First observation of radiolytic bubble formation in unstirred nano-powder sludges and a consistent model thereof

Mel O’Leary,Oliver Fox,Thomas Donoclift,Aliaksandr Baidak,Aaron Mcculloch,Christopher Emerson,Martyn Barnes,Annette Kleppe,Robin Orr,Darryl Messer,Fred Currell,Catarina Figueira

doi:10.1038/s41598-021-01868-1

Abstract

Experiments involving the irradiation of water contained within magnesium hydroxide and alumina nanoparticle sludges were conducted and culminated in observations of an increased yield of molecular hydrogen when compared to the yield from the irradiation of bulk water. We show that there is a relationship linking this increased yield to the direct nanoscale ionization mechanism in the nanoparticles, indicating that electron emission from the nanoparticles drives new radiative pathways in the water. Because the chemical changes in these sludges are introduced by irradiation only, we have a genuinely unstirred system. This feature allows us to determine the diffusivity of the dissolved gas. Using the measured gas production rate, we have developed a method for modelling when hydrogen bubble formation will occur within the nanoparticle sludges. This model facilitates the determination of a consistent radiolytic consumption rate coinciding with the observations of bubble formation. Thus, we demonstrate a nanoscale radiation effect directly influencing the formation of molecular hydrogen.

Highlights

Experiments involving the irradiation of water contained within magnesium hydroxide and alumina nanoparticle sludges were conducted and culminated in observations of an increased yield of molecular hydrogen when compared to the yield from the irradiation of bulk water
This paper investigates a heterogeneous chemical system where a nanopowder particulate phase is embedded inside a continuous aqueous phase
This paper addresses the processes behind the increase in the radiolytic yield in water near magnesium hydroxide and alumina nanoparticles

Summary

Introduction

Experiments involving the irradiation of water contained within magnesium hydroxide and alumina nanoparticle sludges were conducted and culminated in observations of an increased yield of molecular hydrogen when compared to the yield from the irradiation of bulk water. The radiolytic hydrogen production in systems similar to those investigated in this paper, magnesium hydroxide (Mg(OH)2 ) and alumina (Al2O3 ) sludges, is observed to be significantly enhanced compared to water a lone[14,15,16,17,18,19,20,21]. This effect was initially reported by Petrik et al.[14] with similar phenomena observed by LaVerne and co-workers on zirconia15,16, ceria15, urania17, alumina[18], copper oxide[19], ferrous oxide[20] and b ohemite[21]. This method of determining the diffusion coefficient can be used to investigate tortuosity[31] in heterogeneous phases

Methods

Results

Conclusion