Carbon membranes from precursors containing low‐carbon residual polymers

2005

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate and then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of carbonization temperature of PAN hollow fiber precursor on the microstructure, specific surface, pore-size distribution, and adsorption properties of PAN-based carbon hollow fiber (PAN-CHF) and PAN-based activated carbon hollow fibers (PAN-ACHF) were studied in this work. After the activation process, the surface area of the PAN-ACHF increased very remarkably, reaching 900 m 2 g Ϫ1 when carbonization is 1000°C, and the adsorption ratios to creatinine and VB 12 of ACHF were much higher than those of CHF, especially to VB 12 . The different adsorption ratios to two adsorbates including creatinine and VB 12 reflect the number of micropores and mesopores in PAN-ACHF. The dominant pore sizes of mesopores in PAN-ACHF are from 2 to 5 nm.

Section: Introductionmentioning

confidence: 99%

The effects of carbonization temperature on the properties and structure of PAN‐based activated carbon hollow fiber

2005

“…A known quantity of the PAN-based activated carbon hollow fiber (PAN-ACHF) was immersed in a known volume of aqueous solution at 37°C for 24 h. The amount of creatinine and VB 12 adsorbed was determined by the concentration difference before and after immersion in the solution. The creatinine and VB 12 concentrations of the solution were determined with a UV-vis spectrophotometer (Shanghai Techcomp Corp. 7500) at the wavelength of 510 nm and 361 nm, respectively. Absorbency of creatinine and VB 12 in the aqueous solutions reflects the difference of solution concentration.…”

Section: Methodsmentioning

confidence: 99%

“…This study examined the effects of activation temperature of stabilized PAN hollow fiber precursor on the adsorption and structural properties, such as specific surface area, pore size distribution and morphology of PAN-ACHF. We discuss the adsorption properties of the resultant PAN-ACHF to creatinine and VB 12 . According to their molecule sizes, creatinine ϽVB 12 , the molecule size of creatinine is less than 2 nm and primarily adsorbed by micropores (Ͻ2 nm).…”

Section: Introductionmentioning

confidence: 99%

Effects of activation temperature on the properties and structure of PAN‐based activated carbon hollow fiber

2006

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of activation temperature of a precursor fiber on the microstructure, specific surface, poresize distribution, and adsorption properties of PAN-based activated carbon hollow fibers (PAN-ACHF) were studied in this work. After the activation process, the BET surface area of the PAN-ACHF and surface area of mesopores in the PAN-ACHF increased very remarkably and reached 1422 m 2 g Ϫ1 and 1234 m 2 g Ϫ1 , respectively, when activation temperature is 1000°C. The adsorptions to creatinine and VB 12 of PAN-ACHF were much high and reached 99 and 84% respectively. In PAN-ACHF which went through the activation at 700°C and 800°C, the micropore filling mainly occurred at low relative pressures, multimolecular layer adsorption occurred with the increasing of relative pressure, and the filling and emptying of the mesopores by capillary condensation occurred at high relative pressures. But in PAN-ACHF which went through the activation at 900°C, a mass of mesopores resulted in the large pore filling by capillary condensation. The dominant pore sizes of mesopores in PAN-ACHF are from 2 nm to 5 nm.

“…Although the porous carbon materials such as activated carbon fibers were usually prepared by chemical and/or steam activation treatments, the control of pore size needs a careful regulation of the activation condition. Recently, the PAN-based activated carbon hollow fiber (PAN-ACHF) has brought on many investigators' interests, [2][3][4][5][6][7] since PAN-ACHF shows the largest adsorption capacity among the carbon surfaces.…”

Section: Introductionmentioning

confidence: 99%

Effects of activation time on the properties and structure of polyacrylonitrile‐based activated carbon hollow fiber

Wang

2005

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of activation time of a precursor fiber on the microstructure, specific surface area, pore-size distribution, and adsorption properties of PAN-based activated carbon hollow fibers (PAN-ACHF) were studied in this work. The BET surface area of PAN-ACHF and surface area of mesopores gradually increase with activation time extending, and reach the maximum values, 780 and 180 m 2 g Ϫ1 , respectively, when fibers are activated at 800°C for 100 min. The adsorption ratio to creatinine changes little with activation time extending and all values over all activation time are above 90%. The adsorption ratio to VB 12 gradually increases with activation time extending before 60 min, and then becomes relatively constant from 60 to 100 min. The number of pores on the surface of PAN-ACHF increases with activation time extending. The amount of mesopores in PAN-ACHF made of fibers activated for different time increases with activation time extending and the dominant pore sizes of mesopores in PAN-ACHF range from 2 to 5 nm.