The Effect of pH on the Decomposition of Hydrophenols in Aqueous Solutions by Ultraviolet Direct Photolysis and the Ultraviolet–Hydrogen Peroxide Process

Abstract

The decomposition of catechol (o-hydrophenol) and resorcinol (m-hydrophenol) in aqueous solution by 254-nm UV direct photolysis and the UV-hydrogen peroxide (H 2 O 2 ) process under various solution pH values was studied. The light absorbance and photolytic properties of catechol and resorcinol were found to be highly dependent on solution pH and can be adequately described with a three-species distribution model. For the UV-H 2 O 2 process, the individual contribution to the decomposition of pollutants by direct photolysis and indirect hydroxyl radical destruction was differentiated by studying the linear addition of UV light absorbance of various reactant species. The contribution to the decomposition of the two hydrophenols by hydroxyl radical destruction was more than 95% in acidic and neutral solutions for treatment with the UV-H 2 O 2 process. Water Environ. Res., 75, 54 (2003).

Electrocatalytic Oxidation of Hydroxide Ions by Co3O4 and Co3O4@SiO2 Nanoparticles Both at Particle Ensembles and at the Single Particle Level

“…No decline over time in the UV absorbance was observed. Figure 7b shows that the absorbance (at 254 nm) scaled linearly with H 2 O 2 concentration, but the spectra are consistent with HO 2 À rather than H 2 O 2 , reflecting the pK a of 11.6 for the H 2 O 2 /HO 2 À equilibrium at 298 K. [32][33][34] Next, in the presence of Co 3 O 4 NPs, the UV aborbance ( Figure 7c) of HO 2 À was found to linearly decrease with time, showing the catalytic activity of the NPs towards the chemical decomposition under the alkaline condition via Equations (7) and (8):…”

Reaction and Mass Transfer Kinetics Model of Hydrogen Peroxide Oxidation of Starch under Influence of Ultraviolet Irradiation

“…The optimum pH for coupled H 2 O 2 /UV degradation of organic substances is strongly dependent on the type of the respective compounds [44]. To investigate the effect of the initial pH of H 2 O 2 solution on the oxidation of corn starch, oxidation experiments were conducted with an initial pH between 3 and 9 at 30 o C, initial hydrogen peroxide concentration of 0.50 M and starch-water ratio (S/L) = 1/20.…”

“…These findings are in good agreement with previous works reported in the literature. During treatment with UV/ H 2 O 2 process, the contribution to the degradation of two hydrophenols by hydroxyl radical destruction was more than 95% in acidic and neutral solutions [44]. De Laat et al observed that the efficiencies of UV/ H 2 O 2 processes were not affected by pH below 8, while a decrease was observed for higher pH [46].…”

Physico‐Chemical Processes

“…Einschlag et al (2003) determined the rate constants for OH radical reaction toward nitroaromatic compounds in a UV/H 2 O 2 process, and found a quantitative structurereactivity relationship using the Hammett equation. In a UV/H 2 O 2 process for the decomposition of two hydrophenols, Shen and Lin (2003) determined the relative contribution to be 5% and 95% due to direct UV photolysis and indirect OH radical destruction, respectively.…”