Ozonation of phenol in the presence of biochar and carbonaceous materials: The effect of surface functional groups and graphitic structure on the formation of reactive oxygen species

Abstract

To develop a novel oxidation process using ozone and carbonaceous materials for water treatment and groundwater remediation, the effect of carbonaceous materials on the ozonation of phenol was investigated via batch experiments. Anode carbonaceous material (ACM) recovered from spent Li-ion batteries, graphite, granular activated carbon (GAC), and rice straw-derived biochar were evaluated as catalysts to enhance the ozonation of phenol. Compared with direct ozonation (28% removal in 2 h), the addition of carbonaceous materials enhanced the oxidation of phenol by ozone, showing 47%, 45%, 81%, and 74% removal with ACM, graphite, GAC, and biochar, respectively. According to the quenching experiments with chemical reagents and electron paramagnetic resonance analysis, reactive oxygen species, such as hydroxyl radicals (·OH), superoxide radicals (O2·-), and singlet oxygen (1O2), as well as electron transfer in the mediated-reaction, are included in the ozonation of phenol in the presence of carbonaceous materials. The oxygen-containing surface functional groups and graphitic structure are responsible for the reactive oxygen species and electron transfer reactions, respectively. Our results suggest that carbonaceous materials may be effectively used as catalysts to promote the ozonation of recalcitrant contaminants in water.