Acidic-thermal coupled degradation of tylosin by using magnetic sulfonated resins under microwave irradiation

Acidic- and alkalic-hydrolyses are selective in breaking functional bonds and falling off pharmacological moieties of antibiotics in production wastewater in comparison with advanced oxidation processes. Elevating temperature can accelerate hydrolytic kinetics and improve efficiency. In this work, magnetic sulfonated polypropylene resin (Fe₃O₄@PS-S) composites were reported for acidic-thermal hydrolysis of tylosin by employing the acidic feature of sulfonic group, the dielectric effect of resin, and the magnetic-loss effect of magnetite under microwave irradiation. As observed, a rapid and complete mitigation 100 mg/L of tylosin was achieved within 15 min by the catalysts. Acidic cleavage of tylosin was fulfilled by sulfonic groups in the composites, and microwave thermal accelerated the hydrolysis reactions due to the dielectric and magnetic-loss effects. Differentiating the dielectric and magnetic-loss effects through electromagnetic analyses indicated that the latter contributed more in converting microwave energy to heat. The interactions under multiple operational conditions were quantitatively fitted using the Behnajady model and visually demonstrated, which indicated that a synergic effect of microwave thermal- and acidic-hydrolyses contributed to the efficient mitigation of tylosin. The transformation products were identified and the pathways were supposed. Cleaving deoxyaminosugars groups and destructing lactone structures led to reduced antibacterial potential and toxicity reduction. The acute toxicity of tylosin and transformation products to fish, daphnia, and green algae were all classified as non-toxic. This work suggested that this synergistic acid-thermal hydrolytic method is attractive and promising in pretreating tylosin production wastewater in field.