Photocatalytic unification of iodine species using platinum-loaded titanium dioxide

Removal of iodine from water contaminated by nuclear accidents or releasing radioactive waste is complicated and costly because iodine exists in various forms in the water. We investigated the unification of iodine species by photocatalysis as a pretreatment for removing radioactive iodine species from water. The effect of the TiO2 crystal phase of Pt-TiO2 and solution pH on the photocatalytic redox reactions of iodide (I-), iodate (IO3-), and o- iodobenzoic acid were evaluated. When anatase Pt-TiO2 was used at pH 12 or higher, the mixture of I -and IO3- was converted to IO3-. In contrast, when anatase/rutile mixed-phase Pt-TiO2 was used at pH 9 or 10, the mixture of iodine species in the solution was converted to I-. Regardless of the type of Pt-TiO2, the iodine in o-iodo-benzoic acid was mineralized to I -under alkaline conditions. Because the iodine species can be unified into a single species by selecting the photocatalyst and the solution pH, this photocatalytic treatment could be applied to remove iodine species with high efficiency.

Automated summary

It was found that photocatalysis can be used to unify iodine species in water contaminated by nuclear accidents, enabling the efficient removal of radioactive iodine. The crystal phase of the Pt-TiO2 catalyst and the solution pH have significant effects on the photocatalytic reactions of iodide, iodate, and o-iodobenzoic acid. Under alkaline conditions (pH 12 or higher), anatase Pt-TiO2 converts the mixture of iodide and iodate to iodate, while anatase/rutile mixed-phase Pt-TiO2 converts the mixture of iodine species to iodide at pH 9 or 10. Regardless of the type of Pt-TiO2, iodine in o-iodobenzoic acid is mineralized to iodide under alkaline conditions. This photocatalytic treatment shows promising potential for efficient removal of iodine species.