Desulfurization Performance Of Activated Carbon Fiber After Oxidation Modification

The burning of fossil fuels generates a large amount of SO₂,which is discharged into the atmosphere and increases the secondary pollutants.It will cause serious damage to the tissues,organs and genetic materials of human body and mammals.It is difficult to change the energy structure dominated by fossil energy and improve air quality in the short term.The task of controlling air pollution requires long-term efforts.With the improvement of material living standards,the development of the Internet and the modernization of life style,people spend more than 93%of their time indoors every day,and pay more attention to indoor air quality.The installation of high-efficiency filters in air conditioners can effectively improve indoor air quality and provide a comfortable and clean living environment for people.In order to apply activated carbon fiber?ACF?to air conditioning field to achieve the filtration optimization of fresh air and improve the adsorption efficiency of ACF on polar molecule SO₂,the non-polar ACF was modified by liquid phase oxidation?HNO₃?to make the polar fold-type composite filter?mACF?,and the desulfurization mechanism of ACF and mACF were explored.Through SEM observation,BET characterization and spectrum analysis of FTIR,XPS,C1s,N1s and O1s,the surface microstructure,species and content of oxygen-containing functional groups and nitrogen-containing functional groups of ACF and mACF were qualitatively and quantitatively analyzed.The direct flow system test bench is designed and built.The formaldehyde absorption-pararosaniline spectrophotometric method was used to detect the concentration of SO₂ before and after outdoor air enters the filter.The dynamic desulfurization performance of the filter was evaluated at different initial SO₂concentration and reaction temperature.The results show that:?1?Acid oxygen-containing functional groups on ACF surface have cationic exchange characteristics,and acidic oxygen-containing functional groups can enhance the surface polarity of ACF.According to the principle of similar phase solubility,it is conducive to adsorption of polar molecule SO₂.After HNO₃ oxidation modification,changes in the types of mACF surface functional groups and increase in the content of acidic oxygen-containing functional groups can effectively improve the adsorption,oxidation and hydration processes,and further improve the dynamic desulfurization efficiency.?2?Through SEM observation,BET characterization,FTIR analysis,XPS full spectrum analysis,C1s,N1s and O1s spectrum analysis,the surface microstructure of ACF was significantly changed after HNO₃ oxidation modification.The specific surface area,pore volume and pore diameter respectively decreased from 653.70 m²/g,0.43 cm³/g and 2.64 nm to 488.84m²/g,0.32 cm³/g and 2.58 nm.The transmittance of O-H and C-O decreased from 96%and 95%to 65.5%and 75%respectively,namely,the content of surface acidic oxygen-containing functional groups?hydroxyl,carboxyl and ether group?increased.The part C of ACF was replaced by the O and N after HNO₃ oxidation modification,the content of C decreased by 13.54%,the content of O increased by 12.97%,the content of N increased by 0.57%,the content of oxygen containing functional groups increases,and the content of nitrogen-containing functional groups remained basically the same.I.e.,the types of surface functional groups,and the content of acidic oxygen-containing functional groups?C-O-C,C-O-H,C=O,O=C-O?of mACF all changed significantly.The surface acidity and polarity of mACF were enhanced.?3?The matters needing attention and operation points of SO₂ calibration series in formaldehyde absorption-pararosaniline spectrophotometry were summarized,and the regression equation of the SO₂ calibration curve was obtained accurately,with slope of 0.0396,intercept of-0.0029 and fitting degree of R² of 0.9987,which ensured the accuracy of converting absorbance into SO₂mass concentration.?4?At low SO₂ concentration in the winter,the adsorption amount of SO₂depends on the adsorption position of SO₂ provided by the filter surface,which is related to the pore structure and surface chemical state.The average dynamic desulfurization efficiency of ACF and mACF are 33%and 75%,respectively.I.e.,after HNO₃ oxidation modification,due to the change of surface functional groups and the increase of the content of acidic oxygen-containing functional groups,the average dynamic desulfurization efficiency of mACF was increased by 42%.At low SO₂ concentration in the summer,the recation temperature in the 20³5?range,the average dynamic desulfurization efficiency of ACF and mACF are 40.52%and 79.01%respectively,compared to the reaction temperature in 6⁸?,the average dynamic desulfurization efficiency increased7.52%and 4.01%respectively.That is,the adsorption and oxidation process of the filter can be improved by increasing the reaction temperature,and the dynamic desulfurization efficiency can be improved.Therefore,the application of mACF in air conditioning can effectively improve indoor air quality and has a high application prospect in air conditioning field.