Title : Photo-oxidation reaction scheme triggered by the nozzle of submerged plasma torch
Abstract:
The French Atomic Energy Commission develops innovative processes for the treatment of radioactive organic liquids. One of them, named ELIPSE, involves a thermal plasma working under a water column, which ensures the cooling, the filtration and the scrubbing of the gases coming from the degradation. Studies in progress deals with the ability of the ELIPSE process to destroy the pure organic liquids and then to reduce the amount of organic matter remaining in the aqueous solution by means of the thermal or radiative properties of plasma.
Preliminary test have shown how efficient the process is for the destruction of the organic liquids when they are directly fed in the plasma hearth. Extensive researches have been performed to assess the ability of the submerged plasma to destroy the remaining organic matters either by reinjecting them with the aqueous solution into the plasma or by using the UV ray coming from the plasma itself. A comparison of the experimental results obtained with various mechanisms proposed by the work carried out highlighted that this UV radiation could, by excitation of water molecules, produce radicals OH° which may either dimerise to produce hydrogen peroxide H2O2, or react with organic substances present. The calculation of an activation energy of 8.5 ± 0.9kJ.mol-1 during the experiments shows that these radicals OH° act directly after having been formed which explains a low H2O2 content stability when the solution contains organic compounds. Thus, this photo-oxidation taking place in the water column could be used to improve the destruction of residual organic matter in the solution by maintaining the plasma after processing a given amount of organic liquids. It could also be used to help the decontamination of various aqueous solutions coming from different industrial or medical activities.
