Interaction of Ozone with Formic Acid: A System which Supresses the Scavenging Effect of HCO3-/CO32-

Abstract

Formic acid, mainly found in its ionized form at pH values greater than 3.75, is among the major by-products of drinking water ozonation. This study focusses on ozone decomposition reactions when formate ion is present. A mechanistic model was developed for ozone decomposition in the presence of formate ion and alkalinity. n-chlorobutane (BuCl) was used as a hydroxyl radical probe. The proposed mechanism is a combination of all the reactions provided in the literature for ozone decomposition, ozone-formate ion interactions, and formate ion and certain inorganic radical interactions in aqueous solutions. The validity of the proposed mechanism was tested by comparing the experimental data collected at different initial ozone and formate ion concentrations, pH and alkalinity to the model predictions. The model was capable of predicting the ozone decomposition and BuCl oxidation data extremely well when 1.53 M-1s-1 (knew) was used as the reaction rate constant for the reaction between ozone and formate ion, as opposed to the value provided in the literature (100 M-1s-1). Furthermore, according to the proposed model formate ion suppresses the scavenging effect of HCO3- and CO32- ions because the reaction of formate ion with CO3*- radical regenerates the OH* radical that is scavenged by the HCO3- and CO32- ions. This was tested by observing ozone decomposition at different levels of alkalinity in the presence of formate ion. The experimental data did not present any significant effect of alkalinity on the decomposition rate. In addition, the model provided highly reliable predictions of the experimental data collected in the presence of alkalinity when knew was used.

Combination of ozonation and photocatalysis for purification of aqueous effluents containing formic acid as probe pollutant and bromide ion

“…The values of the kinetic constant obtained by a least squares best fitting procedure are 2.36 and 2.05 M À1 s À1 for the formate and the formic acid, respectively. These values differ from 100 M À1 s À1 obtained by Hoigné and Bader (1983) but are quite closely agreeing with k value of 1.53 M À1 s À1 reported by Yapsakli and Can (2004). The discrepancy may come from the type of hydroxyl radical scavengers used (Hoigné and Bader utilized n-propanol), or from differences in ozone concentrations.…”

“…The direct oxidation of formate anion is an electrophilic addition that leads to an intermediate adduct generated by ozone insertion followed by formation of CO 2 , molecular oxygen and hydroxide ions (Yapsakli and Can, 2004):…”

Comparative study of diethyl phthalate degradation by UV/H2O2 and UV/TiO2: kinetics, mechanism, and effects of operational parameters

“…Furthermore, according to the report, the reaction rate of CO 3 2− and hydroxyl radical is faster than that of HCO 3 − and hydroxyl radical (Du et al 2007;Yapsakli and Can 2004). It is a good explanation of the phenomena that the hindrance of CO 3 2− is bigger than that of HCO 3 − .…”

High Stability of Immobilized Polyoxometalates on TiO2 Nanoparticles and Nanoporous Films for Robust, Light-Induced Water Oxidation

“…[1][2][3] Efficient water oxidation using durable systems and devices is a principal challenge for the production of fuel from water. 4,5 To date, molecular WOCs such as those based on oxidatively stable POMs, provide high turnover numbers under conditions driven chemically by Ce IV (NH 4 ) 2 (NO 3 ) 6 , 6, 7 photochemically by light, photosensitizer, and sacrificial oxidant, 8 and electrochemically.…”

“…15,20,[24][25][26][27] To date, the principle applications of supported POM catalysts are for organic substrate oxidations. 20 Water splitting research has been conducted on dye-sensitized cells incorporating metal oxides such as TiO 2 and IrO 2 catalysts. 3,28-33 There are fewer reports of POM immobilization chemistry for the catalysis of multi-electron reactions associated with solar fuel generation in aqueous media.…”