Activated carbon fibers (ACF) are highly porous materials in the form of fibers with an aspect ratio of at least 10, with a well-defined porous structure and narrow pore size distribution. Alfa Chemistry offers a range of ACFs to meet your needs in porous materials and adsorption applications.
Introduction
After high-temperature activation (the activation temperature is different for different activation methods), the fiber surface produces nano-scale pores, which increases the specific surface area, and changes the physical and chemical properties. Generally, the fiber diameter of activated carbon fiber is 5~30 μm, the average specific surface area is about 1000~1500 m2/g, the average pore diameter is 1.0~4.0 nm, and the micropores are evenly distributed on the surface of the fiber.
ACF is a typical microporous carbon, which is considered to be "a combination of ultra-fine particles, surface irregular structures, and extremely narrow spaces". [1] Its structural features make the diffusion path of the adsorbate to the adsorption site shorter than that of activated carbon, the driving force is larger, and the pore size distribution is concentrated. This is the main reason for the larger specific surface area, faster adsorption and desorption rate and higher adsorption efficiency of ACF than activated carbon.
Features
ACF has notable properties, including:
- Excellent volume capacity
- High bulk density
- High specific surface area
- Uniform pore volume
- Excellent adsorption capacity
- Fast adsorption/desorption rates
- Enhanced design flexibility
- Ease of regeneration
ACF is essentially the intersection of activated carbon (AC) and carbon fiber. The advantages of ACF over other AC forms are high porosity and higher adsorption rate. However, the cost and additional processing steps to convert the starting material into fiber form are the main shortcomings of ACF. The comparison of the characteristics of AC and ACF is shown in the figure below. [2]
Application
ACF is a novel, efficient and multifunctional adsorption material. Based on their unique characteristics and advantages over other carbon materials, researches on the applications of ACF in CO2 capture, volatile organic compound (VOC) removal, wastewater treatment, and energy have been widely reported. This also illustrates the development potential of ACF in emerging fields such as smart fabrics, energy storage, healthcare, water and air purification, and advanced instruments. For example, Debasish Das et al. studied the applicability of ACFs to efficiently adsorb VOCs in inert gas streams under different operating conditions. In addition, the results showed that ACF repeatedly showed good regenerative ability after desorption by direct current heating. [3]
Manufacturing Process
Similar to the traditional carbon fiber manufacturing process, ACF is converted from various precursors, such as polyacrylonitrile (PAN), pitch, and phenolic resin, etc., involving an additional activation step in addition to CF. The general steps of ACF production include spinning, stabilization, pretreatment such as acid impregnation (before carbonization), carbonization/pyrolysis and activation. The figure below shows the general preparation process of ACF.
Synthesis process of ACF.
References
- Y. Alyousef, et al. Applied Thermal Engineering, 2012, 38, 124-130.
- Muhammad Faheem Hassan, et al. Journal of Analytical and Applied Pyrolysis, 2020, 145, 104715.
- Debasish Das, et al. Carbon, 2004, 42(14), 2949-2962.
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