Photocatalytic Reduction of Perrhenate and Pertechnetate in a Strongly Acidic Aqueous Solution.

Pertechnetate (TcO), a physiologically toxic radioactive anion, is of great concern due to its high mobility in environmental contamination remediation. Although the soluble oxyanion can be photoreduced to sparingly soluble TcO·HO, its effective removal from a strongly acidic aqueous solution remains a challenge. Here, we found that low-crystalline nitrogen-doped titanium oxide (N-TiO, 0.6 g L) could effectively uptake perrhenate (ReO, 10 mg L, a nonradioactive surrogate for TcO) with 50.8% during 360 min under simulated sunlight irradiation at pH 1.0, but P25 and anatase could not. The nitrogen active center formed by trace nitrogen doping in N-TiO can promote the separation and transfer of photogenerated carriers. The positive valence band value of N-TiO is slightly higher than those of P25 and anatase, which means that the photogenerated holes have a stronger oxidizability. These holes are involved in the formation of strong reducing CO radicals from formic acid oxidation. The active radicals convert ReO to Re(VI), which is subsequently disproportionated to Re(IV) and Re(VII). Effective photocatalytic reduction/removal of Re(VII)/Tc(VII) is performed on the material, which may be considered a potential and convenient strategy for technetium decontamination and extraction in a strongly acidic aqueous solution.