Mechanochemical dechlorination of trichlorobenzene on oxide surfaces

Article abstract of DOI:10.1021/jp0276808

1,2,3-Trichlorobenzene (TCB) was ground with calcium oxide (CaO) powder in air with a planetary ball mill. A mechanochemical reaction was induced, resulting in the decomposition of TCB through dechlorination from the benzene nucleus. The mechanochemical dechlorination was monitored by a suite of analytical methods including X-ray diffraction (XRD), thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, electron spin resonance (ESR), gas chromatography/mass spectrometry (GC/MS), and ion chromatography. With the increase in grinding time, the remaining amount of TCB decreased and reached 0.02% at 360 min grinding. On the other hand, the water-soluble amount of chlorine increased correspondingly and reached 95%, indicating the successful transformation of chlorine from organics into inorganic chloride. Additionally, the other final products detected after grinding were carbon and some minor methane and ethane, although the formation of some chlorine-containing intermediate phases such as dichlorobenzene and tetrachlorobenzene was observed in the early stage of grinding (for 1 h). A possible decomposition pathway based on dechlorination or dehydrochlorination is compared.

Full text of DOI:10.1021/jp0276808

J. Phys. Chem. B 2003, 107, 11091-11097
11091
Mechanochemical Dechlorination of Trichlorobenzene on Oxide Surfaces
Yasumitsu Tanaka, Qiwu Zhang,*,† and Fumio Saito†
Material Solution DeVelopment Department Recording Media Company, Sony Sendai Technology Center,
3-4-1 Sakuragi, Tagajo-shi, Miyagi-ken, Japan
ReceiVed: December 10, 2002; In Final Form: July 21, 2003
1,2,3-Trichlorobenzene (TCB) was ground with calcium oxide (CaO) powder in air with a planetary ball
mill. A mechanochemical reaction was induced, resulting in the decomposition of TCB through dechlorination
from the benzene nucleus. The mechanochemical dechlorination was monitored by a suite of analytical methods
including X-ray diffraction (XRD), thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR),
Raman spectroscopy, electron spin resonance (ESR), gas chromatography/mass spectrometry (GC/MS), and
ion chromatography. With the increase in grinding time, the remaining amount of TCB decreased and reached
0.02% at 360 min grinding. On the other hand, the water-soluble amount of chlorine increased correspondingly
and reached 95%, indicating the successful transformation of chlorine from organics into inorganic chloride.
Additionally, the other final products detected after grinding were carbon and some minor methane and ethane,
although the formation of some chlorine-containing intermediate phases such as dichlorobenzene and
tetrachlorobenzene was observed in the early stage of grinding (for 1 h). A possible decomposition pathway
based on dechlorination or dehydrochlorination is compared.
Introduction
similar to that of photoinduced and radiation-induced dechlo-
rination. It is also worth noting that nanoparticles of the oxides
It is said that more than 10 million different chemicals have
already been produced and the number is increasing annually.
Concern over chlorinated compounds is increasing due to their
toxicity and significant ecological hazards. The most extensively
used method to destroy unwanted chlorinated compounds and
wastes is incineration; however, there is another concern about
the production of toxic byproducts such as chlorine-containing
furans and dioxins. Numerous other methods have been studied
to decompose the compounds at lower temperatures or by a
nonthermal method by means of different types of energy.1-12
For example, it has been reported that the destructive
adsorption of chlorinated hydrocarbons on the nanoparticles of
metal oxides (SrO, CaO, or MgO) is vastly superior to that by
commercial oxides, and that a fast destructive reaction is
obtained at relatively low temperature (573-773 K) and the
byproduct containing chlorine can be eliminated by using an
excess of oxides to give carbon dioxide and metal chlorides as
the final decomposition products.13-18 Another interesting
phenomenon occurring on the metal surface during the optically
and radiation-induced catalytic dechlorination is the charge
transfer observed with photocatalysis19-22 and radiolysis23-25
from the excited oxides such as alumina and silica to the
absorbed molecules.
can be easily obtained in situ by grinding, although the primary
nanoparticles are generally agglomerated into micron sizes.31-33
Considering the close contact in nanoscale of chlorinated
compounds and metal oxide additives, the grinding operation
provides a catalytic effect on the surface of nanoparticles without
the need for elaborate preparation of nanosized materials.
