Efficiency of natural clay as heterogeneous Fenton and photo-Fenton catalyst for phenol and tyrosol degradation

Advanced oxidation processes (AOPs) are particularly useful for cleaning toxic or non-biodegradable materials in wastewater. Among these processes, the advantage of the Fenton processes is the potentially complete mineralization of organic substances. In this work, a naturally containing Fe-clay naturally red clay (NRC) was used as heterogeneous catalyst for the Fenton and photo-Fenton oxidation of two organic pollutants (phenol and tyrosol). NRC was characterized by several complementary methods including chemical analysis, X-ray diffraction, temperature programmed reduction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The influence of different parameters like calcination's temperature and initial H2O2 concentration were examined considering both the pollutant conversion and the total organic carbon (TOC) abatement. This catalyst was very efficient for the mineralization of both compounds in aqueous medium under mild experimental conditions. Indeed, 100% pollutant conversion could be achieved for both pollutants with a TOC abatement of 90 and 85%, respectively, for phenol and tyrosol by photo-Fenton oxidation. Catalytic activity of NRC was mainly attributed to the amount of iron oxide species (12 wt.%) present naturally in the clay.