Heterogeneous photo-Fenton oxidation with pillared clay-based catalysts for wastewater treatment: A review

Due to their excellent properties, pillared clays (PILCs) have been widely used in several applications, particularly in catalysis. In this paper, their use in heterogeneous photo-Fenton-like advanced oxidation for wastewater treatment, employing either model/synthetic effluents or real streams, is reviewed. Particular attention is given to the effect that the main operating conditions have on process performance, namely wavelength of the light source and power, initial H2O2 or parent compound concentration, catalyst load, pH and temperature. Emphasis is also given to the type of catalyst used and its synthesis conditions (e.g. thermal aging or acid treatment). Several important technological aspects that should be accounted for in real practice are also discussed in detail, particularly the catalyst stability, the use of continuous-flow fixed-bed reactors, the mode of oxidant addition, the environmental impact/integration with biological processes and the possibility of using visible light instead of UV only. Then, some simple mechanistic studies reported are summarized, as well as modeling works.