It is reasonable to believe that the mechanochemical dechlo-
rinating process exhibits some advantages; however, there is
still little information about the mechanism. It is easy to imagine
that the mechanism would be very complex, possibly involving
various pathways. When the problem is simplified, for example,
as to whether it is a dechlorinating reaction or a dehydrochlo-
rinating one when chlorinated compounds are decomposed by
grinding with metal oxides, the controversial issue remains and
needs further work. Clear understanding of the reasonable
pathway is helpful for further research to improve the mechan-
ochemical process and to reveal the corresponding reaction
relationship between the structures of chlorinated organic
compounds and inorganic additives.
In this work, a trichlorobenzene sample was chosen as the
target and ground with calcium oxide, presuming that it would
dehydrochlorinate during grinding as follows, resulting in the
most amount of possible product of CaOHCl among chlorinated
aromatic compounds.
A novel dechlorinating method by applying mechanical
energy26-30 has attracted attention due to the advantage of its
simple operation by using a ball mill, especially in the case
where a great deal of waste or soil contaminated by toxic
chlorinated compounds at quite low concentrations requires
disposal. Charge separation occurs during the grinding, and it
is expected that the charge transfers from metal oxides to the
chlorinated absorbers contribute to the chlorination in a way
C6H3Cl3 + 3CaO ) 3CaOHCl + 6C
(1)
Excess addition of CaO (4 times based on eq 1) was used to
facilitate the mechanochemical reaction and to assure that the
neutralizing capacity of the oxide was enough to absorb the
hydrochloric composition. However, the experimental details
do not seem to support this pathway and a dechlorination one
is proposed.
* Corresponding author.
† Institute of Multidisciplinary Research for Advanced Materials (IM-
RAM),Tohoku University, Katahira 2-1-1, Sendai, Japan.
10.1021/jp0276808 CCC: $25.00 © 2003 American Chemical Society
Published on Web 09/12/2003

11092 J. Phys. Chem. B, Vol. 107, No. 40, 2003
Tanaka et al.
Experimental Section
All reagents except for specific descriptions were obtained
from Wako Pure Chemical Industries, Ltd., Japan, and used as
received. The results of the preliminary experiment showed that
there is little difference between 1,2,3-trichlorobenzene (1,2,3-
TCB) and 1,3,5-trichlorobenzene (1,3,5-TCB). 1,2,3-TCB was
used and ground with calcium oxide (CaO), which was prepared
by heating calcium hydroxide (Ca(OH)2) at 1073 K for 2 h in
an electric furnace in an air atmosphere. The TCB was mixed
with the CaO powder at a 1:12 molar ratio. A planetary ball
mill (Fritsch Pulverisette-7, Germany) was used to grind the
starting mixtures. Two grams of the mixture (0.425 g of TCB
+ 1.575 g of CaO) was put in a zirconia pot with an inner
volume of 45 cm3 and seven zirconia balls of 15 mm diameter.
The grinding was operated at 700 rpm in air or with argon
sweeping before grinding for different periods of time. To
prevent excess heating, the milling was stopped 15 min for every
15 min of grinding operation.
The ground samples were characterized as follows. X-ray
diffraction (XRD) (RAD-B system, Rigaku, Japan) using Cu
KR radiation was used to identify phases formed after grinding.
Thermogravimetric analysis (TG) (Rigaku TAS200) was con-
ducted at a heating rate of 10 K/min in air. Infrared spectra of
the ground samples were measured using a Fourier transform
infrared (FTIR) spectrometer (Bio-Rad FTS-40A) with the KBr
disk method. Raman spectra were recorded at room temperature
using a Labspec Raman spectrograph (Horiba) with a He laser
beam at the 632 nm line. Samples for electron spin resonance
(ESR) analysis were charged in a quartz tube of 5 mm diameter,
and measurements were carried out with an X-band ESR
spectrometer (Bruker ESP-380E).
Figure 1. Change in yield of the remaining TCB with grinding time.
Besides the characterization of the ground solid sample, the
gas composition was also analyzed by gas chromatography/mass
spectrometry (GC/MS). The gas was drawn by a syringe just
after the mill was stopped and inserted into the spectrometer
for analysis using a Hewlett-Packard gas chromatograph (Model
6890) equipped with a mass-selective detector (Model 5973).
