Impact of operating parameters on the electrooxidation of methylene blue and ciprofloxacin: a comprehensive analysis and degradation pathway

In recent decades, freshwater bodies have experienced significant stress due to the excessive disposal of dyes from textile industries and waste antibiotic discharges from pharmaceutical industries. The continuous disposal of these substances may harm the natural ecosystem and generate antibiotic resistance in living organisms. Conventional treatment facilities are inadequate in treating these contaminants effectively, leading to a focused interest in advanced technologies, such as electrooxidation. This study aimed to assess graphite sheet electrode’s efficacy in removing methylene blue (MB) dye and antibiotic ciprofloxacin (CIP) under different operating conditions, such as voltage (2.5, 5, and 7.5 V), initial concentration (5, 10, 25, and 50 ppm), pH (3, 6, and 9), and electrolyte (Na₂SO₄ and NaCl). The results indicated that 10 ppm MB and CIP could be removed by more than 99%, with pseudo-first-order reaction kinetics in 2 h. The degradation was more effective in the NaCl medium than in Na₂SO₄ due to the presence of highly active chlorine species_. The degradation by-products revealed successful degradation of MB and CIP molecules in both electrolytes yielding low m/z value by-products and the toxicity analysis via ECOSAR V2.2 reveals that the daughter products are not harmful. The operating cost of the system was between 0.05 and 0.07 $ m⁻³ for degradation in both electrolyte systems. These findings suggest that electrooxidation systems utilizing thin graphite sheet electrodes may be promising for dye and pharmaceutical wastewater treatment due to their effectiveness, versatility, and relatively low environmental impact.

Graphical Abstract