Decomposition of phenols in aqueous solution by a UV/O3 process

The decomposition of several non‐biodegradable phenols by the UV/O₃ and ozonation processes was studied and compared under various solution pH values, O₃ input mass flow rates and UV intensities to investigate the removal efficiencies of reactants and organic intermediates. The decomposition rate of phenols by the UV/O₃ process was found to increase with increasing O₃ input dosage, light intensity and solution pH value. The mineralization efficiencies of phenols in aqueous solution would be above 98% under adequate reaction conditions within three hours, but would be retarded for alkaline solutions because of the dissolution of CO₂ formed by mineralization of phenols. The increment of ozone input dosage had little effect on the mineralization of organic intermediates at the latter course of the reaction. The order of the decomposition rate of the phenols used in this research was 2,4‐dichlorophenol > 2‐chlorophenol > 2‐nitrophenol for low and neutral pH solutions, whereas they were nearly alike for alkaline solutions. The two‐step consecutive kinetic model was found to fit well in modeling the behavior of species during the decomposition of phenols in aqueous solutions by the UV/O₃ process.     

Studies of influence of naphthalene mono/disulfonic acid dopant on thermal stability of polypyrrole

Thermal stability of polypyrrole (PPY) synthesized by in situ doping polymerization in the presence of different naphthalene mono/disulfonic acid dopant like α-naphthalene sulfonic acid (α-NSA), β-naphthalene sulfonic acid (β-NSA), and 1,5-naphthalene disulfonic acid (1,5-NDSA) has been systematically investigated by thermogravimetric analysis (TG). It was found that the thermal stability of as-resulted PPY was greatly affected by type and concentration of dopant. In general, the order of their thermal stability was PPY-(β-NSA) > PPY-(α-NSA) ≈ PPY-(1,5-NDSA). And high concentration of dopant (e.g., 1.2 mol/L) had a negative effect on the thermal stability. Among those three dopants, 1,5-NDSA had a unique influence on thermal stability and crystallinity of as-resulted PPY. In addition, all of room-temperature conductivity and crystallinity of PPY-(1,5-NDSA) changed dramatically after aging for 9 h under N₂ atmosphere and at 230°C, which may be due to a partly dedoping process. These results were confirmed by elemental analysis, FTIR, X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

可见光下Cu2O/TiO2催化臭氧氧化头孢曲松钠性能研究

抗生素是治疗各种传染病的常用药物,但残留在水环境中的抗生素会对生态系统造成威胁。因此,探索去除水环境中抗生素的有效方法具有重要意义。由于光催化臭氧氧化技术可以高效降解和矿化水体中的污染物,该技术受到广泛关注。本工作通过浸渍-化学还原法制备Cu₂O/TiO₂复合材料并将其作为可见光催化臭氧氧化头孢曲松钠(CRO)的催化剂。利用X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FT-IR)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、比表面积分析仪(BET)和紫外-可见漫反射光谱仪(UV-Vis DRS)对Cu₂O/TiO₂形貌结构和光学性能进行表征,考察了Cu₂O/TiO₂配比、Cu₂O/TiO₂投加量、臭氧浓度、头孢曲松钠初始浓度、溶液初始pH值等因素对可见光催化臭氧氧化头孢曲松钠的影响。结果表明,Cu₂O对TiO₂的掺杂改性使材料孔容和平均孔径增大,能带宽度减小,...     

