Transport of Gaseous Hydrogen Peroxide and Ozone into Bulk Water vs. Electrosprayed Aerosol

Abstract

Production and transport of reactive species through plasma–liquid interactions play a significant role in multiple applications in biomedicine, environment, and agriculture. Experimental investigations of the transport mechanisms of typical air plasma species: hydrogen peroxide (H2O2) and ozone (O3) into water are presented. Solvation of gaseous H2O2 and O3 from an airflow into water bulk vs. electrosprayed microdroplets was measured, while changing the water flow rate and applied voltage, during different treatment times and gas flow rates. The solvation rate of H2O2 and O3 increased with the treatment time and the gas–liquid interface area. The total surface area of the electrosprayed microdroplets was larger than that of the bulk, but their lifetime was much shorter. We estimated that only microdroplets with diameters below ~40 µm could achieve the saturation by O3 during their lifetime, while the saturation by H2O2 was unreachable due to its depletion from air. In addition to the short-lived flying microdroplets, the longer-lived bottom microdroplets substantially contributed to H2O2 and O3 solvation in water electrospray. This study contributes to a better understanding of the gaseous H2O2 and O3 transport into water and will lead to design optimization of the water spray and plasma-liquid interaction systems.

On the formation of hydrogen peroxide in water microdroplets

“…the Henry's law constants for the solubility of ozone and H 2 O 2 in water are, respectively, $10 À3 M atm À1 and $10 4 M atm À1 . 45…”

“…Mol/L-atm at NTP45 ) and it would take a much longer time for bulk water to equilibrate with the ambient atmosphere than the duration of our experiments (5-40 min). Thus, water microdroplets in our experiments will have always have an aqueous ozone concentration that is lower than the equilibrium concentration specified by the Henry's law, i.e.,43 10 -9 10 -2 = 𝐶 o = 𝑃 O 3 × 𝐻 𝐶𝑃 O 3 ≈ × × 0.4 nM.…”

Plasma-droplet interaction study to assess transport limitations and the role of ⋅OH, O⋅,H⋅,O2(a 1Δg),O3, He(23 S) and Ar(1s 5) in formate decomposition

“…Our previous work on the determination of the reactivity transfer of • OH from the gas phase plasma to the liquid micro-droplets was likely the first measurement that showed quantitative agreement with a one-dimensional reactiondiffusion model without fitting parameters of decomposing a model hydrocarbon (formate), demonstrating the dominance of the near-interfacial reactions with • OH radicals and the limitation of the diffusion of formate in the droplet to the reactive plasma-droplet interface on the formate oxidation rate [10]. Recently, the transport of gas-phase H 2 O 2 and O 3 into water micro-droplets was investigated illustrating the solvation efficiency and mass transfer of these important plasma-produced species into bulk and electrosprayed water [26]. Despite extensive research involving plasma-droplet interactions, a quantitative understanding of plasma-induced liquid phase chemistry remains in the hindsight, particularly, the chemistry of short-lived reactive species.…”

Ozone-Facilitated Formation of Uranyl Peroxide in Humid Conditions

“…17 The limiting factor is the solubility of ozone in water mediated by vapor pressure. 47 Formation of studtite from metaschoepite in the absence of added H 2 O 2 in high RH atmospheres and a uranyl hydroxide hydrate (UOH) formed from uranyl fluoride was previously reported. 46 The interlayer spacing of the uranyl hydroxide produced from hydration of uranyl fluoride expanded and contracted with hydration and dehydration, respectively.…”