Abstract
The removal of priority pollutants by nanocomposites has recently received much attention. In the present study, the dechlorination as well as photodegradation of trichloroethylene (TCE) by the combination of nanoscale zerovalent iron (NZVI) with Degussa P-25 TiO2 (Fe/TiO2 nanocomposites) in the presence of nickel ions under anoxic conditions were studied. The Fe/TiO2 nanocomposites were synthesized by a novel and simple method using polyethylene glycol and sodium borohydride as the cross-linker and reducing agent, respectively. Scanning electron microscopy (SEM) images showed that the NZVI was spherical with the average particle size of 60±5nm. Electron-probe microanalysis elemental maps showed that the distribution of Fe and Ti in nanocomposites was uniform. The Fe/TiO2 nanocomposites exhibited excellent ability in dechlorination as well as photodegradation of TCE in the presence of nickel ions. Ethane was found as the major end product of TCE in both dark and photocatalytic reactions, depicting that hydrodechlorination was the major reaction mechanism. In addition, the dechlorination of TCE by Fe/TiO2 nanocomposites followed the pseudo-first-order kinetics and the rate constant (kobs) for TCE dechlorination was (1.3±0.1)×10−2h−1, which was higher than that by NZVI alone ((7.4±0.2)×10−3h−1). The photodegradation efficiency of TCE by Fe/TiO2 nanocomposites was enhanced in the presence of nickel ions under illumination of UV light at 365nm. The kobs for TCE photodegradation increased 6.0–11.6 times when Fe/TiO2 was illuminated with UV light in the presence of nickel ions. A rapid and complete dechlorination of TCE by Fe/TiO2 nanocomposites was observed after 7 cycles of injection in the presence of nickel ions and UV light, indicating the stability of nanocomposites towards TCE dechlorination.
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