Oxidation of bisphenol A by ozone in aqueous solution

Based on the literature data, an efficient removal of bisphenol A (BPA) during ozonation can be expected under water treatment conditions. However, up to now, the degradation products have not been identified. This has been the main point of this study. Aqueous solutions of BPA have been analyzed by LC-UV, LC-MS or MS/MS at different ozone doses. Under our experimental conditions, up to five major transformation products were evidenced. According to UV, MS and MS/MS spectra characteristics, chemical structures are consistent with catechol, orthoquinone, muconic acid derivatives of BPA, benzoquinone and 2-(4-hydroxyphenyl)-propan-2-ol. Moreover, three additional minor transformation products have been observed for which chemical structures have been tentatively proposed. In the case of major transformation products, the reaction pathway may involve an initial ozone reaction by electrophilic substitution or 1,3-dipolar cycloaddition. In the presence of ozone, these primary transformation products were shown to be unstable. Further transformation products, with smaller molecular weight and more polar character such as aliphatic acids or aldehydes, are then expected during ozonation. The identification of minor transformation products was more complex to assess. However, oligomeric structures have been evidenced, certainly arising from secondary reaction between various oxidation products of BPA. The formation of these latter products would not be favored under water treatment conditions.     

Kinetics of triclosan oxidation by aqueous ozone and consequent loss of antibacterial activity: relevance to municipal wastewater ozonation

Oxidation of the antimicrobial agent triclosan by aqueous ozone (O(3)) was investigated to determine associated reaction kinetics, reaction site(s), and consequent changes in antibacterial activity of triclosan. Specific second-order rate constants, k(O(3)), were determined for reaction of O(3) with each of triclosan's acid-base species. The value of k(O(3)) determined for neutral triclosan was 1.3(+/-0.1)x10(3)M(-1)s(-1), while that measured for anionic triclosan was 5.1(+/-0.1)x10(8)M(-1)s(-1). Consequently, triclosan reacts very rapidly with O(3) at circumneutral pH (the pH-dependent, apparent second-order rate constant, K(app,O(3)) , is 3.8x10(7)M(-1)s(-1) at pH 7). The pH-dependence of K(app,O(3)) and comparison of triclosan reactivity toward O(3) with that of other phenolic compounds indicates that O(3) reacts initially with triclosan at the latter's phenol moiety. k(O(3)) values for neutral and anionic triclosan were successfully related to phenol ring substituent effects via Brown-Okamoto correlation with other substituted phenols, consistent with electrophilic attack of the triclosan phenol ring. Biological assay of O(3)-treated triclosan solutions indicates that reaction with O(3) yields efficient elimination of triclosan's antibacterial activity. In order to evaluate the applicability of these observations to actual wastewaters, triclosan oxidation was also investigated during ozonation of effluent samples from two conventional wastewater treatment plants. Nearly 100% triclosan depletion was achieved for a 4 mg/L(8.3x10(-5)mol/L)O(3) dose applied to a wastewater containing 7.5 mg/L of DOC, and approximately 58% triclosan depletion for dosage of 6 mg/L(1.3x10(-4)mol/L)O(3) to a wastewater containing 12.4 mg/L of DOC. At O(3) doses greater than 1mg/L(2.1x10(-5)mol/L), hydroxyl radical reactions accounted for <35% of observed triclosan losses in these wastewaters, indicating that triclosan oxidation was due primarily to the direct triclosan-O(3) reaction. Thus, ozonation appears to present an effective means of eliminating triclosan's antibacterial activity during wastewater treatment.     

Kinetic of benzotriazole oxidation by ozone and hydroxyl radical

Ozonation experiments were performed in batch reactors in order to determine the rate constants for the reaction of molecular ozone and OH radicals with benzotriazole (BT) at different pHs. The first group of ozonation experiments was carried out for the determination of the rate constant for the direct reactions between ozone and BT. Two different kinetic models were used for the determination of kinetic rate constants: (i) the log-reduction of BT with ozone in excess, (ii) the competition kinetic model. The second-order rate constants for BT with molecular ozone were determined to be 36.4 ± 3.8 M⁻¹ s⁻¹ and 18.4 ± 0.8 M⁻¹ s⁻¹ at pH 2 from the two methods respectively. With the competition method, the value at pH 5 was found to be 22.0 ± 2.0 M⁻¹ s⁻¹. In a following stage, the reaction of BT with OH radicals was investigated at pH values ranging from 2 to 10.2. Using a method involving two probe compounds during the ozonation, the second-order rate constants of the BT reaction with hydroxyl radicals were determined. The rate constants were found to vary from 6.2 × 10⁹ M⁻¹ s⁻¹ at pH 10.2 to 1.7 × 10¹⁰ M⁻¹ s⁻¹ at pH 2.     

