Homogeneous and Heterogeneous Advanced Oxidation Processes: Treatability Studies on Artificially Contaminated Soils with Creosote

Creosote is a complex mixture containing mainly polycyclic aromatic hydrocarbons (PAHs). The remediation of creosote-contaminated sites becomes a challenge due to the numerous compounds and the specific soil properties. Treatability tests using advanced homogeneous (HM system) and heterogeneous (HT system) oxidative processes were applied with sandy soil artificially contaminated with creosote. The creosote was collected in a contaminated site in the state of São Paulo, Brazil. Sodium persulfate (SP) was the reaction oxidizing agent used. For the HM system, SP was activated by ferrous ions (Fe2+) chelated by citric acid (C6H8O7) and in the HT system, clay-based iron catalyst (CAT) was used for the SP activation. These two methods can be applied for in situ processes, without generating waste and effluents that need further treatment. Experimental designs were applied to determine the appropriate reagent concentrations to provide better removal efficiency for the total of 9 selected PAHs. As far as we know, this is the first study comparing homogeneous and heterogeneous systems while applying CAT to remediate PAH-contaminated soils. The results indicated that the HT system was more efficient than the HM system, with PAH removal of 97% and 61%, respectively. The treatability tests performed provide an efficient application of in situ chemical oxidation (ISCO) in tropical regions, such as Brazil, for the remediation of areas contaminated by PAHs.