Performance Study In Removal Of Indoor Formaldehyde By Integrating Photocatalysis With Electro Catalysis

This study concentrated on catalysts performances in oxidation of air pollutant formaldehyde in air purification by preparing well-performed materials and designing reasonable and applicable reactors.It is an important area in air purification.For the development of efficient and practical full range of air catalytic purification system,in this thesis,formaldehyde a common indoor air pollutant was chosen as target pollutant.For its efficient purification and removal,several new composites of catalysts were prepared and methods of integrating photocatalysis with electro-catalysis were investigated by experiments to increase the removal efficiency.The results are as follows:?1?The preparation of catalysts:Ag₃PO₄ was prepared using silver ion and phosphate ion by ion exchange method,BiVO₄ was prepared using hydrothermal method and Pt/TiO₂ was prepared using sol-gel methodand reduction method respectively.The photocatalytic performance of commercial product Cu₂O was also studied.The catalytic materials were characterized: surface morphology and the aggregate size of the catalyst particles was observed by SEM?scanning electron microscopy?,EDS?X-rayEnergydispersive spectroscopy?for elemental analysis of the prepared composite materials.Redox performance of catalyst was analyzed using CV curves,and UV-Vis analysis provides information about the catalyst absorption of visible light.SEM images indicated the size of catalyst in nano range,thus nano-materials had been prepared.Results from EDS were the same with corresponding preparation method.UV-Vis indicates the capacity of bismuth vanadate in absorb visible light.Several prepared materials have good light absorption properties in the visible range.?2?Those four catalysts were loaded onto the surface of the conductive matrix?Carbon cloth,stainless steel mesh,finished manganese oxide?for the study of photoelectrocatalytic oxidation of formaldehyde.In the specific tests,simulating single reactor indoor air purifier and dual chamber reactor,were introduced in photoelectrocatalysis.Apply a voltage to both ends of the conductive substrate with catalysts,created an integrated photocatalytic and electrocatalytic system.In the simulated indoor air purifier experiment,set the gas flow rate as 1000 m L/min,and the initial concentration of formaldehyde as 0.45 mg/m3.Photoelectrocatalysis performed better than purely photo-catalysis and simply electro-catalysis.The photoelectrocatalytic formaldehyde removal efficiency was 57.3% when using BiVO₄ as catalyst and carbon cloth as carrier,while using stainless steel as carrier and Ag₃PO₄ and BiVO₄ as catalyst was 64.3% and 77.9%,respectively.When the manganese oxide was used as carrier,Cu₂O,BiVO₄ and Pt/TiO₂ was used as catalysts,the formaldehyde removal efficiency was 83.3%,85.2% and 89.9%,respectively.Experiments showed that integrated photoelectrocatalysis is the most effective.?3?In the double chamber reactor experiment,set the gas flow rate at 1000 m L/min,and the initial concentration of formaldehyde at 0.45 mg/m3.When stainless steel mesh was used as carrier,the photoelectrocatalytic efficiencies of Cu₂O,BiVO₄ and Pt/Ti O2 were 79.2%,79.2% and 75.1% respectively.When manganese oxide was used as carrier,the photoelectrocatalytic formaldehyde removal efficiency with Cu₂O,BiVO₄ and Pt/TiO₂ was 88.3% 84.6%,86.5%.It is also proved that integrated photoelectrocatalysis is the best.?4?The kinetics of formaldehyde degradation was analyzed,and the reaction rate constant under integrated photoelectrocatalysis was the highest.