Abstract
In this study a composite of activated carbon and carbon nanofiber (AC/CNF) was prepared to improve the performance of activated carbon (AC) for adsorption of volatile organic compounds (VOCs) and its utilization for respirator cartridges. Activated carbon was impregnated with a nickel nitrate catalyst precursor and carbon nanofibers (CNF) were deposited directly on the AC surface using catalytic chemical vapor deposition. Deposited CNFs on catalyst particles in AC micropores, were activated by CO2 to recover the surface area and micropores. Surface and textural characterizations of the prepared composites were investigated using Brunauer, Emmett and Teller’s (BET) technique and electron microscopy respectively. Prepared composite adsorbent was tested for benzene, toluene and xylene (BTX) adsorption and then employed in an organic respirator cartridge in granular form. Adsorption studies were conducted by passing air samples through the adsorbents in a glass column at an adjustable flow rate. Finally, any adsorbed species not retained by the adsorbents in the column were trapped in a charcoal sorbent tube and analyzed by gas chromatography. CNFs with a very thin diameter of about 10-20 nm were formed uniformly on the AC/CNF. The breakthrough time for cartridges prepared with CO2 activated AC/CNF was 117 minutes which are significantly longer than for those cartridges prepared with walnut shell- based activated carbon with the same weight of adsorbents. This study showed that a granular form CO2 activated AC/CNF composite could be a very effective alternate adsorbent for respirator cartridges due to its larger adsorption capacities and lower weight.
Highlights
Volatile organic compounds (VOCs) are a class of chemical pollutants in the environment that can cause severe health problems
Activated carbon (AC).carbon nanofibers (CNF) Prepared adsorbents the surface area decreased to 422 m2/g with disappearance of the micropores
Surface area and pore distribution of AC/CNF composites As shown in Table 1 after impregnation of activated carbon with Ni catalyst and growth of carbon nanofibers on it, the specific surface area and the micropore volume have decreased
Summary
Volatile organic compounds (VOCs) are a class of chemical pollutants in the environment that can cause severe health problems. Adsorption of contaminants on sorbents is one of the most important methods for controlling VOC emissions. Activated carbon (AC) is the most versatile and frequently used sorbent for environmental control in the Activated carbon is structureless and has complex physicochemical properties [6]. It has poor selectivity, especially for aromatic compounds [7]. The adsorptive capacity of activated carbon is limited by the following factors: the density of surface active sites, the activation energy of adsorptive bonds, the slow kinetics and nonequilibrium of sorption in heterogeneous systems, the mass transfer rate to the sorbent surface and its relatively large dimensions [8]
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