Rate constant determination of ozone‐organic fast reactions in water using an agitated cell

Abstract

Rate constants of the direct reaction between ozone and some organic pollutants (phenol and azo dyes) in water have been determined from experiments carried out in an agitated cell of known interfacial area. Kinetic equations derived from the Danckwerts model for gas to liquid absorption have been applied. By varying the ozone partial pressure, the regime of ozone absorption can be changed from instantaneous to fast. In the first case, the volumetric mass transfer coefficient was obtained, while in the second, the rate constant of the ozoneorganic direct reaction studied was determined. The procedure is recommended for ozonation reactions with rate constants in the range 10 2 -10 5 m 3 mol -1 S -1 .

Decolorization of methyl orange by ozonation in combination with ultrasonic irradiation

“…Therefore, ozonation process may proceed via free radical pathway. However, the radical contribution to the decolorization of azo dyes could be neglected during ozonation in combination with ultrasonic irradiation because azo dyes present in their structure functional groups and double bonds very prone to the direct ozone attack [35]. Shu and Huang [33] also observed ozone in aqueous phase would tend to react with azo dyes rather than free radicals in UV enhanced ozonation process.…”

“…The peak at 273 nm was associated with "benzene-like" structures in the molecule [28], and that at 465 nm was originated from an extended chromophore, comprising both aromatic rings, connected through the azo bond. The disappearance of the vis- ible band with the time was due to the fragmentation of the azo links by direct ozone attack [35]. In addition to this rapid bleaching effect, the decay of the absorbance at 273 nm was considered as evidence of aromatic fragment degradation in the dye molecule and its intermediates [28].…”

Ozone oxidation kinetics of Reactive Blue 19 anthraquinone dye in a tubular in situ ozone generator and reactor: Modeling and sensitivity analyses

“…Beltran and Alvarez [34], studied the ozonation of phenol and three azo dyes (Direct Yellow 27, Direct Blue 1, and Black Acid 52) in an agitated cell and determined the second order rate constant using the kinetic equations derived from Danckwerts' model for gas-liquid absorption. As shown in their article, the rate constant did not follow a consistent pattern to make conclusions on the dependency of the rate constant on dye concentration.…”

Oxidation of methyl methacrylate from semiconductor wastewater by O3 and O3/UV processes

“…The radical ozonation is non-selective and vigorous. The ozonation process in the acid condition mainly takes place through the direct oxidation reaction, which is selective [7,8]. Ozonation combined with ultraviolet (UV) radiation is deemed as a more effective process to remove organics comparing to the sole ozonation.…”