The Performance And Mechanism Of Manganese-based Catalyst（δ-MnO₂） Catalytic Oxidation Of Formaldehyde

In today’s society,while rapid economic development has improved people’s material living standards,photochemical smog,smog,sulfuric acid smog,and the greenhouse effect continue to endanger people’s health.Among the many pollutants,the volatile organic pollutants in indoor air pollutants are particularly harmful.Formaldehyde is considered to be the main volatile indoor air due to its easy production,high toxicity,long release period,and great harm to the human body.One of the organic pollutants.Therefore,efficient removal of formaldehyde is one of the most important ways to improve indoor air quality and improve people’s living standards.In this study,purified diatomite was used to synthesize diatomite-supportedδ-MnO₂ catalyst by methanol in-situ reduction method and ammonium oxalate hydrothermal reduction method,and the performance experiment of catalytic oxidation of formaldehyde was carried out.The waste after the attapulgite adsorbs the dye is treated by a thermal activation method to form a layer of carbon film covering the surface of the attapulgite,and on this basis,the birnessite-type manganese dioxide is loaded and used to catalyze the oxidation of formaldehyde.And based on first-principles density functional theory,using the VASP software package to calculate,construct the birnessite surface with oxygen vacancies(Mn_xO_2x-1)and without oxygen vacancies(Mn_xO_2x)to study the oxidation mechanism of formaldehyde,and discuss the The effect of oxygen-free vacancies on the catalytic oxidation of formaldehyde.The main conclusions of the study are:（1）Compared with the Mnx/DM-MT catalyst,the Mnx/DM-AO catalyst exhibits excellent activity for catalytic oxidation of formaldehyde from ambient temperature to250°C.The high performance of the Mnx/DM-AO catalyst is attributed to the highly defective structure,abundant hydroxyl groups,abundant lattice oxygen and Mn³⁺species.（2）The coated carbon film greatly improves the ability of attapulgite to adsorb formaldehyde.At the same time,birnessite as the active component is evenly dispersed on the surface of the carrier,which improves the efficiency of catalytic oxidation of formaldehyde.This research has well dealt with the secondary pollution problem of dye wastewater adsorbent waste,and provides a new and high value-added solution for the reuse of solid waste.（3）The catalytic oxidation of formaldehyde on the birnessite（001）crystal surface follows the LH mechanism.Formaldehyde and oxygen are first adsorbed on the surface of the catalyst,and then O is added to form DOM,which removes H to form HCOO^-,and further oxidizes to form HCO₃^2-.Eventually CO₂ and H₂O are produced.When there are oxygen vacancies on the surface,not only the adsorption energy of gas molecules is greatly reduced,but formaldehyde and oxygen are more easily adsorbed around the oxygen vacancies,and various elementary reactions are easier to proceed,which further promotes the catalytic oxidation of formaldehyde.