光催化臭氧联用降解糖蜜酒精废水的研究

采用光催化臭氧联用手段降解糖蜜酒精废水。用紫外可见分光光度计检测,以糖蜜酒精废水的脱色率为评价基准,考察了光催化臭氧联用降解糖蜜酒精废水的工艺条件,发现催化剂用量、光照时间、臭氧流量、物料的pH值等都影响糖蜜酒精废水的降解。实验结果表明：光催化与臭氧联用对糖蜜酒精废水的降解效率高于单一光催化和单一臭氧催化的降解效率;最佳反应条件：光照时间120min,气流量为48L/h,催化剂用量和臭氧流量的最佳值分别为0.25g/L和0.2g/L,pH〈4或pH〉12,脱色率达到90%以上。     

Ozonization of Aromatic Amines in Water

The oxidation of the following ami no compounds with ozone in aqueous solution (pH 7–2) was investigated: “4–chloroaniline, 2–aminophenol, 4–aminobenzoic acid, 4–amino–2–nitrophenol, 4–amino–5–hydroxynaphthalene–2,7–disulfonic acid, 4–aminobenzene sulfonic acid ( initial conentrations 1 mmole1). Total destruction of the compounds is achieved with 4 to 6 mmole ozone mmole amine. 20–40 % of the amine nitrogen is found as ammonia and a small part as nitrate (4%). In the initial stages of the ozonation the solutions turn colored. In the further course of the reactions the colored intermediates are oxidized and after 6 mmole ozone/mmole amine the solution are colorless. In all cases the colored intermediates are not or only to a small extend biodegradable but the final oxidation products are better biodegradable.     

Ozone oxidation of β-lactam antibiotic molecules and toxicity decrease in aqueous solution and industrial wastewaters heavily contaminated

In this work, ozone oxidation of the antibiotics amoxicillin (AMX), cephalexin, and ceftriaxone was investigated in different samples: (i) aqueous solutions (100 mg L^?1), (ii) an industrial wastewater containing AMX at 125 mg L^?1 (chemical oxygen demand 6000 mg O₂ L^?1), and (iii) a heavily contaminated industrial wastewater containing the antibiotics at a total concentration of 320 mg L^?1. High performance liquid chromatography, molecular absorption spectrophotometry in the ultraviolet/visible region, and total organic carbon measurements showed that ozonation of antibiotics solutions led to removal higher than 95% with 10–20% mineralization. Industrial wastewater also showed very good efficiency for antibiotic removal (80–98%) after ozonation. Moreover, Microtox® test showed 86% toxicity reduction for the industrial wastewater.     

Ozonation of Primary Sludge and Digested Sludge to Increase Methane Production in a Chemically Enhanced Primary Treatment Facility

The purpose of this research was the investigation of the ozonation of sludge as a method to improve anaerobic digestion performance in a chemically enhanced primary treatment facility. Batch tests were conducted to evaluate the effect of ozonation on the physicochemical characteristics of both primary and digested sludge. Then, the performance of semi-continuous anaerobic digesters in combination with ozone treatment was investigated (pre-ozonation and post-ozonation). Ozonation of primary sludge did not increase the soluble COD nor the biodegradable COD, but resulted in the mineralization of a fraction of the organic matter into CO₂. However, the ozonation of anaerobic digested sludge resulted in an increase in soluble COD and biodegradable COD and in a small level of mineralization at the dose of 90 mg O₃/g COD. Pre-ozonation of primary sludge was not effective in enhancing the performance of the anaerobic digester. The coupling of ozonation and anaerobic digestion by means of the post-ozonation of digested sludge was found to be effective in improving methane production (+16%), for COD removal efficiency and for the dewaterability of anaerobic digesters compared to the control digester.     

Degradation of Carbamazepine by Photo-assisted Ozonation: Influence of Wavelength and Intensity of Radiation

