Microwaves and their coupling to advanced oxidation processes: Enhanced performance in pollutants degradation

Abstract

This review assesses microwaves (MW) coupled to advanced oxidation processes (AOPs) for pollutants degradation, as well as the basic theory and mechanisms of MW dielectric heating. We addressed the following couplings: MW/H₂O₂, MW/UV/H₂O₂, MW/Fenton, MW/US, and MW/UV/TiO₂, as well as few studies that tested alternative oxidants and catalysts. Microwave Discharge Electrodeless Lamps (MDELs) are being extensively used with great advantages over ballasts. In their degradation studies, researchers generally employed domestic ovens with minor adaptations. Non-thermal effects and synergies between UV and MW radiation play an important role in the processes. Published papers so far report degradation enhancements between 30 and 1,300%. Unfortunately, how microwaves enhance pollutants is still obscure and real wastewaters scarcely studied. Based on the results surveyed in the literature, MW/AOPs are promising alternatives for treating/remediating environmental pollutants, whenever one considers high degradation yields, short reaction times, and small costs.

Keywords:

• AOP
• microwave
• pollutant
• MDEL
• degradation

Acknowledgments

Authors acknowledge financial support from the Federal Agency of Support and Evaluation of Postgraduate Education (CAPES), Brazil. We also thank Prof. Maria Olímpia de Oliveira Rezende (DQFM/IQSC/USP) for encouraging the writing of this review.