Abstract
This paper summarizes recent studies performed at Marcoule Institute for SeparationChemistry (ICSM) in the topic of multibubble sonoluminescence (MBSL) andsonochemistry of UO22+ and lanthanide(III) ions in aqueous solutions and at the solidliquid interface. Power ultrasound has showed to be effective for excitation of volatileand non-volatile species in solutions in many cases. The observed effects are generallyattributed to acoustic cavitation which is the nucleation, growth, and rapid implosivecollapse of vapor filled micro-bubbles during the ultrasonic irradiation of a liquidmedium.Bubble collapses in liquids produce chemically active species (excited species andradicals such as OH°) as well as sonoluminescence (SL, emission of light from the core ofcollapsing bubbles). MBSL spectra of pure water sparged with noble gases consist of OH°radical emissions from A2+ and C2+ electronically excited states and a broadcontinuum spanning from the UV to the near IR spectral range.1 This continuum isgenerally attributed to bremsstrahlung, to H + OH° recombination, and possibly to watermolecules deexcitation or OH(B2Σ+-A2Σ+) emission. SL from alkali-metal salt solutionsexhibits emission from the excited alkali-metal atoms M and M·Ar exiplex species.2 Suchkind of SL was explained by nanodroplet injections into the hot cores of collapsingbubbles.3 Recently, the SL of lanthanide ions was reported in concentrated (0.5-1.0 M)aqueous lanthanide salt solutions under the effect of 20 kHz ultrasound.4 It wassuggested that the SL of lanthanides would be governed by two major processes: (i)sonophotoluminescence, when the excitation of Ln(III) ions occurs through the lightemitted from cavitation bubbles and (ii) collisional excitation of Ln(III) ions by ʺhotʺparticles at the bubble/solution interface. However, the mechanism of metal ionsexcitation under sonication is still under debate.In this paper, we report on the parameters that influence MBSL of f-elements and on itsquenching by sonolytical products and collisions with hot species at the bubbleinterface. Under proper conditions, the uranyl ion exhibits ultrabright sonoluminescenceeven in relatively diluted solutions. On the other hand, we show that SL can be used as asource of excitation for fluorescent f-elements contained in an extended solid phase.5