This article presents the results of an investigation into the function of UV in a photo-assisted ozonation process for treatment of carbamazepine (CBZ) in treated domestic wastewaters. Experiments were conducted on synthetic spiked water and secondary treated municipal wastewater. Degradation of CBZ was studied for various combination of O₃ dosage ranging from 4.8 to 14.4 mg/h and UV intensities with varying intensity and wavelength (UVC: λ = 254 nm and UVA: 352 nm). In synthetic spiked water, CBZ was degraded to below detectable limits within 0.5 min for ozone dose of 14.4 mg/h. The rate of degradation of CBZ increased exponentially with increase in ozone dose following a zero-order rate at each dose level. The degradation rate of CBZ in wastewater was slower compared to deionized water (DI) water by 40–75% for various doses of ozone, presumably due to the presence of organic matter remaining in treated wastewater. Optimal UV intensities for UVA and UVC were obtained as 0.62 and 0.82 mW/cm² for all doses of ozone in synthetic spiked water samples and UV intensities beyond this resulted in lower rates of degradation of CBZ. For photo-assisted ozonation with ozone doses of 9.6 and 14.4 mg/L, rate constants were two times higher for UVA irradiations as compared to UVC irradiation. Contrary to observations in DI water, experiments in wastewater showed increase in rate of degradation with higher UV intensities. Overall, photo-assisted ozonation was found to be appropriate for both water and wastewater treatment by exploiting the benefit of direct attack of ozone and of produced ^?OH radicals to yield a greater extent of mineralization of CBZ.     

Ozonation of complex industrial park wastewater: effects on the change of wastewater characteristics

BACKGROUND: Ozonation of complex industrial park wastewater was carried out in a semi‐batch reactor. The variation of wastewater characteristics was evaluated based on the analysis of 5‐day biochemical oxygen demand (BOD₅) concentration, BOD₅/chemical oxygen demand (COD) ratio, COD fractionation, and dissolved organic carbon (DOC) molecular size distribution before and after ozonation. RESULTS: The experimental results indicated that low efficiency of COD removal with increasing tendency of BOD₅ concentration generally appeared after ozonation. Also, the BOD₅/COD ratio increased from an initial of 0.27 to a maximum of 0.38. The COD fractionation tests revealed that most of the inert soluble COD was transformed to biodegradable soluble COD at 30 min of reaction time. Additionally, the DOC molecular size distribution tests showed that the fraction larger than 500 kDa was significantly decreased and the fraction smaller than 2 kDa was increased when the reaction time was prolonged to 240 min. CONCLUSION: This study verified that partial oxidation of the complex industrial park wastewater by ozonation could enhance wastewater biodegradability. The biodegradability enhancement was primarily because the inert soluble COD fraction was converted to the biodegradable soluble COD and the high molecular weight fraction of DOC was shifted toward the low molecular weight fraction. Copyright © 2009 Society of Chemical Industry     

污水出水有机物对臭氧氧化舒必利的影响

臭氧氧化可以有效去除诸如药物及个人护理品(PPCPs)等新兴有机污染物, 但去除效果受污水出水水质波动的影响。本研究选择了腐殖酸(HA)、牛血清蛋白(BSA)和海藻酸钠(AGS)3种典型有机物作为模型污水出水有机物(EfOM), 从降解速率和矿化程度两方面出发, 考察了EfOM对臭氧氧化去除一种常用抗精神病药物残留舒必利(SP)的影响。结果表明, 臭氧氧化能有效降低水溶液中SP的浓度, 在各反应条件下, 反应8min后去除率均可达85%以上。然而, 在研究条件下, 臭氧氧化对SP的矿化效果不佳, 反应25min后的TOC去除率小于10%。加入HA和BSA后, SP的臭氧氧化反应受到抑制, 随着HA和BSA浓度的增加, 臭氧氧化SP的反应速率逐渐降低, 反应溶液的矿化程度有所提高;而浓度为0~3.0mg/(L TOC)的AGS对臭氧氧化SP的影响较小。     

