Rates of Ozonation of Cresol Isomers in Aqueous Solutions

This research used a stopped–flow spectrophotometer system to study the kinetics of the fast oxidation of cresols by ozone in aqueous solutions. The overall reaction between ozone and a cresol isotner is second order, with first order in each reactant. At the same operating condition, the ozonation rate of m–cresol is the fastest and that of o–cresol the slowest. For the oxidation of o–cresol in neutral solutions, the overall rate constant increases from 422,000 to 1,550,000 1/M–s as the temperature changes from 10 to 40°C. In aqueous solutions with the pH range of 2.4 to 9.0 at temperatures varying from 5 to 40°C, the ozonation rate of the cresols increases with temperature and pH.     

苯酚液相臭氧化动力学特性的研究

应用Stopped-flow光谱仪对苯酚在288－313K温度和pH=3.2-9.3的液相臭氧化反应动力学特性进行了实验研究。通过实验及分析认为：苯酚的O3氧化降解反应，O3与苯酚的计量比为3；在不同酸度的实验条件下，苯酚的液相O3氧化降解的途径及动力学不同。     

苯酚的O_3/H_2O_2化学氧化反应动力学研究

应用 Stopped- flow光谱仪研究苯酚在 2 88～ 30 8K和 p H=3.2～ 9.8的 O3 / H2 O2 氧化反应动力学。通过实验及分析认为 :在不同酸度的实验条件下苯酚 O3 / H2 O2 氧化降解的途径及动力学不同。在酸性及弱酸性(p H=6 .5 )下苯酚 O3 / H2 O2 氧化反应机理是苯酚直接为 O3 氧化 ,在碱性 (p H=9.8)时为自由基机理     

Ozonation Kinetics of Six Dichlorophenol Isomers

This paper investigates the kinetics of reactions between dichlorophenol (DCP) isomers and dissolved ozone in solutions of pH varying from 2 to 6 at 5 to 35 °C. A DCP can exist as dichlorophenol molecules and dichlorophenoxide anions in the aqueous solution, and both forms are reactive toward ozone. The overall reaction is second order requiring two moles of ozone for conversion of each mole of DCP. The ozonation rate of 2,6-DCP is the fastest and that of 3,4-DCP is the slowest at an identical condition. The Arrhenius equation is applicable to correlate temperature effects; the activation energy ranges from 46.5 to 55.3 kJ/mol. The reaction rate increases very rapidly as the acidity decreases, and the overall rate constant is greater than 1x106 M-1s-1 in solutions with pH of 5 or larger at 25 °C. The results of this study suggest that DCPs can be removed rapidly from wastewaters by ozone treatment.     

A DATA ACQUISITION SYSTEM FOR RAPID KINETIC EXPERIMENTS

A data acquisition system has been developed to collect, analyze and store large volumes of rapid kinetic data measured from a stopped-flow spectrophotometer. A digital minicomputer, with an A/D converter, tape drive unit and formatter, analog recorder, oscilloscope, and input/output terminal interfaced to the stopped-flow spectrophotometer provides the complete system. Timing for actual data collection is generated through internal computer software with inclusion of A/D conversion time. After a simple initialization from the computer console, software programming provides complete interaction between a user and the terminal. The user is directed through the initialization by a series of decision steps. The first step is to choose a data file, either existing or new. Once the desired file is selected, several options including data collection, analysis, storage, and printing are selectable.

Ozone decomposition and the rapid reaction between ozone and cyclohexene in neutral solutions were studied using the data acquisition system. At 25°C, the ozonation reaction was found to have a second order rate constant of 2.19 × 10⁶ l/mole-sec (less than 10^-3 sec. half life).     

Kinetics of the direct reaction between ozone and phenol by high-gravity intensified heterogeneous catalytic ozonation

In this study, high-gravity intensified heterogeneous catalytic ozonation is utilized for treatment of phenol-containing wastewater, and the kinetics of the direct reaction between ozone and phenol in the presence of excess tertiary butanol (TBA) is investigated. It is revealed that the direct reaction between ozone and phenol in the rotating packed bed (RPB) follows the pseudo-first-order kinetics with a reaction rate constant higher than that in the conventional bubbling reactor (BR). Under different conditions of temperature, initial pH, high-gravity factor, and gaseous ozone concentration, the apparent reaction rate constant varies in the range of 0.0160–0.115 min^-1. An empirical power-exponential model is established to characterize the effects of these parameters on the direct reaction between ozone and phenol by high-gravity intensified heterogeneous catalytic ozonation.     

