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This paper presents the degradation of the most widely used antibiotics for the treatment of tuberculosis, isoniazid (INH), by Fenton, photo-Fenton on bench-scale, and solar photo–Fenton on a pilot scale. The INH dosage in tuberculosis treatment varies according to disease stage, between 300–400 mg d-1patient-1, and its excretion range via urine is 50–70% within 24 h. The photodegradation processes were performed with 25 mg L-1 of INH, 10 mg of Fe2+, and 125 mg L–1 of H2O2 for 120 min. The degradation of INH was monitored by HPLC–DAD and dissolved organic carbon (DOC). The degradation by-products were analyzed by UPLC QToF-MS and the toxicity was evaluated by Daphnia magna (acute toxicity) and Lactuca sativa (phytotoxicity). INH removal was higher than 99% at 60 min for Fenton, 10 min for photo-Fenton, and 15 min for solar photo–Fenton. The DOC results indicated that under light irradiation (photo–Fenton and solar photo–Fenton), the mineralization rate was > 70%. The nitrite ion analysis indicated the complete oxidation of nitrogen. Besides the main INH degradation by-products, isonicotinic acid, isonicotinamide, and N'-(pyridyl-4-carbonyl)-hydrazide, we detected four unknown by-products by mass spectrometry. The Fenton treatment decreased the toxicity of D. magna by 75% in 15 minutes, achieving 87% in 60 minutes of treatment, while the photo–Fenton process conducted with artificial radiation reduced 87% of the toxicity of D. magna and resulted in no significant effect in L. sativa seeds in 15 minutes (QUV-A 1.29 kJ L-1). However, solar photo-Fenton (QUV-A 3.38 kJ L–1) did not reduce toxicity. |
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