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Influence of chlorine substitution on adsorption of gaseous chlorinated phenolics on multi-walled carbon nanotubes embedded in SiO2
Tulaphol, S.; Bunsan, S.; Kanchanatip, E.; Miao, H.-Y.; Grisdanurak, N. & Den, W.
Abstract
Multi-walled carbon nanotubes (MWCNTs)
embedded in SiO2 particles were prepared through the
floating-catalyst chemical vapor deposition method. The
parameters reaction time and flow rate of the carbon source
(CH4) were studied to obtain optimum conditions for
MWCNT synthesis. The obtained MWCNTs were characterized
by transmission electron microscopy, scanning
electron microscopy, Raman spectroscopy, and Fourier
transform infrared spectroscopy to confirm their morphology
and crystallinity. The optimum conditions were a CH4
flow rate of 100 ml/min in a H2–Ar mixture at a flow rate
of 500 ml/min and a reaction time of 20 min. Under these
conditions, MWCNTs with average outer and inner diameters
of around 50 and 10 nm, respectively, were obtained.
SiO2 particles with embedded MWCNTs were studied for
their adsorption of gaseous chlorinated phenolic compounds
(CPCs), with emphasis on the effect of number
of chlorine substituents. The CPC compounds of
2-chlorophenol (CP) and 2,4-dichlorophenol (DCP) were
compared against phenol (P). Adsorption of P and CPCs on
the particles fit well the Langmuir isotherm. The adsorption
capacities of P, CP, and DCP on SiO2 particles with
embedded MWCNTs were found to be 3.12, 13.83, and
44.25 mg/g, respectively. Desorption activation energy
was determined by thermogravimetric analysis. Chlorine
substitution on P changed the adsorption process from
physical to chemical adsorption. The particles showed high
potential for use as a pre-concentration unit for solid-phase
microextraction.
Keywords
Multi-walled carbon nanotubes; Phenolic compounds; Adsorption
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