The following further treatments of the ground samples were
performed for additional analysis. The ground samples were
heated at 803 K for 60 min, and the crystalline phases formed
in heated samples were determined by X-ray diffraction (XRD)
analysis. The ground samples were also washed with water and
some organic solvents, respectively. An 0.5 g sample was
agitated in 100 mL of distilled water or 50 mL each of organic
solvent such as toluene (C6H5CH3), acetone (CH3COCH3), ethyl
alcohol (C2H5OH), ethyl acetate (CH3COOC2H5), or hexane
(C6H14) with a magnetic stirrer for 30 min to extract chemicals
into the solution. After filtration, the filtrates were subjected to
an ion chromatograph (IC) (LC10 series, Shimadzu Co. Ltd.)
and GC/MS analysis (the same spectrometer as the above with
a different column), respectively. The yield of soluble chlorine
in water was obtained by measuring the chlorine concentration
in the filtrate. The remaining percentage of TCB in the ground
sample was obtained by measuring the remaining amount of
TCB from toluene washing. The identification of possible
products was attempted by changing the solvents from the polar
to the nonpolar. The data obtained by washing with acetone
were used in this paper unless otherwise specified.
Figure 2. Yield of water-soluble Cl as a function of grinding time.
ground for 6 h. For confirmation, the 6 h grinding test was
repeated and washed with various solvents. It was found that
the remaining yields of TCB vary from 0 to 0.3% at maximum
within the experimental range. The water-soluble chlorine was
measured, and the results are shown in Figure 2. The yield of
the soluble chlorine increased rapidly with the increase in
grinding time and reached 95% with the sample ground for 6
h. The results obtained together clearly indicate that TCB was
decomposed through a mechanochemical reaction and the
chlorines were transformed from the aromatic chlorides into
water-soluble inorganic chlorides.
Inorganic Products after Decomposition. As the only
inorganic compound used, CaO was observed in the ground
samples from the XRD patterns (not shown here). However,
there were no other peaks observed except those corresponding
to the CaO phase. This means that any other reaction products
formed after the grinding operation were amorphous ones. The
ground samples were heated at 803 K for 1 h in order to obtain
some crystalline phases. Figure 3 shows the XRD patterns of
the 1 and 6 h samples ground and then heated, respectively.
Although the peak intensity of the products in the 1 h ground
Results
Decomposition of TCB. In Figure 1, the change in the
remaining yield of TCB with grinding time is shown. It is clear
that the yield decreases rapidly with the increase in grinding
time and only 0.02% of the initial TCB is detected in the sample

Mechanochemical Dechlorination of TCB on Oxides
J. Phys. Chem. B, Vol. 107, No. 40, 2003 11093
Figure 3. XRD patterns of 1 and 6 h ground mixtures of TCB and
CaO, subsequently calcined at 803 K for 1 h.
Figure 5. GC/MS spectra of products extracted by acetone from ground
samples. A, 1,2,3-TCB; B, 1,3,5-TCB; C, DCB; D, 1,2,4,5-TeCB.
in the reaction system before calcination. The only possible
reason for the formation of carbonate, namely CO2 formation
and later absorption by CaO, is due to the oxidization of carbon-
containing materials in the ground sample calcined in the air.
As shown in many related reports, the ground sample typically
consists of an agglomerate with the primary particles in
nanoscales. The close contact within the nanoscale, the possible
chemical absorption between the constituents of the agglomer-
ates, and the excess existence of CaO contribute to the easy
absorption of the CO2 gas during calcination to form a carbonate.
On the other hand, even if the complete dechlorination was not
achieved at 6 h grinding, the subsequent calcination at low
temperature will totally decompose the chlorinated compounds
because the grinding operation not only produces nanosized
oxide particles in situ but also homogenizes the oxide sample
and the absorbate within the nanorange at the same time.
Organic Products after Decomposition. Both of the gases
in the pot and the products extracted from the ground samples
were identified by GC/MS analysis. Figure 5 shows the spectra
of products extracted by acetone. In the spectrum of the sample
ground for 1 h, small peaks corresponding to dichlorobenzene
(DCB) and tetrachlorobenzene (TeCB), besides those of TCB
and column, have been observed. The peaks due to DCB and
TeCB disappear from the spectrum of the sample ground for 6
h, where only a small peak from TCB is detected. The peak
area is calculated at almost 0% that of the initial TCB.
