Idea Transcript
Industrial
Health,
1975, 13, 243
CAPTURE
OF
MERCURY
VAPOR
IN AIR WITH
PERMANGANATE
SOLUTION
Noboru
National
Institute of Industrial
POTASSIUM
HARA
Health,
Kizuki-Sumiyoshi,
Nakahara-ku,
Kawasaki
(Received July 30, 1975)
The
vapor
author
tried
in air.
solution
a series
Mercury
of potassium
solutions.
Though
permanganate
all the types
This solution
pling solution changes educes out gradually. educed
manganese
in amount. and sulphuric dioxide.
Mercury
vapor
permanganate
and sulphuric
of
under
high
impingers efficiency,
mercury
vapor.
of capture
various
there The
were author
of mercury,
for the analysis
and mercury necessary
in air was
with
of mercury
and sampling excellent
a
solu-
sampling
permanganate
in liquid phase part
in the sam-
was rather
in capture
of mercury
impinger
containing
efficiency
was observed
unknown a series
all the types
factors
in
of the most
little
of mercury, on manganese
a mixture using
of potassium several
of impingers
the
of experiments
mechanisms
types
had a very of
capturing
for the study of the mechanism suitable
method
of air sampling
vapor.
EXPERIMENTS
Vapor
mercury
containing
acid (H2SO4) as sampling
mercury
adsorption
Though
and for the research
of mercury
the
Sampling
many
of capturing
of impingers
potassium
captured
for
conditions.
tried
between
played a great
captured
acid.
purpose
types
dioxide, and granules of manganese dioxide part of captured mercury was adsorbed on
permanganate
was
the
used had a very
dissolved
to manganese The greater
dioxide,
acid
of reaction of impingers
is unstable:
Potassium
for
with various
(KMnO4) in sulphuric
the mechanism
tion is complicate, efficiency.
of experiments
was captured
AND RESULTS
used in all the experiments
was produced
by a reduction
reaction
between mercuric chloride (HgCl2) and stannous chloride (SnCl2.2H2O) in dil. H2SO4.
Sampling
procedure1.2)
Sampling
was proceeded
using
four types
of
impingers
with
their
transformations
(Fig. 1). Two
impingers
and worked
and two bottles
as buffering
zones during
were
arranged
sampling 243
as in Fig. 2. procedures.
Two bottles were empty
Two
impingers
were
the
N. HARA
Fig.
1.
Types
of used
impingers
1 normal impinger
Fig.
same
each
each
sampling
conditions.
other
2.
and
normal impinger (with filter)
3
Muenke : washing
4
midget impinger
Arrangement tank
B
impinger
C
bottle
D
impinger
E
bottle
F
flow meter
equal
of vapor
zone
of sampling
vapor
captured
procedure.
zone
for buffer
volume
for sampling
of mercury
for buffer
Mercury
of mercury
bottle for gaseous material
of instruments
A
an
procedure. Amounts
2
was
passed
in the first 244
solution
and
was poured
through the
them second
into them under
impingers
the
on set were
CAPTURE shown
as
calculated
a, as
b
(ƒÊg)
OF
respectively,
MERCURY
and
then
VAPOR sampling
IN
AIR
efficiency
of
the
impinger
r
was
follows.
a-b r= a
Sampling procedures were made under the following conditions and all the types of impingers had a very excellent sampling efficiency for mercury vapor. Concentration Sampling
Table
1.
Normal
(a)
of mercury
solution
1.
vapor
in air
:
0.5% KMnO4=1 N H2SO4
Sampling
efficiencies
sampling
solution:
sampling
time
of impingers 0.5%
depth of sampling solution (3 cm)
Normal impinger
KMnO4=1
: 10 mins
impinger
(b) depth of sampling solution (2 cm)
2.
(Table 1)
10•`1000 ƒÊg/m3
(with filter)
(a)
depth of sampling solution (3 cm)
(b)
depth of sampling solution (2 cm)
245
for vapor N H2SO4
of mercury.
N. 3.
HARA
Muenke
Volume of sampling solution (about 60 ml) (the surface of the sampling solution reached the most constricted of inner tube)
4.
Midget
point
impinger
Volume of sampling solution (5 ml)
Figures
Determination
show
the percentage
of sampling
efficiencies.
of mercury
Reducting solution* was dropped
into sampled
solution slowly until the
solution
became colorless, and one more droplet was poured. (MnO2=H2SO4 solution which contained no KMnO4 in it was also used as sampling solution. In such cases, reducting solution was dropped until granules
of MnO2 were dissolved thoroughly.)
