Heterogeneous catalytic ozonation of benzothiazole aqueous solution promoted by volcanic sand.

This paper presents experimental results on the catalytic effect of volcanic sand on benzothiazole ozonation. Experiments were assessed at laboratory scale, in a differential circular flow reactor composed of a volcanic sand fixed bed column of 19 cm3 and a 1 dm3 storage tank, operated in batch mode at 20 degrees C and pH 2-7. Experimental results show that ozone self-decomposition is enhanced by the presence of volcanic sand at all pH. At pH>pH(PZC), the increase in aqueous ozone decay could be related to ozone interaction with strong Lewis acid on metal oxide surface sites of the volcanic sand. Ozone self-decomposition reactions occurring on the volcanic sand are less affected by the presence of radical scavengers. Benzothiazole removal by ozonation is also enhanced by the presence of volcanic sand. Moreover, the inhibitory effect of free radical scavengers is also impaired by volcanic sand, suggesting that strong Lewis acid surface sites play a key role on the reaction mechanism.