Kinetics and mechanisms of polyethyleneglycol fragmentation by ozone in aqueous solution

The oxidative fragmentation of Polyethyleneglycol by ozone is investigated by means of batch and semibatch ozonation experiments in the pH range 4.0–9.0. Chemical mechanisms and reaction kinetics of the ozonation processes are determined by also exploiting chemical information from experiments on Diethyleneglycol and Ethyleneglycol ozonation. A kinetic model is proposed capable of describing the fragmentation process due to the direct polymer oxidation by ozone.     

Advantages and disadvantages of chemical oxidation and disinfection by ozone and chlorine dioxide

Ozone and chlorine dioxide present definite advantages and disadvantages over chlorination. Chlroination, particularly for the removal of ammonia and the maintenance of a disinfectant residual in the distribution system has decisive advantages and will be difficult to replace. Ozone and chlorine dioxide seem to produce fewer carcinogenic by-products but the risk fur acute toxicity, especially from the chlorites which follow chlorine dioxide, is higher than with chlorine.Chlorine dioxide and more particularly ozone should be considered as usefulcomplements to chlorination, but no strong oxidative treatment should be applied before most of the organic matter has-been removed.     

Quantification of aqueous cyanogen chloride and cyanogen bromide in environmental samples by MIMS

Membrane introduction mass spectrometry (MIMS) was developed and verified for the direct quantification of cyanogen chloride (CNCl) and cyanogen bromide (CNBr) in environmental samples without any sample workup. Factors including the membrane temperature and the liquid flow rates were examined for system optimization. The MIMS method provided linear responses for three orders of magnitude of concentrations. The instrument detection limits of CNCl and CNBr were 1.2 and 3.8 microg/L, respectively, and the method detection limits of CNCl and CNBr were both 1.7 microg/L. Effects of pH and the water matrix including synthetic water, saline water, natural surface water, and wastewater, on the responses were also examined. A pH ranging from 3 to 10 did not affect the quantification. The average recoveries of CNCl and CNBr in the water matrixes tested were 98.5% and 92.7%, respectively. The use of the MIMS method in on-line monitoring of the formation of cyanogen halide was demonstrated in chlorination of aqueous solutions containing glycine and bromide ions. The results indicated the important role of bromide ions in cyanogen halide speciation.     

Treatment of 2-chlorophenol aqueous solutions by wet oxidation

In the present work, the wet oxidation (WO) of 2-chlorophenol (2-CP) was studied in aqueous solutions, in a high-pressure agitated autoclave reactor. Specifically, the effect of temperature (160-190 degrees C), oxygen partial pressure (5-40 bar) and 2-CP initial concentration (250-1500 mg L(-1)) was examined. The process was attended via total organic carbon (TOC), 2-CP, chloride ion, acetic acid, formic acid and pH measurements. Significant rates of 2-CP disappearance and TOC removal were achieved above 170 degrees C. A decrease in 2-CP initial concentration below 1000 mg L(-1) resulted in a dramatic decrease in the TOC removal achieved, whereas an increase in oxygen partial pressure enhanced greatly the decontamination of the 2-CP aqueous solution, especially from 10 to 20 bar. Much attention was given on the chloride ion removal from the phenolic ring in order to attend the dechlorination of 2-CP during WO. In the WO process, the majority of chloride ions were detached from organic compounds. Finally, a parallel and in series reaction scheme has been proposed for the interpretation of the experimental results.     

Spectrophotometric method for determination of ozone in aqueous solutions

A sensitive spectrophotometric method for determination of ozone in small volumes of water is presented. It was performed in order to meet the requirements of a kinetic study of virus and bacteria inactivation by ozone.The proposed method involves oxidation of a buffered iodine solution and spectrophotometric measurement of the triiodide ion liberated by ozone. Two procedures are used: one for low ozone concentration (0·01–0·30 ppm) and another for higher concentrations (0·30–2·0 ppm). The reproducibility of results is very high when the procedure used corresponds with the ozone level for which it is intended.This spectrophotometric method is compared with the standard volumetric method and the differences are presented and discussed.Some applications of the method for a kinetic study of virus inactivation by ozone are presented.     

