Construction Of Iron-Containing Piezo-Fenton Nanosystems And Their Piezocatalytic Properties

With the progress of society,the productivity level of chemical industry is getting higher and higher,and the three industrial wastes have a huge impact on natural resources,taking the pollution of freshwater resources as an example,the dyestuffs and heavy metals in the wastewater of printing and dyeing industry and the antibiotics,hormones and anti-inflammatory drugs in the wastewater of pharmaceutical industry will have an impact on human health through the enrichment of food chain.Among the many advanced oxidation technologies(AOPs),Fenton oxidation technology has been widely used to treat environmental wastewater due to its simple equipment process and high mineralization capacity.Piezocatalysis as a new technology for AOPs has also attracted the interest of researchers in recent years.Rational design of the coupling of these two AOPs technologies(i.e.,Piezo-Fenton catalysis)can utilize the piezoelectric process to initiate/accelerate the Fenton cycle,which is expected to create a new environmental remediation tool with high energy efficiency and high pollutant treatment capacity.New piezocatalysts developed in recent years,such as MoS₂,MoSe₂,BN,Bi VO₄,Bi OCl and graphitic phase carbon nitride,are structurally different from conventional piezoelectric crystals,which do not have an asymmetric central structure,and the morphological dimensions have a significant influence on the piezoelectricity of these materials.The discovery of novel piezocatalysts and their mechanism of action plays an important role in expanding the application field of piezocatalysis,lowering the trigger threshold and designing process coupling for AOPs.In this thesis,Piezo-Fenton systems were constructed by introducing piezoelectricity(via nanosizing)into Bi₂Fe₄O₉ with Fenton-like capability and Fenton-like properties into graphite-phase carbon nitride(g-C₃N₄)with piezocatalytic capability,respectively,to achieve the reduction of heavy metal Cr(VI),the removal of pharmaceutical pollutant APAP and dye-based pollutant The Piezo-Fenton catalyzed antibacterial study was also carried out.The main research of this paper is as follows:(1)Piezoelectric catalytic activity of Bi₂Fe₄O₉ nanosheets and their Piezo-Fenton synergistic catalytic degradation of APAPBi₂Fe₄O₉ as a typical bismuth ferrite due to the high content of iron in its constituent elements allows it to undergo Fenton-like reaction with hydrogen peroxide like Fe₃O₄ and other iron oxides.We found that Bi₂Fe₄O₉ nanosheets(BFO-Ns)have the ability of piezoelectric catalysis and their piezocatalytic activity is strongly influenced by the material thickness,and micron-scale Bi₂Fe₄O₉ does not have piezoelectric effect(as predicted by crystal symmetry theory).We also found a mechanism of Piezo-Fenton catalyzed oxidation of BFO-Ns in the removal of organic pollutants based on their piezoelectric effect.Finally,we verified the specific reaction pathway of piezocatalytic activation of molecular oxygen by BFO-Ns and the occurrence of in situ Fenton-like reactions for the removal of pollutants by,among others,experimentally monitoring the key active species in the system.(2)Removal of methylene blue dye and sterilization by g-C₃N₄-Fe Piezo-Fenton systemThe ordered triangular pore structure in g-C₃N₄ enables it to exhibit a significant piezoelectric effect,and g-C₃N₄ has an excellent ability to activate molecular oxygen to produce hydrogen peroxide under the effect of ultrasonic irradiation.In this part of work,g-C₃N₄ containing different Fe-doping ratios was firstly prepared using a modified thermal condensation method,and it was determined by characterization and related experiments that Fe was doped into g-C₃N₄ in the form of Fe-N bonds.Secondly,the piezoelectric catalytic performance and mechanism of the catalysts were investigated by removing the simulated dye contaminant methylene blue,and the optimal conditions and optimal catalysts were found experimentally.The results of contamination removal kinetics were combined with the results of ESR,quencher experiments and determination of the hydrogen peroxide content of the system to propose and verify the mechanism of piezoelectric catalysis of the material under ultrasonic excitation in synergy with the Fenton reaction.Finally,the feature that the system can generate a large number of strong oxidative hydroxyl radicals is exploited to extend the application of the material from environmenta remediation to antibacterial field.The catalyst exhibits excellent performance in antimicrobial processes and shows potential as a carrier for in vivo antimicrobial therapies.