Effect of ascorbic acid to improve the catalytic performance of metallurgical copper slag in the photo-Fenton type process for hydroxyl radical production applied to the degradation of antibiotics

This study proposes an efficient strategy for enhancing metallurgical copper slag (CS) performance, which has photodegradation properties for a photo-Fenton-like reaction. The addition of ascorbic acid in the reaction promotes the Fe(III)/Fe(II) redox cycle on the surface of copper slag due to its reducing and chelating properties, which help to produce Fe(II) species and avoid iron precipitation as hydroxides. Generally, in the reaction process, the values of salicylic acid (SA) degradation, H2O2 decomposition, and •OH production increase as ascorbic acid (AA) increases. At the same time, the iron leaching remains below 1 mg/L. The system with the best result is CS0.100/AA0.150/H2O2, where the percentage of SA degradation, •OH production, and H2O2 degradation present twelve, thirty, and sixteen times more than that using the CS alone with H2O2, respectively. Also, the reusability experiments of CS in the CS0.100/AA0.150/H2O2 system suggest their outstanding chemical stability. The CS0.100/AA0.100/H2O2 system was used to degrade two antibiotics of the quinolones group, extensively used in respiratory diseases as a practical example of an application. The optimal system to photodegrade levofloxacin and ciprofloxacin was CS0.100/AA0.100/H2O2, where the AA addition significantly affected the degradation speed of the levofloxacin than in the ciprofloxacin. It reaches 98.8 ± 0.4% of levofloxacin degradation at 60 min of reaction and 94.6 ± 1.2% for ciprofloxacin, with mineralization efficiencies higher than 60% and, in the reusability experiments, the percentage of antibiotics degradation stayed above 90%.