| Activated carbon fiber(ACF), known as a new-born adsorbing material, is featured withmany advantages such as a high speed of absorption rate, massiveness of its specific surface area,a high quality of processed moldability, environment-friendly, etc. and has been wildly applied inthe fields of air filtration, water filtration and so on. But it also has some disadvantages such aslimited adsorption capacity and easiness to cause a second contamination. Nano TiO2is praised byits great merits such as its stable performance, non-toxic, cheap price, preeminent activity underphotocatalysis, degradability and oxidizability to a great number of refractory VOC. This thesiscomposites TiO2and ACF under the period of electrostatic spinning to realize the complementaryadvantages of the two materials.In this thesis, we prepared the composite nanofiber membrane via electrostatic spinning byadding dibutyl phthalate gel, the precursor of TiO2, into polyacrylonitrile (PAN) solution. Then,we prepared the TiO2/activated carbon fiber composite membrane via pre-oxidation, carbonizationand activation. We studied the influence which each experiment parameter caused on the fibermembrane of its structure, morphology, distribution of pore size, filtering quality, molecularstructure, mechanical property, mechanical loss, hygroscopic properties, load rate of TiO2andadsorptive property by scanning electron microscope, aperture tester, filtration efficiency tester,IR–Raman spectrometer, thermal analyser, electronic strength tester, optical contact angle tester,VOC adsorption detector and dynamic adsorption model. Also, we studied the collaborativefiltering mechanism of TiO2/ACF via dynamic adsorption model.The results of the study manifested that the best electrostatic spinning parameters were18%of the PAN mass fraction,18kv of the voltage,1.5ml/h of the injection speed,10:1.5of the volume ratio as a mixture combined PAN solution and TiO2gel. Meeting all these conditions, themorphological structure and filtering quality of the mixed fiber membrane could reach the toplevel, with the prepared nanofiber possessing445nm of average diameter,4.5μm of average poresize,99.4%of filter efficiency.The best pre-oxidizing temperature turned out to be270℃. Under such circumstance, thediameter of the fiber reduced and the fiber became curved and cracked, and with thedecomposition of functional group inside the molecule, causing the reaction of dehydrogenationand cyclization. The aromatic ring structure and the better heat-resistant trapezoidal structure wereformed in this process, which made it ready for carbonization.During the process of carbonization, the stable structure of the fiber macromolecule wasgradually formed with the ongoing reaction of cyclization, cyano decomposition anddehydrogenation. The activator chosen here was H3PO4, by which the activated carbon fibrebecame more symmetrical, with less breakage of the entire fiber. The loss ratio of the fibermembrane reduced little by little and load rate of TiO2increased under the process of the gradualincreasing of the butyl phthalate gel. The suitable mixed ratio turned out to be10:1.5after overallconsideration on account of the fact that when the volume ratio of PAN solution and butyl-phthalate gel was10:2, the load ratio of nano TiO2could reach its top to11.2%, but would causedifficulties of spinning. At this point, the breaking strength of the fiber membrane was18.5N, theelongation at break4%, the loss ratio after carbonization41.24%, the contact angle136.5°, as wellas the fiber membrane enjoying a strong hydrophobicity.We also studied the adsorptive property of TiO2/Activated carbon fiber membrane. Theanalysis demonstrated that the lower concentration of the formaldehyde, the higher load rate ofTiO2and prepared by phosphoric acid activation, the filter material got higher formaldehydeadsorption rate. which made it clear that it was more applicable to use TiO2/Activated carbon fibermembranes in the environment with a relatively low concentration of formaldehyde. This thesisresearched the formaldehyde adsorption dynamical characteristics of TiO2/Activated carbon fibermembrane by two dynamic models. The results show that the Lagergren pseudo-second dynamicalmodel fit for the dynamic description of TiO2/Activated carbon fiber membrane adsorptionformaldehyde, and the curve fitting is very well, the correlation coefficient R2reached0.98. |
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