The effect of polyaniline doping on the TiO2 and ZnO nanoparticles in the pyrene degradation on the contaminated soils

The use of a photocatalyst that is active under sunlight, is one of the cost-effective methods for the removal of pollutants from contaminated soil. In this study, an interfacial polymerization method was used to prepare ZnO- polyaniline (PA) and TiO2-PA nanocomposites. The SEM images confirmed the particle size distribution ~200 nm in diameter. In both XRD and FTIR data, the peaks relating to PA were identified in the nanocomposites. For the extraction of pyrene of the soil samples, a continuous batch extraction was carried out and evaluated. The data analysis showed the positive effect of PA on pyrene degradation under UV and sunlight radiation, by decreasing the electron hole recombination in modified photocatalysts. The PA coated photocatalysts, improved the extent of pyrene removal, which was more than 95% for both the ZnO and TiO2 nanocomposites in the bentonite samples under the visible light condition. This value was lower than 80% for the clay soil under UV radiation, which increased to 90% under sunlight. However, only a maximum degradation of 60% was obtained with the unmodified photocatalysts. The increase in the degradation efficiency was due to the increase in adsorption of the organic molecules from the bentonite and clay soils by polyaniline, and also the semiconducting behavior of polymer, that prevented the electron-hole recombination, causing an increase in the photocatalytic activity under both UV and visible radiation. The new ZnO/PA and TiO2/PA photocatalysts are believed to be promising photocatalytic materials, which can be widely used for the treatment of environmental pollution [1-2].