A Kinetic Method for HO₂^•/O₂^•- Determination in Advanced Oxidation Processes

Abstract

A new kinetic method is developed for the determination of hydroperoxyl radical (HO(2)(*))/superoxide radical (O(2)(*)(-)) in aqueous solution, and the calibration using a kinetic half-life technique is also established for determining the concentration of HO(2)(*)/O(2)(*)(-) as produced in the UV/H(2)O(2) process. This new method is based on the reduction of Fe(3+)-EDTA into Fe(2+)-EDTA by HO(2)(*)/O(2)(*)(-) and the well-known Fenton-like reaction of H(2)O(2) and Fe(2+)-EDTA to yield the hydroxyl radicals (OH(*)). Benzoic acid scavenges the OH radicals to produce hydroxybenzoic acids, which are analyzed by fluorescence detection (lambda(ex) = 320 nm; lambda(em) = 400 nm). The limit of detection for the new method depends on the pH values, and it is determined as 3.22 x 10(-)(11) M with signal-to-noise ratio of 2 at pH 5. In addition, the present technique has the advantage of using inexpensive and easily available nonenzymatic reagents that do not require the specific instrument and chemicals and of being insensitive to the moderate concentration of possible interferences often found in aqueous phase.

Adiabatic runaway studies for methyl ethyl ketone peroxide with inorganic acids by vent sizing package 2

“…In Fig. 3, the phosphorus species (H 3 PO 4 , H 2 PO 4 − , HPO 4 2− , and PO 4 3− ) will abstract OH free radicals to become more stable intermediates because phosphorus species act as an OH radical scavenger [22][23][24][25][26]. Therefore, the heat of reaction only increased from 43.15 J g −1 (pure MEKPO) to 70.41 J g −1 , as compared to 93.00 J g −1 of the sulfuric acid.…”

In-situ Calibration of the Hydroperoxyl Radical Using an Immobilized TiO2Photocatalyst in the Atmosphere

“…The basic principle of calibration employed in this work is described in detail in a previous study. 15 In the absence of additives, HO 2 · /O 2 ·− is disproportionated by self-reactions 6-8:…”

“…11 Although it is possible, in principle, to measure the sensitivity of a given field instrument, the result is unreliable, as many assumptions need to be made about instrumental parameters, some of which may vary with time. 11,13 For example, even though the vacuum-ultraviolet photolysis of water vapor using a penray mercury lamp has been widely used as a calibration method, it is highly desirable to perform this calibration in moist air to ensure that the conditions are very similar to 14,15 Importantly, all the aforementioned methods are still under development 10 and requires in-situ field calibration method. For this reason, the present work aims at developing an insitu calibration method that is simple, fast, and inexpensive while overcoming many other limitations of the present methods.…”

Determination of hydroxyl radical rate constants in a continuous flow system using competition kinetics

“…1 [22]. Then, the premixed solution was transferred into the quartz coil-type photo-reactor (PR) as shown in Fig.…”