Influence of desorption process and pH adjustement on the efficiency of O_3, O_3/H_2O_2 and O_3/UV treatment of water and soil samples contaminated by crude petroleum

摘要

The influence of the pH and the contaminant desorption/emulsification on ozone (O-3), ozone-hydrogen peroxide (O-3/H2O2) and ozone-photolysis (O-3/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 O-3/H2O2 or O-3/UV were improved with sonication system and surfactant addition. In the case of O-3/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 O-3/H2O2 process provided better results than the O-3/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.