Intensification strategies for thermal H2O2-based advanced oxidation processes: Current trends and future perspectives

H2O2-based advanced oxidation technologies, commonly Fenton process or Catalytic Wet Peroxide Oxidation (CWPO), have been widely studied and applied over the past decades for wastewater treatment due to their ability to generate highly oxidizing species, HO• and HOO• radicals, along with a low selectivity which allow the degradation of a wide range of pollutants . Nonetheless, these technologies present some limitations. In the case of Fenton, the requirement of acidic media (pH: 3), the loss of catalyst at the end of reaction because it is dissolved, and the catalyst inactivation caused by certain reaction intermediates (i.e. oxalic acid) that forms complexes compromising its efficiency. For CWPO, the main drawbacks in this heterogeneous process are mainly associated to the relative low activity and stability of the catalysts employed. All these shortcomings can be solved through process intensification, which generally involves in Fenton and CWPO increasing the temperature or the application of an external radiation, being the most interesting ones UV–vis radiation (photo-assisted technologies), and microwave radiation, which inherently presents the advantages of working at high temperature. This paper gathers the most recent advances explored in thermal-intensified H2O2–based advanced oxidation technologies, summarizing the main results obtained for each intensification strategy and outlining where future efforts should be focused.