The recent developments in the field of Advanced Oxidation Processes (AOP) require improvements in reactor design. Indeed, light-induced procedures cannot be used for the removal of micropollutants in strong absorbing solutions. In this work, the technical design concept for mixing in a cylindrical reactor has been approached in a rational way for the treatment of compounds in highly absorbing solutions. The new photochemical reactor perfected in our laboratory consists of an annular reactor with one UV lamp in axial position. However, this reactor differs from classical ones since the rotation of the quartz sleeve protecting the lamp associated with the flux of the solution establishes a Couette-Taylor type flow. This means that toroïcal eddies are formed between the two surfaces of the cylindrical reactor and thus, periodically, each fraction of liquid comes near the UV source. Three photochemical processes with irradiation at 254 nm have been examined: direct photolysis, H2O2/UV and TiO2/UV for the removal of organic micropollutants such as atrazine and aliphatic acids in strongly absorbant solutions. Para-nitrophenol in the concentration range 1.0 to 2.3 mmol.L−1 (3.0-6.4 cm−1) has been added to the water to be treated as a product that absorbs the 254 nm light. The overall effect simulates that of an inner filter absorbing incident photons. In several experiments, para-nitrophenol was replaced by a mineral component bentonite. Experiments showed that under these experimental conditions, for the three photochemical systems, the yield of oxidation was significantly increased as a result of the rotating movement of the central cylinder. This new design will be able to improve the efficiency of commonly used industrial reactors.

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