Photocatalytic degradation of DDT mediated in aqueous semiconductor slurries by simulated sunlight

The degradation of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) by simulated sunlight ( > 340 nm) has been investigated in the presence of aqueous suspensions of semiconductor particulates (TiO2, ZnO, CdS, WO3, α-Fe2O3 and TiO2/5 wt.% Pt). Titanium dioxide appears to be the most effective catalyst; the half-life for the processes is −40 min (at initial DDT concentration 1 mg L−1 and 2 g L−1 TiO2, photon flux 3 × 10−5 einstein/min, over a cell cross-section of 4 cm2). The near quantitative recovery of chloride ions after long irradiation periods suggests that the end products of the degradative process are CO2 and HCl. To the extent that neither DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene) nor DDD (1,1-dichloro-2,2-bis(p-chlorophenyl)ethane) were observed by gas chromatographic techniques, the reaction proceeds through hydroxyl radical attack on the aromatic moieties with subsequent ring opening.