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Degradation of pesticides by UV and UV-based advanced oxidation processes: State-of-the-art

Liu Chao,Qiang Zhimin and,

环境科学学报 , 2011,
Abstract: The micro-contamination of drinking water resources with pesticides is of great concern nowadays due to their persistence in aquatic environment and potential adverse health effects. Among various water treatment processes, UV and UV-based advanced oxidation processes (AOPs) have gained great attention due to their effectiveness in bacteria inactivation and low yield of disinfection byproducts. This work reviewed, in a comprehensive manner, the degradation of several classes of pesticides including organochlorines, organophosphates, carbamates, chloroacetamides and triazines by UV and UV-based AOPs. The degree of pesticide removal, reaction kinetics, degradation byproducts identification and possible degradation pathways, and evaluation of toxicity of degradation byproducts are covered and discussed.
Degradation of 2-hydroxybenzoic acid by advanced oxidation processes
Zanta, C. L. P. S.;Martínez-Huitle, C. A.;
Brazilian Journal of Chemical Engineering , 2009, DOI: 10.1590/S0104-66322009000300006
Abstract: in this study, advanced oxidation processes (aops) such as the uv/h2o2 and fenton processes were investigated for the degradation of 2-hydroxybenzoic acid (2-hba) in lab-scale experiments. different [h2o2]/[2-hba] molar ratios and ph values were used in order to establish the most favorable experimental conditions for the fenton process. for comparison purposes, degradation of 2-hba was carried out by the uv/h2o2 process under fenton experimental conditions. the study showed that the fenton process (a mixture of hydrogen peroxide and fe2+ ion) was the most effective under acidic conditions, leading to the highest rate of 2-hydroxybenzoic acid degradation in a very short time interval. this same process led to a six-fold acceleration of the oxidation rate compared with the uv/h2o2 process. the degradation of 2-hydroxybenzoic acid was found to follow first-order kinetics and to be influenced by the type of process and the experimental conditions. the experimental results showed that the most favorable conditions for 2-hba degradation by the fenton process are ph around 4-5, [fe2+] = 0.6 mmol.l-1, and [h2o2]/[2-hba] molar ratio = 7. the hydroxylation route is explained here for the two processes, and the results are discussed in the light of literature information.
Ultrasonic Degradation of Fuchsin Basic in Aqueous Solution: Effects of Operating Parameters and Additives  [PDF]
Rui-Jia Lan,Ji-Tai Li,Bao-Hua Chen
International Journal of Photoenergy , 2013, DOI: 10.1155/2013/893131
Abstract: Ultrasonic degradation is one of the recent advanced oxidation processes (AOPs) and proven to be effective for removing low-concentration organic pollutants from aqueous solutions. In this study, removal of fuchsin basic from aqueous solutions by ultrasound was investigated. The effects of operating parameters such as ultrasound power (200?W–500?W), initial pH (3–6.5), and temperature (15, 22, 35, and 60°C) on the ultrasonic degradation were studied. The degradation of fuchsin under ultrasound irradiation basic was found to obey pseudo first-order reaction kinetics. Addition of catalyst Fe(II) had a markedly positive effect on degradation. 84.1% extent of degradation was achieved at initial dye concentration 10?μmol?L?1, ultrasound power 400?W, ultrasound frequency 25?kHz, dosage of Fe(II) 4?mg?L?1, initial pH 6.5, and temperature 22°C. But addition of heterogeneous catalyst TiO2 affected degradation slightly. Addition of radical scavenger suppressed fuchsin basic degradation significantly. 1. Introduction Dyes are classified into various groups, such as azo, phthalocyanine, xanthene, and arylmethane, on the basis of their chemical structure. At present, approximately 10,000 different dyes and pigments are utilized in industry, with total estimated annual global consumption of 7 × 105 tonnes [1]. People are aware that cationic dye molecules are more toxic than anionic dye molecules [2]. Furthermore, most of these dyes are biorefractory and do not undergo effective degradation using conventional biological techniques [3]. Advanced oxidation processes (AOPs) are very efficient methods for degradation of recalcitrant organic compounds in industrial and agricultural effluents [4, 5]. They act through the use of free radicals, especially reactive attack. Sonolytic oxidation is one of the AOPs techniques and has proven to be an effective method for degrading organic effluents into less toxic compounds [6–9]. Sonochemistry is a complex process, which depends on physical parameters and also on the process conditions. All efforts have been devoted to the optimization of physical parameters and the process conditions [10, 11]. Some efforts have been devoted to improve the degradation efficiency in sonochemical processes by adding various kinds of catalysts [12–15]. Fuchsin basic, a cationic triphenylmethane dye, was chosen as a typical representative pollutant. Fuchsin basic is traditionally used as colorant in dyeing textiles such as cotton, artificial fiber, leather, and paper [16]. When someone is exposed to fuchsin dye by the physical contact, ingestion, or
Comparison among some advanced oxidation processes in the degradation kinetics of the crude tannery effluent  [cached]
Camila Lopes Maler,Keiko Takashima
Semina : Ciências Exatas e Tecnológicas , 2011,
Abstract: In this work it was investigated the degradation kinetics of the crude tannery wastewater, collected in the homogenized reservoir with a chemical oxygen demand of 3340 mg L-1 at pH 8.1, through the advanced oxidation processes as photocatalysis mediated by semiconductor, photolysis in presence of hydrogen peroxide and photo-Fenton process at 30 oC. The experiments were performed using a 1:50 proportion in distilled water inside the double wall cylindrical reactor opened to the atmospheric air by varying the oxidant concentration. The degradation rate constants, kobs, determined under pseudo-first order conditions in pH ca. 7.3 and 30 oC, were higher for the photocatalytic process mediated by ZnO (kobs= 1.23x10-1 to 2.74x10-1 min-1) followed by TiO2 (0.90x10-2 min-1 to 3.35x10-2 min-1). As to for the rate constants under photolysis in presence of H2O2 (9.36x10-3 to 7.44x10-3 min-1) at pH ca. 6.8 as well as in photo-Fenton (7.30x10-3 to 12.0x10-3 min-1) at pH 5.8 was significantly lower than photocatalysis at 30°C. The chemical oxygen demand of the wastewater was completely removed after 2 h on photocatalytic process at 30 °C.
Kinetics and Mechanism Analysis of the Degradation of Hexachlorbenzene in Water by Advanced Oxidation Process

