Oxidation of Acid Red-151 Aqueous Solutions by the Peroxone Process and its Kinetic Evaluation

Oxidation of an azo dye solution, namely, Acid Red 151 by the peroxone process was investigated experimentally at different pH values, initial dye and ozone concentrations, and the initial molar ratios (r) of hydrogen peroxide to ozone. At pH 2.5 in this process, the obtained color and chemical oxygen demand (COD) removals were higher than those at pH of 7 and 10. The best value of r yielding the highest treatment efficiency at each pH was determined as 0.5. The application of the “initial rates method” to the kinetic data for peroxone oxidation of aqueous Acid Red 151 solutions showed that the individual orders with respect to O₃ and dye were one, the total order of the reaction being two. The rate constants based on the initial rates of dye degradation were determined as 98.9, 77.3 and 65.7 mM^?1min^?1 at the pH values of 2.5, 7 and 10, respectively.     

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     

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.     

Application of Regression Analysis for Ozone and Catalytic Ozonation of Organic Compounds from Landfill Leachate with Ceramic Raschig Rings and Natural Manganese Ore

Treatment of landfill leachate could be improved by adding ceramic raschig rings and manganese ore as catalysts for ozonation. Regression analysis were carried out to assess effects of parameters (pH, reaction time, the amount of H₂O₂, the surface area of ceramic raschig rings and the amount of manganese ore) on removing organic compounds from landfill leachate by ozone alone, peroxone, ozone/ceramic raschig rings, peroxone/ceramic raschig rings, ozone/manganese ore and peroxone/manganese ore. Results showed that parameters of reaction time, the amount of H₂O₂ and the amount of manganese ore were the high effects on removal of organic compounds from landfill leachate, following by pH paremeter. Ceramic raschig rings did not have significant effect on color, COD and TOC removal.     

Peroxone Oxidation of Toluene and 2,4,6-Trinitrotoluene

This paper discusses oxidation of toluene and 2,4,6-trinitrotoluene (TNT) by ozone and hydrogen peroxide mixtures (known as peroxone oxidation) at 25[ddot]C. The overall reaction in alkaline solutions is first order with respect to the concentration of dissolved ozone, and is nearly independent of the pollutant concentrations. The oxidation of toluene is one-half order in hydrogen peroxide, and the rate constant changes in proportion to the hydroxyl ion concentration with an exponent of 0.67.

In the pH range of 7 to 9, the TNT destruction rate increases with the hydrogen peroxide and hydroxyl ion concentrations with exponents of 0.104 and 0.15 respectively. It is technically feasible to treat toluene and TNT contaminated waters by the peroxone oxidation process to achieve the residual level of a few parts per billion in treated waters to meet environmental requirements.     

Remediation of Kraft Effluent by Ozonation: Effect of Applied Ozone Concentration and Initial pH

In this study, the impact of ozone concentration (14 and 7mg/L^?1 applied for 120min) and pH (10 and 12) on color removal, and reduction of dissolved organic matter (DOC) and total phenol of Kraft E₁ effluent was investigated. The degradation kinetics for the all parameters at pH 12 were slower than of those at pH 10. The degradation at pH 10 ceased after approximately 120min, while for the ozonation at pH 12, ozone was still being consumed even after 5h of treatment. When the ozone dose was increased, the removal efficiency increased; however, the DOC removal efficiency continued limited.     

Kinetics and mechanism of the reaction between ozone and hydrogen peroxide in aqueous solutions

A kinetic model has been developed, taking into account both decomposition of ozone molecules and interactions between ozone and hydrogen peroxide for formation of hydroxyl radical and subsequent reactions. Experiments were carried out at 25°C in the pH range of 3 to 13, indicating that the depletion rate of ozone increases with the concentrations of ozone, hydrogen peroxide and hydroxyl ion, as predicted by the kinetic model. Adverse scavenging reactions, however, also play significant roles at sufficient concentration ratios of hydrogen peroxide to ozone and high concentrations of hydroxyl ion in reducing the depletion rate. Results of this research suggest, that it is most desirable to conduct the peroxone oxidation for pollutant destruction by the hydroxyl radical reaction in alkaline solutions of pH below 11, while maintaining about the same concentration of ozone and hydrogen peroxide.     