Considering that some products formed may not dissolve in
acetone, different solvents such as toluene, ethanol, ethyl acetate,
and hexane were used to wash the ground samples. However,
in any case, no other new intermediate phases could be detected
from the ground samples excepting the above intermediate
phases. Although the chlorinated aromatic compounds have been
obtained as the intermediate phases in the early stage of grinding
(1 h), they are finally decomposed by the prolonged grinding
(6 h).
Figure 4. TG curves of ground samples for different periods of time.
sample is much lower than that of 6 h, the same crystalline
productsscalcium hydroxide chloride (CaOHCl) and calcium
carbonate (CaCO3)sare identified as having formed in the
calcined samples. Since the peak intensity of the products by
calcination is found to correspond to the degree of mechano-
chemical dechlorination, it is reasonable to say that the formation
of these products is related to the dechlorination reaction,
although not the direct products. Figure 4 shows the TG curves
of the ground samples. The weight loss in the region of 373-
423 K attributed to the vaporization of TCB is observed in the
curves of the sample ground within 2 h. The weight loss due to
the TCB vaporization has disappeared from the curves of the
sample ground over 4 h, indicating the absence of the free TCB
after the prolonged grinding. Instead, a weight increase is clearly
observed until 873 K, and the longer the grinding time is, the
greater this weight increases. The final weight loss at over 923
K can be attributed to the decomposition of the formed calcium
carbonate. If the TG analysis is conducted under N2 gas stream,
only a weight loss is observed. Combined with the results shown
in Figure 3, it is understood that the formation of carbonate
contributes to the weight increase because CO2 is not contained
Figure 6 shows the spectra of the gases collected from the
pot immediately after grinding. Compared with the results of
solid samples, similar ones (not shown here) have been

11094 J. Phys. Chem. B, Vol. 107, No. 40, 2003
Tanaka et al.
Figure 7. FTIR spectra of mixture grinding samples for different
periods of time.
Figure 6. GC/MS spectra of gases collected from mill pot headspace
immediately after 1 and 6 h grinding.
observed: chlorinated aromatic compounds are observed to
occur as the intermediate phases when the sample is ground
for 1 h, and these phases have disappeared when the grinding
time is extended to 6 h. Different results show that some light
gases such as methane, ethane, and CO2 have been found to
occur in the pot, irrespective of the grinding time. A comparative
test was performed by injecting Ar gas into the pot before
starting the operation (compared to that without Ar gas
substitution). Almost the same results were obtained, clearly
indicating that these light gases are the products of a mechan-
ochemical reaction. An atmosphere of air or Ar gas does not
make a difference for the reaction products. Evidently the
dechlorination induces considerable instability in the benzene
ring structure. Absorption on oxide to form new bonding, shown
later in the following IR spectra, is the most plausible way for
stabilization. However, there exists the other possibility for some
to go through a complete splitting of the aromatic structure to
produce these light gases as well as carbon due to the lack of
sufficient hydrogen.
Figure 8. FTIR spectra of 6 h grinding and subsequently 1 h calcined
at 803 K sample.
with the former more reasonable, implying basically that the
organic phase still exists in the 1 h ground sample. The CdO
stretches strongly suggest that the C atoms in organics (TCB
or intermediates) have been bound to O atoms in inorganics
(oxide). It is also worth mentioning that these peaks are not
observable in the spectrum of 6 h ground sample. The different
states of organics after prolonged grinding may be explained
by that the dehydration occurs with more formation of C-O
bonding after the complete dechlorination.34 Furthermore, the
formation of CaCl2 will facilitate the dehydration due to its
strong tendency to absorb water to form a hydrated one. The
dehydration leads to the cutoff of C-O bonding, and the
subsequent disappearance of CdO bonding peaks from the
spectrum of 6 h ground sample.
The ground sample (6 h) and the calcined one were compared
in order to understand whether water-related phases are in a
hydrated or hydroxide state. The IR spectra are shown in Figure
8. In the spectrum of the ground sample, the OH stretch, in the
shape of a very broadened peak positioned from about 3650 to
about 3300 cm-1, is observed, indicating that strong hydrogen
bonding occurs in the phases, the typical pattern of a hydrated
chloride/bromide such as CaCl2‚nH2O.35 On the other hand, after
calcination at 803 K, this peak is reduced to a relatively small
FT-IR and Raman Monitorings of the Ground Samples
and Subsequently Calcined Ones. Figure 7 shows the IR
spectra of ground samples. The spectra are typical of the large
peaks from inorganic compounds. The large broad peaks in the
region from 1650 to 1350 cm-1 due to the existence of calcium
carbonate and hydroxide/hydrate in the samples make it difficult
to identify the bands related the aromatic structure lying in the
region. However, several small peaks positioned in the range
from 1800 to 1650 cm-1 (1800, 1778, 1765, 1711, 1685 cm-1
)
are observed in the spectrum of 1 h ground sample. These peaks
can be assigned as CdO stretches or C-Cl overtone bands,

Mechanochemical Dechlorination of TCB on Oxides
J. Phys. Chem. B, Vol. 107, No. 40, 2003 11095
Figure 10. ESR spectra of ground samples.
