The influence of various factors on aqueous ozone decomposition by granular activated carbons and the development of a mechanistic approach

• Published in: Carbon (New York) Vol. 44; no. 14; pp. 3102 - 3112
• Main Authors: Alvárez, P.M., García-Araya, J.F., Beltrán, F.J., Giráldez, I., Jaramillo, J., Gómez-Serrano, V.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-11-2006; Elsevier Science
• Subjects: Activated carbon; Adsorbents; Chemistry; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; General and physical chemistry; Materials science; Oxidation; Physics; Reaction kinetics; Specific materials; Surface oxygen complexes; Surface physical chemistry; Oxidation; Surface oxygen complexes; Activated carbon; Reaction kinetics; Surface complex; Oxygen; Mechanistic approach; Ozone; Decomposition; Kinetics
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2006.03.016

The decomposition of aqueous ozone in the presence of various granular activated carbons (GAC) was studied. The variables investigated were GAC dose, presence of
tert-butyl alcohol (TBA), aqueous pH as well as textural and chemistry surface properties of GAC. All the GAC tested enhanced the rate of ozone decomposition to some extent. From the analysis of experimental results it was deduced that ozone transformation into HO
radicals mainly occurred in the liquid bulk through a radical chain reaction initiated by OH
− and
HO
2
-
ions. Hydroperoxide ions arise from the formation of H
2O
2 on surface active sites of GAC and its further dissociation. No direct relationship between textural properties of GAC and the rate of ozone decomposition was found. However, a multiple regression analysis of data revealed that basic and hydroxyl surface oxygen groups (SOG) of GAC favor the kinetics of the ozone decomposition process. It is thought that these groups are the active sites for ozone transformation into H
2O
2. Repeated used of GAC in ozonation experiments resulted in loss of basic and hydroxyl SOG with formation of carboxyl, carbonyl and lactone-type groups. Then, pre-ozonation of GAC reduces its ability to enhance the aqueous ozone transformation into hydroxyl radicals.