Environmental Engineering Reference
In-Depth Information
neutral complexes or chelates; the adsorption constant is dramatically increased by the
use of classical reagents such as pyrrolidinedithiocarbamate or diethyldithiocarbamate.
A complementary comparative study on the adsorption of organometallic complexes on
RP-C 18 and silica gel 100, among others, showed C 60 to be superior as sorbent.
McHedlov-Petrossyan et al. (2001) reported interactions of various cationic dyes
with the dispersed phase of the aqueous colloidal solution of buckminsterfullerene.
Electrostatic and hydrophobic interactions facilitated the binding of cationic dyes onto
the fullerene particles. Mostly, the presence of C 60 in aqueous media enhanced the
association of dye ions. Such adsorption processes are accompanied by the
neutralization of the negative surface charge of the colloidal particles by the positively
charged -electron system of the dye. Chen et al. (2004) studied the sorption of
polycyclic aromatic compounds (PAHs) such as naphthalene onto the fullerenes. It was
found that the enhanced dispersal of C 60 could affect the adsorption of naphthalene by
several orders of magnitude. A solid-water distribution coefficient of 10 2.4 mL/g was
obtained for adsorption of naphthalene to poorly dispersed C 60 , whereas coefficients of
10 4.2 to 10 4.3 mL/g were obtained for well-dispersed C 60 samples. In addition, desorption
of naphthalene from dispersed C 60 samples into aqueous solutions was found to exhibit
strong hysteresis. For desorption over a period of 60 days, only about 11% of total
naphthalene was desorbed from C 60 . It is proposed that during the adsorption process,
naphthalene molecules probably penetrate into the micropores in C 60 crystals, which is
either due to the crystal defects or the breaking of weak van der Waals bonding between
C 60 molecules. The pressure exerted by adsorbate molecules could cause expansion of
some of the pores. If the pore deformation is not completely reversible, some pore
entrances, available for the adsorption, might be blocked in the desorption process
leaving some naphthalene molecules entrapped and causing the hysteresis on its
desorption (Cheng et al., 2004).
Recent interest on toxicity effect of nanomaterials has tremendously helped
environmental research as well. A recent study based on fullerene water suspensions
(FWS) confirmed its properties differ from those of bulk solid C 60 . A study based on
antibacterial activity of different FWS products towards Bacillus subtilis showed that all
suspensions exhibited relatively strong antibacterial activity; fractions containing
smaller aggregates had greater antibacterial activity, although the increase in toxicity
was disproportionately higher than the associated increase in the putative surface area.
This suggests the need for improved understanding of the behavior of FWS towards
organisms and in the environment to determine how C 60 can be safely used and disposed
of (Lyon et al., 2006). Jin et al. (2007) reported estrogenic compounds removal by
fullerene-containing membranes. The removal, adsorption rate and capacity of estrogen
by membranes with different fullerene compositions through dead-end filtration and
static adsorption experiments were investigated. It was observed that all of the
membrane showed very good removal of estrogen (more than 96%). Results for long-
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