Catalytic ozonation of naphthenic acids in the presence of carbon-based metal-free catalysts: Performance and kinetic study.

• CX made at pH 5.5 showed high surface area than CX prepared at pH 6.9. • Catalytic ozonation of ADA using carbon-based metal-free catalysts were evaluated. • The first-order rate constant of O 3 /CX5.5 (0.1367 min−1) was almost 2.4 times higher than that of single ozonation (0.0567 min−1). This study examined the use of carbon-based metal-free materials as catalysts for the catalytic ozonation of a model naphthenic acid (NA) compound (1,3-Adamantanedicarboxylic acid; ADA). Adsorption, single ozonation and catalytic ozonation experiments were performed using ADA concentration of 50 mg/L, 0.5 g/L of carbon materials, and 30 mg/L of applied ozone (O 3) dose, at pH 8. The results showed that, after 15 min of reaction, less than 5 % of ADA was removed by adsorption, while 33 % of ADA was removed by single ozonation. For the catalytic ozonation study, among the materials tested, the best performance was obtained using carbon xerogels prepared at pH 5.5 (CX5.5), reaching 65 % of ADA removal after 15 min of reaction. The first-order rate constant of O 3 + CX5.5 (0.0631 min−1) was almost two times higher than that of single ozonation (0.0258 min−1). Hydroxyl radicals were the main responsible species for the ADA degradation. In general, the results confirmed that catalytic ozonation process is an efficient and promising approach for environmental applications. [ABSTRACT FROM AUTHOR]