Environmental Engineering Reference
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O
O
N
H
OH
OH
figure 7.19
Iminodiacetic acid.
Br
N
N
N
CH 3
HO
N
CH 3
figure 7.20
2-(5-Bromo-2-pyridylazo)-5-diethylamino-phenol.
that the use of histidine as substrate, associated with the inherent features of MWCNTs, avoids the incompatibility problem
between MWCNTs and aqueous medium in flow injection analysis. efficient functionalization with histidine was confirmed
from 100 preconcentration/elution steps without loss of adsorption capacity toward Cd 2+ . The same nanocomposite was also
applied for selective preconcentration of V(V) and its online ultrasensitive determination in a variety of biological and
environmental samples [47]. With the consumption of 5.0 ml sample solution and a preconcentration time of 1 min, an
enhancement factor of 35 with a detection limit (3 s) of 9 ng/l or 0.2 nM was achieved. In addition, an amperometric glassy
carbon biosensing electrode for glucose, based on the immobilization of a highly sensitive glucose oxidase (gO x ) by affinity
interaction on carbon nanotubes (CNTs) functionalized with iminodiacetic acid (Fig. 7.19) and metal chelates, was fabricated
[48]. This technique for immobilization exploits the affinity of Co(II) ions to the histidine and cysteine moieties on the
surface of gO x . The resulting biosensor was found to be capable of detecting glucose at levels as low as 0.01 mM and had
excellent operational stability.
7.5.4
other N,o ligands
Poly[aniline- co -5-sulfo-2-anisidine] nanograins with a rough and porous structure demonstrated ultrastrong adsorption
and highly efficient recovery of silver ions [49]. The 50/50 copolymer nanograins exhibited much stronger Ag + adsorp-
tion than PANi and all other reported sorbents. The maximum Ag + sorption capacity of less than or equal to 2034 mg/g is
the highest found thus far and also much higher than the maximum hg ion sorption capacity. It was revealed that Ag +
sorption occurs mainly due to the redox mechanism involving reduction of Ag + to separable silver nanocrystals, chelation
between Ag + and -Nh-/-N=/-Nh 2 /-SO 3 h/-OCh 3 , and ion exchange between Ag + and h + on -SO 3 -h. Copolymer NPs
bearing many functional groups on their rough and porous surface can be directly used to recover and separate silver
nanocrystals from practical Ag + wastewaters containing Fe, Al, K, and Na ions. A sorbent extraction procedure for Pb(II),
Cu(II), Ni(II), and Fe(III) ions on single-walled carbon nanotube disks was established [50]. Analyte ions were converted
to 2-(5-bromo-2-pyridylazo)-5-diethylamino-phenol (Fig. 7.20) chelates, then adsorbed on the disk, and further desorbed
by 10 ml 2 M hNO 3 .
high performance was reported for NP γ-alumina coated with sodium dodecyl sulfate and 4-(2-pyridylazo)-resorcinol
(SDS-PAr, Fig. 7.21) in sorbent solid-phase extraction [51]. A sorbent with adjusted nanometer-sized alumina was used to
preconcentrate and separate Cu in plants belonging to the legume family and natural water samples. The method was applied
to detect Cu ions at trace levels in substantial samples such as cucumber, eggplant, mint, tomato, potato, parsley, spinach, apple
and apple core, mangosteen, kiwi, banana, macaroni, pea, wheat flour, red beans, lentil, barley, tap water, river water, and sea
 
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