异丙醇的O3/H2O2复合氧化动力学研究

采用停流光谱仪研究了异丙醇在T=298K和pH=3～11范围内O3 / H2O2复合氧化的反应动力学.结果表明异丙醇的O3 / H2O2复合氧化反应动力学随反应体系的pH值不同而不同.在酸性和中性条件下,反应相对于O3浓度、异丙醇浓度都为1级;在碱性条件下,异丙醇较容易被O3/H2O2复合氧化降解,总反应级数为2级,相对于O3浓度、异丙醇浓度和H2O2浓度分别为1级、0级和1级,可见异丙醇的降解速率与它的浓度无关.在T=298K,当pH值从9增大到11, 反应速率常数从3486.1(mol·L-1)-1·s-1增大到38239.2(mol·L-1)-1·s-1. 表明在酸性条件下,异丙醇的O3/H2O2复合氧化是O3分子直接攻击异丙醇的反应占主导;在碱性条件下,自由基型反应占主导.     

Absorption kinetics of ozone in aqueous O-cresol solutions

The kinetics of ortho-cresol ozonation in water has been studied using the film theory. At most experimental conditions investigated, the kinetic regime of the absorption has been fast pseudo first order with respect to ozone. At 30°C mass transfer plays an important role in controlling the absorption rate of ozone. The selfdecomposition reaction of ozone does not take place because of the great reactivity of o-cresol with ozone. Reaction rate constants have been determined at pH 7 for different temperatures below 30°C. The following Arrhenius equation was obtained: k_T = 2.2 × 10²³ exp(-11784/T), L/mol ? s At temperatures below 30°C there exists an ozone partial pressure value above which the ozone absorption kinetic regime changes to fast second order regardless of experimental conditions.     

Simultaneous harvesting and cell disruption of microalgae using ozone bubbles: optimization and characterization study for biodiesel production

In the present study, ozone was introduced as an alternative approach to harvest and disrupt microalgae cells (Chlorella vulgaris) simultaneously for biodiesel production. At the optimum ozonation conditions (6.14 g·h^–1 ozone concentration, 30 min ozonation time, 1 L·min^–1 of ozone flowrate at medium pH of 10 and temperature of 30 °C), the sedimentation efficiency of microalgae cells increased significantly from 12.56% to 68.62%. It was observed that the microalgae cells aggregated to form flocs after pre-treated with ozone due to the increment of surface charge from –20 to –6.59 mV. Besides, ozone had successfully disrupted the microalgae cells and resulted in efficient lipid extraction, which was 1.9 times higher than the control sample. The extracted microalgae lipid was mainly consisted of methyl palmitate (C16:0), methyl oleate (C18:1) and methyl linolenate (C18:3), making it suitable for biodiesel production. Finally, utilization of recycled culture media after ozonation pre-treatment showed robust growth of microalgae, in which the biomass yield was maintained in the range of 0.796 to 0.879 g·h^–1 for 5 cycles of cultivation.     

Kinetic aspects of the formation of lead zirconium titanate

The kinetics of the second calcination step in the formation of PZT solid solution (with perovskite ABO₃ lattice) has been investigated by using two different particle sizes of the B-site precursor (1.91 and 5.08 μm), the finer size being obtained by prolonged milling. In-situ analysis performed by high-temperature X-ray diffractometry in a non-isothermal mode (20–800 °C) revealed a reduction of the calcination temperature by 100 °C with a decrease in particle size of the precursor. In order to clarify the mechanism of the solid-state reaction to PZT, isothermal heat treatment of the mixtures was performed in the temperature range 540–700 °C. The activation energies for the fine and the coarse powders were estimated as 150 and 210 kJ mol⁻¹ respectively, and the reaction was found to follow the Jander model for diffusion-controlled solid-state reaction kinetics.     

