Photochemical reaction of Tl in aqueous solution and its environmental significance

The valence state of thallium determines its toxicity, distribution and mobility. Tl(I) can be oxidized to Tl(III) under photoirradiation of the high-pressure mercury arc lamp and solar light. A photooxidation experiment of thallium showed that the photooxidation rate could be affected by the pH of the solution, and the intensity and wavelength of the light source. Lowering the pH and increasing the light intensity have the effect of increasing the photooxidation rate. UV radiation (UVB and UVC regions) plays an important role in the photooxidation of Tl(I). However, the microbial effect is not obvious in comparison with photooxidation effect in this experiment. The study can provide important scientific groundwork for handling of thallium pollution.