不同形貌的纳米Mg(OH)2催化臭氧化降解甲硝唑

采用化学沉淀法分别以六水合氯化镁和取自察尔汗盐湖的天然水氯镁石为原料制备了不同形貌的纳米 Mg(OH)₂催化剂,通过扫描电子显微镜、X射线衍射、傅里叶变换红外光谱等手段对所合成的催化剂的表面形貌、晶体结构和表面官能团等性质进行了表征。将两种不同形貌的纳米Mg(OH)₂材料首次应用于催化臭氧化过程,研究了两种不同形貌的纳米Mg(OH)₂[Mg(OH)₂-1和Mg(OH)₂-2]催化剂对甲硝唑的降解和矿化能力。结果表明,在单独臭氧化过程中,反应10min时甲硝唑的降解和矿化效率均较低,分别为51.9%和17.4%,而在臭氧化系统中分别加入Mg(OH)₂-1和Mg(OH)₂-2,甲硝唑的去除效率和矿化效率均明显提高,且Mg(OH)₂-2的催化臭氧化性能要优于Mg(OH)₂-1。另外,单独臭氧化过程、Mg(OH)₂-1催化臭氧化以及Mg(OH)₂-2催化臭氧化过程中甲硝唑的降解均较好地符合伪一级动力学反应模型（R²>0.97）。除此之外,对这两种不同形貌的纳米Mg(OH)₂催化剂的稳定性进行了考察,结果表明,催化剂在循环使用六次后对甲硝唑仍有较高的催化臭氧化去除效率。因此,所合成的两种形貌的纳米Mg(OH)₂催化剂将是一种很有前景的、能用于去除抗生素的臭氧化催化剂。     

Treatment of Water Contaminated with Chlorinated Organic Herbicide 2,4-D by an Ozone/Gamma Process

Radiation-induced degradation of 50 ppm 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated in different ozonation times. Co-60 gamma-source was used as a gamma-source with a dose rate of 0.07 kGy/h. Ozonized samples were irradiated for the 0.2 kGy dose. It is observed that irradiation enhances the degradation of 2,4-D with ozone. The amount of passed ozone from samples is between 0.0695 g/L and 8.33 g/L with a flow rate of ozone at 0.078 L/min (10 g/h), from 10 s to 1200 s with the ozone generator. Aliphatic acids and chloride were determined with ion chromatography. Formaldehyde, dissolved oxygen, pH and total acidity were also measured. Both species and amounts of radiolytic intermediates were determined. 2,4-dichloro phenol (2,4-DCP) is one of the toxic intermediates of 2,4-D observed with GC/MS and it decomposes at further ozonation times. It is observed that combination of ozone/gamma irradiation is more effective for degradation of 2,4-D and its intermediate 2,4-DCP. Chloride ions are observed as completely released with combined processes at lower ozonation times although nearly 98% are released with 20 min' ozonation. Intermediate 2,4-DCP decomposes at earlier ozonation times than 2,4-D.     

臭氧催化氧化机理及其技术研究进展

臭氧催化氧化技术可以提高污水中总有机碳（TOC）的去除效率和臭氧的利用率,近年来得到了广泛的研究。但由于催化反应过程复杂、影响因素多,导致其反应机理一直存在较大的争议。本文回顾了近年来国内外对臭氧催化氧化技术的研究结果,对均相、非均相臭氧催化氧化机理以及非均相催化剂的组成、活性影响因素进行了总结,并对非均相臭氧催化氧化技术用于降解模型化合物和处理典型工业污水的研究进展进行了介绍。文章最后指出催化剂的结构和表面化学性质与催化机理、有机物的降解途径之间的相互关系还需要更深入的研究。     

Aqueous Pesticide Degradation by Ozonation and Ozone-Based Advanced Oxidation Processes: A Review (Part I)

Pesticide pollution of surface water and groundwater has been recognized as a major problem in many countries because of their persistence in aquatic environment and potential adverse health effects. Among various water and wastewater treatment options, ozonation and ozone-based advanced oxidation processes, such as ozone/hydrogen peroxide, ozone/ultraviolet irradiation, and ozone/hydrogen peroxide/ultraviolet irradiation, are likely key technologies for degrading and detoxifying these pollutants in water and wastewater. In this paper, ozone-based treatment of four major groups of pesticides, namely carbamates, chlorophenoxy compounds, organochlorines, and organophosphates, are reviewed. Degree of pesticide degradation, reaction kinetics, identity and characteristics of degradation by-products and intermediates, and possible degradation pathways are covered and discussed.     

