Preparation Of Mn_xO_y Loaded Bimetal Composites And Their Removal To Typical PPCPs In Water

Fluoroquinolone antibiotics（FQs）and sulfonamide antibiotics（SAs）are difficult to be biodegraded due to their complex structures,resulting in their residues and by-products lingering in the environment for a long time and also entering surface water with various wastewaters,posing a serious threat to human health.Fenton/Fenton-like oxidation and peroxy monosulfate oxidation are considered as two effective,simple and practical technologies for the treatment of FQs and SAs,with the advantages of effective degradation of recalcitrant organics,fast reaction rate and high stability.Fe-based amorphous alloys have been considered as effective catalysts for the removal of organic pollutants due to their excellent soft magnetic properties,the unique structure of non-equilibrium metastable state,good corrosion resistance and superior oxidation properties.However,the high degree of aggregation,easy oxidation by air and metal leaching leading to the unavailability of some active sites and the reduction in catalytic activity have seriously limited the wide application of Fe-based amorphous alloys in wastewater treatment.These defects can be well overcome by immobilizing Fe-based amorphous alloys on structural and functional scaffolds.Layered double hydroxides（LDHs）have attracted widespread attention in the field of environmental remediation processes due to their stable layered structure,sufficient surface active sites and environmental friendliness.The performance and stability of LDHs and their composites synthesized by goal-oriented synthesis strategy can be significantly improved,so as to give full play to the advantages of LDHs materials.In this thesis,two bimetallic composites with excellent catalytic properties were synthesized using functionalized manganese oxides（Mn_xO_y）as the substrate materials,and two kinds of PPCPs,fluoroquinolones and sulfonamides,were used as the target pollutants to explore the comprehensive application capabilities of the prepared catalysts in terms of physicochemical properties,catalytic performances,reusability,stability and practical application potential.The main research contents of this thesis were as follows.（1）Iron-based amorphous alloy（FeNiB）supported on Tannin-functionalized Mn₃O₄（Mn₃O₄-TA@FeNiB）were prepared by chemical reduction method and used as a heterogeneous catalyst to degrade ciprofloxacin（CIP）and norfloxacin（NOR）in aqueous solution by the ultrasound（US）-assisted Fenton-like process.The physicochemical properties of the resulting Mn₃O₄-TA@FeNiB were characterized by SEM,TEM,XRD,BET,FTIR,XPS and other techniques.The results showed that92.04%and 90.34%of CIP and NOR at their initial concentration of 10 mg L^-1 were removed by the sono-Fenton-like system after 60 min in comparison with 85.24%and82.52%of CIP and NOR removal after 300 min by Mn₃O₄-TA@FeNiB alone and the rate constants of the former were 6.65 and 6.80 times higher than those of the latter,respectively.Excellent catalytic performances were benefited from synergistic interactions between US,H₂O₂ and Mn₃O₄-TA@FeNiB.Mn₃O₄-TA as a support and stabilizer could effectively load and disperse FeNiB,meanwhile providing reactive area and active sites(Mn²⁺/Mn³⁺).FeNiB was corroded to produce Fe²⁺and Ni²⁺,thus forming reversible redox reactions between polyvalent metals,which ensured Fenton-like reaction to be effectively proceeded.While US accelerated the oxidation process to generate more reactive species,which resulted in higher catalytic efficiencies and reaction rates of CIP and NOR degradation.Metal leaching and cycling experiments showed that Mn₃O₄-TA@FeNiB exhibited good stability and reusability.Finally,the degradation intermediates of CIP were analyzed and the possible degradation mechanisms and pathways were proposed.These results indicated that Mn₃O₄-TA@FeNiB had great potential as an effective and low-cost catalyst in US-assisted Fenton-like process for removal of the emerging pollutants.（2）Environmentally friendly composite catalysts（MnO₂@CS-CaCo LDHs）with chitosan functionalized sea urchin-like MnO₂ loaded with CaCo layered double hydroxides were prepared by a simple hydrothermal method,and the physicochemical properties such as surface morphology,crystalline structure,elemental composition and chemical valence of the catalysts were analyzed by various characterization methods,and their activation by peroxymonosulfate（PMS）was used to degrade CIP,NOR and sulfamethoxazole（SMX）to test their catalytic performance and practical application capability.Sea urchin-like MnO₂ modified by CS created a unique interface with multiple reactive groups for the loading of CaCo LDHs,and it could be observed that the MnO₂ particles were uniformly attached to the surface of CaCo LDHs while exhibiting the unique structural features of both.The experimental results showed that the MnO₂@CS-CaCo LDHs composites had more excellent catalytic properties compared with monomeric MnO₂,MnO₂@CS and CaCo LDHs,and the enhanced catalytic properties were mainly due to the synergistic effects between LDHs and MnO₂promoted by the layer-like structure of LDHs.The removal efficiency of the composite material under the optimal experimental conditions was as high as 96.45%and 96.58%for CIP and NOR,respectively,in only 20 min,and 93.12%for SMX in 30 min.The quenching experiments demonstrated that ¹O₂ was the main active species for the catalytic degradation of the three PPCPs.Moreover,the degradation rate of NOR was still as high as 93.78%after the 10th cycle of degradation experiments,indicating that the composite catalysts had excellent reproducibility and stability.Therefore,this study will provide reference ideas,basic theoretical data as well as technical support for the design and synthesis of environmentally functional layered catalysts and their application in the water treatment containing PPCPs.