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A preliminary experimental study conducted with a conventional bubble ozonation contactor column has shown that small amounts of Mn(II) greatly enhanced the destruction of atrazine by ozone. There is an inversely linear relationship between the dosed Mn(II) concentration and the residual ozone concentration at a specific reaction time. The ozone transfer efficiency into water is greater with the increase of Mn(II) dosage. Hydrous manganese dioxide prepared by reacting permanganate with manganese sulfate, also was shown to be effective in catalyzing the destruction of atrazine by ozone. The efficiency of catalytic activity for the destruction of atrazine caused by preformed hydrous Mn(IV) is slightly lower than the case of Mn(II). A lower residual ozone value using manganese dioxide compared to the case of ozone alone suggests that ozone also may be decomposed by hydrous Mn(IV). However, a commercial MnO2 did not show any catalytic activity for atrazine destruction. The very much greater degree of atrazine oxidation by manganese-catalyzed ozonation compared to ozone alone is speculated to be the result of the generation of highly oxidative intermediate species such as hydroxyl radicals during the reaction between ozone and manganese species. 相似文献
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试验研究了气泡在颗粒床层表面的生成脱离过程及其行为特性,利用高速摄像技术揭示了进气管管径、颗粒床层高度、颗粒粒径等因素对气泡脱离直径及其生成周期的影响规律,对比分析了颗粒床层表面和进气管管口的气泡生成脱离行为差异。研究结果表明:在1500~3000μm粒径范围的床层表面所生成气泡的初始形态相对更扁小,气泡也更快向扁平状演变;颗粒粒径的增大使得进气流量对气泡形态的影响减弱;管径和颗粒床层高度的增大可以有效促进气泡脱离直径的增长,但延缓了气泡的生成脱离,增加了气泡的生成周期;颗粒粒径对气泡生成周期的影响随着进气流量的增大而逐渐减弱;气泡在颗粒床层表面和管口的生成脱离行为存在显著差异,相比之下,150~300μm粒径范围的颗粒床层对气泡的生成脱离具有更明显的阻碍作用,其表面所生成气泡的脱离直径和生成周期相对较大。 相似文献
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Manickam Matheswaran Il Shik Moon 《Journal of Industrial and Engineering Chemistry》2009,15(3):287-292
The ozonation of phenol wastewater treatment system has been investigated with effective mass transfer between gas and liquid phase in a bubble column reactor. The designed bubble column reactor was investigated for increasing the rate of mass transfer of ozone, the rate of oxidation of phenol in the solution, the solubility and decomposition rate of ozone in the distilled water were also studied at different flow rates. The decomposition rate constants were calculated based on pseudo first order kinetics. The oxidation of phenol was investigated in order to provide the overall reaction rate constant for the reaction between ozone and phenol at 25 °C. The influence of the operating parameters like initial phenol concentration, ozone flow rate and pH for the destruction of phenol by ozonation were studied. The pseudo first order rate constant was depending on the initial concentration of phenol solution. A comparison of TOC removal percentage between bubble column reactor and bubble diffuser using ozonation were reported. 相似文献
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In this paper we study the mass transfer process of ozone dissolution in a bubble plume inside a rectangular water tank, as a model problem for a water purification system. The effect of bubble diameter and plume structure on mass transfer efficiency of ozone in bubble plumes is investigated numerically. In order to capture the detailed plume structure, the interaction between liquid and bubbles is treated by a two-way coupling Euler-Lagrange method. The motion of the continuous phase (a mixture of liquid and gas bubbles) is solved using a finite difference method in an Eulerian framework. The motion of the dispersed phase (bubbles) is tracked individually in a Lagrangian approach. The ozone transfer process from bubbles to liquid is computed by modelling the mass transfer rate of individual bubbles. Our numerical results show a nonlinear dependence of the ozone dissolution efficiency on the initial bubble size. The dissolution efficiency varies rapidly when the initial bubble size reaches certain value while the change of efficiency is much slower at other bubble sizes. Therefore, for a given tank size it is not necessary to generate bubbles much smaller than the optimal size. This result is of importance for engineering since it is difficult to generate small bubbles in practice. Our results also show that the instantaneous dissolution rate of ozone could be increased by increasing the initial volumetric fraction of ozone inside bubbles even up to 20% while maintaining the dissolution efficiency. 相似文献