O3 based advanced oxidation for ibuprofen degradation

The degradation of the anti-inflammatory ibuprofen (IBP) was evaluated by several advanced oxidation processes. IBP was treated by single ozonation and oxidation with hydrogen peroxide (H₂O₂), as well as a combination of these treatments. In order to improve the efficiency, the presence of catalysts such as original carbon nanotubes, labelled as CNT, and iron oxide supported on carbon nanotubes, named as Fe/CNT sample, was considered. The evolution of IBP degradation, mineralization and toxicity of the solutions was assessed. The formation of intermediates was also monitored. In the non-catalytic processes, IBP was faster removed by single ozonation, whereas no significant total organic carbon (TOC) removal was achieved. Oxidation with H₂O₂ did not present satisfactory results. When ozone and H₂O₂ were combined, a higher mineralization was attained (70% after 180 min of reaction). On the other hand, in the catalytic processes, this combined process allowed the fastest IBP degradation. In terms of mineralization degree, the presence of Fe/CNT increases the removal rate in the first hour of reaction, achieving a TOC removal of 85%. Four compounds were detected as by-products. All treated solutions presented lower toxicity than the initial solution, suggesting that the released intermediates during applied processes are less toxic.     

Degradation of Two Persistent Surfactants by UV-Enhanced Ozonation

In this study the treatment efficiency of different ultraviolet (UV)-enhanced ozonation processes for degradation of two surfactants, sodium dodecylbenzene sulfonate [200 mg/L or 0.3 critical micelle concentration (CMC)] and a nonylphenol ethoxylate with 40 oxyethylene units (200 mg/L ~0.5 CMC), were investigated in laboratory-scale experiments at ambient temperature. The absorbance band of the aromatic ring of the surfactants was monitored during the oxidation process. The reduction in chemical oxygen demand (COD) and total organic carbon (TOC) of the surfactant solution was evaluated. The results showed that a combination of UV irradiation and ozonation was considerably more efficient than the individual processes (at least two times more efficient in terms of COD and TOC reductions). The synergistic effect of ozonation and UV irradiation was particularly pronounced when medium-pressure UV irradiation was used. By adding alkali to the solution, the efficiency of the UV-enhanced ozonation increased with respect to COD reduction but decreased with respect to TOC reduction. This indicates partial oxidation with lower degree of mineralization of the surfactants.     

Ozonation of Phenol-Containing Wastewater Using O3/Ca(OH)2 System in a Micro Bubble Gas-Liquid Reactor

The degradation of phenol in aqueous solution was investigated in an integrated process consisting of O₃/Ca(OH)₂ system and a newly developed micro bubble gas-liquid reactor. The effects of operating parameters such as Ca(OH)₂ dosage, reactor pressure, liquid phase temperature, initial phenol concentration and inlet ozone concentration on degradation and mineralization (TOC removal) were studied in order to know the ozonation performance of this new integrated process. It is demonstrated that the degradation and TOC removal efficiency increased with increasing inlet ozone concentration and increasing Ca(OH)₂ dosage before 2 g/L, as well as decreasing initial phenol concentration. The optimum Ca(OH)₂ dosage should exceed Ca(OH)₂ solubility in liquid phase. The reactor pressure and liquid phase temperature have little effects on the removal and TOC removal efficiency. When Ca(OH)₂ dosage exceeded 3 g/L, the degradation and TOC removal of phenol almost reached 100% at 30 and 55 min, respectively. The intensification mechanism of Ca(OH)₂ assisted ozonation was explored through analysis of the precipitated substances. The mechanism for Ca(OH)₂ intensified mineralization of phenol solution is the simultaneous removal of CO₃^2- ions, as hydroxyl radical scavengers, due to the presence of Ca²⁺ ions. Results indicated that the proposed new integrated process is a highly efficient ozonation process for persistent organic wastewater treatment.     