臭氧催化氧化技术应用研究进展

随着臭氧氧化技术的不断发展,臭氧催化氧化技术应用十分广泛。从工业废水处理、污泥处置、有机废气处理三方面,对目前关于臭氧催化氧化的技术应用情况进行梳理和归纳,提出目前臭氧氧化技术存在的缺陷,旨在为今后臭氧氧化技术的加强和优化起到积极的作用。     

利用二氯化铁的氧化反应改色花岗石的研究

利用二氯化铁高温氧化反应,对普通灰白色花岗石进行了改色研究。考察了花岗石改色的主要影响因素,确定了较理想的工艺条件,并对改色后的花岗后时行了性能测试。测试结果表明,本方法改色的花岗石耐酸、耐碱、耐有机溶剂、耐沸水、耐紫外光。     

Improved ammonia oxidation by ozone in the presence of bromide ion during water treatment

Ammonia oxidation by ozone proceeds more rapidly in the presence of bromide ion than in its absence. Unlike the direct ozonation of ammonia, the bromide-catalyzed process is little affected by changes in pH. A reaction scheme is proposed in which bromide is oxidized to HOBr, which then brominates ammonia to produce NH₂Br. NH₂Br in turn reacts with O₃ to form NO₃⁻ and also to generate Br⁻, which thus acts as a catalyst. In accordance with the reaction model, zero-order kinetics for ammonia consumption are observed. This work points out once again the importance of Br⁻ as a water quality parameter due to its role as a catalyst in both ozonation and chlorination processes in general.     

Acute toxicity removal in textile finishing wastewater by Fenton's oxidation, ozone and coagulation-flocculation processes

This study evaluates the effectiveness of Fenton's oxidation (FO) process and ozone (O3) oxidation compared with a coagulation-flocculation (CF) process to remove effluent toxicity as well as colour and COD from a textile industry wastewater. Daphnia magna was used to test acute toxicity in raw and pre-treated wastewater. The operational parameters for each process were determined on the basis of complete toxicity removal. The FO process removed COD at a higher rate (59%) than O3 (33%) while colour removal was similar (89% and 91%, respectively). The CF process removed both COD and colour at rates similar to the FO process. A colour range of 150-250 platin-cobalt (Pt-Co) unit was assessed for toxicity.     

电化学/过硫酸盐耦合体系降解水中有机药物卡马西平

采用电化学/过硫酸盐耦合体系(E-PS过程)降解水中的有机药物卡马西平(CBZ)。实验采用了分批模式进行,研究了温度、过硫酸钠浓度、初始pH值、电压等因素对E-PS过程降解CBZ的影响。反应100min后,单独过硫酸钠、电解和E-PS过程对卡马西平的降解率分别为25.5%、59.3%、78.1%,TOC去除率分别为8.25%、23.48%、26.68%。升高温度可以有效提高CBZ的降解率。反应100min后,在288K,CBZ降解率为60.2%;在298K,CBZ降解率达到78.1%;而在308K,CBZ降解率为90.1%。CBZ的降解率随着过硫酸盐浓度的增加而提高。当过硫酸盐浓度为40g/L时,反应100min,CBZ降解率达94.7%。初始pH值对CBZ降解率的影响为pH 3.0pH 5.0pH 7.0;电压对CBZ降解率的影响为6V5V4V。     

烷基二甲基苄基氯化铵在水溶液表面的吸附与胶束性质

在298.2 K下,用吊环法测定了烷基二甲基苄基氯化铵水溶液的表面张力,结果表明,随着该类表面活性剂的疏水基链长从12增加到18个碳原子,其临界胶束浓度(CMC)从9.1 mmol/L降低至0.053 mmol/L;其在溶液表面的饱和吸附量(Γmax)减小,吸附效率(pC20)增大。还用电导率法研究了该类表面活性剂在不同温度下的CMC及胶束化热力学函数,在298.2³18.2 K,CMC随着温度的升高而增大;胶束形成的自由能△G0m均为负值,表明该表面活性剂溶液胶束化过程是自发的;胶束形成的主要驱动力是熵。     

Decomposition of aqueous ozone in the presence of aromatic organic solutes

The decomposition of aqueous ozone is mainly due to the OH(*) radical chain reaction. Some aromatic compounds have been found to tremendously accelerate ozone decomposition in buffered water although their direct reactions with ozone are very low. Hydrogen peroxide has been detected as an important intermediate product in this process. Therefore, a reaction pathway (aromatic ring=>olefin=>H(2)O(2)=>HO(2)(-)) is proposed in this study. Aromatic rings react with OH(*) radicals or ozone to yield olefins. The olefin formed immediately reacts with ozone and is converted to H(2)O(2). Parts of H(2)O(2) dissociate to HO(2)(-), which strongly accelerates aqueous ozone decomposition. Therefore, a new chain reaction appears. The proposed reaction pathway is much faster than another promotion pathway, such as aqueous ozone decomposition promoted by methanol, formic acid or glucose.     

