Biomedical Engineering Reference
In-Depth Information
Thermal treatment in oxygen-free conditions is the essence of
Salix viminalis
wood processing described in the current paper. The treatment of dried wood is ap-
parently an ordinary technological measure. However in some cases, this process may
trigger several interesting phenomena like those which may be accounted to widely
understood nanotechnology because of the properties of materials obtained during
pyrolysis. Two basic products may be obtained after pyrolysis of the wood: porous
carbonaceous solid and vapors that evolve during the treatment. The first product is an
active carbon. In general, such carbons are capable to adsorb selectively various spe-
cies from gas and liquid phase. Adsorption properties of carbons and their application
range depend (among other) on pore size distribution (PSD) and pore volume. Nar-
rowed PSD of solid adsorbents let them consider as potential molecular sieves. Nu-
merous experiments proved that sieving properties of active carbons can be exploited
to solve problems like (beside many other); air separation by PSA method (Hassan et
al., 1986; Rege and Yang, 2000), noble gas separation (Gorska, 2009), hydrogen and
carbon monoxide separation (Gorska, 2009), methane and hydrogen storage (Cheng
et al., 1997; Dillon and Heben, 2001), and so on. Released vapors partly liquefy after
cooling. The distillate of
Salix viminalis
wood has not been investigated, yet. There-
fore, there is a need to know whether the distillate is a useless waste, a hazardous
byproduct or a valuable product containing precious organic and inorganic substances.
eXPerimeNtal
Harvested
Salix viminalis
stems were dried and ground into shavings ca. 1 cm long,
then pyrolysed in inert gas atmosphere. Pyrolysis (carbonization) was carried out in
two stages: (i) the preliminary stage 1 hr at 600°C for expelling some volatile species,
(ii) the secondary stage 1 hr at arbitrarily chosen temperature (600, 700, 800, 900°C)
for expelling residual volatile fractions and for the formation of micropore-rich poly-
crystalline carbon matrix.
Micropore analyzer ASAP 2010 was applied to the collection of nitrogen adsorp-
tion data (N
2
adsorption at -196°C versus relative pressure of nitrogen). Nitrogen
adsorption data were regressed according to Horvath-Kawazoe theory (Horvath and
Kawazoe, 1983) using commercial software provided by equipment manufacturer
(Micromerotics, Inc.).
Volatile products were collected during the first stage of carbonization in the tem-
perature range 140-600°C. The volatiles were cooled to room temperature yielding
a dark brown viscous liquid. The product was subjected to water and organic solvent
extraction aiming at separation of its components (mainly polyphenols). Finally in
this study, two phenolic fractions were isolated through solvent extraction: extract (A)
ether-soluble and extract (B) methylene chloride-soluble. The content of extracts was
characterized by chromatographic analysis. The GC-MS analyses were performed on
a Autosystem XL gas chromatograph with MS TURBOMASS mass selective detec-
tor (Perkin Elmer) and a 30 m long, 0.25 mm ID, 0.25 mm thick SLB-5MS column
(Supelco). Helium was the carrier gas. 700 MHz NMR and FT-IR spectrometers were
used to characterize extract composition and in the experiment testing antioxidant
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