Photooxidation of insecticide residues by ZnO and TiO2 coated magnetic nanoparticles under natural sunlight

The photocatalytic efficiency of magnetic nanoparticles using different coatings between Fe3O4 and semiconductor oxides (ZnO and TiO2) was evaluated by their capability to degrade four insecticides (etoxazole, fenpyroximate, flonicamid and metaflumizone) in water exposed to sunlight. Magnetic particles coated with SiO2 (MSPs) showed higher photodegradation activity. Sol-gel TiO2-SiO2 coated TiO2 P25 magnetic particles (MSTi(2)Ps) and sol-gel ZnO-SiO2 coated ZnO magnetic particles (MSZn(2)Ps) were more efficient than magnetic particles consisting of a silica undercoat followed by a TiO2- or ZnO- sol-gel coating as the photocatalytic layer for catalysing the removal of these pesticides. Finally, the addition of Na2S2O8 increased the photooxidation activity of both MSTi(2)Ps and MSZn(2)Ps. A comparison of the semiconductor oxides showed MSZn(2)Ps to be the most effective for the removal of the studied pollutants. As a consequence, the tandem MSZn(2)Ps/Na2S2O8 provides an interesting combination to remove pesticides in water.