Plasma-Treated Soybean Dregs Solution With Various Gas Mixtures

Plasma technology has already been applied to agronomy recently. To increase the nitrogen use efficiency (NUE) of fertilizers, plasma-activated organic fertilizer (PAOF) has become a potential alternative to traditional ones. In this study, soybean dreg solution was treated by atmospheric pressure plasma jet (APPJ) directly via various feeding gas. The effect of argon plasma with the addition of nitrogen or air was investigated. The dominant reactive nitrogen species (RNSs), such as nitrite, nitrate, and ammonium, were measured. The results showed the greatest NO $_{2}^{-}$ and NO $_{3}^{-}$ concentrations of the solution after argon and air plasma treatments. Furthermore, the pH of the solution ranged from 7.8 to 9.0 after plasma treatment, which is beneficial to plant growth. The higher electrical conductivity (EC) revealed excellent performance in the degradation of soybean dregs. The aromatic residues could be observed by the UV-vis spectrum. The abundant ion concentration and suitable pH value were the advantages of plasma-activated soybean dregs solution, making it a prospective candidate in agriculture fields.