Application of Natural Zeolite as Catalyst in the Degradation of the Azo Dye DO39 by Plasma

The discharge of industrial wastewater with dyes into natural tributaries has serious environmental consequences on aquatic ecosystems and the health of living beings. Atmospheric plasmas have proven to be very useful for the degradation of organic contaminants in water; in this context, corona type discharge, owing to its physical characteristics, is capable of degrading and even mineralizing dyes dissolved in water. In this work, zeolite was used as a catalyst in the degradation of the textile azo dye Direct Orange 39 (DO39) through interaction with plasma generated at atmospheric pressure. The zeolite was characterized by microscopic analysis, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). Microscopic analysis was carried out to determine the roughness and grain size of the zeolite, and scanning electron microscopy and energy-dispersive spectroscopy were carried out to understand the morphology and chemical composition of this material, respectively. The initial concentrations were 1.0 mM for the dye and 4.0 g/L for zeolite, in an initial volume of 250 mL. The results indicate that the coloration of the samples was reduced depending on the treatment time, which was verified by the absorption spectrum in the UV/vis range. The mineralization of the dye after 120 min, using zeolite, was 95%. In addition, the removal percentages in relation to chemical oxygen demand were greater than 96%. Notably the zeolite did not undergo chemical changes during its use as a catalyst in the plasma treatment.