辅助光催化降解阿特拉津的表观动力学 总被引:1,自引:0,他引:1
以内分泌干扰物阿特拉津为目标物,建立循环流化床微波辅助光催化体系,研究其微波辅助光催化降解规律。表观动力学研究发现,当阿特拉津初始浓度较低时,其在微波辅助光催化体系中的降解符合表观一级反应动力学特征。降解反应速率常数与阿特拉津初始浓度呈负线性相关,与紫外光强呈正线性相关,与催化剂浓度呈抛物线性相关。表观反应速率常数kobs=3.95×10-4c-0.27030I1.2224W0.3283,该模型计算值与实验值吻合较好,平均相对偏差仅为0.5%,可用于预测微波辅助光催化降解低浓度有机污染物的反应规律。 相似文献
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Sue Ellen C. Bottrel Camila C. Amorim Mônica M.D. Leão Elizângela P. Costa Igor A. Lacerda 《Journal of environmental science and health. Part. B》2013,48(4):263-270
In this study, photocatalytic (photo-Fenton and H2O2/UV) and dark Fenton processes were used to remove ethylenethiourea (ETU) from water. The experiments were conducted in a photo-reactor with an 80 W mercury vapor lamp. The mineralization of ETU was determined by total organic carbon analysis, and ETU degradation was qualitatively monitored by the reduction of UV absorbance at 232 nm. A higher mineralization efficiency was obtained by using the photo-peroxidation process (UV/H2O2). Approximately 77% of ETU was mineralized within 120 min of the reaction using [H2O2]0 = 400 mg L?1. The photo-Fenton process mineralized 70% of the ETU with [H2O2]0 = 800 mg L?1 and [Fe2+] = 400 mg L?1, and there is evidence that hydrogen peroxide was the limiting reagent in the reaction because it was rapidly consumed. Moreover, increasing the concentration of H2O2 from 800 mg L?1 to 1200 mg L?1 did not enhance the degradation of ETU. Kinetics studies revealed that the pseudo-second-order model best fit the experimental conditions. The k values for the UV/H2O2 and photo-Fenton processes were determined to be 6.2 × 10?4 mg L?1 min?1 and 7.7 × 10?4 mg L?1 min?1, respectively. The mineralization of ETU in the absence of hydrogen peroxide has led to the conclusion that ETU transformation products are susceptible to photolysis by UV light. These are promising results for further research. The processes that were investigated can be used to remove pesticide metabolites from drinking water sources and wastewater in developing countries. 相似文献
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Removal of grease and oil by biological treatment processes 总被引:2,自引:0,他引:2
J C Young 《Journal - Water Pollution Control Federation》1979,51(8):2071-2087
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Judge DN Mullins DE Berry DF Walker HL 《Journal of environmental science and health. Part. B》2000,35(6):647-675
Solid state fermentation (SSF) was investigated as a means to dispose of two commonly used pesticides, chlorpyrifos (O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioate) and atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine). SSF experiments were carried out in bench-scale bioreactors (equipped with CO2 and volatile organic traps) containing a mixture of lignocellulosic materials and a radiolabeled pesticide. Ethyl acetate-extractable, alkali soluble, and alkali insoluble fractions were evaluated for radioactivity following a 60-d incubation period at 40 degrees C. The majority of the [2,6-pyridyl-14C]chlorpyrifos was associated with the ethyl acetate extract (about 74%), 17% was trapped as organic volatiles by polyurethane foam traps and < 0.5% of the chlorpyrifos was mineralized to CO2. Only small amounts of the radioactivity were associated with alkali soluble (0.0003%) and alkali insoluble (0.3%) fractions. In the [14C-U-ring]atrazine bioreactors, very little of the radioactivity volatilized (<0.5%) and less than 0.5% was mineralized to CO2. Approximately 57% of the applied radioactivity was associated with the ethyl acetate extract while 9% and 24% of the radioactivity was associated with the alkali soluble (humic and fulvic acids) and alkali insoluble fractions, respectively. Possible reaction mechanisms by which covalent bonds could be formed between atrazine (or metabolites) and humic substances were investigated. The issue of bound atrazine residue (alkali soluble fraction) was at least partially resolved. Oxidative coupling experiments revealed that formation of covalent bond linkages between amino substituent groups of atrazine residue and humic substances is highly unlikely. 相似文献
