Research Of Carbon-based Metal Nanocatalysts For Activation Of PMS To Remove Tetracycline In Water

Although the development of science and technology has provided great convenience to human life,it has also caused a lot of pollution to the environment.Meanwhile,water pollution control and remediation are particularly important due to the increasing scarcity of water resources.Advanced oxidation processes（AOPs）have become one of the most widely studied water treatment methods in recent years due to their environmental friendliness,ease of operation,low cost and high efficiency.A typical reaction process of AOPs is to use transition metals as initiators to activate peroxymonosulfate（PMS）to generate free radicals to attack the target pollutant,degrading it into low toxic/harmless small molecule compounds or even completely mineralizing it into inorganic substances such as CO₂ and H₂O.Antibiotics are one of the pollutants in the category of pharmaceuticals and personal care products（PPCPs）,among them tetracyclines（TCs）have been used in large quantities,which have been frequently detected in various water environments,so it has received great attention in recent years because of the environmental hazards associated with its heavy use and emissions.Therefore,this thesis focused on the problem of organic pollutants in water bodies and combined the demand for green materials for water pollution control and remediation to synthesize a series of carbon-based nanocatalysts using solid wastes such as mangosteen shells and waste masks as porous carbon source precursors.Scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,elemental analysis（EDS）,BET specific surface area,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,X-ray photoelectron spectroscopy（XPS）and other technologies were used to analyze the physical and chemical properties of the as-synthesized materials.AOPs were constructed to remove tetracycline（TC）in water through the activation of PMS by carbon-based metal nanocatalysts.The catalytic performances,degradation mechanisms and practical application potential of the resulting oxidation systems were investigated from the aspects of environmental parameter control,active oxygen species identification and intermediate product determination.The carbons derived from solid waste as good carrier of metal oxides to synthesize porous carbon-loaded metal catalysts with high added value could not only change"waste"into"treasure",but also treat"waste"with"waste",which would realize the dual purposes of solid waste recycling and water pollution control and treatment.The main contents of this thesis were as follows:1.The mangosteen shells-derived biochar（BC）was functionalized with polypyrrole and used as a carbon-based support for ZIF67 to prepare BC-PPy@ZIF67nanocomposites.Then the thermal decomposition of the resulting BC-PPy@ZIF67 to produce N-doped BC loaded Co₃O₄（N-BC@Co₃O₄）.Two kinds of composites were characterized and used as catalysts to activate PMS for TC degradation with the assistance of ultrasound（US）.The results showed that the BC-PPy with large surface area and N-containing functional groups could effectively immobilize ZIF67,thus greatly decreasing the leaching of Co ions.Compared with BC-PPy@ZIF67,the as-synthesized N-BC@Co₃O₄ not only exhibited higher removal efficiency and faster reaction rate for TC degradation,but also possessed better stability and wider p H applicability,which derived from the synergistic effects between N-BC@Co₃O₄,PMS and US.2.To further obtain the rapid and efficient degradation of TC,waste medical masks were functionalized with PPy as N-doped carbon source precursor to support LaFeO₃to form NC@LaFeO₃ composite,which was used as an efficient catalyst for PMS activation to remove TC in water.XRD pattern showed that graphene-like structure was observed after carbonization.The experimental parameters were optimized by changing the catalyst dosage,PMS concentration and initial TC concentration,and the results showed that the NC@LaFeO₃/PMS system achieved 99.9%of TC removal in only 20min.In addition,NC@LaFeO₃ showed good reuse performance.The intermediates were detected by LC-MS and UV-Vis spectra of TC solution along with reaction time were performed with combination of XPS analysis of the recovered catalyst and identification of active oxygen species,the possible reaction mechanisms and degradation paths of TC by NC@LaFeO₃/PMS system were proposed.3.On the basis of NC@LaFeO₃,the N/S co-doped carbon-based support was prepared by using thioacetamide（TAA）as the N/S source to anchor the Co-doped LaFeO₃ to synthesize NSC@LaFe_xCo_1-xO₃ composite catalyst.The results showed that NSC@LaFeO₃/PMS system exhibited excellent catalytic capability,and the catalytic performances were significantly enhanced after doping a small amount of Co.The environmental parameters affecting the catalytic performances,were systematically analyzed.The influence of inorganic anions on the TC degradation process was also investigated,and the stability and reusability of the as-prepared NSC@LaFe_0.95Co_0.05O₃were evaluated through several repeated cycles.The possible catalytic mechanisms and degradation pathways of TC by NSC@LaFe_0.95Co_0.05O₃/PMS system were proposed by identifying active oxygen species and intermediate products in the system.