| Water molecules confined in the inner pores of carbon nanotubes exhibit intriguing physical and chemical properties,including flow velocity,diffusion,polarity and phase transitions,etc.Especially when water transports through the inner pores of carbon nanotubes,its flow velocity is 2～5 times higher than that in the ordinary membrane pores with the same diameter.This implies that the atomically smooth inner pores of carbon nanotubes are promising channels for high-speed transportation of water molecules,laying foundation for the design of high-flux membranes.However,most of researches have studied the flow characteristics in the inner pores of carbon nanotubes through calculation and simulation so far,and limited experimental studies are all based on the vertical aligned carbon nanotube array(VACNT),of which the process is timeconsuming,complicated,extremely costly and relatively small effective membrane area.In order to further understand,verify and improve the characteristics and mechanism in the inner pores of carbon nanotubes and develop correspondingly novel membrane materials consisting of them,thus practical experiment researches are more necessary.Therefore,in this study,we have firstly used MWCNT100 powders to obtain CNT innerpores membrane successfully with the electric field induced orientation method,combined with a series of characterization for detecting its structure and properties,and finally carried out filtration experiment to explore the flow characteristics and flow regularity based on previous studies.In this paper,electric field induction method was investigated for the preparation of carbon nanotube(MWCNT100)inner pore membrane,and the optimized preparation conditions are as follows:PES was selected for filling polymer;the mass fraction of MWCNT100 was 0.5%;the signal was AC 9.6 V;the electric field application time was 2-2.5 h;the signal frequency was 800 HZ;the curing temperature of the polymer solution was 80℃.Subsequently,SEM,TEM,fluorescence emission,polarized Raman spectra and other characterization results all confirmed the successful preparation of MWCNT100 inner-pore membrane.The membrane exhibited excellent performance in membrane filtration experiments,and water velocity in the inner pore of MWCNT100(3.4 cm/s/bar)was four orders of magnitude higher than that in other common membrane channels with the same pore size.Furthermore,compared with R-CNT/PES with the same mass fraction(the flux decreased to 10.8%of the initial),MWCNTioo inner-pore membrane performed more excellent BSA anti-fouling performance and the flux remained at 60.8%of the initial.We continued to change the membrane interface structure by electrochemical oxidation process,the internal water velocity of MWCNT100 increased by 34%,indicating that the CNT tip charge also affected the water flow in inner pores of carbon nanotubes.In addition,under our experimental conditions,the applied electric field(～2.12 KV/cm)had a limited improvement for the flow rate,about 10%,whereas significantly enhanced BSA anti-fouling performance,rising to 90.1%from 60.8%without E.Surprisingly,when the influent temperature rose from 298 K to 318 K,water velocity flowing through MWCNT100 inner pores increased remarkably,which was 3.83 times higher than that at 298 K.In conclusion,this study put forward a novel method based on electric field induced orientation technology to assemble a new type of MWCNT100 inner-pore membrane with high flux,excellent anti-fouling performance and verified its feasibility.Then we tried to gain insight into the fluid flow in the CNT inner pores and designed experiments to investigate the influence on its membrane filtration process(flux and anti-fouling)caused by various types of electric and thermal signals,including tip charges,ex-situ and in-situ electric field,temperature difference,which would offer a well preliminary method and demonstration for designing efficient and low energyconsuming membrane material and development of coupling force(field)with membrane separation technology. |
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