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研究了鼓泡塔中臭氧在对硝基苯酚溶液中的吸收传质过程。首先探讨了pH值和气速对对硝基苯酚降解速率的影响。在 298K下,臭氧被连续通入对硝基苯酚溶液中,臭氧的传质速率因为溶解臭氧与对硝基苯酚的快速反应而大大加强。然后运用与实验条件相同的操作参数,进行了臭氧在鼓泡塔中吸收过程的模拟研究,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酚浓度的变化,并与实验值进行了比较。结果表明,在短的鼓泡塔中,应用全混流模型来描述气相和液相的流体状态是可行的,在 80%的对硝基苯酚降解之前,模拟值和实验值能很好地一致。 相似文献
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ABSTRACT In order to improve the mass transfer efficiency of ozone in water, stainless steel wire mesh (SSWM) corrugated structure was packed into a microbubble ozone reactor to enhance the mass transfer efficiency. The results showed that the SSWM/O3 system could effectively improve the mass transfer efficiency. When the concentration of ozone in the liquid phase reached a stable state, it was about 21 mg/L, which was about 14% higher than that of ozone alone; the apparent mass transfer coefficient (KLa) was 0.7255 min?1, which was about 51% higher than that by ozone alone systems. The hydroxyl radicals in the SSWM/O3 system were more generated than that of ozone alone. After 6 min of operation, the concentration of hydroxyl radicals increased by 60 µmol/L compared with that in ozone alone system. The Chemical Oxygen Demand (COD) removal efficiency of biologically treated leachate by SSWM/O3 system was about 10% higher than that of ozone alone system after 120 min of reaction. The effects of pressure, temperature, ozone inlet concentration, and flow rates on the ozone concentration in the liquid phase and the generation of hydroxyl radicals were also investigated. The results indicated that reactor pressure has little effect on ozone concentration in liquid phase, but increasing pressure helps to generate ·OH; ozone concentration and ·OH generation in liquid phase increase with the increase of inlet ozone concentration and flow rate; ozone concentration in the liquid phase decreases with the increase of temperature, but ·OH generation increases with the increase of temperature. Our results indicate that the system consisting of SSWM and microbubble column reactor is an efficient process for the intensification of ozone-based advanced oxidation processes. 相似文献
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The experimental results obtained in three different types of ozone contactors were analyzed to study the effects of the ozone contactor design, configuration, operating conditions, and scale-up on the: (1) ozonation process induced reduction efficiencies of color, AOX, COD, and TOC from biologically treated Kraft pulp mill effluents; (2) the increase in biodegradability of this type of wastewater; and (3) the dynamics of the ozone gas absorption process. The three types of ozone contactors included: (1) an extra-coarse-bubble diffuser ozone contactor; (2) an impinging-jet ozone contactor; and (3) a fine-bubble diffuser ozone contactor. Similar treatment levels were achieved in those ozone contactors although the impinging-jet bubble column was more effective in treating Kraft pulp mill effluents due to its smaller reactor volume and lower off-gas ozone concentrations. Consequently, the operating costs of an ozonation process and ozone off-gas destruction facilities will be greatly reduced when using the impinging-jet bubble column design for treating Kraft pulp mill effluents. 相似文献
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This research combined micro/nano bubble techniques with ozone disinfection to determine feasibility of applying micro/nano bubble ozonated water in preventing tomato airborne disease. Results indicated that dissolving ozone in micro/nano bubbles is more efficient than using a mixing pump. In our in vitro studies, when dissolved ozone concentration was 1.6 mg/L, a 5.2 to 3.3 log reduction in Alternaria solani Sorauer conidia was observed; with concentration of 1.8 mg/L, there was a 5.0 to 3.7 log reduction in Cladosporium fulvum conidia. Furthermore, spraying ozonated water in a certain concentration range (0.6–1.8 mg/L) had no significant negative effects on tomato growth. 相似文献
