A NEW PHOTOCHEMICAL REACTOR DESIGN FOR THE TREATMENT OF ABSORBING SOLUTIONS

The recent developments in the field of Advanced Oxidation Processes ( AOP) require improvements in reactor design. Indeed, light-induced pro cedures cannot be used for the removal of micropollutants in strong ab sorbing solutions. In this work, the technical design concept for mixi ng in a cylindrical reactor has been approached in a rational way for the treatment of compounds in highly absorbing solutions. The new phot ochemical reactor perfected in our laboratory consists of an annular r eactor with one UV lamp in axial position, However, this reactor diffe rs from classical ones since the rotation of the quartz sleeve protect ing the lamp associated with the flux of the solution establishes a Co uette-Taylor type flow. This means that toroical eddies are formed bet ween the two surfaces of the cylindrical reactor and thus, periodicall y, each fraction of liquid comes near the UV source,Three photochemica l processes with irradiation at 254 nm have been examined : direct pho tolysis, H2O2/UV and TiO2/UV for the removal of organic micropollutant s 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, Experiment s showed that under these experimental conditions, for the three photo chemical systems, the yield of oxidation was significantly increased a s a result of the rotating movement of the central cylinder, This new design will be able to improve the efficiency of commonly used industr ial reactors. (C) 1997 IAWQ. Published by Elsevier Science Ltd.