Magnéli phases TinO2n−1 as novel ozonation catalysts for effective mineralization of phenol

Magnéli phases Ti_nO_2n-1 have been demonstrated as promising environmentally friendly materials in advanced oxidation processes. In this study, Magnéli phases Ti_nO_2n-1 have been used as catalysts for the ozonation of phenol in aqueous solution for the first time. The materials exhibited excellent catalytic ozonation activities both in phenol degradation and mineralization. When Ti₄O₇ was added, the reaction rate was six-fold higher than that of with ozone alone, while the total organic carbon removal rate was substantially elevated from around 19.2% to 92%. By virtue of the good chemical stability of the materials, a low metal leaching of less than 0.15 mg·L^-1 could effectively avoid the secondary pollution by metal ions. Radical quenching tests revealed ·O₂^- and ¹O₂ to be active oxygen species for phenol degradation at pH 5. As semiconductor catalysts, Ti_nO_2n-1 materials show electronic transfer capability. Ozone adsorbed at B-acid sites of the catalyst surface can capture an electron from the conversion of Ti(Ⅲ) to Ti(IV), and is thereby broken into the active oxygen species. It was interesting to observe that Ti_nO_2n-1 exhibit better catalytic activity for phenol degradation and mineralization with lower n value. The difference in electrical conductivity can be considered as a major factor for the catalytic performances. More highly conductive catalysts show a faster electron-transfer rate and better catalytic activity. Thus, significant evidences have been obtained for a single-electron-transfer mechanism of catalytic ozonation with Magnéli phases Ti_nO_2n-1.     

2. Sensitized degradation of chlorophenols on iron oxides induced by visible light: Comparison with titanium oxide

The sensitized photocatalytic degradation of mono-, di- and trichlorophenols on iron oxides aqueous suspensions of -Fe₂O₃ and -FeOOH is reported in detail. The degradation of these compounds followed pseudo-first-order kinetics when -Fe₂O₃ was used as photocatalyst. -FeOOH was found to be inactive for chlorophenols degradation with the exception of 2,4-dichlorophenol (2,4-DCP) where a modest effect was observed. The formation of a surface complex by the chlorophenols with the iron oxide and the solubility of the particular chlorophenol in aqueous solution were observed to be the controlling parameters during the photodegradation. The results obtained with the most active catalyst -Fe₂O₃ are compared with TiO₂. Total mineralization of chlorophenols was observed on TiO₂ while on -Fe₂O₃ only partial mineralization was observed. In either case, the intermediates produced in solution during the photodegradation were found to be significantly more biodegradable than the initial compound. For mono-, di- and trichlorophenols the overall photocatalytic degradation was observed to increase in the order: 2,4,6-trichlorophenol (2,4,6-TCP)<2,3-dichlorophenol (2,3-DCP)<2-chlorophenol (2-CP)<2,4-DCP. The former sequence shows that the recalcitrant 2,4-DCP degrades more rapidly than other chlorophenols tested during this study. The photodegradation of chlorophenols on -Fe₂O₃ and TiO₂ proceeds mechanistically through para-hydroxylation of the initial compound as suggested by the intermediates found by high-pressure liquid chromatography HPLC during the course of the degradation.     

Ozonation of polycyclic aromatic hydrocarbon in hexane and water: Identification of intermediates and pathway

The recalcitrant nature of pyrene and other polycyclic aromatic hydrocarbons (PAHs) lies in part in their low solubility in water, rendering them less susceptible to chemical and biological degradation. To overcome this remediation obstacle, this work investigates the use of a 2-stage ozonation process, first in nonpolar hexane phase then in polar aqueous phase, for the treatment of hydrophobic contaminants using pyrene as a model compound. The objectives of this research are to break down pyrene by using ozonation, identify the intermediates of pyrene, show a general degradation pathway of pyrene subject to ozonation and test the biodegradability of intermediates and byproducts of pyrene in the aqueous phase. The first stage briefly ozonates the contaminant at high concentration in organic solvent hexane, which facilitates very efficient conversion of the hydrophobic compounds into ring-opened polar intermediates containing alcohol, aldehyde, and acid functional groups.