Then the
sampled solutions were removed to volumetric flasks and water was added to the mark. The
aliquot volume of the solutions was used for determination
determination, As very
the
analytical
high,
volume impinger
only
of
of
therefore, the
were vapor
sensitivity
0.1 ƒÊg
air, was
experiments mercury
an atomic absorption spectrophotometer
most
will
be
in
for
the
of sampling
Velocity
of passing
spectrophotometer
for
its
for
conditions.
solution
5•`20
For the
ml
the
mercury
(in
All
cases
each
mercury
A
purpose.
In
following
air
of
this
impingers.
for
determination.
determination
sufficient
midget
Volume
absorption
sufficient
enough and
with
sampled
atomic was
convenient
performed was
of
mercury
of mercury.
was used.
of
very
was small
in
it.
A
of
the
following
midget
midget
impingers,
impinger)
0.5∼2.5 l/min
DISCUSSION
Mercury *Reducting
(NaCl)
vapor
solution:
dissolves 20 g of
were dissolved
in conc.
hydroxylamine
H2SO4 hydrochloride
in 100 ml of water. 246
and
it does (NH2OH•EHCl)
not
dissolve and
12 g
in dil. of
sodium
H2SO4. chloride
CAPTURE
Mercuric
sulfate
OF
MERCURY
VAPOR
IN
AIR
(HgSO4) dissolves in dil. H2SO4. It was, therefore, guessed that Hg°
(vapor of mercury) was oxided to Hg+2 by KMnO4 at the first step, and Hg+2 dissolved in the sampling solution at the second step. Capturing of mercury vapor, however, may not wholly be proceeded by such simple chemical mechanisms. Change
of composition
of potassium
permanganate
in
diluted
sulphuric
acid
(KMnO4=H2SO4) The sampling
solution
to MnO2 gradually.
in this experiment
KMnO4 dissolved
in it changes
MnO2 educes out from the solution, and the concentration
in the solution decreases slowly. concentration
is unstable:
of KMnO4
The speed of decrease was especially effected by the
of H2SO4 in the solution.
In addition, it was
centration of KMnO4 even if in same concentration
also effected by the
of H2SO4. (Fig. 3) The speed was
very diverse according to individual conditions, and Fig. 3 shows the average various experimental
results.
con-
values of
(The solutions were put in the room keeping away from
direct sunshine.)
Fig.
3.
Decrease
of con.
concentration Letters
of KMnO4
in
KMnO4=H2SO4
the
beginning
solution.
of H2SO4 1N
on the curves
show
concentration
of KMnO4.
Sorption of mercury As the composition mechanism
for mercury
in liquid phase and on granules of KMnO4=H2SO4 vapor
changes
solution
naturally. 247
of manganese
changes Mercury
every
dioxide
moment,
was captured
(MnO2)
the sampling into the liquid
N.
HARA
phase and it was also adsorbed on educed MnO2. If very fresh sampling solution is used, the greater part of mercury will be captured into the liquid phase. (At this time, the
amount
elapsed
of educed MnO2 is very
small.)
Using KMnO4=H2SO4 solution which
one day after its preparation, however, the majority of mercury is adsorbed on
granules of MnO2. KMnO4=H2SO4 solution containing no MnO2 can hardly be prepared. In addition, MnO2 was produced little by little owing to reduction of KMnO4 during the sampling procedure. amount
The ratio of capacity of sorption
in liquid phase and adsorbed
elapsed after the preparation
Fig.
4.
Aging
of sampling
passing
The
in
of
the
sampling
was
investigated
0.1%, was If
KMnO4
the less
experiments
in
1 N
(Fig. efficiency 0.1%,
very
diluted
solution
KMnO4
during
sampling
be
oxided
showed
H2SO4
for
sorption
were
for 5). was the
the always
efficiency of
KMnO4 procedure.
into
between
dissolved
used
: 1% KMnO4=1N
volume
: 15 ml
Hg
: about
velocity
: 2l/min
time
: 10 mins
the
50 ƒÊg/m3
as
vapor
mercury which
sampling
solutions,
the
about
100%.
declined
as
(0.001•`0.002%) was solution.