Studies on oxidation of benzo [a] pyrene by sunlight and ozone

The destruction of the carcinogen benzo[a]pyrene (BaP) by light is well known; laboratory workers are routinely advised to cover fluorescent lamps with yellow filters while treating samples containing BaP. However until recently the mechanism of oxidation by sunlight and ozone had not been studied in detail. Concentrations of benzo[a]pyrene in urban air are in the range of 5–10 μg/1000 m³. Oxidant concentrations (predominantly in the form of ozone) are reported to be in the range of 0.01 ppm (22 μg per m³). Thus a sampling system with a filter paper would filter about 22,000 μg of ozone passing through and collect about 5 μg of BaP for analysis. The effect of interactions of such large ozone concentrations with BaP deposited on the filter paper is reported; data for the oxidation rates for benzo[a]pyrene coated on quartz surface and exposed to ozone or sunlight are presented. The oxidation products were analysed by thin-layer chromatography and highpressure liquid chromatography. From about eight products detected in these experiments, three have been identified as quinones based on UV-absorption spectrometry and mass spectrometry. Oxidation rates as high as 100% per hour of exposure are observed when less than 0.1 μg of BaP is coated inside the quartz tubes and exposed to ozone or sunlight. Oxidation rates for benzo[a]pyrene (using tritiated BaP) were determined for two types of experimental conditions. In the first set, tritiated BaP was spotted onto a glass fibre paper and sampling continued for 24 h; the loss of BaP was found to be 88%. In the second set tritiated BaP was spotted at intervals of one hour, for eight hours, while sampling is being carried out and the loss of BaP during the period was estimated to be 50%.     

Formation of mutagens from the aqueous reactions of ozone and anilines

Azobenzenes, azoxybenzenes and benzidines were the products of interest obtained from the aqueous reactions of anilines with ozone. The reaction mechanisms for their formation are discussed. Conditions favoring ozone decomposition and the presence of carbonate species increased the yield of these polyaromatic nitrogen compounds. Fulvic acid inhibited the formation of azobenzene without decreasing the amount of aniline degraded. The effects of pH and inorganic buffers on the formation of N-substituted polyaromatic compounds from aniline can be explained by the decomposition of ozone by OH⁻ and OOH⁻, scavenging of the hydroxyl radical and suppression of ozone decomposition by carbonate species, and selective oxidation of aniline by carbonate radicals.     

The hydroxide-assisted hydrolysis of cyanogen chloride in aqueous solution

The hydrolysis of cyanogen chloride (ClCN) was studied as a function of temperature and pH. Results were used to resolve discrepancies among previously reported kinetic constants. The pH dependence was studied over a range of 9.54-10.93 at a temperature of 21.0 degrees C. The effect of temperature was investigated over the range of 10-30 degrees C at a pH of approximately 10. Changes in the concentrations of ClCN and the reaction products cyanic acid and chloride ion were monitored with time. For the conditions corresponding to these experiments, the hydroxide-assisted hydrolysis pathway predominated. Collision frequency factor and activation energies recommended to represent the hydrolysis of ClCN in aqueous solution are A = 2.06 x 10(11) M-1 s-1 and Ea = 60,980 J mol-1 for the hydroxide-ion-assisted reaction, and A = 9.97 x 10(8) s-1 and Ea = 87,180 J mol-1 for the water-assisted reaction.     

东太湖水源水臭氧氧化过程中溴酸盐控制技术

针对东太湖水中溴离子含量较高,采用臭氧-活性炭工艺很可能会导致出厂水中溴酸盐超标的问题,研究了加氨和高锰酸钾预氧化对东太湖水源水在臭氧氧化中溴酸盐生成的控制作用。结果表明,加氨可以有效抑制溴酸盐的生成,在加氨量低于0.04 mmol/L时,随着加氨量的增加,其抑制效果逐渐增强;当加氨量超过0.04 mmol/L时,加氨对溴酸盐抑制率不再继续增加。当水中溴离子质量浓度为120~260μg/L,p H值为6.8~8.7,水温为8~40℃时,加氨可以有效抑制水中溴酸盐的生成,且对原水水质影响较小。当高锰酸钾投加量低于6μmol/L时,其对溴酸盐的生成具有一定的抑制作用;高猛酸钾投加量高于6μmol/L时,反而会提高溴酸盐的生成量;同时较高的p H值和水温均不利于高锰酸钾对溴酸盐的控制,反而会增加其生成量。通过比较可知,对于东太湖水源水,加氨控制溴酸盐生成的效果比高锰酸钾更稳定和有效,实际生产中可以选用加氨控制臭氧-活性炭工艺中溴酸盐的生成。