Oxidation of Activated Carbon Fibers:  Effect on Pore Size, Surface Chemistry, and Adsorption Properties

Abstract

Activated carbon fibers (ACFs) were oxidized using both aqueous and nonaqueous treatments. As much as 29 wt % oxygen can be incorporated onto the pore surface in the form of phenolic hydroxyl, quinone, and carboxylic acid groups. The effect of oxidation on the pore size, pore volume, and the pore surface chemistry was thoroughly examined. The average micropore size is typically affected very little by aqueous oxidation while the micropore volume and surface area decreases with such a treatment. In contrast, the micropore size and micropore volume both increase with oxidation in air. Oxidation of the fibers produces surface chemistries in the pore that provide for enhanced adsorption of basic (ammonia) and polar (acetone) molecules at ambient and nonambient temperatures. The adsorption capacity of the oxidized fibers for acetone is modestly better than the untreated ACFs while the adsorption capacity for ammonia can increase up to 30 times compared to untreated ACFs. The pore surface chemical makeup was analyzed using elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS).

Water adsorption with hysteresis effect onto microporous activated carbon fabrics

“…On the other hand, both virgin and hydrogen-treated samples depicted similar average micropore and total pore sizes indicating small influence of hydrogen and heat treatment on the pore structure of ACFC. The decrease in the micropore volume and the absence of prominent effect on the micropore size is consistent with previous results reported by other researchers (Mangun et al 1999).…”

“…With >20% oxygen, the primary adsorption sites are plentiful and water adsorption increases with increasing RH throughout the isotherm. Although this treatment yields increased water adsorption in high-humidity situations, which may be undesirable, it has utility in also increasing adsorption of other difficult-to-adsorb compounds, such as hydrides (Mangun et al 1999).…”

Asymmetric capacitive deionization utilizing nitric acid treated activated carbon fiber as the cathode

“…Nitric acid treatment is a simple, yet effective way to introduce oxygen containing functional groups and modify Epzc of carbon materials and has been widely investigated [46][47][48]. In this study, Epzc of ACF was shifted positively by nitric acid treatment (ACF-HNO3).…”

Microbial fuel cells operated with iron-chelated air cathodes

“…In the case of the oxidized activated carbon cloth, an oxidation treatment was applied by submerging it in a mixture of concentrated HNO 3 and concentrated H 2 SO 4 (1/1 ratio) for 60 min after which it was rinsed intensively with water [21]. The Fe-EDTA activated carbon cloth cathode was prepared by submerging a piece of activated cloth for the duration of 4 h in a 100 mM EDTA-4S solution, after which it was dried at 40 • C and submerged for 1 h in a 50 mM Fe 2 (SO 4 ) 3 solution.…”