An efficient elution method of tetravalent uranium from anion exchanger by using formic acid solution

Heterogeneous photocatalytic removal of U(VI) in the presence of formic acid: U(III) formation

“…The initial spectrum showed the characteristic U(VI) signals in the region 350-500 nm (see inset) [14][15][16], while the final one showed U(IV) signals at 435, 490, 554 and 663 nm together with a broad band at 800-900 nm [17][18][19][20][21]. This result confirms that uranium remains in solution in the form of a U(IV)-formate complex [13], being reoxidized to U(VI) by O 2 during the filtration and increasing U(VI) concentration in solution after approximately 7 min (Fig. 2).…”

“…(1).Remarkably, the formation of precipitates was observed only at 0.001 and 0.01 M HCOOH, either with QP or with QAN. At lower HCOOH concentrations, not enough U removal was probably achieved, and, as said, at higher HCOOH concentrations, soluble complexes are formed[13]. Dark grey precipitates were observed for QP/0.001 and GP/0.001, while for QAN/0.001 and QAN/0.01, precipitates were light grey, in agreement with the lower U(VI) removal.…”

“…(13). As stated before, as the characteristic blue color of trapped e CB − was not observed, a significant oxidation of U(III) by h BV + in the studied conditions can be discarded.…”

“…In HCOOH, U(IV) stays in solution as a formate complex [13], allowing further reduction to U(III). On the other hand, U(III) was not observed in the 2-PrOH system because (CH 3 ) 2…”