The discharge of metal-complex dyes from textile industries poses significant environmental challenges due to their chemical stability and resistance to conventional biological treatment. This study examined the degradation of Acid Black 194 (AB–194), a 1:2 chromium-complex azo dye, using Co2+-activated peroxymonosulfate (PMS). A central composite design based on response surface methodology was used to evaluate the effects of Co2+ (5.93–20.07 µM), PMS (1.67–7.33 mM), and dye (13.79–56.21 mg L−1) concentrations on decolorization and mineralization. The polynomial models demonstrated strong predictive accuracy (R2 > 0.9896), identifying Co2+ and dye concentrations as the most influential factors. Under optimal conditions (18.0 µM Co2+, 6.5 mM PMS, 20.0 mg L−1 dye), 99.19% decolorization was achieved at 30 min and 41.43% TOC removal at 240 min. Degradation kinetics were described by a mechanistic model incorporating 15 elementary reactions that comprise the Co2+/Co3+ redox cycle, radical generation, and dye oxidation, yielding a global R2 of 0.9617. Estimated rate constants for dye oxidation (k14 = 3.52 × 109 M–1 s–1 for and k15 = 2.00 × 1010 M–1 s–1 ) were consistent with values reported for aromatic compounds in sulfate radical systems. Radical contribution analysis confirmed sulfate radicals as the principal oxidizing species, accounting for 96.75% of the overall process.
Cardona-Castaño et al. (Fri,) studied this question.