Coupling Supported Photocatalysts and ferrate oxidation : towards an innovative solution for wastewater treatment – COPHOTOFE

COPHOTOFE in an industrial research project that aims proposing new solutions for wastewater treatment. The consortium is made of four complementary partners: two CNRS teams experts in different aspects of photochemical/photocatalytic treatment and oxidation processes (IPREM-Université de Pau and ICPEES-Université de Strasbourg), of one VSME, SICAT working on the synthesis of tunable beta-SiC support materials and of another SME, PSI, specialized in environmental engineering and waste and effluents treatment in the eco-industry area.
COPHOTOPHE aims the coupling of two complementary oxidation processes with an expected synergy effect: heterogeneous photocatalysis on one hand and chemical oxidation by potassium ferrates on the other hand. The originality of the project stems from the use of solar-light activated photocatalyst supported on beta-SiC alveolar foams. These photocatalytic supports have many advantages in addition to their tunable size and shape:
- their alveolar structure is designed for optimized light penetration and limited mass transfer loss. This is an actual improvement relative to other supported planar and opaque materials such as papers, fabrics, …) where only the surface is activated.
- their chemical structure allows for an easy incorporation/grafting of the photocatalyst whatever its composition. The soundness of the photocatalyst on the surface of the material is a critical lock limiting further applications of photocatalysis for water treatment.
One of the points addressed by the project is the synthesis of new photocatalysts immobilized on beta-SiC in order to activate them under solar light. Two approaches will be used:
- either organic photocatalysts such as cyanoaromatics or anthraquinone derivatives
- or conventional or commercial TiO2 modified or not by anionic or cationic doping

Their photocatalytic efficiency will be first analyzed in batch reactors with the powder materials against model pollutants. In a second step, the coupling of the photocatalysts with the ferrate chemical oxidant will be studied. This reactant is an iron salt where iron +VI is known as a very efficient oxidant able to oxidize most organic compounds. In the following steps of the project, the synthesis of alveolar beta-SiC foams containing either co-included TiO2 or surface-modified to graft the photocatalyst will be made. The last step, in strong collaboration with PSI, specialized in wastewater treatment, will involve the design of a semi-pilot reactor for real wastewater treatment.

The coupled use of ferrates that coagulate in water and are thus easily removed after treatment with stable supported photocatalyst will avoid any filtration step and should provide an economical (inexpensive chemical oxidant and recyclable photocatalysts) and energy-saving (using solar light) process for the treatment of wastewater. The objective of COPHOTOFE is thus to firmly establish this proof of concept.