WEI Dong-yang,JIA Xiao-shan,LU Gui-ying,LIU Guang-li,

环境科学 , 2008,
Abstract: The degradation characteristics and rule of hexachlorobenzen (HCB) in water were studied and the results were compared by the advanced oxidation process UV, O3 and UV/O3. The experimental results showed that UV itself did not contribute to the removal of HCB obviously and HCB could be quickly degraded by O3 and UV/O3, namely UV < O3 < UV/O3. But in the case of O3 and UV/O3, raising the initial pH value of the system could not raise the removal rate of HCB, and the removal efficiency of 0.2 mg/L HCB could reach 50% within 40 min when the initial pH value was equaled to 3 and the degradation velocity could be accelerated in the acidic solution. Whether in the cases of ozone action alone or UV/O3 combined action, the degradation of HCB satisfied basically the rule of pseudo-first order reaction kinetics; and this rule was more remarkable if a constant pH value of the system was maintained. The degradation pathway and mechanism of HCB were discussed according to the measured results of the intermediated substances from the HCB degradation process by IC, GC and GC-MS.
Oxidation of Pentachlorophenol by Fenton’s Reagent
M Farrokhi,AR Mesdaghinia,S Naseri,AR Yazdanbakhsh
Iranian Journal of Public Health , 2003,
Abstract: Several authors have indicated that PCP is a toxic chemical and recalcitrant to biodegradation. AOPs is one of the moste effective process for degradation of persistant compound.Since the mineralization of recalcitrant compound by AOPs (Advanced Oxidation Processes) often requires long reaction time and strong doses of oxidant, the combination of this process with biological one, considered as an efficient and economic method. In this worke degradation of pentachlorophenol in aqueous solution with fenton reagent (H2O2 +Ferrous ion)was studied. The experiment was done in batch mode, and the initial concentration of PCP was 0.055mM, in pH=3, H2O2=0.6mM, Fe=0.2mM, more than 95% of PCP was degraded in first minute after the reaction was started.Therefor this reaction is very fast and in the initial phase degredation of PCP follows first order kinetics and kineticts constant (K) was 0.026 (S-1). Chloride ion generatation as PCP degredation by product was investigated ,and it was found that the scavenging effect of chloride is negligible. pH and UV215 absorbance analysis, after reaction completion, indicated that generated intermediates have the less chlorinated nature, acidic properties and nonphenolic structure. Chloride ion increases from 0 mg/L to 6 mg/L, pH decreases from 3 to 2.82 and UV215 absorbance decreasees from 0.48 to 0.1, therefor it can be resulted that their biodegradability modified and their recalcitrance reduced. In the long time reaction (10hr) experiments, TOC and COD analysis indicated that PCP did not mineralize and TOC and COD reduction was only 20% and 30% respectively. Results from this study indicated that scavenging effects of generated intermadiate is important in highe doses of H2O2.
Degradation Kinetics of Activated Carbon Catalyzed Persulfate Oxidation Orange G

