Sonocatalytic Degradation of Basic Blue 3 Using Plasma-treated Magnetite Nanostructures

Abstract

Background: Excessive consumption of synthetic dyes in various industrial processes leads to the production of a considerable amount of wastewater polluted with these chemicals. Therefore, the discharge of wastewater containing these chemicals with stable structures into natural streams reduces light penetration, and accordingly affects photosynthetic phenomena, and increases toxicity and chemical oxygen demand. Thus treatment of industry wastewater containing dyes prior to discharge is of paramount importance. In this study, the nanostructured magnetite, which treated using effective and cheap nitrogen plasma, was used as the iron source in sonocatalytic process to degrade Basic Blue 3 (BB3) dye in aqueous solutions. Methods: Magnetite particles placed in plasma rector under low pressure N2 atmosphere. DC high-voltage was applied on electrodes to generate glow discharge plasma. Then, the magnetite nanostructures were obtained and collected for using as catalyst in sonocatalytic reaction for decolorization of BB3 solution. Sonocatalytic experiments with PTM were carried out in a 250-mL erlenmeyer immersed into the ultrasonic batch. Typically, 100 mL BB3 solution with appropriate quantity of plasma-treated magnetite (PTM) was added to the erlenmeyer. Throughout the experiments, about 5 mL of the solution was withdrawn from the erlenmeyer at specific time intervals to determine concentration of BB3 in solutions by photometrically using UV–Vis spectrophotometer. Results: The results show that the BB3 degradation efficiency was 61%, and 98% at 90 min in the ultrasonic, and sonocatalytic reaction, respectively. The highest decolorization efficiency was achieved at an initial pH of 3 in the presence of 0.75 g/L PTM. Integrated gas chromatography–mass spectrometry showed five intermediate compounds that were identified with high match factor of mass spectrum. Conclusion: Plasma technique is an appropriate treatment method to decrease the size of natural magnetite, and to enhance the catalytic ability of this compound in the sonocatalytic process. The catalytic performance of PTM was dependent on the initial dye concentration, ultrasonic power density, pH, and catalyst dosage. The PTM dose, as predicts by ANN model with a relative importance of 31.08 %, appeared to be the most effective parameter in this process. Keywords: Iron oxide, nanostructure magnetite, non-thermal plasma, sonocatalytic process.