Activation of homogeneous and heterogeneous Fenton processes by ultrasound and ultraviolet/visible irradiations for the removal of ibuprofen in water

摘要

Due to booming consumption and only partial removal by conventional water treatment processes, ibuprofen, a non-steroidal anti-inflammatory drug, has been detected in water resources, raising increasing concerns for possible environmental and health impact. On the other hand, advanced oxidation processes (AOPs), among which Fenton reaction, have shown successful results forremoval of various organic compounds. Traditionally based on the use of hydrogen peroxide and ferrous ions in solution, large-scale application of this AOP is still limited by narrow pH window (2 to 4) and uneasy recovery of iron catalyst. This work investigated Fenton-based oxidation of ibuprofen, and reaction activation by ultrasound (US) irradiation and ultraviolet/visible light (UV/Vis) so as to lower the required concentration of dissolved iron catalyst or improve the activity of heterogeneous counterparts. To that purpose, the efficacy of individual homogeneous AOPs (sonolysis, photolysis, ultrasound/H2O2, light/H2O2, Fenton oxidation) was evaluated first, varying operating parameters such as light wavelength and ultrasound frequency. Then, their two-by-two and overall combinations (sonophotolysis, sono-Fenton, photo-Fenton and sono-photo-Fenton oxidation) were examined with emphasis on the identification of synergistic effects. In particular, combined US/Fenton and Vis/Fenton oxidation were found more effective than the sum of individualprocesses due to sono- and photo-regeneration of ferrous ions. These results also served as a reference for the assessment of heterogeneous systems. Among tested solids, iron-containing zeolite (Fe-ZSM5 type) was shown to be a promising catalyst for peroxide oxidation of ibuprofen due to high efficiency at natural pH and low iron leaching. However, in this case, no more than additive effects was observed between ultrasound/light irradiation and heterogeneous Fenton oxidation. Beside pollutant and Total Organic Carbon conversion, main degradation products were monitored for different processes and some plausible degradation pathways were proposed. Water matrix impact was also addressed using wastewater plant effluent, which resulted into hindered performance of all oxidation processes either due to alkaline buffer or light attenuation effect.