Green synthesis of ammonium nitrate (NH ₄ NO ₃ ) fertiliser: production via plasma water/ice interaction with air and NH ₃ plasma

This study introduces a green and sustainable method for synthesising ammonium nitrate (NH₄NO₃) using plasma activated water (PAW). Nitrate ions (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>NO</mml:mi></mml:mrow><mml:mn>3</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math>) were generated via air plasma treatment, and ammonium ions (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>NH</mml:mi></mml:mrow><mml:mn>4</mml:mn><mml:mo>+</mml:mo></mml:msubsup></mml:math>) were introduced using low pressure ammonia (NH₃) plasma exposure to nitrate-rich PAW in frozen form to produce NH₄NO₃. Results demonstrated that process parameters, including NH₃ gas pressure, applied voltage, and treatment time, significantly influenced PAW properties, with NH₃ plasma treatment time showing the most substantial impact. Extending the treatment time from 0.5-1.5 hours increased <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>NH</mml:mi></mml:mrow><mml:mn>4</mml:mn><mml:mo>+</mml:mo></mml:msubsup></mml:math> ion concentration by 134.2%, achieving a maximum of 168.2 mg L^-¹ with an energy consumption of 74.8 mg <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>NH</mml:mi></mml:mrow><mml:mn>4</mml:mn><mml:mo>+</mml:mo></mml:msubsup></mml:math> ions kWh^-¹. The <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>NO</mml:mi></mml:mrow><mml:mn>3</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math> ion concentration reached 63.5 mg L^-¹ with an energy yield of 222 mg <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>NO</mml:mi></mml:mrow><mml:mn>3</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math> ions kWh^-¹. This method achieved a total yield of 27.6 mg NH₄NO₃ kWh^-¹ and produced a neutral to slightly basic PAW suitable for agricultural applications, offering a promising alternative to traditional NH₄NO₃ production processes.