Separation of Re(VII) from aqueous solution by acetone-enhanced photoreduction: an insight into the role of acetone

Efficient separation of rhenium (Re) from aqueous solution is pivotal in the resource recovery, and suitable to simulate the elimination of radiotoxic technetium (Tc) due to their similar properties. In this work, we achieved a high Re(VII) separation ratio of 95.2% within 30 min from aqueous solution via an acetone-enhanced photoreduction method, in which soluble ReO4- was reduced to insoluble ReOx and Re(0) in the presence of acetone and isopropanol. Compared with the situation in absence of acetone, acetone absorbed most of the UV energy, and the produced triplet acetone could abstract H-alpha, atoms from isopropanol to form more strongly reductive ketyl radicals, leading to the enhancement in photoreduction. Isopropanol was the most qualified for Re(VII) photoredction due to its low C-H-alpha bond energy. The addition of alkali also benefited the Re(VII) separation by eliminating produced protons, and stabilizing the intermediate Re(VI) to preventing the re-formation of Re(VII) through disproportionation of Re(VI). Furthermore, selective and effective separation of Re(VII) from simulated high level liquid waste containg Nd(III) was realized as well. This work gains an insight into the role of acetone in the enhanced Re(VII) photoreduction, which may be of great significance in developing novel approaches for hydrometallurgy and spent nuclear fuel reprocessing.