Sulfaquinoxaline oxidation by UV-C activated sodium persulfate: Degradation kinetics and toxicological evaluation

This study evaluates the efficiency of sulfate radicals used in advanced oxidation process in water treatment. The targeted pollutant is an antibiotic, sulfaquinoxaline (SQ-Na) sodium, widely used in the veterinary field. The results show a degradation of SQ-Na until 90% after 300 min of irradiation at optimal sodium persulfate (SPS) concentration (200 mg/L). Degradation of the antibiotic obeys a pseudo-first-order kinetics when the concentration of sulfate radicals ranging from 0 to 240 mg/L. The decomposition of SQ-Na via the UV/SPS method is favored significantly under acidic conditions but becomes slow at neutral pH and almost inhibited under alkaline conditions. The contribution of the sulfate radicals alone and of both radicals hydroxyl and sulfate on the SQ-Na degradation is evaluated at 69% and 80%, respectively. Toxicity tests with Sinapis alba and Daphnia magna on treated samples, before and after irradiation, indicate the formation of new by-products more toxic during the treatment process. Practitioner points: SQ-Na was significantly degraded (90%) under UV/SPS system. SQ-Na decay exhibited a pseudo-first-order kinetics. SQ-Na was completely degraded via UV/SPS process under acidic conditions. The shoot growth appears to be more sensitive to oxidation by-products toxicity than root growth. Ineffectiveness in eliminating the ecotoxicity.