Combined Use Of Ozone Research Articles

A TiO2/Al2O3 catalyst to improve the ozonation of oxalic acid in water

Removal of oxalic acid from water has been accomplished through TiO2/Al2O3 catalytic ozonation. The combined use of ozone and the titanium catalyst leads to a conspicuous 80% of oxalic acid conversion in 3h which compares favorably to the hardly 2% reached in the absence of the catalyst at pH 2.5. At the experimental conditions applied, the catalytic process develops under complete carbon mineralization and does not proceed through hydroxyl radical oxidation. The process rate can be described by considering an Eley–Rideal mechanism. Thus, it is proposed that adsorbed oxalic acid reacts directly with ozone in solution, the oxalic acid adsorption stage being the rate-limiting step. This mechanism justifies the experimental kinetic orders found in the range 1 and 0–1 for oxalic acid and ozone, respectively. The apparent activation energy of the catalytic ozonation was also found to be 14kcalmol−1.

Effect of ozone and ozone/activated carbon treatments on genotoxic activity of naphthalenesulfonic acids

AbstractNaphthalenesulfonic compounds are widely used, mainly by the textile industry in the synthesis of azoic colorants. The presence of the sulfonic group is known to endow these compounds with high water‐solubility and low biodegradability, although its influence on their genotoxic activity is unknown. The use of energetic oxidants is recommended for the degradation of organic compounds which are refractory to biological treatment. Ozone and ozone/activated carbon have been proposed as the best alternatives to remove these compounds. The results showed that the more sulfonic groups there are on the aromatic ring of this family of contaminants, the lower is their genotoxic activity. All the compounds studied presented genotoxic activity at elevated concentrations. Ames test results indicate that DNA damage was produced by substitution of nitrogenated bases. The system based on the combined use of ozone and activated carbon was the most efficacious in the depuration of water containing these contaminants. This approach rapidly degraded the naphthalenesulfonic acids, eliminated their genotoxic activity and reduced their organic material content using low doses of ozone.© 2002 Society of Chemical Industry

Effect of Ozone Treatment on Surface Properties of Activated Carbon

The combined use of ozone and activated carbon has recently started to be developed for the treatment of toxic effluents. However, the effect of ozone on the properties of activated carbon is not fully elucidated. A study was undertaken of modifications in the surface properties of a commercial activated carbon produced by its ozonation during different time periods. Surface chemistry of the activated carbon samples was characterized by selective neutralization, temperature-programmed desorption, X-ray photoelectron spectroscopy, and pH of the point of zero charge. Surface area and volume of micropores and mesopores were obtained from nitrogen adsorption isotherms at 77 K. Adsorption properties were determined by methylene blue adsorption index. Results show that the higher the ozone dose, the higher is the oxidation of the carbon and the greater is the number of acid groups present on the carbon surface, especially carboxylic groups, whereas the pH of the point of zero charge decreases. The surface area,...

Modeling Cyanogen Chloride Kinetics in Distribution Systems: A Semi-Batch C t Protocol for Natural Waters

Experiments were undertaken with the primary objective of developing kinetic relationships for the formation of cyanogen chloride (CNCl), which could then be integrated into a multi-constituent water quality model. The use of ozone in combination with monochloramine has been reported in the literature to enhance CNCl formation. A procedure to determine C t, a surrogate used to estimate the level of microbial inactivation achieved, was also developed using a semi-batch methodology. Water collected from the Mannheim Water Treatment Plant (WTP) (Waterloo, Ontario, Canada) at 7°C and 20°C was ozonated using a semi-batch procedure to achieve a desired level of inactivation. A series of specific steps were then followed to simulate treatment at the Mannheim WTP as closely as possible at bench-scale. Three different levels of microbial inactivation were selected to simulate 0.5-log Giardia inactivation, and both 1.0-log and 3.0-log Cryptosporidium inactivation. Kinetic relationships were developed which described CNCl formation as a function of log Cryptosporidium inactivation, monochloramine concentration, and time. It was concluded that CNCl formation followed an exponential function of time that depended on both monochloramine concentration and microbial inactivation level.

Initiation of the paraffin oxidation process with ozonized air

1. The optimum ozone content in air for oxidation of paraffin in the presence of Mn-K soaps of C5−C9 acids is equal to 0.3% by wtif ozonized air is used throughout the course of the whole oxidation process; and is 1.0–1.5% if ozonized air is used only for the duration of the first 30–60 min of oxidation. 2. The combined use of ozone and an accelerator containing manganese offers the possibility of increasing the rate of paraffin oxidation threefold while maintaining the qualities of the oxidation products obtained. 3. On oxidation of paraffin with air containing ozone, the presence of potassium salts does not affect the rate of the oxidation process, nor the composition of the substances formed.