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The mass transfer characteristics of packed bubble columns were studied by employing various packings of different sizes and shapes in 10–38·5 cm i.d. columns. The theory of absorption accompanied by pseudo-mth order reaction was used to obtain the values of effective interfacial area. The values of liquid side mass transfer coefficient were obtained by using the theory of absorption accompanied by slow chemical reaction. The superficial gas velocity was varied from 5 to 25 cm/sec. The packed bubble columns showed a considerable improvement in the performance over empty bubble columns. A criterion for the scale-up of these columns has been suggested. 相似文献
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The ozone transfer for the ozonation of the azo dye Reactive Black 5 (RB5) and indigo was investigated using a bubble column at semi-batch conditions. The results were analyzed by applying film theory and surface renewal theory. The ozonation of both dyes was so fast that an instantaneous reaction directly at the bubble surface can be assumed. The ozone balance in the gas phase was used to determine the volumetric mass transfer coefficient kLa and the enhancement factor E. Besides the measured concentrations, temperature and pressure only the Henry coefficient was required for the determination of kLa and E. By varying the ozone inlet and the dye concentration the reaction regime was identified. The Hatta number Ha which requires uncertain parameters did not have to be determined. 相似文献
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A multiphase Volume‐of‐fluid (VOF) model was developed to gain further insights into the reactive flow parameters and electrical capacitance tomography (ECT) measurements on the remediation of hazardous organic pollutants. Low ozone bubble frequencies were obtained for high surface tension fluids, and the liquid viscosity affected the ozone bubbling frequency. The VOF model indicated that the increase of inlet gas velocity enriched the ozone bubble detachment and concomitantly generated larger ozone bubbles, decreasing the detoxification rates. VOF mappings and ECT visualizations of gas‐liquid unveiled preferential routes and highlighted the attenuation of the axisymmetric behavior of the ozonation bubble column under high‐interaction regimes. 相似文献
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Takafumi Uchiyama Hiroyuki Kobayashi Hussein Tawfeek Znad Masahiro Tokumura 《臭氧:科学与工程》2007,29(1):65-72
The ozonation of a nonionic surfactant, Sannonic SS-90 (polyoxyethylene alkyl ether), which is one of polyoxyethylene nonionic surfactants, in water has been investigated using a bubble column. The effects of initial nonionic surfactant concentration, ozone gas flow rate, inlet ozone concentration in the gas-phase, liquid-phase temperature and hydrogen peroxide dose on decomposition of Sannonic SS-90 were systematically examined. The decomposition rate of Sannonic SS-90 decreased with the increase in the initial surfactant concentration and increased with increasing ozone flow rate and temperature. It was found that the rate of Sannonic SS-90 mineralization was weakly dependent on the gas-phase inlet ozone concentration in the range of the gas-phase inlet ozone concentration in this study. The oxidation rate increased with increasing concentration of H2O2, reached a maximum value and then decreased with further increasing of H2O2 concentration. The dynamic performance of the ozonation in a semi-batch bubble column was simulated using a mathematical model based on a tanks-in-series model. Reasonable agreement between the present experimental data and the simulated results was found. 相似文献
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Shu Liu Qunhui Wang Tichang Sun Chuanfu Wu Yang Shi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(2):206-215
BACKGROUND: Comparison experiments were carried out with three kinds of micro‐bubbles on the coagulation flotation process treatment of coke waste‐water under optimum coagulation conditions obtained from zeta potential measurement. RESULTS: Micro‐bubble flotation with ozone showed the best performance. The ozone micro‐bubbles exhibited high absolute zeta potential values, creating repulsion forces thus avoiding the coalescence of bubbles as well as creating attractive interaction between bubbles and particles in the waste‐water. Moreover, the fluorescence intensity of three micro‐bubble samples showed that the ozone micro‐bubble system produced the most hydroxyl radicals, which contributed to the degradation of organic material in the coke waste‐water. Compared