The Impact of Traces of Hydrogen Peroxide and Phosphate on the Ozone Decomposition Rate in “Pure Water”

To obtain an idea of the magnitudes of the ozone loss rates r_O3 in practical applications of ozone, an overall determination of the ozone decay profiles and rate constants was carried out in four different systems. These systems resemble different conditions for industrial application of ozone and the peroxone process, such as in the field of micro electronics, drinking water purification, disinfection, etc. Therefore, the behavior of ozone was monitored in the pH range from 4.5 to 9.0, in pure water and phosphate buffered systems in absence and presence of small amounts of hydrogen peroxide (10^?7 M to 10^?5 M H₂O₂). First the reproducibility of the ozone decay profiles was checked and from the various kinetic formalism tests, the reaction order 1.5 for the ozone decay rate has been selected. As expected, hydrogen peroxide increases the decay rates. In pure systems, added concentrations of 10^?7M H₂O₂ already cause a remarkable acceleration of the ozone decay in the acidic and neutral pH range compared to the pure systems. However for alkaline pH conditions almost no effect of the low hydrogen peroxide concentrations was noticed. Contradictory to literature data, in the absence of hydrogen peroxide, ozone displays faster decays in the buffered systems of low ionic strength of 0.02 compared to pure water. This acceleration is more pronounced for acidic pH conditions. Low concentrations of phosphate may indeed accelerate the ozone decay in the presence of organic matter. Adding H₂O₂ concentrations below 10^?5M to phosphate buffered solutions has a negligible effect on the ozone decay rate compared with pure water systems, except for pH 7. It appears that phosphate masks the effect of hydrogen peroxide below 10^?5 M as tested here. Thus the application of AOP's by adding low concentrations of hydrogen peroxide is not well feasible in the presence of phosphate buffers in pure water systems.     

Destruction of Helminth (Ascaris suum) Eggs by Ozone

Based on the properties of ozone as a strong germicidal agent, the inactivation kinetics or disintegration of Ascaris suum eggs in water were studied. Ozone was applied in synthetic samples, the concentration of dissolved ozone in the liquid phase was typically between 3.5 to 4.7mg/L, pH 5, 9. The value of 90% inactivation (t₉₀) obtained was at 1 h, the remaining 10% being inactivated in 2 h. A linear correlation between the logarithm of bacterial or yeast concentration (N) and contact time was found, being the linear significant correlation coefficient (r of 0.95). That 2-log inactivation occurred at a CT value near 4.7mg/min/L. The best reduction percentage was of 99.00 in 120min. It therefore could be demonstrated that ozone indeed induces effects on the helminth eggs.     

Advanced Oxidation and Degradation of Vinyl Chloride in Water

A kinetic model has been developed for the degradation of organic pollutants, by considering both the decomposition of ozone molecules and the interaction between ozone and hydrogen peroxide in the formation of a hydroxyl radical, and the subsequent reactions. Rate equations were derived for the depletion of ozone and pollutants in the advanced oxidation processes (known as the peroxone oxidation). Experiments were carried out at 298 K in the pH range 3 to 11. Kinetic data obtained experimentally from the hydrogen peroxide‐ozone reaction and advanced oxidation of vinyl chloride were analyzed by using the proposed rate equations, indicating that the depletion rate of ozone increases with the concentrations of ozone, hydrogen peroxide, and hydroxyl ion, as predicted by the kinetic model.     

Degradation of Organic Pollutants by the Advanced Oxidation Processes

A kinetic model hss been developed for the degradation of organic pollutants concerning with hydroperoxide ion as the initial step for generation of hydroxyl radical and its subsequent reac-tion mechanisms. Rate equstions were derived for depletion of ozone and pollutants in the peroxone oxidation process using ozone and hydrogen peroxide as combined oxidants. Kinetic data obtained experimentally form the hydrogen peroxide-ozone reaction and peroxone oxidstion of nitrohenzene were analyzed by using the proponse rate equations.     

