Intensification of oxidation capacity using chloroalkanes as additives in hydrodynamic and acoustic cavitation reactors

Abstract

The effect of the presence and absence of the chloroalkanes, dichloromethane (CH 2Cl 2), chloroform (CHCl 3) and carbon tetrachloride (CCl 4) on the extent of oxidation of aqueous I − to I 3 - has been investigated in (a) a liquid whistle reactor (LWR) generating hydrodynamic cavitation and (b) an ultrasonic probe, which produces acoustic cavitation. The aim has been to examine the intensification achieved in the extent of oxidation due to the generation of additional free radicals/oxidants in the reactor as a result of the presence of chloroalkanes. It has been observed that the extent of increase in the oxidation reaction is strongly dependent on the applied pressure in the case of the LWR. Also, higher volumes of the chloroalkanes favour the intensification and the order of effectiveness is CCl 4 > CHCl 3 > CH 2Cl 2. However, the results with the ultrasonic probe suggest that an optimum concentration of CH 2Cl 2 or CHCl 3 exists beyond which there is little increase in the extent of observed intensification. For CCl 4, however, no such optimum concentration was observed and the extent of increase in the rates of oxidation reaction rose with the amount of CCl 4 added. Stage wise addition of the chloroalkanes was found to give marginally better results in the case of the ultrasonic probe as compared to bulk addition at the start of the run. Although CCl 4 is the most effective, its toxicity and carcinogenicity may mean that CH 2Cl 2 and CHCl 3 offer a safer viable alternative and the present work should be useful in establishing the amount of chloroalkanes required for obtaining a suitable degree of intensification.