Degradation Of 4-Chlorophenol And Copper Dissolution Properties And Mechanism Of Piezoelectric Catalyst MoS₂

The essence of piezoelectric catalysis technology is to exert a mechanical force on the piezoelectric material that can make it deform,so that the electrons and holes move to the two ends of the piezoelectric material respectively,forming a built-in electric field.Due to the built-in electric field,a large number of active oxides are produced,and then participate in various chemical reactions.At present,the mechanical forces that have been used by humans for piezoelectric catalysis include tides,vortex shear force,wind force,etc.,and ultrasound is the most widely used.In this study,molybdenum disulfide（MoS₂）piezoelectric catalysts were synthesized by hydrothermal and solvothermal methods,and the target pollutant 4-chlorophenol（4-CP）was selected to study the piezoelectricity of this material in the piezoelectric system of PMS.Electrocatalytic properties.In addition,since the ultrasonic vibration can generate a large amount of energy,these energy can peel off the copper attached to the circuit board into the solution.On the other hand,the ultrasonic process can also generate a certain amount of free radicals,which further attack the copper element,making the Copper dissolution.Therefore,this study also used MoS₂ as a catalyst to study the application of piezoelectric catalysis in the recycling of circuit board scrap copper.The main research contents are as follows:（1）Two kinds of piezoelectric catalysts with petal nanosphere morphology were synthesized by simple hydrothermal method and solvothermal method（MoS₂synthesized by hydrothermal method is denoted as MoS₂-H,and synthesized by solvothermal method is denoted as MoS₂-S）.The phase composition,morphological structure,element composition and chemical valence state of the two synthetic catalysts and commercial MoS₂（denoted as MoS₂-C）were characterized.4-CP was selected as the target characteristic pollutant to explore the piezoelectric catalytic performance of MoS₂.PMS could be directly activated by ultrasound to form·OH radicals.However,catalyst-assisted reactions dominated the entire PMS activation process.In MoS₂,both surface in-plane sulfur vacancies（V_S）and edge V_S were observed.Although in-plane V_S feature a stronger PMS adsorption energy compared with edge V_S（–1.64 vs./–0.94e V）,PMS activation is not favorable at the in-plane V_S sites of MoS₂.In piezo-polarized MoS₂,the separated charge carriers accumulate at the edges,where edge V_S,as the active site,strengthens the coupling between electrons and PMS.As a result,the O–O bond length in PMS is increased from 1.467 to 1.470（?）,enabling the facile activation of PMS with the generation of more abundant·OH and·SO₄^-radicals.Scanning electron microscopy（SEM）shows that the morphology of the catalysts synthesized by both methods is flower-like layered nanospheres.In addition,the results of radical quenching experiment and electron sequential resonance spectroscopy（EPR）test showed that there were two active oxides,hydroxyl radical（·OH）and sulfate radical（·SO₄^-）in the reaction system,and the hydroxyl radical（·OH）plays a major role in the whole chemical reaction system.（2）MoS₂ with nanoflower-like morphology was synthesized by a simple hydrothermal method using sodium molybdate dihydrate and thiourea as molybdenum and sulfur sources.The phase composition,morphological structure,element composition and chemical valence state of the catalyst and commercial MoS₂（denoted as Commercial MoS₂）were characterized.In this study,copper powder was used as the target substrate,MoS₂ was used as the catalyst,and the copper element was converted into copper ions under the action of ultrasound.The complex process of recycling is realized in the same catalytic material.The difference of the dissolved Cu²⁺was compared by weighing method and atomic absorption spectrometry.The concentration of Cu²⁺measured by atomic absorption spectrometry was 39.46 mg/L.At the same time,the concentration of Cu²⁺in the solution was determined by 2,9-dimethyl-1,10-phenanthroline spectrophotometry.In addition,the results of radical quenching experiment and electron sequential resonance spectroscopy（ESR）test showed that two reactive radicals,hydroxyl radical（·OH）and superoxide radical（·O₂^-）existed in the reaction system.