Study On The Structure And Properties Of Polyacrylonitrile-Based Activated Hollow Carbon Fiber

In this work, polyacrylonitrile (PAN) hollow fibers are pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen, activated with carbon dioxide and coated with polyvinylalcohol (PVA) solution. There are a lot of micropores and mesopores in the resultant PAN-based activated carbon hollow fibers (PAN-ACHF) which have high surface area and high adsorption ratios to creatinine and VB₁2. Those properties make PAN-ACHF suitable to adsorb not only in the gas area, liquid and low molecule area, but also in the area of catalyzing, medicine and liquid adsorption which is involved in biggish molecules. Moreover, the structure, properties, reaction mechanism and pore structure token of PAN-based oxidation fibers, carbonization fibers and activation fibers are tested by some testing way such as FTIR SEM DSC X-diffraction, element analyzing and auto-adsorption apparatus and so on. The research is as follows:1. In this research, PAN hollow fibers were pretreated with five different Compounds Containing Phosphorus including ammonium dibasic phosphate, ammonium dihydrogen phosphate, triammonium phosphate, phosphoric acid and metaphosphoric acid. The structure and properties of PAN-ACHF pretreated with five different compounds were studied and the best compound was chosen as a pretreating reagent. The results show that ammonium dibasic phosphate is the best pretreating reagent to PAN hollow fibers. The BET surface area of PAN-ACHF pretreated with ammonium dibasic phosphate reaches maximum, 766 m² ·g^-1 and the surface area of mesopores in PAN-ACHF pretreated with ammonium dibasic phosphate also reaches maximum, 174 m² ·g^-1. And the adsorption ratio to mesomolecule adsorbate, VB₁2 of PAN-ACHF reaches maximum, 97.7% (wt%).2. PAN was pretreated with ammonium dihydrogen phosphate, and the structure and properties of resultant PAN-ACHF were studied. The best pretreatingcondition is chosen. The results show that when PAN hollow fibers were dipped in the ammonium dihydrogen phosphate of 4% concentration for 30min, PAN-ACHF has the best structure and properties, the BET surface area of resultant PAN-ACHF reaches maximum(766 m²Â·g^-1), the adsorption ratio to mesomolecule adsorbate, VB₁2 of PAN-ACHF reaches maximum, 86% (wt%), and the amount of mesopores in PAN-ACHF is much more.3. Effects of oxidation condition on the structure and properties of PAN-ACHF are studied during the process of oxidation, and the best oxidation condition is chosen. The results show that the best oxidation condition is 230 ℃ for 5hr. The BET surface area of resultant PAN-ACHF reaches maximum(666 m²Â·g^-1), and the surface area of mesopores in PAN-ACHF also reaches maximum(76 m²Â·g^-1). The adsorption ratio to mesomolecule adsorbate, VB₁2 of PAN-ACHF reaches maximum, 96% (wt%). The number of pores on the surface of PAN-ACHF obviously increases, and the diameter of pores is much even. The beginning value of incremental pore volume reaches maximum, 0.0093mL·g^-14. Effects of carbonization condition on the structure and properties of PAN-ACHF are studied during the process of carbonization, and the best carbonization condition is chosen. The results show that the best carbonization condition is 900℃ for 70min. The BET surface area of resultant PAN-ACHF reaches maximum(506m²Â·g^-1 .). The adsorption ratios to creatinine and VB₁2 of PAN-ACHF reach maximum. The number of pores on the surface of PAN-ACHF increases, and the diameter of pores is much even.5. Effects of activation condition on the structure and properties of PAN-ACHF are studied during the process of activation, and the best activation condition is chosen. The results show that when PAN-CHF is activated at 900℃ for 40min, the BET surface area of resultant PAN-ACHF reaches maximum(1422 m²Â·g^-1), the surface area of mesopores in PAN-ACHF also reaches maximum(1234 m²Â·g^-1), and the dominant pore sizes of mesopores in...