YANG Mei-mei,ZHOU Shao-qi,LIU Dan,ZHENG Ke,

环境科学 , 2013,
Abstract: The oxidation degradation of orange G(OG)in aqueous solutions by the activated carbon catalyzed peroxydisulfate(PDS) has been kinetically investigated. These processes are based on the generation of sulfate radicals, which are powerful oxidizing species found in nature. The results demonstrated that OG could be degraded by GAC/PDS reagent effectively. Moreover, the dosage of PDS and GAC, temperature and initial concentration of OG had an impact on OG oxidation, higher temperature and GAC dosage resulted in higher OG degrading rates. In addition, the empirical kinetic equation for OG oxidation by GAC/PDS combined system under the conditions of 0.050-0.125 mmol·L-1 of OG, 5.0 of pH, 10/1-160/1 of n(PDS)/n(OG), 0.1-1.6 g·L-1 of GAC, 298-338 K of temperature, could be reasonably represented by the first order kinetics, which was fitted very well with the experimental data. In addition, the catalytic properties of reused GAC have been investigated.
Decolorization and removal of cod and bodfrom raw and biotreated textile dye bath effluent through advanced oxidation processes (AOPS)
Muhammad, A.;Shafeeq, A.;Butt, M. A.;Rizvi, Z. H.;Chughtai, M. A.;Rehman, S.;
Brazilian Journal of Chemical Engineering , 2008, DOI: 10.1590/S0104-66322008000300003
Abstract: in this paper, a comparative study of the treatment of raw and biotreated (upflow anaerobic sludge blanket, uasb) textile dye bath effluent using advanced oxidation processes (aops) is presented. the aops applied on raw and biotreated textile dye bath effluent, after characterization in terms of cod, colour, bod and ph, were ozone, uv, uv/h2o2 and photo-fenton. the decolorization of raw dye bath effluent was 58% in the case of ozonation. however it was 98% in the case of biotreated dye bath effluent when exposed to uv/h2o2. it is, therefore, suggested that a combination of biotreatment and aops be adopted to decolorize dye bath effluent in order to make the process more viable and effective. biodegradability was also improved by applying aops after biotreatment of dye bath effluent.
Kinetics and Photodegradation Study of Aqueous Methyl tert-Butyl Ether Using Zinc Oxide: The Effect of Particle Size  [PDF]
Zaki S. Seddigi,Saleh A. Ahmed,Shahid P. Ansari,Ekram Danish,Abdullah Abu Alkibash,Shakeel Ahmed
International Journal of Photoenergy , 2013, DOI: 10.1155/2013/206129
Abstract: Zinc oxide of different average particle sizes 25?nm, 59?nm, and 421?nm as applied in the photodegradation of MTBE. This study was carried out in a batch photoreactor having a high pressure mercury lamp. Zinc oxide of particle size of 421?nm was found to be the most effective in degrading MTBE in an aqueous solution. On using this type of ZnO in a solution of 100?ppm MTBE, the concentration of MTBE has decreased to 5.1?ppm after a period of five hours. The kinetics of the photocatalytic degradation of MTBE was found to be a first order reaction. 1. Introduction Fuel oxygenates like methyl tert-butyl ether (MTBE) are usually added for the complete combustion of gasoline. MTBE has low vapor pressure, high octane rate, very good blending compatibility with gasoline, and low production cost [1, 2]. The speed of migration of MTBE resembles that of water and it has high resistance to biodegradation [3, 4]. MTBE has been found to be a potential carcinogen; thus it poses serious health threats. The presence of MTBE can be easily detected in water even at very low concentrations from its characteristic smell which in turn lowers the quality of water. The serious hazardous effects of MTBE have attracted the attention of many researchers to develop efficient techniques that can be applied for the remediation/elimination of MTBE from water [5, 6]. Those techniques include adsorption using activated carbon, biodegradation, and air-stripping; however, the results obtained were not satisfactory. For instance, the removal of MTBE by adsorption on activated carbon has been found to be ineffective because of the low adsorption of MTBE on the activated carbon. The adsorption process has been found to be costly because carbon has to be changed frequently [4]. Moreover, ethers are generally resistant to biodegradation because the presence of the bulky tertiary methyl group renders MTBE nonbiodegradable by the traditional methods [7–9]. Recently, advanced oxidation processes (AOPs) have been applied for the remediation of different contaminants in water. Complete oxidation of organic pollutants into CO2 and H2O can be achieved by applying AOPs. The application of AOPs in heterogeneous photocatalysis is highly promising and good results have been obtained when this type of photocatalysis was applied to treat nonbiodegradable toxic organic molecules that exist in water [10, 11]. The heterogeneous photocatalytic reaction performed to degrade organic pollutants requires electromagnetic radiation of specific wave length, a catalyst (i.e., semiconducting metal oxide), and oxygen.
Degradation Kinetics of Ozone Oxidation on High Concentration of Humic Substances

ZHENG Ke,ZHOU Shao-qi,YANG Mei-mei,

环境科学 , 2012,
Abstract: Humic substance oxidation(HS) degradation by ozone was kinetically investigated. The effects of O3 dosage, initial pH, temperature and initial concentration of HS were studied. Under the conditions of 3.46 g·h-1 ozone dosage, 1000 mg·L-1 initial HS, 8.0 initial pH and 303 K temperature, the removal efficiencies of HS achieved 89.04% at 30 min. The empirical kinetic equation of ozonation degradation for landfill leachate under the conditions of 1.52 -6.10 g·h-1 ozone dosage, 250-1000 mg·L-1 initial HS, 2.0-10.0 initial pH,283-323 K temperature fitted well with the experimental data (average relative error is 7.62%), with low activation energy Ea=1.43×104 J·mol-1.
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