248
KMnO4 But
the
in the
had
is
used,
be
oxided
various
and
the
relation
KMnO4
in
the
solution
was
concentration of the that
of
between
the
solutions more
mercury
lost
than
KMnO4
KMnO4
solution
for
concentra-
of
concentration
demonstrated
to
contained
concentration of
it
of
solutions
concentration
sampling
H2SO4
(KMnO4)
and
So
of Hg.
composition
The
mercury
If
and sorption
that
solution.
efficiency
than
solution
air
KMnO4=H2SO4
tion
solution
of potassium permanganate
following
sorption
for mercury
on granules of MnO2 changed as time
of sampling solution are shown in Fig. 4.
sampling
Concentration
amount
in
it
decreased. its
color
of
vapor
had
to
CAPTURE
Fig.
5.
OF
Sampling con.
MERCURY
efficiency
passing
IN
AIR
of solution.
of H2SO4
sampling
VAPOR
1N
solution air
volume
: 10 ml
Hg
: about
50 ƒÊg/m3
velocity : 1.5 l/min time
Concentration
of H2SO4
The effect of H2SO4 in sampling investigated. centration
: 10 mins
Concentration
solution on the sampling
efficiency was also
of KMnO4 in sampling solution was kept at 0.5% and con-
of H2SO4 in it was fluctuated.
Sampling procedure for mercury vapor was
proceeded with these solutions. Results of the experiments showed that the sampling efficiency was always 100%, and was not affected at all by fluctuation of concentration of H2SO4 (Fig. 6).
Even KMnO4 aq. (containing no H2SO4) had an efficiency of 100%
for capturing mercury vapor.
Fig.
6.
(It may be that mercury was oxided to Hg+2 by KMnO4
Sampling con.
efficiency
of solution.
of KMnO4
sampling passing
0.5%
solution air
volume
: 10 ml
Hg
: about
50 ƒÊg/m3
velocity : 1.5 l/min time 249
: 10 mins
N.
and Hg+2 dissolved into HMnO4.)
HARA
So it may be guessed that mercury must be oxided
first of all, and part of H2SO4 is not so great in sorption of mercury. Affection of manganese
dioxide (MnO2)
Solubility of MnO2 in H2O is very small. but its solubility
MnO2 dissolves scarcely
in dil. H2SO4,
in conc. H2SO4 is not so small (Fig. 7). From the results of the
experiments, it became clear that saturated solution of MnO2 in H2SO4 had no power of sorption for mercury vapor in it, regardless of the concentration saturated solution of MnO2 in H2SO4 suspended with granules ability
of sorption
for mercury
Fig.
Fig.
8.
vapor if the concentration
7.
Solubility
Sampling
sampling, passing,
of
saturated
MnO2=H2SO4
solution. solution
air
volume
: 15 ml
Hg
: about
50 ƒÊg/m3
velocity : 1.5 l/min time 250
But
of H2SO4 is large (Fig. 8).
of MnO2 in H2SC
efficiency
suspending
of H2SO4 used.
of MnO2 had a large
: 20 mins
CAPTURE
OF MERCURY
VAPOR
Sampling efficiency decreased in very concentrated of captured
mercury
concentrated
H25O4. In such cases, the amounts
in the first impinger decreased, by that in the second one did not
decrease so rapidly as concentration ing MnO2, amount
IN AIR
of H2SO4 increased.
of captured
In concentrated
H2SO4 was used, the larger became the percentages
in liquid phase
(Table 2). Table
2.
H2SO4 suspend-
mercury in liquid phase was not so small.
The more
of dissolved mercury
These phenomena showed that granules of MnO2 adsorbed
Distribution
mercury only if H2SO4 existed.
of captured
Hg in midget
impingers.
These might be due to the reduction
of MnO2.3) In
con. H2SO4, Mn+4 was not reduced to Mn2+. MnO2 dissolve in con. H2SO4 and Hg0 is oxided to Hg+2. Hg+2 was adsorbed liquid phase.
on remained
granules
of MnO2 or dissolves in
But MnO2 is not reduced to Mn+2 in dil. H2SO4, and Hg° is not oxided
to Hg+2. Mercury neither is adsorbed nor dissolves.
In other words, captured
mercury
was Hg+2 and not Hg0 (vapor of mercury).
REFERENCES
1) Sandell, E. B. (1959). science
2) Yasuda,
Publichers,
Tokyo.
Determination
of Trace Metals,
3rd ed. p. 635.
Inter-
New York.
K. and Hasegawa,
scopy), p. 344. 3) Chitani,
Colorimetric
Kodansha,
N. (1972).
Genshi Kyuko
Bunseki
(Atomic
Absorption
Spectro-
Co., Tokyo. (in Japanese)
T. (1956). Muki Kagaku
(Inorganic Chemistry),
(in Japanese)
251
4th ed., p. 962. Sangyo Tosho Co.,