Effect of Argon in Nitrogen Gliding Arc Plasma for Ammonium Ions Enrichment in Water

Abstract

This work investigates the effect of Ar addition on N₂ gliding arc plasma to enhance ammonium ions concentration in water. The concentration of ammonium ion \(\left({\text{N}\text{H}}_{4}^{+}\right)\) increased by 50.2% when Ar gas was added upto 40% by volume to the N₂ gliding arc plasma, thus indicating the significant contribution of Ar in \({\text{N}\text{H}}_{4}^{+}\) synthesis. Adding 20% Ar in N₂ resulted in a maximum \({ \text{N}\text{H}}_{4}^{+}\) concentration of 16.5 ppm and a production rate of 1.31 mg hr^-1. While adding 40% Ar into N₂ plasma, the highest energy efficiency of 0.036 g-\({\text{N}\text{H}}_{4}^{+}\)KWh⁻¹was obtained with a specific energy input of 742.5 J/L. The mechanisms of \({ \text{N}\text{H}}_{4}^{+}\) enrichment with Ar addition were investigated by studying the electrical properties, vibrational, rotational and electron temperature of the gliding arc plasma with respect to the addition of Ar concentration in N₂ plasma. Results show that the addition of Ar raises the vibrational and electron temperatures, and decreases the rotational temperature of the gliding arc plasma. (As per the reviewer-2 suggestion, this line has been removed from the abstract). Particularly, the presence of 26.5% Ar by volume in N₂ plasma results in a significant ion current, which generates high ionization of \({\text{N}}_{2}^{+}\).