Study On Formaldehyde Removal Performance Of Sepiolite Modified By Transition Metal Oxides

Formaldehyde is a major air pollutant in indoor environment.Exposure to high concentrations of formaldehyde for a long time will cause serious health problems.Therefore,it is of great significance to study the removal of formaldehyde at room temperature.The specific surface area of sepiolite is large,and it has high adsorption performance for VOC,which is suitable for formaldehyde removal.In this paper,the removal performance of sepiolite on formaldehyde was studied by purification and acid treatment of sepiolite and further loading of transition metal oxides.MnO₂ was successfully loaded on sepiolite by stirring and impregnation method,and its formaldehyde removal performance was tested.The characterization results showed that the specific surface area of sepiolite increased greatly after purification and acid modification,and decreased to a certain extent when loaded with MnO₂.TEM showed that sepiolite has a fibrous structure and MnO₂ is evenly dispersed on the surface of sepiolite.XRD and FTIR showed that MnO₂ was successfully loaded on sepiolite surface,and the crystallinity was weak.The results showed that the most suitable acid for the modification of sepiolite is HCl,the most suitable acid concentration is 1.5 mol/L,the most suitable manganese loading is 30%,and the most suitable stirring time is 12 h.The results of formaldehyde removal performance showed that the formaldehyde removal rate of MnO₂（30）/HCl-Sep material could reach 94.3%under the conditions of initial formaldehyde concentration of 32 ug/L,adsorbent dosage of 5 g and 298 K.According to the adsorption model and thermodynamic calculation analysis,the formaldehyde adsorption data fitting on MnO₂（30）/HCl-Sep is close to the Freundlich adsorption isotherm model,which belongs to the Pseudo-first-order kinetic reaction,and the reaction can be carried out spontaneously and emit heat.Co₃O₄ was loaded on sepiolite by precipitation method,and its formaldehyde removal performance was tested.The results showed that the most suitable base for the preparation process is KHCO₃.XRD,FTIR and TEM analysis showed that Co₃O₄ was successfully loaded on sepiolite and showed weak crystallization.Compared with K₂CO₃-Co₃O₄/Sep-400 and KOH-Co₃O₄/Sep-400,KHCO₃-Co₃O₄/Sep-400 has the largest specific surface area,the lowest reduction temperature and the highest mobility of reactive oxygen species,which can effectively promote formaldehyde removal.The optimal concentration of KHCO₃ is 2 mol/L,the optimal cobalt loading is 30%,and the optimal calcination temperature is 400°C.The formaldehyde removal performance results showed that the formaldehyde removal rate of KHCO₃-Co₃O₄/Sep-400 material reached 85.7%under the conditions of initial formaldehyde concentration of 32 ug/L,adsorbent dosage of 5 g and 298 K.According to the adsorption model and thermodynamic calculation analysis,the fitting curve of formaldehyde adsorption experiment data on KHCO₃-Co₃O₄/Sep-400 is close to the Freundlich model and the Pseudo-first-order kinetic reaction,and the reaction can be spontaneous,and heat will be released in the reaction process.CeMn and CoMn bimetallic oxides were loaded on sepiolite by co-precipitation method,and their formaldehyde removal performance was investigated.It is found that CeMn/Sep has better removal effect on formaldehyde.Under the conditions of initial formaldehyde concentration of 32 ug/L,adsorbent dosage of 2 g and 298 K,the formaldehyde removal rate of CeMn/Sep material reaches 96%.In addition,the adsorption model analysis shows that the adsorption data of CeMn/Sep for formaldehyde is close to Freundlich model and Pseudo-first-order kinetic reaction,and the thermodynamic calculation shows that it is a spontaneous exothermic reaction.XRD and FTIR analysis showed that CeMn and CoMn bimetallic oxides were successfully loaded on sepiolite surface and showed weak crystallization.H₂-TPR analysis showed that the mobility of reactive oxygen species in CeMn/Sep was higher,which could effectively promote the removal of formaldehyde.In this paper,sepiolite was modified with transition metal oxides to greatly improve the formaldehyde removal performance,which has a great application prospect for indoor air purification.