Regulation Of Metal Oxide Charge Distribution And The Catalytic Degradation Mechanism For Waste Water

The refractory poisonous organic pollutants pose a serious threat to the safety of the water environment due to their strong toxicity.Advanced oxidation processes（AOPs）have obvious advantages in the degradation of toxic organic pollutants due to its small selectivity,strong oxidation ability,and high processing efficiency.The core of AOPs research is that using of catalysts can accelerate the occurrence of redox processes.Due to the abundant reserves,economic availability,safety and high efficiency,metal oxide catalysts are widely used in AOPs.However,there are some problems such as low charge utilization efficiency,slow electron transfer rate,few active sites,and easy dissolution of metal ions in the catalytic process.Thus,the purpose of this subject is to build an efficient and stable metal oxide catalyst.The control of crystal defects,the addition of surfactants,the construction of heterojunctions,differentiated metal coordination and combination were used to control the electron distribution and optimizes the internal arrangement of electrons,builds a built-in electric field,promotes the occurrence of electron transfer,and improves the efficiency of charge utilization,making it adaptable to a variety of AOPs.The main research contents are as follows:（1）A series ofα-Fe₂O₃ catalysts with different oxygen vacancies（V_O）were orientedly constructed by using MIL-53（Fe）,Fe Cl₂?6H₂O,and commercial-grade Fe₂O₃ as precursors,respectively.By regulating the V_O content,the electron distribution of Fe₂O₃ was optimized.Results have shown that 500-Fe₂O₃ which was prepared by pyrolyzing MIL-53（Fe）at 500°C has the highest V_O content.The presence of V_O reduced the charge recombination rate,enhanced the current density,and promoted electron transfer.Compared with other Fe₂O₃,the efficiency of 500-Fe₂O₃ in synergistic visible light catalyzed activation of persulfate to degrade rhodamine B（Rh B）is increased by 20%,and the degradation efficiency reached 100%in 60 min.（2）The glutamic acid was used to orient the electronic structure of the g-C₃N₄-Cu₂O heterojunction catalyst to make the absorption band edge red-shifted to 460 nm.Therefore,the separation efficiency of photogeneratedelectron-hole pairs was facilitated and the electron transfer was promoted.After the addition of glutamic acid,the specific surface area of g-C₃N₄-Cu₂O was increased by 1.5 times,and the larger specific surface area increased the contact area of its heterojunction interface,which improved the heterojunction effect.Compared with single g-C₃N₄ or Cu₂O,the efficiency of photocatalytic degradation of methyl orange is increased by 70%.The methyl orange（MO）was completely degraded within 30min,and the morphology and structure of the catalyst were unchanged basically and catalytic efficiency is still higher after six cycles of reaction.（3）A 20S-13Fe OCN catalyst with a three-phase heterostructure of Fe₃O₄ and g-C₃N₄was constructed through the strong interaction between dicyandiamine,sodium dodecyl benzene sulfonate,and potassium ferricyanide.By optimizing the preparation conditions,regulating the electron distribution of 20S-13Fe OCN,increasing the surface electron density,increasing the three-phase heterojunction effect,and enhancing the efficiency of20S-13Fe OCN to catalyze the activation of PMS to degrade bisphenol A（BPA）,the degradation efficiency reached 100%within 30 min.Unlike traditional free radical reactions,the main reaction mechanism of the 20S-13Fe OCN/PMS system is the non-radical theory of20S-13Fe OCN mediated singlet oxygen and electron transfer.（4）CN/Zn Mn-Al₂O₃ was constructed through the differential coordination and combination of Zn,Mn,and Al.The template is Al₂O₃ and the substrate is g-C₃N₄.The electron transfer efficiency was improved by regulating the metal valence bonds.EPR and DPBF molecular probes were used to clarify the pathway of ¹O₂ generation,and the direction of electron transfer was determined by electrochemical analysis.A non-radical degradation mechanism for ¹O₂ oxidation and electron transfer was proposed.The efficiency of CN/Zn Mn-Al₂O₃ activated PMS to degrade DCF up to 100%within 30 min,which is increased by 80%than before.Meanwhile,CN/Zn Mn-Al₂O₃/PMS has a wide p H adaptation range,and can show good DCF degradation effect in both natural water and continuous flow fixed bed reactors.