Study On The Modification Of Activated Carbon Fiber And Its Formaldehyde Adsorption Characteristics

Activated carbon fiber?ACF?is a new generation of highly efficient adsorbent material developed on the basis of the combination of activated carbon technology and carbon fiber technology.It has the characteristics of large specific surface area,large pore content,rich surface functional groups and good adsorption capacity.Formaldehyde?CH2O?is a volatile organic pollutant gas,planar polar molecules,molecular diameter of gaseous formaldehyde about 0.45nm.In view of the unsatisfactory present situation of formaldehyde gas purification,the effect of modified activated carbon fiber by different modification method on the adsorption of formaldehyde was studied in this paper.The viscose-based activated carbon fiber was used as the object of study.VACF was modified by re-activation technology and EDA grafting.Pore structure and surface functional group,as the main factors influencing the formaldehyde adsorption performance were studied.VACF/TiO₂ composites and VACF/Ag composites were prepared by using nano-TiO₂ and nano-Ag as catalyst loading,which owned formaldehyde removal ability and antibacterial ability at the same time.A new re-activation process improved by power ultrasound is proposed for the first time.When the activator used phosphoric acid,zinc chloride,hydrogen peroxide and nitric acid,the new re-activation process can improved the surface structure of VACF better.After re-activation,the specific surface area and total pore volume and pore volume of VACF increased,the average pore size decreased,and the pore size distribution of micropores was more uniform.When ultrasonic impregnated for 12h,the order of VACF surface physical structure parameters with different activator is:specific surface area H-VACF>Z-VACF>N-VACF>P-VACF>VACF0,total pore volume H-VACF>Z-VACF>P-VACF>N-VACF>VACFO.The contents of oxygen groups in the surface of re-activated VACF are mainly composed of hydroxyl groups,carbonyl groups and carboxyl groups.The relative contents of oxygen groups are:hydroxyl groups>carboxyl groups>carbonyl groups.The new re-activation process has a significant effect on the adsorption capacity of VACF.The order of iodine adsorption is P-VACF>Z-VACF>N-VACF>H-VACF>VACFO.When re-activated VACF purify formaldehyde gas of lmg/m³,the order of formaldehyde removal rate is P-VACF>H-VACF>Z-VACF>N-VACF>VACFO.Phosphoric acid re-activated VACF has the best formaldehyde adsorption capacity,the formaldehyde removal rate and the formaldehyde adsorption mass of phosphoric acid re-activated VACF are 68.93%,5.11 mg/m² respectively,Aminated viscose-based activated carbon fiber?VACF-EDAx?was prepared by ethylenediamine grafting technology.The formaldehyde adsorption capacity of VACF-EDAx increased first and then decreased with the increase of EDA treatment concentration.When the concentration of EDA was 0.5mol/L,the formaldehyde removal rate and formaldehyde adsorption mass at adsorption equilibrium of VACF-EDA0.5 are the best in the VACF-EDAx.VACF-EDA0.5 with a unit volume dosage of 0.14m²/m³ treatment formaldehyde gas at a concentration of 3mg/m³,it can handle 100%formaldehyde gas in 28min.Actual formaldehyde adsorption capacity is 22.0mg/m².Bolzman fitting prediction value of formaldehyde adsorption mass at adsorption equilibrium reached 29.30mg/m²,and the Bolzman predicted value increased by 91.50%compared with VACFO.The results of IR spectra and X-ray photoelectron spectroscopy showed that the main reaction of ethylenediamine grafting process was mainly the reaction between carboxyl groups in VACF surface and EDA,which formed amide groups finally.The side reactions was mainly the ionization reaction of primary amine and secondary amine.In the composites of VACF/TiO₂ and VACF/Ag,synergistic reaction is produced between the adsorption performance of VACF and the catalytic performance of nano-Ti02,nano-Ag,which urging the composites achieved an effective treatment of formaldehyde and providing good antibacterial properties meanwhile,The formaldehyde purification ability of VACF/TiO₂ composites and VACF/Ag composites both increases firstly and then decreases with the increase of catalyst loading rate.VACF-3.57%TiO₂ has the best formaldehyde purification ability in VACF/Ti02 composites,formaldehyde purification rate is 79.61%and formaldehyde adsorption mass at adsorption equilibrium is 5.90mg/m² at the 1 mg/m³ formaldehyde concentration,the inhibition rate to Escherichia coli and Staphylococcus aureus are 96%and 98%respectively.VACF-2.38%Ag has the best formaldehyde purification ability in VACF/Ag composites,formaldehyde purification rate is 60.58%and formaldehyde adsorption mass at adsorption equilibrium is 4.68mg/m² at the 1mg/m³ formaldehyde concentration,the inhibition rate to Escherichia coli and Staphylococcus aureus are both greater than 99%.