Critical factors in chemical characterization for the evaluation of decontamination in solids using advanced oxidation

Influence of desorption process and pH adjustement on the efficiency of O3, O3/H2O2 and O3/UV treatment of water and soil samples contaminated by crude petroleum

The influence of the pH and the contaminant desorption/emulsification on ozone (O₃), ozone-hydrogen peroxide (O₃/H₂O₂) and ozone-photolysis (O₃/UV) oxidation reactions were performed to treat crude petroleum (CP) contaminated soil and water samples. Oxidation efficiency is also related to both free radicals formation in reaction medium (which is dependent of the pH), and contaminant availability (which is dependent of the compounds solubilization or desorption processes). Thus, batch basic processes of O₃/H₂O₂ or O₃/UV were improved with sonication system and surfactant addition. In the case of O₃/H₂O₂ process, the reactions were performed at adjusted (pH = 11) and natural pH (free pH= 4-5). The effectiveness of the improved advanced oxidation processes were evaluated through the time-course analysis of the chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), and total organic carbon (TOC) values. For both improved treatment processes, CP-contaminated water samples displayed higher values for TOC removal and BOD₅/COD ratios than CP-contaminated soil samples. The O₃/H₂O₂ process provided better results than the O₃/UV process regarding degradation efficiency, but the former is associated with higher treatment costs due to H₂O₂ consumption. Overall, oxidation treatment processes increase their efficiencies when reactions are carried out associated with solubilization and desorption systems promoted by sonication/surfactant action.