Structural Design Of Biochar Materials And Their Catalytic Degradation Of Ciprofloxacin By Persulfat

Ciprofloxacin（CIP）,as a quinolone antibiotic,has an important application in medical antibacterial and other aspects,but it is difficult to degrade,resulting in a large number of antibiotics remaining in the water,causing water pollution and endangering human health,so it is urgent to deal with antibiotics.Persulfate oxidation is a highly efficient treatment method that generates sulfate radicals(SO₄^·-)by activating peroxonosulfate（PMS）.Compared with·OH,SO₄^·-has a higher redox potential（2.5e V to 3.1 e V）,a longer half-life（30μs to 40μs）and a higher selectivity for electron transfer reaction.Common ways to activate PMS include heat,alkali,ultrasound,ultraviolet radiation,transition metals,and carbon materials.The activation of transition metal materials has the advantages of low energy consumption and no need to add additional chemicals,but the shortcomings of complex preparation steps and easy agglomeration and precipitation of transition metals restrict the development.The preparation of catalysts for activating PMS using carbon materials as disperse carriers can effectively solve the above problems.As a natural biomass material,wood has the advantages of wide sources,low cost,green sustainability,and a large number of pore structures and polar functional groups.Biomass can be transformed into biochar by simple pyrolysis.The evolved biochar belongs to hard carbon that is difficult to graphitize.The interior exhibits random stacking of microcrystalline graphite,and there are a large number of defect sites,such as broken and suspended bonds,unpaired electrons and oxidized carbon sites.Biochar has many active sites and is easy to modify,so it has great potential to catalyze the degradation of pollutants.This study is based on wood biomass to construct biochar based Fenton catalyst to enhance the degradation of ciprofloxacin.The main research contents are as follows:（1）A natural wood-derived catalyst composed of biochar and Fe/Co dual sites was designed to activate peroxonosulfate to enhance the degradation of ciprofloxacin.The prepared biochar has excellent electrical conductivity,high stability,a large number ofπelectrons,and has the dual role of catalyst and carrier.Bimetallic Fe/Co can be better dispersed on biochar by adjusting the functional groups on wood surface,and the biochar based material prepared still has rich pore structure.The removal rate of the catalyst for ciprofloxacin can reach 100%within 4 min,and the removal rate is still86.3%even after 5 consecutive cycles.The catalyst showed good degradation performance in the p H range of 2.0～8.0.Density functional theory（DFT）calculations revealed that Fe/Co sites supported by biochar have high adsorption energy,which can induce interfacial electron transfer and enhance O-O bond breakage.SO₄^·-,·OH and¹O₂ were the main active species,contributing 13.51%,17.54%and 68.95%to the degradation of ciprofloxacin,respectively.Simulation analysis showed that the by-products and intermediates degraded by ciprofloxacin had little toxicity.In this work,a structure design of biochar material to enhance the degradation of antibiotics was proposed,which created a new idea for the development of wastewater treatment technology.（2）Based on the above research,a preparation method of non-metallic biochar catalyst for ciprofloxacin degradation was proposed.Using Paulownia wood with more abundant pore structure as the research object,nitrogen-doped biochar catalyst（N-WC）was obtained by embedding nitrogen atoms into the carbon material with the introduction of melamine.N-WC was characterized by scanning electron microscopy,energy dispersion spectroscopy,X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy,and the effect of N-WC on PMS activation was studied.The results showed that 86.7%of ciprofloxacin was removed at a concentration of 20mg L^-1 and a PMS of 1.0 m M for 30 min.The quenching experiment and EPR test showed that non-free radical singlet oxygen played a major role in the degradation process of ciprofloxacin,while free radicals played a minor role.The intermediate products in the degradation process of ciprofloxacin were investigated by liquid chromatography-mass spectrometry（HPLC-MS）.Four possible degradation paths of ciprofloxacin were proposed.After 5 cycles of experiments,the removal rate of ciprofloxacin by the catalyst can still reach 75.4%.In this work,a preparation method of non-metallic biochar is proposed,which provides a new idea for the study of antibiotic degradation.