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gelation with CTAB-containing CS solution (CSBN4). The adsorption capacities
of composite for CR were in the order of: CSBN4 > CSBN1 > CSBN2 > CSBN3.
The adsorption capacity of CSBN1 was slightly higher than CSBN2 for CR. This
could be due to the dispersion in SDS molecules resulting in negatively charged
CNTs as a result of adsorption of SDS molecules onto CNTs. The CR adsorption
onto CSBN4 increased as the concentration of CNTs increased because of bet-
ter dispersion of CNTs in SDS solution than in CTAB solution. CSBN3 showed
poor adsorption capacity because CNTs were dispersed in CTAB and aggregates
of CNTs blocked the adsorption sites on CS, CTAB, and SDS molecules in the
beads [72].
However, covalent functionalization of CNTs with polymers has proved to
be an effective way to improve their dispersion stability and make the result-
ing composites more stable and controllable CS, a natural polysaccharide with
similar structural characteristics to cellulose, obtained by the deacetylation of chi-
tin. It is a biocompatible, biodegradable, and non-toxic natural biopolymer and
has excellent film-forming abilities. CS can selectively adsorb some metal ions,
and has been successfully used in wastewater treatment. However, because CS
is very sensitive to the pH of ionic solutions, its applications are limited. Several
strategies have been devised to prepare CS derivatives that are insoluble in acid
solutions and to preserve the adsorption capacity of CS. In order to increase the
chemical stability of CS in acid solutions and improve its metal-ion-adsorbing
properties, Schiff base-chitosan (S-CS) was produced by grafting aldehydes onto
the CS backbone. Although the preparation of CS-modified MWCNTs via co-
valent interactions have been reported by a few groups, so far no work has been
published on the application of MWCNTs covalently modified with CS derivative
is to SPE column pre-concentration for ICP-MS determination of trace metals. A
novel material was synthesized by covalently grafting S-CS onto the surfaces of
MWCNTs, and used for pre concentration of V(V), Cr(VI), Cu(II), As(V), and
Pb(II) in various samples, namely herring, spinach, river water, and tap water,
using an SPE method. The results demonstrated that the proposed multi ele-
ment enrichment method can be successfully used for analysis of V(V), Cr(VI),
Cu(II),As(V), and Pb(II) in environmental water and biological samples. The
method is fast and has good sensitivity and excellent precision. Compared with
previously reported procedures, the present method has high enrichment factors
and sensitivity. In short, the proposed method is suitable for pre concentration and
separation of trace/ultra-trace metal ions in real samples.
1.1.6.2 CNT-ACF AS ADSORBENT
To resolve the aggregation and dispersion problem of CNTs, prepared the CNTs/
activated carbon fabric (CNTs/ACF) composite and its application was investi-
gated for the removal of phenol and basic violet 10 (BV10). CNTs/ACF was pre-
pared via directly growing nanoscaled CNTs on micro scaled carbon matrix. Poly
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