Formation of inorganic nitrogenous byproducts in aqueous solution under ultrasound irradiation.

The effects of ultrasonic frequency, power intensity, temperature and sparged gas on the generation of nitrogenous by-products NO and NO have been investigated, and the new kinetics model of NO and NO generation was also explored. The results show that the highest primary generation rate of NO and NO by direct sonolysis in the cavitation bubbles (represented by k' and k', respectively) was obtained at 600 kHz and 200 kHz, respectively, in the applied ultrasonic frequency range of 200 to 800 kHz. The primary generation rate of NO (represented by k') increased with the increasing ultrasonic intensity while the primary generation rate of NO (represented by k') decreased. The lower temperature is beneficial to the primary generation of both NO and NO in the cavitation bubbles. The optimal overall yields of both NO and NO were obtained at the N/O volume (in the sparged gas) ratio of 3:1 which is near to the ratio of N/O in air. The dissolved O is the dominant oxygen element source for both NO and NO, compared with water vapor. Ultrasonic irradiation can significant enhance the recovery rates of dissolved N and O and thus keep the N fixation reaction going even without aeration.