PHOTOCATALYTIC REDUCTION OXIDATION PROCESSES OCCURRING AT THE CARBON AND NITROGEN OF TETRANITROMETHANE/

Oxygenated and oxygen-free aqueous suspensions of titanium dioxide con taining tetranitromethane (TNM) were irradiated with near-UV light in the presence of titanium dioxide. The transformation processes were fo llowed by monitoring intermediates and final products. TNM degradation can only be initiated by conduction band electrons or by superoxide a nions. Further reductive and oxidative steps lead to the formation of carbon dioxide and to rather stable intermediates, such as formate ion and formaldehyde. Nitrogen is finally found as nitrate and as ammoniu m ions. Nitrite appears in the early steps of the process. The presenc e of oxygen has not been found to be crucial for the progress of the p hotocatalytic process, but affects the product distribution. In alkali ne media (pH 11) higher concentrations of formate ion and formaldehyde are found together with a few percent of C-2 derivatives. Reaction pa thways are presented to explain these experimental results.