Degradation of dyes using reactive species of atmospheric pressure dielectric barrier discharge formed by a pencil plasma jet

Abstract

The dye degradation efficacy of the cold plasma pencil jet is presented in the present investigation. Dye degradation studies were performed using air plasma, six different types of selected dyes (erythrosine, metanil yellow, sudan I, crystal violet, rhodamine B, and Indigo). The degradation of dyes is analyzed using UV visible spectroscopy, total organic carbon, and chemical oxygen demand. The results showed complete degradation of all types of dyes in UV visible analysis with minimum time for indigo (3 minutes) and maximum time for erythrosine (45 minutes). Moreover, erythrosine (k = 1.08 mg L-1 min-1), sudan I (k = 3.46 mg L-1 min-1), rhodamine B (k = 3.955 mg L-1 min-1), and Indigo (k = 18.915 mg L-1 min-1) follows approximate zeroth-order degradation kinetic, and metanil yellow (k = 0.094 min-1) and crystal violet (k = 0.25 min-1), closer to first-order degradation kinetics. Additionally, a substantial enhancement in mineralization and reduction in chemical oxygen demand of all the dyes occurs after plasma treatment. In this study, air plasma is produced in the cylindrical coaxial dielectric barrier discharge configuration. Electrical characterization of plasma is performed and the plasma species are identified using optical emission spectroscopy. The toxicity of plasma degraded dyes solutions toward freshwater algae species (Chlorella Sorokiniana and Chlorella Pyrenoidosa) are significantly low compared to virgin dyes solutions. The study reveals that pencil plasma jet substantially degrades dyes as well as converts the dyes solutions non-toxic.