Investigations on the Effect of Ozone as a Disinfectant of Egg Surfaces

The feasibility of gaseous ozone to reduce the number of microorganisms on the shell surface, of Salmonella Enteritidis (S.E.) in particular, of avian hatching eggs was investigated. Shell eggs were externally contaminated with S.E. to contain either 10²–10⁴ or 10⁵–10⁶ cfu/shell. Subsequently, the eggs were exposed to several ozone concentrations ranging from 0.5% to 5% wt/wt in combination with two relative humidities (< 30, > 70%) at room temperature. Exposure times varied between 20 minutes and 24 hours. A complete inactivation of 10²–10⁴cfu S.E./egg shell was reached by using an ozone concentration of 1% (wt/wt) for 120 min. Considering higher concentrations of S.E. on the shell ozone treatment caused approximately a 6 log₁₀ reduction. This demonstrates that gaseous ozonation is suitable for applications in hatcheries provided that high-power ozone generators are available. The parameters should be verified in large ozone cabinets.     

Application of O3 and O3/H2O2 as post-treatment processes for color removal in swine wastewater from a membrane filtration system

This study was aimed to evaluate the use of ozone (O₃) alone and peroxone (a combination of ozone and hydrogen peroxide; O₃/H₂O₂) as post-treatment processes for color removal in swine wastewater from a membrane filtration system. Results showed that the application of ozone-alone process or the peroxone process could reduce both capital and operating costs compared to reverse osmosis (RO) treatment. Of the two oxidation processes, the ozone-alone process was the most effective for treating nanofiltration (NF)-filtered wastewater, while the peroxone process was the most effective for treating ultrafiltration (UF)-filtered wastewater.     

臭氧降解水中邻苯二甲酸二甲酯的效能及动力学

利用臭氧降解含较高浓度邻苯二甲酸二甲酯(DMP)的模拟废水,考察了pH、DMP初始浓度、臭氧投加量和温度对臭氧降解DMP效果的影响,并对臭氧降解DMP的效能及动力学进行了研究。结果表明,pH为5～10时DMP的降解效果较好;DMP初始浓度越大,DMP降解率越小,但DMP降解量增加;臭氧投加量的增加有利于DMP降解,但臭氧利用效率降低;温度低时,升高温度DMP降解率增大,24℃后提高温度对DMP降解率影响不大。在pH为5～10、DMP初始浓度为14～66 mg·L^-1、O₃投加量为14～24 mg·min^-1、20～30℃条件下反应40 min,DMP降解率达85%以上。在实验条件范围内,臭氧降解DMP符合拟一级动力学,建立了幂指数表达的动力学模型。在pH为2～12范围内,因臭氧反应机理不同,表观动力学常数k_obs与pH不呈线性关系,pH为2～5时,k_obs快速增加,pH为5～9时,k_obs缓慢增加,pH大于9时k_obs反而降低,pH为9时k_obs最大,为0.0929 min^-1。     

Decay Rate Kinetics of Ozone Gas in Rice Grains

The present study was carried out to evaluate the effects of ozone on rice grains for the following three conditions: saturation time, decay rate, and half-life of ozone. Experiments were performed in different bed thicknesses (5 and 10 cm) and moisture content (11.4 and 14.2% wb) at atmospheric conditions. The lowest saturation time of ozone was 119 min, with the concentration of 516 ppm for rice grains ozonated at 5-cm bed thickness with 11.4% (wb) moisture content. The decay rate kinetics of ozone obtained were consistent with a first-order model. Regarding the half-life of ozone, the lowest value obtained was 6.78 min for rice grains ozonated at 10-cm bed thickness with 14.2% (wb) moisture content.     

