Preparation Of Nitrogen-doped Active Carbon Fiber And Study On Its Formaldehyde Adsorption Capacity

With the increasing environmental pressure,people's awareness of environmental protection has gradually increased,and there has been increasing concern about indoor air quality.As a common volatile organic air pollutant,formaldehyde has received more and more attention.Various adsorption materials have been used to remove formaldehyde,such as porous carbon materials,MOF,calcium carbonate,and metal particles.particularly,porous carbon materials are the most commonly used.As a new type of adsorption material,Activated carbon fiber(ACF),as a new type of adsorption materials,has a larger specific surface area and more developed micropores than powdered activated carbon and granular activated carbon.Therefore,its adsorption rate is faster.However,the surface of ACF has fewer functional groups.In the adsorption process,non-polar small molecules are mainly adsorbed,which belongs to the category of physical adsorption.However,the adsorption capacity for polar molecules is poor,the adsorption affinity is weak,and it is easy to desorb.Therefore,the adsorption capacity of ACF to formaldehyde is not ideal.In view of this problem,the adsorption capacity of ACF with nitrogen-doped modification treatment on the surface was studied,and the temperature,urea concentration and surface during the hydrothermal reaction were investigated.The carboxyl group content has a significant impact on the nitrogen doping effect.This thesis starts from the research department to improve the adsorption capacity of ACF to formaldehyde,mainly through the surface nitrogen doping modification of ACF to increase the surface chemical adsorption site of activated carbon fiber,so as to achieve the selective adsorption of formaldehyde.Mainly studied the influence of the concentration of potassium permanganate in the oxidation system on the effect of oxidation treatment,and also discussed the influence of temperature,urea concentration,and surface carboxyl group content on the effect of nitrogen doping in the process of hydrothermal reaction.Finally,a single factor experiment was designed and discussed When nitrogendoped activated carbon fiber is prepared under the conditions of different oxidant concentration and different urea concentration,its formaldehyde adsorption capacity changes,and it also characterizes the physical adsorption capacity of by ACF oxidation treatment and hydrothermal nitrogen-doping modification treatment.Influence.The experimental results are as follows:(1)SEM analysis of the structure shows that the surface of the ACF obtained by the potassium permanganate treatment is etched and the grooves are unevenly distributed.The hydrothermal treatment has little effect on the appearance of the ACF,whether it is the ACF after the oxidation treatment or the nitrogen doping The miscellaneous ACF maintains the form of flexible textiles;(2)Boehm titration,FT-IR,XPS,EDX,elemental analysis and other results show that after ACF is treated with potassium permanganate,the carboxyl content on the surface of ACF increases,and the carboxyl content on the surface of ACF can increase from 0.4288 mmol/g to the highest1.29384mmol/g;After hydrothermal treatment,nitrogen is present in three forms: pyridine-N(398.4 e V),pyrrole-N(399.9 e V)and graphite-N(401.06 e V);compared with untreated ACF,The oxygen content of OACF increased from 31.15 wt/% to 38.14 wt%,the nitrogen content of NACF increased from 0.36 wt/% to 7.13 wt%,and the oxygen content decreased to 30.85 wt/%.(3)Discussion on the influencing factors in the oxidation process and hydrothermal reaction.The experimental results show that: when the concentration of potassium permanganate is 0.06 M,the concentration of urea is 200g/L,the temperature of hydrothermal reaction is 180?,the nitrogen in ACF is mixed Impurities can reach 7.13 wt%.(4)The nitrogen-doped activated carbon fiber was used in the adsorption experiment of formaldehyde.The result found that: oxidation treatment and hydrothermal reaction will reduce the specific surface area and pore volume of the activated carbon fiber,and after oxidation,the modified ACF with hydrothermal nitrogen doped Reduce more;when the potassium permanganate concentration is 0M to 0.1M,the adsorption capacity of nitrogen-doped ACF prepared under phase reaction process conditions for formaldehyde increases from 173mg/g to 226mg/g,while the untreated activated carbon fiber The adsorption capacity of the activated carbon fiber is 161.5g/mg,and the activated carbon fiber only after oxidation treatment is only 168 g/mg;when the input urea concentration is in the range of 10 g/L to 300g/L,the nitrogen element on the activated carbon fiber is doped with nitrogen.The maximum content can be increased to 7.235wt%,and the adsorption capacity of the nitrogendoped activated carbon fiber prepared corresponding to the urea concentration can be increased to 241mg/g.