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Degradation and toxicity reduction of textile effluent by combined photocatalytic and ozonation processes 总被引:5,自引:0,他引:5
To minimize the environmental impact of textile effluents, mainly related to their high coloration and the presence of toxic or carcinogenic reactive dyes, the efficiency of photochemical and ozonation processes, applied in the form of isolated and combined procedures, were evaluated. The investigation was focused on the reduction of total organic carbon content (TOC), color and acute toxicity (monitoring by inhibition of Escherichia coli respiration). For a reaction time of 60 min, the anatase TiO2-assisted photocatalytic process produces color and TOC reduction of about 90% and 50%, respectively. Meanwhile, the ozonation process gives a decolorization of about 60% but negligible TOC reduction. When the processes were applied in a simultaneous form, the decolorization was almost complete and the TOC reduction was higher than 60%. The three treatments studied yield an acute toxicity reduction of around 50%. 相似文献
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Erick R. Bandala Zair DomÍnguez Fernanda Rivas Silvia Gelover 《Journal of environmental science and health. Part. B》2013,48(1):21-26
Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) was degraded using cobalt-peroximonosulfate (Co/PMS) advanced oxidation process (AOP). Three Co concentrations (0.00, 0.25 and 0.50 mM) and five peroximonosulfate (PMS) concentrations (0, 5, 8, 16 and 32 mM) were tested. Maximum degradation reached was 88% using dark Co/PMS in 126 minutes when 0.25 mM of cobalt and 32 mM of PMS were used. Complete atrazine degradation was achieved when the samples were irradiated by the sun under the same experimental conditions described. Tests for identification of intermediate products allowed identification and quantification of deethylatrazine in both dark and radiated conditions. Kinetic data for both processes was calculated fitting a pseudo-first order reaction rate approach to the experimental data. Having kinetic parameters enabled comparison between both conditions. It was found that the kinetic approach describes data behavior appropriately (R2 ≥ 0.95). Pseudo-kinetic constants determined for both Co/PMS processes, show k value of 10?4 for Co/PMS and a k value of 10?3 for Co/PMS/ultraviolet (UV). This means, that, with the same Co/PMS concentrations, UV light increases the reaction rate by around one order of magnitude than performing the reaction under dark conditions. 相似文献
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Bandala ER Domínguez Z Rivas F Gelover S 《Journal of environmental science and health. Part. B》2007,42(1):21-26
Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) was degraded using cobalt-peroximonosulfate (Co/PMS) advanced oxidation process (AOP). Three Co concentrations (0.00, 0.25 and 0.50 mM) and five peroximonosulfate (PMS) concentrations (0, 5, 8, 16 and 32 mM) were tested. Maximum degradation reached was 88% using dark Co/PMS in 126 minutes when 0.25 mM of cobalt and 32 mM of PMS were used. Complete atrazine degradation was achieved when the samples were irradiated by the sun under the same experimental conditions described. Tests for identification of intermediate products allowed identification and quantification of deethylatrazine in both dark and radiated conditions. Kinetic data for both processes was calculated fitting a pseudo-first order reaction rate approach to the experimental data. Having kinetic parameters enabled comparison between both conditions. It was found that the kinetic approach describes data behavior appropriately (R2 > or = 0.95). Pseudo-kinetic constants determined for both Co/PMS processes, show k value of 10(-4) for Co/PMS and a k value of 10(-3) for Co/PMS/ultraviolet (UV). This means, that, with the same Co/PMS concentrations, UV light increases the reaction rate by around one order of magnitude than performing the reaction under dark conditions. 相似文献