Mineralization of paracetamol by ozonation catalyzed with Fe, Cu and UVA light

Acid solutions containing up to 1 g l⁻¹ of the drug paracetamol have been treated with ozone alone and ozonation catalyzed with Fe²⁺, Cu²⁺ and/or UVA light at 25.0 °C. Direct ozonation yields poor degradation due to the high stability of final carboxylic acids formed, whereas more than 83% of mineralization is attained with the catalyzed methods. Under UVA irradiation, organics can be efficiently destroyed by the combined action of generated H₂O₂ and UVA light. In the presence of Fe²⁺ and UVA light, the process is accelerated due to the production of oxidant hydroxyl radical (OH) and the photodecomposition of Fe³⁺ complexes. The highest oxidizing power is achieved by combining Fe²⁺, Cu²⁺ and UVA light, because complexes of final acids with Cu²⁺ are more quickly degraded than those competitively formed with Fe³⁺. For all catalyzed methods, the initial mineralization rate is enhanced and the percent of degradation generally drops with increasing drug concentration. The paracetamol decay always follows a pseudo-first-order reaction with slightly higher rate constant for catalyzed systems than direct ozonation. Aromatic products such as hydroquinone, p-benzoquinone and 2-hydroxy-4-(N-acetyl)aminophenol are identified by gas chromatography–mass spectrometry (GC–MS) and reversed-phase chromatography. Acetamide is generated when hydroquinone is produced. These products are degraded to oxalic and oxamic acids as ultimate carboxylic acids, as detected by GC–MS and ion-exclusion chromatography. Oxalic acid is generated via glycolic, glyoxylic, tartronic, ketomalonic and maleic acids. While Fe³⁺-oxalato complexes are photolyzed by UVA light, Cu²⁺-oxalato, Fe³⁺-oxamato and Cu²⁺-oxamato complexes are oxidized with OH. NH₄⁺ and NO₃⁻ ions are produced during mineralization.     

间甲酚臭氧化反应动力学研究

本文采用停流光谱仪研究了溶解臭氧和间甲酚在液相中的均相反应动力学,探讨了反应温度为298K和pH值在3～7范围内,间甲酚臭氧化反应的动力学参数。间甲酚臭氧化总的反应呈二级,对臭氧浓度和间甲酚浓度分别呈一级。臭氧化反应速率常数随溶液pH值的增大而增大,在T为298K时,当pH值从3变化到7,总的反应速率常数从6 28×103(mol L)-1·s-1增大到9 15×105(mol L)-1·s-1。     

Removal of Fe(III) ion from aqueous solution by adsorption on raw and treated clinoptilolite samples

Iron (III) adsorption from aqueous solutions onto raw and pretreated clinoptilolite was investigated here. Various parameters for iron removal; initial solution pH, contact time and metal ion concentration were optimized. The equilibrium data were modeled by both the Langmuir and Freundlich adsorption isotherms at optimal conditions. Adsorption capacities of raw samples and those pretreated with Na₂S₂O₈ at 20 °C , 70 °C and with HNO₃ at 20 °C were all similar but samples pretreated with HNO₃ at 70 °C were significantly different; iron (III) removal from samples pretreated with HNO₃ decreased with increasing pretreatment temperature. Tests with Fe⁺³ solutions containing phenol, CsCl or KCl, indicated the continued presence of these ions in zeolite which either promoted or retarded the adsorption of iron. The Fe⁺³ adsorption capacity of clinoptilolite pretreated with HNO₃ at 70 °C was about two times greater with, than without, CsCl and KCl. The kinetics of iron adsorption from aqueous solution were also investigated using the first-order Lagergren equation and a pseudo-second-order model.     

Oxidation kinetics of Fe(II)NTA to Fe(III)NTA by oxygen

The oxidation of aqueous solutions of Fe(II)NTA was investigated in a bubble column reactor. The rate of the oxidation reaction was found to be proportional to the partial pressure of oxygen and to have an order of 0.5 with respect to the Fe(II)NTA concentration. The overall transfer of oxygen appears to be predominantly reaction controlled for Fe(II)NTA concentrations in the order of 1 mmol l⁻¹, whereas for high concentrations (100 mmol l⁻¹) mass transfer becomes the controlling factor. Overall mass transfer coefficients and reaction rate constants were determined in the range between 25 and 60°C and for a wide range of Fe(II)NTA concentrations (5-250 mmol l⁻¹).     

ELIMINATION OF BENZENE AND CHLOROBENZENES BY PHOTODEGRADATION AND OZONATION PROCESSES

Benzene (B) and two representative chlorobenzenes (1,4-dichlorobenzene (DCB) and 1,2,3-trichlorobenzene (TCB)) were oxidized by means of UV irradiation alone, ozone alone, and the combinations UV/H₂O₂ and O₃/H₂O₂. In the single photolytic process, the influence on the photodegradation of the pH, temperature, and type of radiation source used was established. A kinetic study was performed by evaluating the first-order rate constants and the quantum yields. The effect of the additional presence of hydrogen peroxide was pointed out in the combined process UV/H₂O₂,with the determination of the specific contribution of the radical pathway to the overall photodegradation system. In the oxidation by ozone based systems (ozone alone and the combination O₃/H₂O₂), the rate constants at 20°C for the reaction of each compound with ozone and hydroxyl radicals were determined.     