with either air micro‐bubble flotation and oxygen micro‐bubble flotation processes, pyridine removal efficiency of the ozone micro‐bubble flotation process was, respectively, 4.5 and 1.7 times higher, and benzene removal efficiency 3.6 and 1.5 times higher. Finally, drainage models and oxygen diffusion models of the three kinds of micro‐bubble water samples verified the long persistence of the three kinds of micro‐bubbles in the water. CONCLUSION: The application of ozone micro‐bubble technology in coagulation processes may provide an efficient and cost‐effective approach to the treatment of waste‐water containing refractory organic compounds. Copyright © 2011 Society of Chemical Industry 相似文献
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A new method using the axial dispersion model for estimation of ozone self-decomposition kinetics in a semibatch bubble column reactor was developed. The reaction rate coefficients for literature equations of ozone decomposition and the gas phase dispersion coefficient were estimated and compared with literature data. The reaction order in the pH range 7–10 with respect to ozone 1.12 and 0.51 the hydroxyl ion were obtained, which is in good agreement with literature. The model parameters were determined by parameter estimation using a nonlinear optimization method. A sensitivity analysis was conducted to obtain information on reliability and identifiability of the estimated parameters. 相似文献
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《Chemical engineering journal (Lausanne, Switzerland : 1996)》2001,81(1-3):331-335
The gas holdup, frictional pressure drop and liquid dispersion have been investigated in a packed bubble column at elevated pressures for the air–water system. The bubble column, which had an internal diameter of 0.15 m and which was packed with 15 mm plastic Pall rings was operated in the semibatch mode. The operating pressures ranged from 0.1 to 0.66 MPa. It was found that increasing the pressure increases both the gas holdup and the dispersion coefficient. In contradiction to the results obtained from packed bubble columns fed with a continuous net flow of liquid, a maximum point of the frictional pressure drop was observed at the transition point between bubble and pulse flow region. 相似文献
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Ozone, ultrasound, and ozone/ultrasound processes were evaluated for the removal of 1,4-dioxane from tap water using a continuous flow reactor with on-line aqueous ozone measurement. The addition of ultrasound to ozone was found to significantly boost removal. The removal of 1,4-dioxane by ozone/ultrasound process exceeded the sum of the removals from ozone alone and ultrasound alone. Ultrasound alone showed less than 20% removal of 1,4-dioxane. The effects of reactor pressurization and bicarbonate as a hydroxyl radical scavenger were also studied. It was observed that at constant aqueous ozone concentration, additional pressure in the reactor tended to mute the 1,4-dioxane removal boost noted in the ozone/ultrasound process, while additional pressure did not affect 1,4-dioxane removal via ozone alone. The removal of 1,4-dioxane was found to be dependent on the consumption of aqueous ozone, and the consumption of ozone was found to be increased by either the addition of ultrasound or by increasing pH. Rate constants were calculated for various ozone concentrations for the ozone and ozone/ultrasound processes and the systems were fitted to a Chick–Watson model. 相似文献
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The mixing efficiency of four alternative ozone dissolution systems, including conventional bubble diffusion and pipeline injection/diffusion reactors, were compared by measuring the variability of ozone residual measurements at the outlet of each reactor. The standard deviation and coefficient of variation of a time series of residual measurements were used to provide a quantitative measure of the level of mixing in the reactor. The results indicate that properly designed pipeline dissolution systems provide significantly improved mixing over oxygen-fed or air-fed bubble diffusion systems. Minimum mixing criteria for bubble diffusion systems cited in the literature may underestimate the level of mixing required to achieve stable ozone residuals downstream of the dissolution chamber of conventional bubble diffusion chambers. 相似文献