Enhancement of p,p′-DDT photodegradation on soil surfaces using TiO2 induced by UV-light

Enhancement of p,p'-DDT photodegradation on soil surfaces using TiO2 induced by UV-light was mainly investigated in this work. After being spiked with pp'-DDT, soil samples loaded with different doses of TiO2 (0%, 0.5%,1%,2%, and 3% wt) were exposed to UV-light irradiation for 24 h. The results indicated that the photodegradation of pp'-DDT followed the pseudo-first-order kinetics. TiO2 accelerated the photodegradation of pp'-DDT significantly as indicated by the half-life reduction from 23.3 h to 10.4 h, corresponding to the TiO2 content from 0% to 3% respectively. In addition, the effects of soil pH, photon flux and humic substances on pp'-DDT degradation were investigated. The photodegradation rate increased with the increase of the soil pH and photon flux. The humic substances (2% wt) inhibited the pp'-DDT photodegradation by reducing the amount of light available to excite the p,p'-DDT and TiO2 or by quenching radicals capable of oxidizing pp'-DDT. pp'-DDE, pp-DDD and DDMU were main degradation intermediates and they were further degraded in the presence of TiO2. (c) 2004 Published by Elsevier Ltd.