INTEGRATED APPROACH USEFUL IN THE MINERALIZATION OF NONBIODEGRADABLE,TOXIC P-NITROTOLUENESULFONIC ACID VIA PHOTOCATALTYIC-BIOLOGICAL PROCESSES

Heterogeneous photooxidation of toluene-4-nitro-2-sulfonic acid or p-n itrotoluene-sulfonic acid (p-NTS) using TiO2 P-25 Degussa suspensions was investigated at lambda>290 nm. Photocatalytic degradation took pla ce with pseudo-first order rate constants of 0.12 h-1 at 20-degrees-C and 0.25 h-1 at 50-degrees-C. When H2O2 (6 x 10(-2) M) was added the o bserved pseudo-first order rate constant was 0.86 h-1 at 20-degrees-C. This confirms that the .OH radical accelerates the photodegradation u nder study. Insight is provided into the factors affecting the nonbiod egradability of p-NTS and to the role of the TiO2 photoassisted redox reactions determining the kinetics of substrate degradation. Using bio chemical oxygen demand (BOD) and dissolved organic carbon measurements (DOC) it is shown that sewage bacteria do not attack p-NTS. This comp ound is totally nonbiodegradable by urban and industrial aerobic activ ated sludges tested in very diverse culture media. Photolytically pret reated solutions have beneficial effects on subsequent biodegradation. The evolution of toxicity in pretreated solutions is reported.