Simultaneous ozonation of ethylbenzene and fluorene in water, soil, and air

Most of the studies regarding aromatic hydrocarbon degradation by ozone focus on individual treatment. Hence, two aromatic hydrocarbons, ethylbenzene (ETB) presented in water and fluorene (FL) distributed in soil, were selected to be eliminated simultaneously in water, soil, and air using ozone. In this study, the effect of the physicochemical properties of ETB and FL, the distribution of FL on sandy and agricultural soils, and the influence of the presence of moisture in both soils were analyzed. The chemical composition of the agricultural soil (mainly metal oxides) enhanced the FL degradation by the possible catalytic ozone decomposition into reactive species, such as •OH, O₂^•−, H₂O₂, O₃^•−, and O^•, which reduced its treatment time 4.5-fold in this solid matrix compared to the sandy soil. Moreover, the moisture liberated from water by the gas flow and adsorbed on the soil bed (up to 0.33% at 180 min) reduced the ozonation time 2-fold in the agricultural and sandy soils, due to the •OH formation. Contrary to FL, the rapid elimination of ETB (< 20 min) in both soils did not allow to observe the possible effect of reactive species generation on ETB decomposition due to the low amount of moisture accumulated during this time (<0.06%). The proposed simultaneous ozonation scheme permitted to achieve up to 96% and 100% of the ETB and FL decomposition. Some identified by-products, such as maleic, malonic, oxalic, and formic acids, suggest that ozone and possible reactive species formed on the soil surfaces reacted with both compounds, leading to non-toxic simple by-products with their partial mineralization (≈80%), which was proven by a toxicity evaluation (phytotoxicity and eco-toxicity). The rapid and efficient simultaneous ozonation of aromatic hydrocarbons in water, soil, and air (only ETB) proves the feasibility of ozone to treat different organic pollutants in more than one phase.