Degradation Of Sulfamethoxazole By Activation Of Peracetic Acid With Biochar Supported Cobalt Ferrite

In recent years,emerging micro-pollutant has become a serious problem in water treatment processes.The abuse of antibiotics increases the content of residual antibiotics in water,leading a negative effect on the ecosystem.Sulfamethoxazole（SMX）is a typical antibiotic that is often detected in surface water.Therefore,we hope to develop more advanced water treatment processes to eliminate SMX antibiotic in the aquatic environment.Advanced oxidation process（AOPs）can efficiently remove refractory organic matter from water by in-situ production of highly active substances.A new oxidant,peracetic acid（PAA,CH₃C（=O）OOH）,is characterized by high oxidation potential and clean degradation products.More and more people focused research on PAA based AOPs and used external energy or catalysts to activate PAA to generate reactive species.At the same time,the transformation of biomass into efficient carbon-based materials is beneficial to resource conservation and utilization,causing extensive research interest.Biochar（BC）has the advantages of cheap and easy to obtain,high thermal and chemical stability,adjustable specific surface area and abundant functional groups,and BC is a natural low-cost carrier.In this work,a novel magnetic catalyst（CoFe₂O₄@BC）was developed by using alkaline lignin,the dominant by-products of papermaking industry,as feedstock for biochar.More importantly,PAA was successfully activated by CoFe₂O₄@BC nanoparticles for SMX elimination.The degradation effect and reaction mechanism of CoFe₂O₄@BC/PAA system were analyzed SMX degradation experiments and various characterization methods,which provides the basis for sulfa antibiotic wastewater treatment project.（1）Degradation of SMX by CoFe₂O₄@BC/PAA system.The experiment adopted hydrothermal synthesis way to prepare CoFe₂O₄and CoFe₂O₄@BC catalysts,and a series of degradation experiments were carried out to analyze the catalytic activity of catalytic materials Degradation experiments of SMX showed that CoFe₂O₄@BC could remove 95.8%of SMX in 60 min at neutral p H,which was better than CoFe₂O₄monomer.The degradation process was strongly p H-dependent,the extremely acidic or alkaline conditions greatly decreased the degradation efficiency.The addition of HA and HCO₃^-caused an inhibitory effect on degradation,while the Cl^-had a little impact.（2）Study on degradation mechanism of SMX.We used electron paramagnetic resonance（EPR）and quenching tests to confirm that acetyl-peroxyl radicals（CH₃C（O）O^·and CH₃C（O）OO^·）were the main active radicals for SMX removal.X-ray photoelectron spectroscopy（XPS）analysis further illustrated that cobalt ions of CoFe₂O₄@BC were the main active components for PAA activation,while iron ions had little impact.The degradation products of SMX were analyzed by HPLC-MS.Seven intermediates were detected and three possible transformation pathways of SMX were proposed,which mainly involved the hydroxylation of SMX benzene ring amino group,the breaking of S-N bond and hydroxylation reaction.（3）Comparison of the stability of CoFe₂O₄@BC and CoFe₂O₄.The catalytic activity of CoFe₂O₄@BC and CoFe₂O₄nanomaterials in five successive degradation cycles were compared by cyclic experiments.Obviously,CoFe₂O₄@BC has a more stable catalytic activity than CoFe₂O₄during the reuse processes.After the fourth cycle test,the catalytic activity of CoFe₂O₄@BC was still 88.7%,while the catalytic activity of CoFe₂O₄was only27.1%.And we also detected the metal leakage of CoFe₂O₄@BC and CoFe₂O₄,both of which meet emission standards.In comparison,the leaching of Co and Fe in CoFe₂O₄@BC/PAA system is less,reducing environmental burden.On the whole,CoFe₂O₄@BC composite improves the catalytic performance of cobalt ferrite.The research also proves that CoFe₂O₄@BC is a kind of high efficiency,stable and excellent magnetic separation material,which can be widely used to treat all kinds of organic wastewater.