Degradation of tetracycline antibiotics by Fe²⁺-catalyzed percarbonate oxidation

Antibiotics improve the quality of human life but their intrusion into water matrices comes with adverse effects on natural bacterial communities that may result in the proliferation of antibiotic resistant bacteria and antibiotic resistance genes. Hence, antibiotic-laden wastewaters require adequate treatment prior to their release to the natural environment. Herein, we investigate the degradation of tetracycline (TC) antibiotics in aqueous solutions by ferrous ion-catalyzed oxidation in the presence of sodium percarbonate (SPC). Control experiments without Fe²⁺ but with SPC, and vice versa resulted in negligible TC removal. The effects of reactant dosing and solution pH on the extent and rate of TC removal were examined. Hydroxyl radicals were the dominant reactive oxygen species (ROS) identified from indirect ROS scavenging experiments and confirmed by electron paramagnetic resonance analysis. Treatment of actual wastewaters was simulated by adding chloride, nitrite, nitrate and ammonium ions to the water matrix at varying concentrations and their effects on TC removal were examined. Negligible impact on TC degradation was noted for N-species while chloride ion accelerated degradation kinetics and reached complete tetracycline abatement in 10 min. Residual chemical analysis showed continued Fe²⁺ consumption and H₂O₂ production even with complete tetracycline elimination. Experimental results showed complete abatement of 0.2 mM TC with k₁ of 9.3 × 10⁻² min⁻¹ and over 40% TOC removal in 45 min of treatment under optimized conditions of 0.5 mM of Fe²⁺, 0.75 mM SPC, at pH 3.0. The study showed the effectiveness of percarbonate oxidation as a tertiary treatment technology and the results can be used in designing treatment systems for wastewaters containing antibiotics and other pharmaceuticals.