Fabrication And Activation Of Millimeter-scale Porous Carbon Beads For Efficient Removal Of Volatile Organic Compounds

The traditional volatile organic compounds?VOCs?adsorbents are facing the problems of complex activation process and limited mass transfer process.In order to prepare efficient adsorbent for VOCs removal,this thesis exploits a method to prepare millimeter-sized spherical activated carbon with excellent adsorption performance.This method was accomplished by following steps:?1?Through the phase inversion process,polyvinylidene fluoride matrix as precursor was formed;?2?Millimeter-scale Porous Carbon Beads?MPCBs?were prepared followed by the carbonization,which has the prospect of engineering application.Ethanol and acetone were selected as the probes of VOCs to investigate the adsorption properties on MPCBs with different porous structure,which were tailored through CO₂ activaton.Furthermore,Cu-MPCBs were synthesized via phase inversion followed by carbonization route with introduced of copper species.Multicomponent simultaneous removal performance of Cu-MPCBs for ethanol,benzene and H₂S were further tested,which were represented by polar,non-polar VOCs and acid gases,respectively.Physicochemical properties of MPCBs and activated samples were analyzed by Scanning electron microscopy,Nitrogen adsorption-desorption,Boehm titration,Particle strength instrument,Fourier-transform infrared spectroscopy and Thermogravimetric differential thermal analysis.The detailed research contents are presented as follow:?1?MPCBs with high sphericity,high particle strength,good thermal stability and abundant porous structure was obtained via phase inversion followed by carbonization route.Compared with commercial activated carbon,MPCBs has larger specific surface area?832 m²/g?and pore volume?0.409 cm³/g?,higher strength?19.9 N/particle?,and more alkaline functional groups on the surface.It also has a unique hierarchical porous structure of spongy pore-finger pore-cortex,which contributes to the better adsorption capacity for weak polar or non-polar adsorbates.The dynamic adsorption of ethanol and acetone by MPCBs conforms to the quasi-second-order kinetic model.MPCBs showed the fastest adsorption kinetics and the highest adsorption capacity for ethanol?146.0 mg/g?and acetone?149.7 mg/g?.MPCBs presents good reusability used as adsorbent.?2?MPCBs with rich grade porous structure was successfully prepared.Activated samples with different specific surface area,pore volume,particle strength and particle size were obtained.During the activation process,CO₂ is beneficial to the formation of developed micropore and macropore,which could lead to the structure of MPCBs etched,the carbon skeleton reduced,the blocked channels opened and new pore structure formed.The specific surface area and pore volume of samples increased significantly,but also resulted in the decrease of the compressive and wear resistance of samples.Under the moderate activation condition,900-1 presented high specific surface area?1712 m²/g?and rich hierarchical porous structure?1.078 cm³/g?,which meets the strength requirement?12.8 N/particle?.The results of dynamic adsorption of ethanol and acetone on activated MPCBs showed that the adsorption performance of adsorbent was positively correlated with activation time and temperature.The dynamic adsorption capacity of 900-1 for ethanol and acetone is 192.8 mg/g and 219.9 mg/g,respectively,which is 1.4 times that of MPCBs.This is mainly due to the fact that the activated MPCBs have larger specific surface area,pore volume and pore structure with gradient distribution,which makes the adsorption process more conducive to the diffusion and adsorption of adsorbate molecules in the adsorbent.?3?Cu-MPCBs with tailored porous structure and chemical property was synthesized via phase inversion followed by carbonization route.The in-situ introduction of copper species onto the porous carbon beads was accomplished via coupling solidification-reduction of copper species and the phase inversion-carbonization process.The obtained Cu-MPCBs possessed uniform spherical shape with good mechanical strength,developed porous structure and abundant chemical groups.Based on the dynamic experiment,the adsorption behavior for benzene,ethanol and H₂S were promoted with introduction of copper species,which exhibits preferably multicomponent simultaneous removal performance.Cu-MPCBs extend the adsorption performance for H₂S.The desorption enhancement of mesoporous structure was verified by ethanol-temperature programmed desorption?TPD?experiment.These results indicated that the Cu-MPCBs would be a promising adsorbent for VOCs.