ena have been reported in other research involving radiation-
induced and optically induced dechlorinating reactions.
Figure 9. Raman spectra of ground samples and calcined samples.
degree, suggesting the hydrogen bond has been weakened.
However, the intensity of a sharp peak positioned around 3750
cm-1 increases to some degree. This sharp one is assigned to
the stretch band of the free OH, more possibly resulting from
a hydroxide. The results suggest that calcining treatment causes
the transformation from a hydrated into a hydroxide state.
Discussion
The above experimental results have clearly indicated that
chlorinated compounds such as TCB can be decomposed by
the grinding operation, and that chlorine is ultimately trans-
formed into water-soluble chloride. There is a need to determine
the pathway of how the TCB is decomposed based mainly on
whether by dehydrochlorination or by dechlorination.
Figure 9 shows the Raman spectrum of the ground sample.
The Raman shifts at 1570 and 1312 cm-1 bands are observed,
and the peak intensity rises with the increase in grinding time.
Although a little lower than others reported, the two peaks are
typical of amorphous carbon. The sharp peak (1570 cm-1) is
the graphite band and the broadened one can be assigned to the
finite in-plane domain size,36,37 with other interpretations of the
simple D band.38 XRD analysis does not offer evident informa-
tion about the carbon sample, suggesting that the small domains
with limited quantity are below the limits of X-ray detection.
Their presence is detected through the 1312 cm-1 peak of
Raman spectroscopy. Also, the widened pattern implies a broad
distribution of the formed domain sizes. The results from Raman
spectroscopy clearly show the carbonization of the organic
phases with the progress of decomposition reaction. In fact, the
color of the ground samples becomes black with an increase in
grinding time, physically confirming the formation of carbon.
The carbonization can be attributed to the dehydration of the
organic phases with CdO bonding. On the other hand, these
broadened peaks due to carbons disappear from the spectrum
of the calcined sample. The spectrum is the same as that of the
CaO sample, with one sharp peak corresponding to CO3 in the
carbonate. The results indicate that the oxidization of the carbons
results in the formation of carbonate during calcination,
consistent with the results by XRD and TG analyses shown in
Figures 3 and 4, respectively.
First, if dehydrochlorination occurs as the main pathway,
CaOHCl will be the ideal product. A previous report has
confirmed the formation of CaOHCl during the mechanochem-
ical reaction between poly(vinyl chloride) (PVC, (CH2CHCl)n)
and CaO. It is found that this compound is generally stable
against grinding and exhibits a clear crystalline state even with
prolonged grinding over 12 h.40 However, no such crystalline
phase of CaOHCl was observed in the ground sample. Although
CaOHCl is observed in the calcined sample shown in Figure 3,
it may result from calcination, not directly after grinding, similar
to the formation of calcium carbonate. Another example of easy
dehydrochlorination is 1,1,1-trichloroethane,15 which undergoes
HCl elimination around 403 K. In fact, when PVC sample is
heated, it undergoes dehydrochlorination below 573 K to form
polyethylene. This may help to understand the dehydrochlori-
nation occurring by grinding with the oxide. Furthermore, if
dehydrochlorination occurs to form CaOHCl as the product,
there exists no need for Ca-O bonding to disconnect. This
implies less chance for the new bonding between C and O to
form. The results from IR analysis, where CdO bonding has
been observed, do not support the dehydrochlorination pathway,
consistent with the XRD analysis results.
