Comparative analysis of ozone-based processes for decolorization of Acid Green 25: experimental parameters and in silico eco-toxicity

Abstract

Dyes are widely used in industries such as textiles, leather, cosmetics, pharmaceuticals, and food. These complex organic molecules can be resistant to degradation and harm aquatic ecosystems by disrupting photosynthesis and increasing oxygen demand. Anthraquinone dyes, like Acid Green 25, are particularly harmful as they and their by-products are toxic or mutagenic. Effective treatment methods, such as Advanced Oxidation Processes, including photolysis and ozonation, are essential to removing color and reducing toxicity in wastewater. The objective of this work was to investigate and compare the Advanced Oxidation Processes O₃, O₃/UV, and O₃/Al₂O₃ in the decolorization and mineralization of the anionic anthraquinone dye Acid Green 25. The ozonation kinetics were studied, and a pseudo-first-order model was fitted to the experimental data. Complete decolorization was achieved within 10 min in all processes, with faster decolorization by O₃/UV under neutral and acidic conditions through direct reactions. On the other hand, the highest mineralization was achieved at pH 11, with O₃ (43%) and O₃/UV (50%) after 30 min. Since alumina adsorbed the dye, the adsorption kinetics were also studied, showing a better fit to the pseudo-second-order adsorption kinetic model based on experimental data, achieving a mineralization rate of 38%. To assess eco-toxicological impacts, an in silico evaluation was conducted using the OECD-QSAR Toolbox, analyzing Acid Green 25 molecule and its metabolites. Overall, the results suggest that the studied ozone-based processes can help reduce the environmental impact of wastewater contaminated with Acid Green 25.