Mirat D. Gurol

Chemical Oxidation of Chlorinated Organics by Hydrogen Peroxide in the Presence of Sand

The objective of this study was to investigate the feasibility of using hydrogen peroxide (H 2 O 2 ) as a chemical oxidant for in-situ treatment of contaminated surface soils. The process has been tested in the presence and absence of ferrous sulfate on sand-packed columns, which contained pentachlorophenol (PCP) and trichloroethylene (TCE) as model compounds. Both column and batch studies have demonstrated that H 2 O 2 decomposed readily by interacting with the natural iron content of sand, and additional ferrous salts further enhanced the extent of H 2 O 2 decomposition. As a result, PCP and TCE adsorbed on the sand surface were oxidized effectively and by stoichiometric release of organic bound chlorine as chloride ion

Chemical Oxidation by Photolytic Decomposition of Hydrogen Peroxide

This paper describes a study of a chemical oxidation process involving simultaneous application of hydrogen peroxide solution and ultraviolet light (H 2 O 2 /UV)for removal of organic pollutants from aqueous solution. The process was investigated experimentally in a continuous-flow stirred tank reactor (CSTR) under various operational conditions, i.e., H 2 O 2 dosage, UV light intensity, and liquid residence time. Synthetic solutions of a model organic compound, n-chlorobutane (BuCI), were oxidized at various pH and in the presence of various amounts of humic material and carbonate/bicarbonate ions in order to examine the effect of water quality on the process efficiency. A kinetic model of the process, which was developed based on H 2 O 2 /UV-induced radical oxidation of organic compounds, was successfully verified in pure water as well as in synthetic solutions.

Oxidation of phenolic compounds by ozone and ozone + u.v. radiation: A comparative study

Abstract This study was designed to investigate the reaction mechanisms of oxidation of various phenolic compounds by ozone and ozone + u.v. radiation at pH 2.5, 7.0 and 9.0. Experimental results indicated that the molecular ozone is the predominant oxidant only at acidic pH; at neutral and basic pH, in the absence or presence of u.v. radiation, free radical reaction is the major pathway in the oxidation of phenolic compounds. The overall removal of phenols and the removal of TOC increase with increasing pH during ozonation with or without u.v. light. For a specific pH, the removal rates of phenol and TOC are highest for ozone + u.v. light followed by ozone and then u.v. light alone.

The effect of humic acids on nitrobenzene oxidation by ozonation and O3/UV processes

Three types of commercially available humic acids from different sources were used to simulate natural organic matter in water for the investigation of nitrobenzene oxidation by ozonation and O(3)/UV. Despite the structural differences among the Fluka, Aldrich and Suwanee River humic acids as reflected by the UV absorptivity, their effects on nitrobenzene removal rate was observed to be similar for the two processes. Removal rate of nitrobenzene was hindered by the addition of humic acids in ozonation as well as in O(3)/UV processes. However, the hindrance by the humic acids was more pronounced in O(3)/UV as compared to the ozonation process. The effect of humic acid in O(3)/UV was primarily a UV light screening. Addition of humic acids above a certain concentration did not cause any further retardation on nitrobenzene removal rate by ozonation and O(3)/UV. Accumulation of hydrogen peroxide as well as probable formation of peroxy radicals in the solutions might induce chain promoting reactions to produce hydroxyl radical during the nitrobenzene oxidation. For waters containing high levels of humic acid, ozonation alone might be as effective as O(3)/UV process for the removal of nitrobenzene.

Dynamics of the ozonation of phenol ― I. Experimental observations

Abstract This first paper presents the results of an experimental investigation of the ozonation of phenol in a semi-batch reactor, in which mass-transfer kinetics of ozone into solution and the kinetics of the reaction between molecular ozone and phenol are considered separately. Attention has been given to distinguishing between direct and indirect reaction pathways involving ozone. Intermediates and final products of the reaction have been measured as a function of time using high pressure liquid chromatography.

Oxidation of diethylene glycol with ozone and modified Fenton processes.

This paper describes a study of oxidation of diethylene glycol (DEG) by ozone and modified Fenton process (hydrogen peroxide and ferric salt mixture) in aqueous solution. Both oxidation processes were able to oxidize relatively high concentrations of DEG effectively. DEG reacted primarily through hydroxyl radical produced by decomposition of ozone, and about 3 mol of ozone were consumed per mole of DEG removed during the process. For modified Fenton oxidation, stepwise addition of hydrogen peroxide (H2O2) and ferric salt (Fe(III)) resulted in much higher removal of DEG than one-time pulse addition of the chemicals. The extent of DEG removal increased with increasing concentrations of both H2O2 and Fe(III). Oxidant consumption per mole of DEG oxidized was one order of magnitude higher for hydrogen peroxide than those observed for ozone. Overall, ozonation produced higher concentrations of aldehydes, and modified Fenton treatment produced higher concentrations of carboxylic acids for the same levels of DEG oxidation. The major products of ozonation were glycolaldehyde, glyoxal, formaldehyde, acetaldehyde, and acetic, formic, pyruvic, oxalic and glyoxalic acids. The major products of modified Fenton oxidation were formaldehyde, and formic and acetic acids.

Dynamics of the ozonation of phenol—II mathematical simulation

Abstract Several investigators have described the rate of ozonation of phenol in an ozone contactor by empirical equations which are system-specific and are limited in their applicability to other systems. In this paper, the rate of mass-transfer of ozone, the oxidation kinetics of phenol and the kinetics of formation and oxidation of the intermediates have been incorporated into a mathematical model which provides a more accurate picture of the process of oxidation of phenol by ozone under dynamic conditions.

Ozone Consumption in Natural Waters: Effects of Background Organic Matter, pH and Carbonate Species

Abstract It was demonstrated that, in natural waters, the overall kineticsof dissolved ozone consumption can be characterized by the “specific ozone utilization rate”, w[time −1]. The dependency of w on the chemical quality of the raw water was analyzed. And, the variation of w values measured in different water samples was explained in terms of the pH, alkalinity, and total organic carbon content of the solution matrix.

Formaldehyde Formation During Ozonation Of Drinking Water

Partial oxidation of natural organic material during ozonation produces oxygenated by-products of low molecular weight. Formaldehyde, being the most common oxygenated by-product of ozone, is considered to be a problematic compound by the water industry due to its potential adverse health effects. This research attempts to provide specific information on the effects of water quality parameters, specifically, pH and alkalinity, the structure of humic material, and the operational parameters, e.g., ozone dosage and contact time, on generation of formaldehyde. The results showed that ozonation caused almost an immediate formation of formaldehyde, which reached a peak value, and then started to decrease with continued ozonation. Ozonation of aqueous fulvic acid produced higher concentrations of formaldehyde compared to other types of humic material. Formaldehyde formation was suppressed by high bicarbonate levels, and enhanced at higher pH. Formaldehyde accumulation was more dramatic at low ozone dosages.

Kinetics and mechanism of ozonation of free cyanide species in water.

The reaction rates of ozone with free cyanide species were determined by a stopped-flow spectrophotometer in the pH range 2.5-12.0. The direct reaction of molecular ozone and the free radical reactions which contribute to the overall reaction were identified. A reaction mechanism consistent with the observations was proposed. The rate constant for the direct reaction of molecular ozone with cyanide ion was calculated to be 2600 +/- 700 M/sup -1/ s/sup -1/. Batch and bubble-column experiments indicated stoichiometric conversion of cyanide to cyanate and an ozone consumption of 1.2 +/- 0.2 mol/mol of oxidized cyanide.