Efficient Degradation of Tetracycline by Peroxymonosulfate Activated with Ni-Co Bimetallic Oxide Derived from Bimetallic Oxalate

In this work, NiCo₂O₄ was synthesized from bimetallic oxalate and utilized as a heterogeneous catalyst to active peroxymonosulfate (PMS) for the degradation of tetracycline (TC). The degradation efficiency of TC (30 mg/L) in the NiCo₂O₄ + PMS system reached 92.4%, with NiCo₂O₄ exhibiting satisfactory reusability, stability, and applicability. Radical trapping test and electron paramagnetic resonance (EPR) results indicated that SO₄^•−, •OH, O₂^•−, and ¹O₂ were the dominating reactive oxygen species (ROS) for TC degradation in the NiCo₂O₄ + PMS system. Seven intermediates were identified, and their degradation pathways were proposed. Toxicity assessment using T.E.S.T software (its version is 5.1.1.0) revealed that the identified intermediates had lower toxicity compared to intact TC. A rice seed germination test further confirmed that the NiCo₂O₄ + PMS system effectively degraded TC into low-toxicity or non-toxic products. In conclusion, NiCo₂O₄ shows promise as a safe and efficient catalyst in advanced oxidation processes (AOPs) for the degradation of organic pollutants.