Ozone sparging

Ozone Sparging at Former Service Station, Bucks County, Pennsylvania... 

Chang B-J, Chian E S K (1981) A model study of ozone-sparged vessels for the removal of organics from water, Water Research 15 929-936. 

Kerfoot et al. [71,72] developed a new ozone sparging device which injects gaseous ozone in microbubbles resulting in a very efficient MTBE, TAME and tBA removal. MTBE and tBA were observed to degrade in similar reaction rates, whereas TAME reacts faster. Other intermediates such as fBF were found to be further oxidized at a slower rate. The authors claim to operate this system with lower costs than other on-site applications. 

In the present study, the mechanism of photolytic ozonation was investigated in the laboratory by measuring ozone, hydrogen peroxide, and total oxidant levels in purified water as a function of time in a two-liter stirred tank reactor in which concurrent ozone sparging and UV irradiation were taking place. Experiments were run in the presence and absence of various radical scavengers and the results Interpreted in terms of reaction rate constants taken from the literature. This paper will discuss the mechanism of photolytic ozonation, show its relationship to other ozonation processes, and... 

Ozone can be analyzed by titrimetry, direct and colorimetric spectrometry, amperometry, oxidation—reduction potential (ORP), chemiluminescence, calorimetry, thermal conductivity, and isothermal pressure change on decomposition. The last three methods ate not frequently employed. Proper measurement of ozone in water requites an awareness of its reactivity, instabiUty, volatility, and the potential effect of interfering substances. To eliminate interferences, ozone sometimes is sparged out of solution by using an inert gas for analysis in the gas phase or on reabsorption in a clean solution. Historically, the most common analytical procedure has been the iodometric method in which gaseous ozone is absorbed by aqueous KI. 

Ozone in the gas phase can be deterrnined by direct uv spectrometry at 254 nm via its strong absorption. The accuracy of this method depends on the molar absorptivity, which is known to 1% interference by CO, hydrocarbons, NO, or H2O vapor is not significant. The method also can be employed to measure ozone in aqueous solution, but is subject to interference from turbidity as well as dissolved inorganics and organics. To eliminate interferences, ozone sometimes is sparged into the gas phase for measurement. 

Intensification can be achieved using this approach of combination of cavitation and advanced oxidation process such as use of hydrogen peroxide, ozone and photocatalytic oxidation, only for chemical synthesis applications where free radical attack is the governing mechanism. For reactions governed by pyrolysis type mechanism, use of process intensifying parameters which result in overall increase in the cavitational intensity such as solid particles, sparging of gases etc. is recommended. 

T0442 IT Corporation, In Situ Air Sparging T0445 IT Corporation, Ozonation... 

At a former manufactured gas facility in Long Beach, California, International Technology Corporation s in situ air sparging apparatus was combined with its ozonation technology. Construction and operation costs for the project from 1998 to 2000 are estimated to be 1,000,000 (D19400N, pp. 5, 6). 

Generally the oxidation of compounds with ozone is considered to be second order, which means first order with respect to the oxidant (03 or OH°) and to the pollutant M (Hoigne and Bader, 1983 a, b). A requirement for the experimental determination of the reaction order with respect to the pollutant is that the ozone concentration in the bulk liquid remains constant. A further requirement for determining kinetic parameters in general, is that the reaction rate should be independent of the mass transfer rate. These are easy to achieve for (very) slow reactions by using a continuously sparged semi-batch reactor. Such a reaction... 

Another aspect to be considered is that ozone also decays during the experiments. To obtain a constant ozone concentration in a system where ozone decay occurs, the reactor can be operated semi-batch. Gaseous ozone is continuously sparged to the reactor and after the ozone concentration reaches steady-state, the investigated compound is injected into the reactor. Another possibility is to measure the ozone decay rate independently and take this into account in the calculations. 

The choice of the saturation gas is critical. When Ar and Kr were sparged in water irradiated at 513 kHz, an enhancement in the production of OH radicals of between 10% and 20%, respectively, was observed, compared with 02-saturated solutions [22]. The higher temperatures achieved with the noble gases upon bubble collapse under quasi-adiabatic conditions account for the observed difference. Because the rate of sonochemical degradation is directly linked to the steady state concentration of OH radicals, the acceleration of those reactions is expected in the presence of such background gases. The use of ozone as saturation gas (in mixtures with 02) provided new reaction pathways in the gas phase inside the bubbles, which also increase the measured reaction rates (see Sect. IV.G.l). 

Nomnicrobial processes for destruction of cyanide wastes have been extensively investigated and are well known. Parga et al. (2003) have reported several oxidation methods for treating cyanide solutions. Such methods include (1) destruction of cyanide by oxidation with chlorine dioxide in a gas-sparged hydrocyclone reactor, (2) destruction by ozone in a stirred batch reactor, and... 

Hydrogen peroxide was measured colorimetrlcally by complexation with Ti(IV) ("Tl4" method) ( ) or by the method of Masschelein et al. ( ) (MDL method). As ozone appears to interfere negatively with hydrogen peroxide measurement using the TI4 method, ozone was quickly and vigorously sparged from solution before peroxide measurements were made. The MDL method was not used on ozone-containing solutions. Total oxidants were measured iodi-metrically by the method of Flamm (30), but with the addition of a... 

In addition to the photolytic ozonation experiments described above, hydrogen peroxide photolysis experiments were performed in the presence and absence of hydroxyl radical scavengers. These experiments were run using distilled water (a) as it came from the lab reservoir, (b) after oxygenation, and (c) after sparging with nitrogen to remove oxygen. The results are shown in Table I, in the form of the observed rate constants. 

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