Behavioral Mechanism Of Co（OH）₂ Derived Iron-doped Co-ZIF Activated Peroxymonosulfate For Removal Of Tetracycline From Water

Tetracycline（TC）has become one of the most widely used antibiotics in the world due to its broad-spectrum antibacterial properties,low cost,and good water solubility.Typically,TCs are used to treat human,animal,and plant diseases.However,tetracycline antibiotics used to treat human and animal diseases cannot be completely consumed by the body and will be transported into water bodies and soils through excrement.Improper disposal often leads to environmental damage.At present,the treatment of antibiotic wastewater by advanced oxidation technology based on peroxymonosulfate（PMS）has become a research hotspot,but the active substances such as SO₄^·-and·OH are relatively limited.Therefore,this study explored a catalyst material derived from insoluble solids to efficiently activate PMS and used it for the oxidative removal of TC from wastewater.The exploration of metal-organic frameworks（MOFs）materials derived from insoluble hydroxides has attracted much attention in recent years.Herein,Fe-doped cobalt zeolitic imidazolate framework(Co-ZIF-（Fe）_x,x meant the different adding amounts of Fe³⁺)were successfully synthesized by using radical cobalt layered double hydroxide（Ca（OH）₂）as a cobalt ion source.Through field emission scanning electron microscopy（SEM）,X-ray diffraction（XRD）,nitrogen adsorption and desorption（BET）,Fourier transform infrared spectroscopy（FT-IR）,X-ray electron spectroscopy（XPS）,Zeta potential Tests and inductively coupled plasma mass spectrometry（ICP-MS）demonstrated the successful synthesis of Co-ZIF-（Fe）_xseries materials.Remarkably,the Co-ZIF-（Fe）_0.5demonstrated the highest catalytic activity that the removal efficiency of TC could reach up to 96.71%within 5 min,which was 1.136times higher than Co-ZIF.The Co-ZIF-（Fe）_0.5have a larger surface area(268.97m²·g^-1)and pore volume(0.25 cm³·g^-1),which can be contributed to a large number of accessible active sites.Compared with the precursor Co（OH）₂,the specific surface area was increased by 12.5 times.The catalytic performance of the samples was evaluated by activating PMS to degrade TC in an aqueous solution.Different TC concentration gradients were set in the experiment,and the removal efficiency increased with the decrease of the concentration,that is to say,the Co-ZIF-（Fe）_0.5/PMS system was more favorable for the removal of low-concentration antibiotics in actual water.In addition,studies have shown that the system has an excellent effect on different practical wastewaters（medical wastewater,river water,and tap water）and is highly reusable.It can be inferred that this sample will have a good prospect in the actual water treatment process.Two possible TC degradation pathways were proposed based on seven intermediates.According to the classical radical-quenching test and electron paramagnetic resonance（EPR）characterization,manifested that the degradation of TC was accomplished by the free radical(SO₄^·-)and the non-radical（¹O₂）pathways.Moreover,the Co-ZIF-（Fe）_0.5/PMS system exhibited high activity in a wide p H range（4-10）and was less influenced by organic and inorganic ions.Therefore,this study can provide a reference for the preparation of MOF-based catalysts for tetracycline-based wastewater treatment.