Ozone-Enhanced Oxidation of Oxalic Acid in Water with Cobalt Catalysts. 2. Heterogeneous Catalytic Ozonation

Abstract

Ozone and a Co 3 O 4 /Al 2 O 3 catalyst have been used to remove oxalic acid from water at acidic pH. The influence of different variables, including the initial oxalic acid and ozone gas concentrations, the catalyst mass, and the temperature, has been investigated under conditions of chemical control. The ozone efficiency was found to reach values of up to 40%, which are higher than those found in homogeneous catalysis (see also the first part of this work, which immediately precedes this paper in this issue), and the mean stoichiometry was determined to be 0.8 mol of ozone consumed per mole of oxalic acid consumed. Metal leaching was also followed to check the stability of the catalyst. As a result, ozonation of oxalic acid was found to be due to both heterogeneous and homogeneous catalytic ozonation. The average contribution of heterogeneous catalytic ozonation for the removal of oxalic acid was found to be 75%. A kinetic study taking into account both catalytic contributions is also presented. The experimental heterogeneous catalysis was found to be first-, one-half-, and zeroth-order with respect to catalyst, dissolved ozone, and oxalic acid, respectively. A mechanism is also proposed to account for the kinetic results.

Fe3O4/multi-walled carbon nanotubes as an efficient catalyst for catalytic ozonation of p-hydroxybenzoic acid

“…However, the application of ozonation is still limited due to its selective reactions with organic pollutants (Beltrán et al 2003). In order to overcome this limitation, a lot of improved ozonation was developed (Guo et al 2015;Lee et al 2011).…”

Catalytic Ozonation of Oxalate with a Cerium Supported Palladium Oxide: An Efficient Degradation Not Relying on Hydroxyl Radical Oxidation

“…MnO 2 , Fe 2 O 3 , Co 3 O 4 , and NiO had been found effective in the catalytic ozonation of oxalic acid but the removal rates at normal pHs in a reasonable reaction time were too low and the ozone doses were too high for practical uses. 5,7,11,12 There are still no data on ozone consumption for oxalate degradation which is critical to evaluate the catalysis efficiency. No evidence shows active sites and active oxidant species that are responsible for oxalate degradation, the information ABSTRACT: The cerium supported palladium oxide (PdO/ CeO 2 ) at a low palladium loading was found very effective in catalytic ozonation of oxalate, a probe compound that is difficult to be efficiently degraded in water with hydroxyl radical oxidation and one of the major byproducts in ozonation of organic matter.…”

“…It was reported that effective catalytic oxalate degradation with several typical metal oxides were achieved only at much lower pHs (e.g., 4.1 and 3.2 for MnO 2 , 2.5 for Fe 2 O 3 and Co 2 O 3 , and 2.4 for NiO) and continuous ozone introduction during the reaction over 30 min. 5,7,11,12 This binary oxide seems to be more efficient for practical catalytic ozonation reaction.…”

Métodos emergentes para aumentar a eficiência do ozônio no tratamento de águas contaminadas

“…Beltrán e colaboradores 49 fizeram um estudo mostrando a eficiência do cobalto em solução, imobilizado sobre Al 2 O 3 . Os resultados apresentados para o metal suportado foram bastante promissores e observou-se uma total mineralização do ácido oxálico.…”