Protocol for the fixation of nitrogen from air using focused ultrasound

Nitrogenous fertilizers, containing nitrate as a key component, are important soil-enriching compounds that support crop growth and yield. Here, we present a protocol for the ultrasonic fixation of nitrogen from air, using focused ultrasound in water. We describe steps for designing, assembling, and configuring the sonoreactor. We detail procedures to achieve the optimal nitrate concentration and pulse width for the applied ultrasound and to apply these conditions to a benchtop reactor to form micromolar concentrations of both nitrite and nitrate. For complete details on the use and execution of this protocol, please refer to Yusuf et al. 1 • Steps for using pulsed focused ultrasound to induce cavitation for nitrogen fixation • Procedures for quantifying nitrogen fixation products (nitrite and nitrate) • Description of the optimization of the experimental setup and parameters • Steps for applying optimized results to a bench-scale prototype Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics. Nitrogenous fertilizers, containing nitrate as a key component, are important soil-enriching compounds that support crop growth and yield. Here, we present a protocol for the ultrasonic fixation of nitrogen from air, using focused ultrasound in water. We describe steps for designing, assembling, and configuring the sonoreactor. We detail procedures to achieve the optimal nitrate concentration and pulse width for the applied ultrasound and to apply these conditions to a benchtop reactor to form micromolar concentrations of both nitrite and nitrate.