Study On Photocatalytic Degradation Of Lindane With Rare Earth Modified TiO₂in Aqueous Solution

POPs are harmful chemicals to human health and environment. The photocatalytictechnique can ultimately mineralize organics into completely harmless substances suchas H₂O and CO₂. So it is widely used in the degradation of organic matter, especiallyrefractory organics. In order to deal with the threat of POPs in the environment, thisdissertation considers lindane as the target pollutants, using TiO₂modified by loadedrare earth as photocatalyst, to study the photocatalytic degradation of lindane in aqueoussolution. The main content is as follows.Firstly, the activity which TiO₂modified by the rare earth shows in thephotocatalytic degradation of lindane is studied. Volumetric method of impregnation isemployed to prepare modified TiO₂, including Yttrium, Cerium, Gadolinium, Erbium.The catalytic activity is investigated through the degradation of lindane under UVirradiation, to optimize the preparation conditions of catalyst. The results show that rareearth loading elements （Ce, Er, Gd） effectively improves the activity of TiO₂in thephotocatalytic degradation of lindane, where the best catalyst is3h-calcined TiO₂loading0.03%Ce under air atmosphere with500℃.Secondly, the effects of catalyst dosage, solution pH, substrate concentration, theelectron capture agent, the inorganic anion and cation on the lindane photocatalyticdegradation by Ce/TiO₂under ultraviolet light are investigated. Experimental resultsshow that with the catalyst dosage as20mg/200ml, pH from5to7, the substrateconcentration as1mg/l, UV catalytic degradation rate can reach to91%. Electroncapture agent KBrO3plays a positive function at first, and with the concentrationincreasing its inhibitory action on the lindane degradation emerges, while K2S2O8keepsplaying a promoting role. Inorganic anions (NO₃^-, SO₄^2-, CO₃^2-) inhibit thephotocatalytic degradation of lindane, and the cations (Cu²⁺, Fe³⁺, Al³⁺) show promotingeffects. The lindane photocatalytic degradation is first-order reaction kinetics at lowconcentration, but zero-order kinetics at high concentration.Finally, the study of photocatalytic degradation of lindane using the modified TiO₂under visible light is conducted. The activity of Ce/TiO₂and Er/TiO₂in thephotocatalytic degradation of lindane is investigated. The experimental results show thatEr/TiO₂with1.0%load behave best in activity, and under the optimal condition, thedegradation rate of200μg/l. lindane can reach at22%.