A dispersed plug flow heterogeneous photocatalytic reactor is investigated. A 2D model adapted to the media, a photocatalyst supported on a macroporous ceramic foam, was built. It is based on the couplings at the local scale between mass transfer, radiative transfer and reaction kinetics. The simulations are compared to experimental results obtained in the case of the degradation of a target organic micro-pollutant. The 2D concentration fields resulting from these couplings brings to light the very specific characteristic operation of the photoreactor. They allow the low performances of the dispersed plug flow mode when compared to the perfectly mixed, a result both unexpected and original, to be explained.

Simulations also reveal the major influence of the foam thickness, the characteristic 2 dimension of the radiative transfer, on the performance of the dispersed plug flow photoreactor.

Advanced oxidation processes (AOPs) represent one of the routes of advanced technologies for water treatment 1 currently being actively explored 2 to address the pollution of surface waters by pharmaceutical 3 and a large number of others organic and non-biodegradable micro-pollutants 4 . The presence of these emerging contaminants in the environment, which directly result from human activity, is now a universally recognized issue 5 . The treatment principle, regardless of the specific oxidation processes used, is based on the production of radical oxygen species (ROS). ROS have an oxidation potential that enables the total or partial mineralization of a wide range of contaminants. Photo-oxidation processes such as the photo-fenton process 6 , now approaching neutral pH operation, and photocatalysis 7 , are based on the use of the energy content of photons to produce ROS. They are particularly relevant given that this energy can be provided directly by natural solar radiation 8 . Under these conditions, these processes fit into the concept of sustainable development 9 . In the case of heterogeneous photocatalysis, photo-activation of a solid semiconductor is the primary mechanism leading to the oxidation of organic micro-pollutants 10 . For this family of AOPs, a number of key challenges must be overcome before they can be disseminated and applied on a large scale. The first challenge is to develop stable, low-cost photocatalysts produced via a green synthesized route 11 leading ideally to photocatalysts activated by visible radiation 12 to enable environmental remediation based on the use of solar radiation. Whatever the level of performances and innovation, stability of the photocatalyst 13 is a key criterion. The second issue concerns the use of photocatalysts. For a long time, particle suspension has been the preferred choice, not only because of its ease and flexibility of use 14 , but also because of its efficiency in terms of light management in the reactor volume 15 . The need for, and difficulty