Antibiotics (ABX) residues occur frequently in milk, causing considerable wastage of medicated milk and serious economic losses, and making the issue a burden for the dairy industry. Improper disposal of medicated milk harms dairy production, animal welfare, and the environment. This work studies the use of ozonation in a vortex reactor for removing ceftiofur hydrochloride (CEF), sulfamonomethoxine sodium (SMM), marbofloxacin (MAR) and oxytetracycline (OTC) from milk. In terms of residual concentration, O3 efficiency and the degradation kinetics of the various O3-involving processes in the vortex reactor, ABX removal via ozonation is better using stronger vortexing, which induces hydrodynamic cavitation. CEF undergoes the fastest degradation, followed by SMM, MAR, and OTC. High ABX hydrophobicity favors ABX degradation via ozonation, O3/H2O2, and O3/Na2S2O8. ABX oxidation by •OH at the O3 gas-bubble/milk interface is the principle degradation pathway, except for MAR. ABX degradation follows pseudo-first-order kinetics and is affected by initial ABX concentration, O3 concentration/flow rate, reaction temperature, and milk components to varying degrees. Under optimal ozonation conditions, ABX residues meet the maximum limits as set by the European Commission and no antimicrobial activity was observed. The decontaminated milk was therefore suggested to be reused as calf food, animal feed, organic fertilizer, etc.
Keywords: Hydrodynamic cavitation; Milk; Ozonation; Removal of antibiotics; Toxicity; Vortex reactor.
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