Effect of ionic strength on the acoustic generation of nitrite, nitrate and hydrogen peroxide

The formation of nitrite, nitrate and hydrogen peroxide was measured following sonication of air-, nitrogen-, argon- and oxygen-saturated water. Hydrogen peroxide formation was greatest in argon-saturated water, and nitrite and nitrate were detected in air- and nitrogen-saturated water respectively. The yields of hydrogen peroxide and nitrogen oxides was six times greater from air-saturated water than from nitrogen-saturated water. The mechanism by which molecular oxygen may enhance these product yields is discussed in terms of the Zeldovich mechanism of combustion chemistry. The potential for environmental nitrogen fixation by hydrodynamic cavitation in seawater was investigated by an initial examination of the effect of sodium chloride on the acoustic generation of nitrogen oxides. Increasing solute concentration was found to enhance nitrite yields up to seven-fold. Hydrogen peroxide formation, however, was reduced, and this is discussed in terms of the scavenging of hydroxyl free radicals by chloride ions. (C) 1999 Elsevier Science B.V. All rights reserved.