Nanoscale Carbon Materials for Contaminant Separation - Nanotechnologies for Water Environment Applications - page 300

than that on activated carbon; the adsorption of humic acids reached equilibrium in 15
minutes, whereas it took 120 minutes to reach equilibrium for F400 carbon (Han et al.,
2003). In addition, the adsorption of dyes on SMC was found to be dependent on the
size of the dye molecules. The larger the size of the dye molecules was, the more
superior affinity of SMC compared to activated carbon was achieved (Han et al., 2000).
10.4.2.2 Mesoporous Activated Carbon (MAC)
Thus far, there have been a number of MACs prepared from various starting
materials and methods, as was mentioned previously. These MACs were examined for
use in the adsorption of a broad range of pollutants in aqueous solutions, such as
quaternary ammonium ions (Akolekar et al., 1998; Tamai et al., 2004), phenolic
compounds (Qi et al., 2004; Tanthapanichakoon et al., 2005; Kennedy et al., 2007a;
Kennedy et al., 2007b), Cr(VI) (Guo et al., 2003a), humic acids (Tamai et al., 1996;
Tamai et al., 1997; Lorenc-Grabowska and Gryglewicz, 2005) and dyes (Tamai et al.,
1996; Tamai et al., 1999; Lin and Teng, 2002; Guo et al., 2003b; Tanthapanichakoon et
al., 2005; Macedo et al., 2006; Lorenc-Grabowska and Gryglewicz, 2007a, b). These
MACs showed excellent adsorption capacity for each of the tested contaminants,
especially for large molecules such as bulky dyes. MACs were found to be superior to
commercial activated carbon for the adsorption of Black 5 and Red 31 dyes
(Tanthapanichakoon et al., 2005) in terms of adsorption capacity, and for the adsorption
of methylene blue and remazol yellow in terms of high adsorption rates (Macedo et al.,
2006). Yasuda and co-workers further exhibited that the adsorption capacity of MACs
for a bulky dye was 3 times higher than that of a commercial activated carbon, although
the adsorption capacity of a small sized dye on MAC was smaller than that of
commercial activated carbons (Tamai et al., 1996; Tamai et al., 1999). In addition, the
adsorption of Congo Red on a bituminous coal-based MAC had a much higher
maximum adsorption capacity (52-189 mg/g) than other adsorbents such as coir pith
(6.72 mg/g), red mud (4.05 mg/g), and orange peel (22.44 mg/g) (Lorenc-Grabowska
and Gryglewicz, 2007a). These results confirm that MACs are more promising
adsorbents for the adsorption of giant molecules than conventional adsorbents.
10.5 Other Nanoscale Carbons
To date, there are few reports that have applied carbon black, carbon
nanoparticles, or carbon nanofibers for environmental separation. However, Yue and
Economy (2005) reported the use of carbon black in the removal of humic acids from an
aqueous solution. Three kinds of carbon blacks were used, with the diameters and
surface areas of about 12, 13, 30 nm and 1500, 560, and 254 m 2 /g, respectively. The
adsorption of humic acids on carbon black and activated carbon exhibited that smaller
nanosized carbon black has a higher adsorption capacity than larger nanosize carbon