Study On The Removal Of Tetracycline Antibiotics From Water By Modified Biochar-activated Persulfate

Tetracycline antibiotics,which have a wide spectrum of antibacterial activity and are inexpensive,are widely used in animal husbandry and human medicine,and the environmental pollution caused by their massive use poses a threat to human health and ecological safety.Due to the limited effect of conventional water treatment processes,the study of advanced oxidation technology for the removal of hard-to-degrade organic pollutants in water by peroxynitrite activation has attracted attention in recent years.Biochar overcomes the limitations of high energy consumption and other disadvantages of traditional activation methods,and gradually becomes a research hotspot in the field of activated peroxynitrite as a low-cost and environment-friendly catalytic material.In this paper,we successfully prepared BBC and Cu Fe₂O₄@BC by modifying biochar with two methods:doping with non-metallic heteroatomic boron and loading with spinel-type ferrite Cu Fe₂O₄,and studied the effectiveness of activated peroxodisulfate（PDS）of BBC and Cu Fe₂O₄@BC in degrading oxytetracycline（OTC）and tetracycline（TC）,respectively,using two typical tetracycline antibiotics in water as the target pollutants.A series of single-factor experiments were conducted to investigate the effects of PDS concentration,initial TC concentration,catalyst dosage and p H on the degradation effect of the activated system,to analyze the activation mechanism of the reaction and to explore the degradation pathways of the pollutants.The main research results are as follows.（1）Boron-doped peanut shell biochar（BBC）was successfully prepared and used for the activation of PDS for the degradation of OTC in water.characterization analysis of the morphological characteristics and other properties of the material proved the successful doping of boron.A controlled experimental study of PDS activation with BBC prepared with different doping ratios showed that BBC-2 was the best activation material,removing 93.8%of OTC at 120 min,which was 52.5%higher than the removal rate of pristine BC+PDS,with the fastest reaction rate of BBC-2+PDS.A series of single-factor experimental studies obtained the optimal reaction conditions for the degradation of OTC by BBC-2+PDS reaction system:OTC=20mg/L,catalyst dosage of 0.3g/L,PDS=2m M,p H=7.The wide p H range means that BBC has some prospects for practical water applications.The activation mechanism of the system was analyzed by combining free radical quenching experiments and EPR tests,including free radical pathways(SO₄^·-,·OH)and non-free radical pathways（¹O₂）.The doping of boron led to the generation of more active sites such as surface functional groups,sp² hybridized carbon and defective structures in the modified biochar,which activated the O-O bond in PDS to generate active species,and each of these active species plays an important role in the activation of PDS by BBC for OTC degradation.The common anion Cl^-in the water slightly promoted the removal of OTC by BBC-activated PDS,H₂PO₄^-had almost no effect,and HCO₃^-played a certain inhibitory role.The total organic carbon analysis showed that the activation system was not completely mineralized for the degradation of OTC.The degradation intermediates of OTC were analyzed by LC-MS,and two possible degradation pathways of OTC were inferred;BBC-2 showed good reusability in the recycling experiments.（2）Cu Fe₂O₄@BC was successfully prepared by sol-gel method and used to activate PDS for the degradation of TC in water.the analysis of Cu Fe₂O₄@BC morphological features,crystal structure and the properties of the contained surface functional groups by different characterization methods showed the successful loading of Cu Fe₂O₄.Under different activation systems,the activation effect of Cu Fe₂O₄@BC+PDS system was the best,and the TC removal rate reached93.3%within 120 min.The degradation rate and reaction rate of the modified biochar material for TC were greatly increased.The optimal reaction conditions of Cu Fe₂O₄@BC+PDS system were obtained by single-factor experiments:TC=30mg/L,catalyst dosage of 0.1g/L,PDS=10m M,p H=5.The combination of free radical quenching experiments and EPR tests showed that the degradation of TC was caused by the combination of free radical and non-free radical pathways,and the interconversion of Cu and Fe valence states.The activation of PDS through electron transfer generates more SO₄^·-with·OH,while the generation of non-radical pathway ¹O₂ may be the involvement of O₂^·-.Among common inorganic anions,Cl^-had almost no effect on the removal of TC from the activated system,while HCO₃^-and H₂PO₄^-played a slightly inhibitory role;the total organic carbon analysis of the solution showed that the mineralization of TC was much lower than the degradation rate,and two possible degradation pathways of TC were inferred from the degradation intermediates analysis of TC by LC-MS;the cycling experiments verified that Cu Fe₂O₄@BC possesses good reusability performance.In summary,both modified biochar synthesized from peanut shells in this study can activate peroxynitrite efficiently and degrade tetracycline antibiotics commonly found in water well,effectively utilizing waste biomass resources,broadening the application research in the field of advanced oxidation of activated peroxynitrite by modified biochar,and also providing a new strategy for the treatment of tetracycline pollution.