Two-Stage Optimization of Coliforms,Helminth Eggs,and Organic Matter Removals from Municipal Wastewater by Ozonation Based on the Response Surface Method

In this study, a set of municipal wastewater (MWW) samples from an actual residual water treatment plant was treated by ozone. The residual water was characterized in terms of organic load and biological contaminants: total coliforms (TC), fecal coliforms (FC) and helminth eggs (HE). Initial values of these parameters were 2.8 × 10⁷ MPN/100 mL, 8.48 × 10⁶ MPN/100 mL, and 470 L^?1, respectively. The experimental setup considered the modification of pH and ozone dose as independent variables. Three different initial pH values (4.0, 7.0, and 11.0) and three different ozone concentrations (6, 15, and 30 mg/L) were used to investigate the pH ozone dose effect. The efficiency of ozone-based treatment was determined by the reduction of the microbiological indicators (TC, FC, and HE) and physicochemical parameters (COD and turbidity). The response surface method was used to determine suboptimal reaction conditions. These conditions were obtained using a two-stage procedure. The conditions under which both microbiological and organics were better removed corresponded to pH 7.8 and ozone concentration of 15.5 mg/L. A decline of biological indicators of 99% for TC, 99% for FC, and 99% for HE was obtained under the same reaction conditions. The reduction of chemical oxygen demand (COD) and turbidity was 75% and 85% under the same operation conditions, respectively.     

臭氧氧化处理苯胺废水

采用臭氧氧化法处理苯胺溶液,考察了反应时间、苯胺浓度、溶液pH、臭氧流量等因素对苯胺降解率的影响。研究结果表明：初始浓度200mg／L时,pH值9．0、臭氧流量为300mg／h,经10min后苯胺去除率达到99％以上。苯胺降解反应符合一级反应动力学。TOC降解速率低于苯胺分子降解速率,反应30min后,TOC去除率比苯胺去除率低40％左右,表明伴随着苯胺的分解,生成一系列中间产物。     

Chemical Oxidation of Thiocyanate Ion by Ozone

Thiocyanate ion and weak ammonia liquor from a coking operation were ozonated in a semi-batch reactor. In a typical case, 500 mg/L thiocyanate ion disappeared in 8 minutes using an ozone dose of 82 mg/min at pH 7. The cyanide ion concentration was maximized immediately after the thiocyanate ion disappeared. The ozone-to-thiocyanate ion stoichiometric molar ratio was found to be 2.0 ± 0.2. The rate constants for the reaction of thiocyanate ion and cyanide ion with ozone under the typical conditions listed above were 5.4 × 10⁴ L²/(mmole²-min) and 1.5 L/(mmole-min), respectively.     

Research Note: Penetration of Ozone Gas Across the Shell of Hen Eggs

Increasing evidence indicates that ozone gas is effective against Salmonella on and within shell eggs. However, information on the penetration of ozone across egg shell is limited. In this study, whole hen egg shells, filled with indigotrisulfonate solution (OD₆₀₀ ～1), were exposed to ozone gas (12–14% wt/wt O₃ in O₂) at 1.5 liters/min and atmospheric pressure for ≤ 40 min with appropriate controls. Ozone penetrated the shells over time (r²?=?0.9974) causing indigo decoloration and increasing its transmittance from 16 to 28% after gas exposure for 40 min. This study confirms ozone penetration through egg shell using a simple qualitative technique.     

Multistage Decomposition Kinetics of Ozone In Dilute Aqueous Solutions

AbstractDecomposition of ozone in dilute aqueous solutions was found to be a complex process kinetically. Initial ozone dose-time had a significant impact on reaction order. Solutions dosed initially for less than one minute displayed uniform second-order kinetics. For doses applied over 5 and 15 min periods at a pH -2, reaction order changed from 2 to 1 to 0 as ozone decomposition progressed. At a pH of 6.65, the transition was from a reaction order of 2.5-3 to 2. This behavior has been ascribed to the effect of accumulated ozone decomposition products on the decomposition process.