MASS TRANSFER IN BANANA CHIPS DURING OSMOTIC DEHYDRATION

The effects of temperature ( 50, 60 and 70 °C ), sucrose concentration ( 50, 60 and 70° Brix ) and pH ( 6,7 and 8 ) on the mass transfer during osmotic dehydration of banana chips were studied. Fitting a diffusion model gave apparent diffusivity values varied from 2.77 to 2.66 × 10^-9 m² s^-1 and depending on temperature and sucrose concentration but not on pH changes. The effct of syrup/product volume ratio on the mass transfer kinetics was also investigated.     

Reaction Kinetics of Ozonation of Trichloroethylene and Benzene in Gas and Liquid Phase

The kinetics of ozonation reactions oftrichloroethylene (TCE) and benzene in gas and liquid phases at101.3 kPa and 298 K was investigated in this paper. The ozonation ofTCE is first order with respect to the ozone concentration and one andhalf order to TCE in the gas phase with the average rate constant 57.30(mol*L-1)-1.5 *s-1, and the TCE ozonation inaqueous medium is first order with respect to both ozone andtrichloroethylene with the average rate constant 6.30(mol*L-1)-1 *s-1. The ozonation of benzene inthe gas phase is first order in ozone but independent of the benzeneconcentration with the average reaction rate constant 0.0011 s-1.The overall kinetics of reaction between ozone and benzene in aqueoussolution is found to be first order with one-half order in both ozoneand bezene, with the average reaction rate constant 2.67 s-1. Itis found that the ozonation rate of pallutants is much quicker than that ofself-decomposition of ozone in both gas and aqueous phase.     

对硝基苯胺臭氧化反应动力学和吸收过程模拟

采用停流光谱法研究了T＝298 K,pH＝2.1～6范围内对硝基苯胺与臭氧在水溶液中的臭氧化反应动力学.研究结果表明,降解1 mol的对硝基苯胺需要4 mol臭氧,对硝基苯胺臭氧化总的反应是二级,对臭氧浓度和对硝基苯胺浓度分别为一级.臭氧化反应速率常数随溶液pH值的增大而加快:在T=298 K时,当pH值从2.1变化到6,总的反应速率常数从6.17×10⁴ (mol•L^-1)^-1•s^-1增大到1.55×10⁶(mol•L^-1)^-1•s^-1.为了验证其适用性,进行了臭氧在搅拌釜中在对硝基苯胺溶液中吸收过程的模拟.采用Matlab软件求解吸收过程的质量平衡方程,模拟了吸收过程中臭氧和对硝基苯胺浓度的变化,并与实验值进行了比较.结果表明,在80％的对硝基苯胺降解之前,模拟值和实验值能很好地一致.     

苯的气相O3氧化动力学

1前言苯是不同行业广泛使用的有机溶剂,因其相对挥发度高,很易从液相蒸发到气相。因此,在它进入大气前使其降解以保护环境是非常重要的。0。氧化法是一种较有效降解有机物的方法’‘·“,它可直接与有机物反应,使其氧化为co。和水。本工作是研究含苯的废气在间歇循环气相反应器中的o。氧化反应动力学过程,以便为苯的气相o。氧化反应器的设计提供参考。2实验2·1实验装置与过程实验装置与过程参考文献［3j。该装置是通过测定有限反应物o。浓度（吸收率）随时间的变化研究反应动力学。用碘滴定法对仪器核核,最大测量误差在3％以内。反…     

Physicochemical surface and catalytic properties of CuO–ZnO/Al2O3 system

A series of CuO–ZnO/Al₂O₃ solids were prepared by wet impregnation using Al(OH)₃ solid and zinc and copper nitrate solutions. The amounts of copper and zinc oxides were varied between 10.3 and 16.0 wt% CuO and between 0.83 and 7.71 wt% ZnO. The prepared solids were subjected to thermal treatment at 400–1000°C. The solid–solid interactions between the different constituents of the prepared solids were studied using XRD analysis of different calcined solids. The surface characteristics of various calcined adsorbents were investigated using nitrogen adsorption at −196°C and their catalytic activities were determined using CO-oxidation by O₂ at temperatures ranged between 125°C and 200°C.

The results showed that CuO interacts with Al₂O₃ to produce copper aluminate at ≥600°C and the completion of this reaction requires heating at 1000°C. ZnO hinders the formation of CuAl₂O₄ at 600°C while stimulates its production at 800°C. The treatment of CuO/Al₂O₃ solids with different amounts of ZnO increases their specific surface area and total pore volume and hinders their sintering (the activation energy of sintering increases from 30 to 58 kJ mol⁻¹ in presence of 7.71 wt% ZnO). This treatment resulted in a progressive decrease in the catalytic activities of the investigated solids but increased their catalytic durability. Zinc and copper oxides present did not modify the mechanism of the catalyzed reaction but changed the concentration of catalytically active constituents (surface CuO crystallites) without changing their energetic nature.