Kinetics of Catalytic Ozonation of Oxalic Acid in Water with Activated Carbon

Abstract

The ozonation kinetics of oxalic acid in water in the presence of an activated carbon has been investigated at acid pH. The presence of the activated carbon significantly enhances the degradation rate of oxalic acid if compared to single ozonation and single adsorption. According to total organic carbon measurements, nearly complete mineralization of oxalic acid can be achieved depending on the experimental conditions. The presence of tert-butyl alcohol, which scarcely adsorbs on the carbon surface at the conditions investigated, led to a significant reduction of the oxalic acid removal rate. Consequently, experimental results suggest that the reaction proceeds in the water phase between oxalic acid and oxidant species, likely hydroxyl radicals, coming from the ozone decomposition on the carbon surface. The proposed mechanism yielded a first-order kinetics with respect to ozone, close to the 0.8 order experimentally observed. Also, the energy of activation was found to be approximately 15 kcal mol-1.

Ozonation of oxalic acid catalyzed by ion-exchanged montmorillonite in moderately acidic media

“…Below pH 6, no free hydroxyl radicals should be produced, as reported for ozonation in the presence of activated carbon [14]. Thus, ozonation of oxalic acid is expected to proceed exclusively through a reaction with molecular ozone, and even higher effectiveness should be obtained [4,12,42].…”

“…This suggests a progressive attenuation of the direct oxidation of adsorbed oxalic acid by molecular ozone. This process is supposed to take place preponderantly below pH 6, while the formation of OH radicals should be of minor importance below neutral pH [14,35].…”

“…For instance, nearly thorough mineralization of oxalic acid was achieved in the presence of activated carbon [14]. Reportedly, the mere presence of dispersed solids, such as alumina alone [15] or containing CuO [16], or TiO 2 [1,2] significantly improves the ozonation effectiveness towards various organic pollutants.…”

Mineralization of Substituted Aromatic Compounds by Ozonation Catalyzed by Cerium Oxide and a Cerium Oxide-activated Carbon Composite

“…A few catalysts have been reported to enhance the ozonation of oxalic acid in aqueous solution. Among them, activated carbon was shown to be an effective catalyst for the mineralization of this particular compound [4,13]. In a previous work [8], cerium oxide-containing catalysts were also found to be highly active for the mineralization of this compound.…”

Development of Novel Mesoporous Carbon Materials for the Catalytic Ozonation of Organic Pollutants

“…Activated carbon has been appointed as a very good catalyst in the ozone decomposition [16,17] and in the mineralisation of dyes [18][19][20][21], aromatic compounds [22][23][24][25][26][27] and carboxylic acids [28][29][30].…”