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生物化学协同除磷研究 总被引:7,自引:0,他引:7
采用聚合硅酸铝和聚合硅酸铁两种混凝剂,比较了将混凝剂直接投加到反应器中和对生物反应器出水再进行混凝沉淀2种工艺的除磷效果,并对2种混凝剂的除磷效果进行了比较。结果表明:对于聚合硅酸铝,没有生物协同作用;对于聚合硅酸铁,投加量在40mg/L以下时具有生物协同作用,30mg/L时协同作用最明显;而且聚合硅酸铁的除磷效果好于聚合硅酸铝。 相似文献
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David N. Judge Donald E. Mullins Duane F. Berry Hubert L. Walker Jr. 《Journal of environmental science and health. Part. B》2013,48(6):647-675
Abstract Solid state fermentation (SSF) was investigated as a means to dispose of two commonly used pesticides, chlorpyrifos (O, O‐diethyl O‐(3,5,6‐trichloro‐2‐pyridyl) phosphorothioate) and atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine). SSF experiments were carried out in bench‐scale bioreaetors (equipped with CO2 and volatile organic traps) containing a mixture of lignocellulosic materials and a radiolabeled pesticide. Ethyl acetate‐extractable, alkali soluble, and alkali insoluble fractions were evaluated for radioactivity following a 60‐d incubation period at 40°C. The majority of the [2, 6‐pyridyl‐14C]chlorpyrifos was associated with the ethyl acetate extract (about 74%), 17% was trapped as organic volatiles by polyurethane foam traps and < 0.5% of the chlorpyrifos was mineralized to CO2. Only small amounts of the radioactivity were associated with alkali soluble (0.0003%) and alkali insoluble (0.3%) fractions. In the [14C‐U‐ring] atrazine bioreactors, very little of the radioactivity volatilized (<0.5%) and less than 0.5% was mineralized to CO2. Approximately 57% of the applied radioactivity was associated with the ethyl acetate extract while 9% and 24% of the radioactivity was associated with the alkali soluble (humic and fulvic acids) and alkali insoluble fractions, respectively. Possible reaction mechanisms by which covalent bonds could be formed between atrazine (or metabolites) and humic substances were investigated. The issue of bound atrazine residue (alkali soluble fraction) was at least partially resolved. Oxidative coupling experiments revealed that formation of covalent bond linkages between amino substituent groups of atrazine residue and humic substances is highly unlikely. 相似文献
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Strong oxidation by titanium dioxide photocatalysis can occur by photodegradation of organic contaminants in air and water. Some endocrine disruptors such as 2,4-dichlorophenoxy acetic acid (;;; ), 2,4-dichlorophenol (;;; ), nonylphenol (; ), bisphenol A (), diethyl phthalate (; ), etc. which can be neither biodegraded by bacteria nor degraded thermally can be degraded by TiO(2) photocatalytic treatment. However, incomplete photomineralization partly occurred, when TiO(2) photocatalytic degradation is employed for the treatment of certain endocrine disruptors. For example, no atrazine pesticide having triazine skeleton can be completely mineralized even by a photocatalytic procedure; the photodegradation of atrazine ultimately stops at the intermediate step of cyanuric acid, which cannot be photodegraded even after long illumination times ().In this study, the decomposition of atrazine and cyanuric acid was carried out with a device combining photocatalytic degradation in supercritical water (scH(2)O) or hydrothermal water (hyH(2)O). Atrazine and cyanuric acid can be degraded by the