More important are the intermediate phases observed in the
1 h ground sample. Although in very tiny amounts, the formation
of dichlorobenzene and tetrachlorobenzene provides important
evidence that dehydrochlorination seems to be impossible. Such
a substitution of H by Cl seems to be possible with dechlori-
nation as the pathway. Generally, the radical Cl formed by
dechlorination from TCB is trapped by CaO oxide to form
chloride. It is still possible for some Cl radicals to have a chance
to contact other TCB molecules and to replace H to form
tetrachlorobenzene, accompanied by the formation of dichlo-
robenzene through the uptake of the substituted H. If HCl is
Figure 10 shows the ESR spectra of the ground samples. Two
radical peaks are observed and the intensity of the broad one
increases with a longer grinding time, while the sharp one
remains unchanged, the same phenomena reported in the case
where CaO was ground with chlorobiphenyl.30,39 It is understood
that the charge transfer induced by the grinding operation is
favorable for the dechlorination occurring in the mechanochem-
ical decomposition of chlorinated compounds. Similar phenom-

11096 J. Phys. Chem. B, Vol. 107, No. 40, 2003
Tanaka et al.
formed through dehydrochlorination, it seems more difficult to
expect that a stable HCl can replace H from TCB to form
tetrachlorobenzene and H2 as a byproduct. The formation of
CH4 and C2H6 does not support the dehydrochlorination
pathway, either, because TCB has the same number of H and
Cl atoms so that only carbon, not hydrocarbon, can be finally
formed if dehydrochlorination occurs.
as the main products through dechlorination and subsequent
dehydration. The successful decomposition of TCB in 6 h
ground sample with a weight ratio as high as 1:3.7 to the additive
oxide indicates that the grinding offers an effective method for
treating wastes and soils contaminated with chlorinated com-
pounds at low concentrations.
Acknowledgment. The authors thank Dr. Ikoma, Tohoku
University, for his assistance in the ESR measurements.
The existence of radicals also offers more evidence that
dechlorination is more reasonable than dehydrochlorination. The
dechlorination pathway means the separation of C-Cl bonding,
leaving free radicals in the ground sample. The dehydrochlo-
rination pathway implies that both C-Cl and C-H bondings
are cut off simultaneously to form HCl absorbed by CaO as
CaOHCl and an intermediate phase with a structure similar to
benzyne. This will leave less chance for the formation of free
radicals. Other reports have indicated that poly(tetrafluoroeth-
ylene) ((CF2)n) and hexabromobenzene (C6Br6) can be decom-
posed by grinding with the oxides to form alkaline earth metal
fluoride and bromide, respectively.35,41 Successful debromination
and defluorination occur as extreme examples where dehydro-
halogenation is impossible without the existence of hydrogen.
In general, when TCB and CaO are ground together, the TCB
is absorbed on the surfaces of the oxide. The grinding operation
induces excitations in metal oxide particles and a subsequent
charge transfer to TCB molecules absorbed at the oxide surfaces.
The dechlorination occurs through the charge transfer induced
by grinding from the inorganic oxide to the organic phases. After
dechlorination and the formation of Ca-Cl bonding, C-O
bonding arises instead. Part of the dechlorinated TCB molecules
may go through a complete decomposition of their structure to
form CH4, C2H6, carbon, etc. The recombination of some
radicals with TCB and dechlorinated TCB molecules to form
some CB, DCB, and TeCB as the intermediate phases is also
apparent. As the grinding progresses and dechlorination pro-
ceeds, the oxygen tends to bind carbon strongly, therefore
allowing Ca more easily to take chlorine to form chloride. The
dehydration will occur with the progress of mechanochemical
dechlorination and the subsequent formation of C-O bonding.
This again results in the formation of carbon and the hydration
of the chloride.
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Based on the discussion with dechlorination as a more
reasonable pathway than dehydrochlorination, further research
on the mechanochemical decompositions of chlorinated aromatic
compounds, such as the search for more efficient inorganic
additives, can be performed toward assessing those oxides from
which chlorides and oxychlorides are easily formed and stable
against grinding, without focusing on those oxides from which
formations of metal hydroxide chlorides (MOHCl) through the
so-called dehydrochlorination occur.
Conclusions
Trichlorobenzene, as an example of chlorinated compound,
can be decomposed by dry grinding with CaO, with calcium
chloride hydrate and carbon as the main final products besides
the excess of CaO, achieving the goal of transforming toxic
organics into inorganics that are safe and can be stored without
problem or can be used in appropriate fields. The prolonged
grinding (6 h) results in calcium chloride hydrate and carbon

Mechanochemical Dechlorination of TCB on Oxides
J. Phys. Chem. B, Vol. 107, No. 40, 2003 11097
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