Remediation Processes

Advanced oxidation processes (AOPs) are one of the most popular remediation processes. Photochemically-induced AOPs are even one of the most investigated because of the potential involvement of natural sunlight, a sustainable source of energy. But what is a photochemical process? And what is an advanced oxidation process and for what purposes is AOP used?

A photochemical process is a set of chemical reactions which are triggered by absorption of light. Photochemical processes are quite common in the natural environment and the everyday life. Indeed, the photosynthesis and the vision are few examples of photochemical processes. The photosynthesis involves plants which are using solar irradiation to transform CO2 and H2O into O2 and glucose. The vision is initiated by interaction of light with photoreceptors in the eye’s retina (rhodopsin and iodopsin).

AOPs are based on the generation of highly reactive inorganic species, called reactive oxygen species (ROS), which include hydroxyl radicals (HO•) and superoxide radicals (O2•−). These ROS are efficient oxidizing agents for the degradation of organic pollutants, more particularly their oxidation into CO2, H2O and other inorganic ions such as (SO42-, CO32-, Cl-, etc.), i.e. mineralization of toxic pollutants into harmless species. To get more insights into ROS, the most important ones are HO• since they have a strong oxidative power (E0(HO•/H2O) of 2.7 V vs. SHE) and they react non-selectively with most of organic compounds with high bimolecular kinetic constants (k = 108–1011 M-1·s-1).

In our research group, we are investigating several types of remediation processes that can trigger AOPs, especially under simulated solar light, to remove organic pollutants from the synthetic and real wastewaters. These remediation processes involve (i) photolysis, (ii) photocatalysis, (iii) Fenton-based processes and (iv) activation of oxidants into ROS. Since photolysis is based on the breaking of chemical bonds under light, high energy radiations such as UVC and UVB are often required to efficiently degrade organic pollutants while the other processes could achieve similar results by using visible light and UVA or even in the dark! 

At the M² group, we are mainly focused on the heterogeneous systems i.e., the presence of nanomaterials to trigger remediation processes for wastewaters treatment. Remediation processes like photocatalysis and Fenton-based processes are environmentally friendly, so such a technology based on the coupling of catalysis and sunlight enters a strategy of sustainable development.

Sources (pictures):
Bjork https://www.sunburnsout.com/timeline/video-le-trailer-de-the-juniper-tree-avec-bjork
Bonnie Rait https://twitter.com/globalsolar_au/status/1252798170360279040/photo/1
Martha Maeda https://all-free-download.com/free-photos/download/highquality-pictures-of-the-sun-leaves_169136.html