cooperation of either scH(2)O or hyH(2)O and UV illuminated TiO(2)-photocatalytic dispersed system under the fixed pressure of 23 MPa at 623 K or 683 K in a 120-ml Hastelloy batch reactor. The photocatalytic degradation method under high temperature and pressure has found appropriate for the photocatalytic oxidation of acetic acid and 2-chlorobiphenyl under continuous flow conditions at 160 degrees C and 20 atm (). In addition, the wet peroxide oxidation of PCBs by high temperature and pressure has been reported (). The main aims of this research are following. (i): the degradation of atrazine and cyanuric acid within the scH(2)O or hyH(2)O, (ii) the decomposition of atrazine and cyanuric acid catalyzed by TiO(2) particles under scH(2)O or hyH(2)O, and the synergistic effect for several reactions with TiO(2) and scH(2)O or hyH(2)O, and (iii) the mineralization yield of nitrogen and chlorine atoms concerning the chemical structures of atrazine or cyanuric acid (only nitrogen). 相似文献
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采用PVA生物处理工艺对某高校生活污水(COD 140~270 mg/L,NH4+-N 20~50 mg/L)进行处理。结果表明:PVA生物系统(85 L)在容积负荷1.5 kg COD/(m3·d)连续运行25 d,系统平均每天处理水量达到272 L,出水平均COD和NH4+-N浓度分别达到27.9 mg/L和1.3 mg/L,此外,经紫外消毒后最终出水菌落数降至1.0×104个/L以下;扫描电镜观察发现,PVA凝胶小球表面和内部均富含大量球菌、丝状菌和杆菌;该系统25 d连续运行过程中污泥产率仅为0.08 MLSS/CODremoved,无污泥外排。 相似文献
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物化-生物组合工艺处理TNT红水 总被引:1,自引:0,他引:1
采用酸析+微电解+混凝沉淀+减压蒸馏+固定化微生物滤池+活性焦吸附组合工艺处理兵器八○五厂(襄樊分部)的TNT红水,出水中的硝基化合物浓度多小于0.8 mg/L,且多次未检出;COD最高值为76 mg/L,平均值为51.6 mg/L;色度为20°;苯胺浓度全部小于1 mg/L,达到了中试方案提出的要求,出水水质指标符合《兵器工业水污染物排放标准火炸药》(GB14470.1-2002)的要求.中试期间设备没有发生堵塞、燃烧等事故,减压蒸馏装置正常稳定运行,证实了减压蒸馏法处理TNT红水的安全可靠性. 相似文献
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进行了厌氧折流板反应器-垂直潜流人工湿地(ABR-VSFCW)、复合厌氧反应器-水平潜流人工湿地(HAR-HSFCW)、膨胀颗粒污泥床-人工快速渗滤系统(EGSB-CRI)3种组合工艺处理农村生活污水的研究。结果表明,在温度为10~29℃,进水COD为325.3~386.5 mg/L的条件下,3种组合工艺对COD均有较高的处理效果,当厌氧段HRT大于16 h时,3种组合工艺出水COD浓度均达到了我国《城镇污水处理厂污染物排放标准》(GB 18918-2002)一级B标准;EGSB-CRI、HAR-HSFCW对TP的去除效果较好,出水TP浓度均达到了我国《城镇污水处理厂污染物排放标准》(GB 18918-2002) 一级B标准, 且显著优于ABR-VSFCW,ABR-VSFCW出水TP浓度达到了二级标准; ABR-VSFCW、HAR-HSFCW、EGSB-CRI出水NH4+-N浓度分别为25.24~42.20、29.59~41.60和9.80~15.35 mg/L,其出水NH4+-N浓度达到了我国《城镇污水处理厂污染物排放标准》(GB 18918-2002)二级标准;3种组合工艺对TN的去除效果无明显差异,去除率仅为23.9%~46.4%。因此,EGSB-CRI对农村生活污水的处理效果最好,HAR-HSFCW次之,ABR-VSFCW较差。 相似文献
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In this study, laboratory experiments are conducted to compare the efficacy using several ozone-based advanced oxidation processes (AOPs), such as O3, O3/H2O2, and O3/UV, to treat landfill leachate. Raw leachate was initially coagulated by ferric chloride (FeCl3) at the experimental-determined optimal dosage of 900 mgl(-1), and the ozone-based AOPs were subsequently applied. Results indicate that all AOPs would result in a significant increase on the ratio of BOD5/COD from 0.06 to 0.5 at the applied ozone dosage of 1.2 gl(-1). The increase on biodegradability for ozonated leachate indicates that these AOPs would be beneficial to the subsequent biological treatment process. To better explain the alteration of high organic molecules after oxidation, ultrafiltration was used to separate the leachate by several molecular weight cutoffs (MWCO). The COD distribution for coagulated leachate is 34% for MWCO>10 kDa, 7% for MWCO between 5 and 10 kDa, 22% for MWCO between 1 and 5 kDa, and 37% for MWCO<1 kDa. Following ozonation or AOPs, the predominant distribution of COD would be obviously shifted to the MWCO less than 1000 gmol(-1) (72-85%) over the other MWCO ranges. In addition, Gel Permeation Chromatograph (GPC) analysis has showed a substantial agreement on the cleavage of larger organic compounds into smaller ones. O3/UV was found to be the most effective approach among these ozone-based AOPs to enhancing the biodegradability and eliminating the color of leachate. 相似文献