A comparison of the absorbance spectra of the filtered suspensions before and after a HP experiment for QAN with 1 M HCOOH is presented in Fig. 3. The initial spectrum showed the characteristic U(VI) signals in the region 350–500 nm (see inset) ,  and , while the final one showed U(IV) signals at 435, 490, 554 and 663 nm together with a broad band at 800–900 nm , , ,  and . This result confirms that uranium remains in solution in the form of a U(IV)-formate complex , being reoxidized to U(VI) by O2 during the Calhex 231 and increasing U(VI) concentration in solution after approximately 7 min (Fig. 2). The peak at 963 nm indicates interneurons U(V) is also formed ,  and .
Fig. 3. Spectra of the initial and final filtered solutions of a HP experiment for QAN in the presence of 1 M HCOOH. Conditions of Fig. 2. Spectra of the initial and final filtered solutions of a HP experiment for QAN in the presence of 1 M HCOOH. Conditions of Fig. 1. Insets: detailed views of the 200–350 nm and 350–500 nm regions.Figure optionsDownload full-size imageDownload as PowerPoint slide