Piezoelectric Catalytic Degradation And Performance Study Of Organic Pollutants Based On ZnO Nanocomposites

Piezoelectric catalysis is a new type of mechanical energy catalysis technology that opens up a new avenue for wastewater purification.Using the mechanical energy of nature（water,wind,ultrasound,etc.）to deform the piezoelectric material,the surface of the material forms a built-in electric field,which promotes the migration and separation of electron-hole pairs,resulting in a redox reaction and the generation of reactive oxygen species（ROS）to decompose pollutant molecules in water.In recent years,more and more stress-sensitive piezoelectric materials with two-or three-dimensional morphological structures have been studied and applied in the field of piezoelectric catalysis,zinc oxide（ZnO）is a potential and promising piezoelectric catalytic material for applications due to its economic,safe advantages.This thesis focuses on the preparation of two ZnO composite piezoelectric catalysts,their morphological and structural characterisation,and finally,the piezoelectric catalytic performance,and the catalytic degradation mechanism of pollutants in water are also investigated.The details of the study are as follows:（1）ZnO/GO nanocomposites were prepared by hydrothermal synthesis and a series of characterisations were carried out to analyse the morphology and structure of the composites.The piezoelectric catalytic degradation of organic dyes such as MB by the ZnO/GO composites was investigated under light-proof conditions,using ultrasound to simulate mechanical energy and organic pollutants as models with rhodamine B（Rh B）,methyl orange（MO）and methylene blue（MB）.It was found that the MB dyes were almost completely degraded after 20 min of ultrasonic vibration,with a degradation rate of up to 98%,and the reaction process corresponded to the basic primary kinetic model.The production of reactive oxygen radicals with strong oxidative properties,such as:superoxide radical（·O₂^-）and hydroxyl radical（·OH）,was confirmed by active species experiments.The composites were tested for antibacterial activity using E.coli cultures and the results showed good antibacterial properties.The piezoelectric catalytic degradation mechanism of ZnO/GO nanocomposites against organic pollutants was further investigated.（2）ZnO/CuO nanocomposites were prepared by an in situ synthesis method and characterised for composition,morphology and structure.Under light-protected conditions,magnetic stirring was used to simulate mechanical energy and Congo red（CR）,rhodamine B（Rh B）and methylene blue（MB）dyes were used as the main contaminant models.The piezoelectric catalytic degradation performance of the Zn/Cucomposites with different amounts of substances on the organic dyes was tested.The experimental results showed that the best degradation effect of up to 90%was achieved after 90 min of stirring when the Zn:Curatio was 1:1.Secondly,the free radical scavenging experiments and ESR characterization tests demonstrated that·O₂^-and·OH with strong oxidizing properties were generated in the piezoelectric catalysis.Antibacterial experiments were carried out against E.coli and S.aureus,and the results showed that the ZnO/CuO composites have good antibacterial properties.Finally,its piezoelectric catalytic degradation mechanism of dyes was also further investigated.In summary,this thesis synthesised and characterised ZnO composite piezoelectric materials and explored their piezoelectric catalytic degradation performance and mechanism in the degradation of dyes.The highly efficient piezoelectric catalytic activity highlights the potential of piezoelectric catalysts in the remediation of organically polluted wastewater and provides a new strategy for wastewater purification applications.