Photocatalytic Reduction of Perrhenate and Pertechnetate in a Strongly Acidic Aqueous Solution
Heng Yang, Hao Deng, Pengliang Liang, Xian-jin Ma, Jing Yin, Long Jiang, Yanyan Chen, Shuying Shi, Huiqiang Liu, Xue Ma, Yuxiang Li, Ying Xiong
Abstract
Pertechnetate ( 99 TcO 4 – ), 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 2 · n H 2 O, its effective removal from a strongly acidic aqueous solution remains a challenge. Here, we found that low-crystalline nitrogen-doped titanium oxide (N-TiO 2, 0.6 g L –1 ) could effectively uptake perrhenate (ReO 4 –, 10 mg L –1, a nonradioactive surrogate for TcO 4 – ) 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 2 can promote the separation and transfer of photogenerated carriers. The positive valence band value of N-TiO 2 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 2 – radicals from formic acid oxidation. The active radicals convert ReO 4 – 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.