Solar activation of persulfate for simultaneous degradation of antibiotic drug and edible dye in a thin-layer flow photo-reactor

Antibiotics are largely used in human and veterinary medicine, and aquaculture to control diseases. These drugs are often produced with edible dyes to distinguish them by color. The present investigation explores solar activation of persulfate (PS) in a homogeneous process for the simultaneous degradation of oxytetracycline (OTC) and erythrosine-B (ERY), an edible dye, employing a newly designed solar photo-reactor. Under mild operating conditions of neutral pH, PS concentration of 180 mg/L, and degradation time of about 70 min, 72.4% and 82.1% degradation efficiencies were achieved for OTC and ERY pollutants, respectively. The efficiencies improved to 82.1% and 92.5% by the addition of 1.5 mg/L ferrous ion. Meanwhile, the effects of the major water matrix coexisting cations and anions were investigated, and the contribution of reactive oxidizing agents was determined via scavenging. The intermediates were identified, and the corresponding degradation pathways were introduced from the results of liquid chromatography-mass spectrometry (LC–MS) analysis. Further, the toxicity of solutions was evaluated via antibiogram test as well as the Virtual Evaluation Global Architecture (VEGA) software, totally revealing low levels of toxicity after treatment. The findings from the Solar/PS/Fe 2+ process highlight an environmentally friendly method in the treatment of pharmaceutical wastewaters and of other relevant sectors.