Mechanistic Study On Adsorption And Oxidation Of NO Over Activated Carbon Fibers

Sulfur oxides （SO₂） and nitrogen oxides （NO_x） are considered to be the most toxicgases resource in our country. SO₂emissions have been effectively curbed with thelarge-scale implementation of coal-fired power plant flue gas desulfurization. Thennitrogen oxide emission control is increasingly important. In this paper, themulti-pollutant gas analyzer was conducted experimental studies of viscose-basedactivated carbon fibers adsorption removal of NO in a small fixed-bed adsorptionreactor under nitrogen and oxygen atmosphere. Combined with XPS, TPD, FTIRcharacterization methods, the mechanism of ACF adsorption oxidization NO wasstudied by comparison of the the samples adsorption properties in differentatmospheres. On this basis, this paper investigates the mechanism of simultaneous ofNO_x and SO_x by ACFs.The methods such as hydrogen peroxide （H₂O₂） solution impregnation, heattreatment were employed separately to modify the activated carbon fibers, and theremoval efficiency of NO by the activated carbon fibers before and after modificationin the inert nitrogen atmosphere, oxygen-containing atmosphere were investigated,furthermore, the change of activated carbon fibers characteristics such as pore structureas well as nitrogenous or oxygenous surface functional groups were also discussed inorder to explore the effect of oxygen-containing functional groups and O₂inatmosphere on the NO catalytic oxidation and the transformation process of NO to NO₂.The results show that the C-O functional groups of activated carbon fiber surfaceplay oxidation on the adsorbed NO in nitrogen atmosphere. adsorbed NO is oxidized to-NO₂by the C-O functional groups; On the other hand, in oxygen atmosphere,-NO₂and-NO₃were detected in activated carbon fibers surface after activated carbon fibersadsorb NO. It was found that NO removal efficiency in stable stage after long time testwas almost unanimous when using the original activated carbon fibers as well as thetwo modified ones, which indicated that the transformation of NO to NO₂was mainlyresulted from the reaction between the adsorbed NO on activated carbon fibers with the free oxygen in atmosphere. O₂volume fraction can significantly promote the NOcatalytic oxidation effect, indicating that the oxygen-containing functional groups onthe initial physical adsorption of NO greater impact, less impact on the wholeadsorption process. The conclusion can be drawn that it is the gaseous O₂makeadsorbed NO oxidize rather than adsorbed oxygen in N2/O₂atmosphere.The adsorption of SO₂/NO and simultaneous adsorption of SO₂and NO wereinvestigated in N₂and O₂atmosphere. FTIR and TPD were used to analyze the changeof surface functional groups and adsorption strength before and after the adsorptionprocess. Based on this, this paper explores the mechanism of simultaneous adsorptionof SO₂and NO. The results showed that the oxygen-containing functional groupsplay oxidation on the adsorbed SO₂and NO in nitrogen atmosphere. O₂can react withthe part of the nitrogen-containing functional groups to nitroso form which providesSO₂adsorption sites in separate adsorption SO₂process.-NO₃was detected inactivated carbon fibers surface after activated carbon fibers adsorb NO. In the processof simultaneous adsorption SO₂and NO, adsorbed NO was oxidized to-NO₂and-NO₃which provide adsorption sites for SO₂. Adsorbed SO₂was oxidized to sulphateform by–NO₂and–NO₃while the nitrogen-containing functional groups wererestored.