The photocatalysis of N,N-diethyl-m-toluamide (DEET) using dispersions of Degussa P-25 TiO2 particles

The photocatalysis of N,N-diethyl-meta-toluamide (DEET) was examined using aqueous Degussa P-25 TiO2 dispersions and a 350 nm Hg lamp UV reactor. Various concentrations of humic acid (HA) were added to the photocatalytic sample matrix in order to simulate the influence of natural organic matter (NOM) present during water treatment. A municipal secondary treatment effluent was also used as a sample matrix to provide a field sample comparison with laboratory matrixes. Pseudo-first-order kinetic rate constants were calculated for each set of samples. Gas chromatography/mass spectrometry (GC/MS) results showed a marked decrease in the photocatalytic degradation of DEET after the addition of HA, which continued to decrease with increasing HA concentration. The rate of degradation was further reduced after the addition of the municipal secondary treatment effluent, likely due to competition from dissolved organic matter and surface interference from soluble salts.