Decay of Ozone in Water: A Review

Abstract

Scientific papers on ozone decay kinetics in water report very wide variations, depending on a multiplicity of factors, such as ozone concentration, pH, temperature, alkalinity, fluid-dynamic conditions, presence of UV radiations, concentration of organic and inorganic carbon. This paper has been intended as an engineering-oriented review which collects and compares the main results reported in the recent literature so that the condensed information can guide the reader in getting operational indications for both applications and research

Promoting catalytic ozonation of phenol over graphene through nitrogenation and Co 3 O 4 compositing

“…In less than 30 min, the total conversion of phenol has been achieved at the presence of Co3O4/NG nanocatalysts, suggesting a fast conversion rate. This was quite important for practical applications since the room temperature (20 o C) half-life time of dissolved molecular ozone was falling in a range from 16.7 min to 278 hr at low pH (< 4) (Bin, 2013;Gardoni et al, 2012).…”

Kinetic Study of Ozone Decay in Homogeneous Phosphate-Buffered Medium

“…The values found in bibliography for k 1 ranges from 40 to 170 M −1 s −1 , k 3 ranges from 0.065 M −1 s −1 to 9.6·10 6 M −1 s −1 , k 6 from 2.7·10 7 to 10 9 M −1 s −1 and k 7 is equal to 7.5·10 9 M −1 s −1 (Fábián 2006;Gardoni et al 2012;Mizuno et al 2007;Sehested et al 1992;Sein et al 2007;Staehelin and Hoigné 1982). The kinetic coefficient k 2 is not referred on bibliography because it corresponds to the apparent kinetic coefficient of ozone decomposition of Subsystem II without the radical branching ( Figure 2b).…”

“…Gardoni et al (2012) have recently reviewed the different reaction mechanisms that describe the complex process of ozone decomposition based on radical initiation postulated originally by Weiss (1935). Recent works hypothesize the decomposition process through the formation of the hydrogen polyoxides adducts HO 4 − and HO 5 − (Merényi et al 2010a(Merényi et al , 2010b, which belongs to two reaction subsystems leading to the formation of O 2 and H 2 O 2 respectively.…”

“…Then, a reliable macroscopic rate equation describing the ozone decomposition is needed to design, scale-up and control the ozonation or the peroxone processes. Although the ozone decomposition kinetics is an active research topic since the 1980s, there are still some controversies, uncertainties and new findings that provide additional information to this subject (Gardoni et al 2012). It is well known that the stability of the ozone in water depends on the temperature, the pH, the fluid-dynamic conditions, the presence of UV radiation and the medium composition (presence of hydroxyl radicals, scavengers, promoters, inorganic or organic carbon, etc.…”

Determination by reactive absorption of the rate constant of the ozone reaction with the hydroperoxide anion

“…This value should correspond to the forward reaction leading to the formation of the adduct HO5 -since it should be the rate limiting step (Gardoni et al, 2012). Different values of the H2O2/HO2 -pKa (in the range from 11.65 to 11.80) were considered in these studies, which influences the determination of k (Sein et al, 2007).…”