Preparation And Application Of Catalyst Degradation Of Low Concentration Indoor Formaldehyde

Indoor air pollution is getting more and more attention.As one of the most serious indoor pollutants,the research on its removal is becoming a hotspot at home and abroad.Studies have shown that the metal oxidation catalysis method does not require light,and can oxidize organic substances such as formaldehyde at normal temperature,transforming them into non-toxic and harmless substances without causing secondary pollution.Among them,manganese dioxide has the highest catalytic degradation efficiency of formaldehyde.Many studies based on manganese dioxide degradation of formaldehyde have found that higher specific surface area,rich surface oxygen species,more reaction sites and defects can significantly improve manganese dioxide.For formaldehyde degradation activity,doped or composite manganese dioxide catalysts have a significant effect on the improvement of formaldehyde degradation activity.However,the preparation of existing manganese dioxide-based catalysts is often complicated,and studies on the degradation of formaldehyde are mostly based on high concentration values above 100 ppm.The manganese dioxide-containing battery cathode material can greatly improve the degradation efficiency of formaldehyde due to the larger specific surface area and more surface oxygen species generated during the discharge process.Based on the above reasons,this standard has separately recovered the cathode materials of carbon batteries and lithium manganese batteries by simple methods,and simulated the cathode materials of lithium manganese batteries after full discharge.Lithium manganate was prepared under different conditions and performed at room temperature.A low-concentration formaldehyde degradation experiment was conducted,the effect of the catalyst on the degradation performance of formaldehyde was explored.The specific work of this article is as follows:（1）、Using carbon batteries as raw materials,by recycling carbon battery cathode materials,the formaldehyde degradation performance of three cathode materials treated with 2.5 mol/L sulfuric acid before discharge,after discharge and after discharge were compared.The study found that the cathode material extracted from the discharged battery cannot be directly used as a formaldehyde degradation catalyst due to its lower specific surface area and lower Mn valence.After treatment with sulfuric acid,its specific surface area significantly increases and Mn valence increases.The catalytic degradation ability of formaldehyde is greatly improved,and its formaldehyde purification rate remains above 98%within 24 hours.（2）、The cathode materials of lithium-manganese batteries at different discharge levels were recovered through simple disassembly,cleaning,and drying steps.The obtained catalyst was labeled as Lix Mn O₂（x=0.00,0.25,0.50,0.75 and 1.00）according to the discharge level,and can be used for catalytic degradation of low concentration of formaldehyde at room temperature.The results show that the discharge changes the structure,surface morphology,oxygen species,and Mn valence of the catalyst.With the progress of the discharge,Li⁺is gradually embedded in manganese dioxide,Mn（IV）is gradually converted into Mn（III）,the lattice gap of the catalyst is gradually increased,defects and surface oxygen species are increased,and the specific surface area is gradually increased.The increase of surface active oxygen and large specific surface area are conducive to improving catalytic activity.The catalytic activity of the catalyst for formaldehyde gradually increases with the progress of the discharge.The fully discharged cathode material Li_1.00Mn O₂has a higher specific surface area and active sites,and can maintain a degradation rate of nearly 100%for low-concentration formaldehyde within 24 hours.（3）、The cathode material of the simulated lithium-manganese battery is completely discharged.Using potassium permanganate and lithium hydroxide as raw materials,lithium manganate was prepared by hydrothermal methods at 130℃,180℃,and 230℃.The low concentration of formaldehyde was catalytically degraded at room temperature,and the effect of hydrothermal reaction temperature on the structure,crystal form and formaldehyde degradation efficiency of the obtained lithium manganate was investigated.Among them,the product was amorphous manganese oxide at 130℃,Li_1.27Mn_1.73O₄at 180℃,and Li Mn₂O₄with better crystal form at 230℃.The catalysts prepared at three temperatures maintained a catalytic efficiency of more than 98%for low-concentration formaldehyde within 10hours.Among them,lithium manganate with good crystal form was successfully prepared at 230℃,and the degradation efficiency of low-concentration formaldehyde was maintained within 10 hours.More than 99%.The prepared lithium manganate has a higher specific surface area,can absorb more water and oxygen to participate in the reaction,and has good catalytic oxidation activity against formaldehyde in air under normal temperature conditions.