Effect on discoloration by nonthermal plasma in dissolved textile dyes: Acid black 194

In this work, we show that cold plasma (electrical discharge) acting on the liquid–atmosphere interface can change some macroscopic and microscopic parameters of wastewater with dissolved dyes, a process characterized by the study of physical and chemical variables, such as the voltage and current of the electrical discharge, temperature, volume, absorbance, electrical conductivity, pH, chemical oxygen demand (COD), and total organic carbon (TOC). The dye used is Acid Black 194 (AB194) in a water solution (250 mL) with a concentration of 0.1 mM and the addition of FeSO4 at 1.0 mM. The initial values of pH and electrical conductivity were 2.54 and 1.55 mS/cm, respectively, at a temperature of 21.5°C. Nonthermal plasma was generated with a DC power supply at a potential of 700 V and 133 mA, which was maintained throughout the process, until an exposure time of 45 min. This physicochemical method is environmentally friendly because it does not generate polluting waste.

Keywords: degradation, cold plasmas, textile dyes.