Documents\Palladium-contents. Pdf

Sources of Human and Environmental Exposure
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platinum alloys used in Japan (Coombes, 1990). Alloys are also used
for  bearings,  springs  and  balance  wheels  in  watches  and  for  mirrors in
astronomical  instruments.  In  jewellery,  palladium  hardened  with  4–5%
ruthenium  provides  a  light, white, strong, tarnish-free alloy for watch
cases,  brooches  and  settings  for  gems  (Budavari  et al., 1996;
Kroschwitz, 1996).
3.2.4
Uses of important palladium compounds
Uses of some important palladium compounds are described
briefly below:
<
Ammine  complexes  of  palladi u m: The compounds and reactions
are  important in the industrial separation of palladium, i.e., chloro-
palladosamine  is  a precurser of metallic palladium sponge. It is
also  used  in  electroless  plating  and  bright  palladium  plating.
Ammonium  hexachloropalladate(IV)  is  important  in  separation
technology.
<
Palladium(II)  acetate: Palladium(II) acetate is of some importance
in preparative chemistry. It is used as a catalyst (Budavari et al.,
1996).
<
Palladium(II)   chloride:  Palladium(II)  chloride  is  used  in  plating
baths.  Pellets  or  monoliths  of oxidation catalysts are either
immersed  in  an  aqueous  solution  of  palladium(II) chloride (impreg-
nation technique) or sprayed with a solution of this chemical
(NAS, 1977).
Other  uses  for  palladium(II) chloride include photography, toning
solutions,  electroplating parts of clocks and watches, detecting
carbon  monoxide  leaks  in  buried  gas pipes, manufacture of indel-
ible  ink  and  preparation  of  metal  for  use  as  a  catalyst  (Budavari  et
al.,  1996;  Olden,  1997).  Different  purity  grades  of  palladium(II)
chloride  ranging  from  99%  to  99.999% are available for chemical
or medical use (Aldrich, 1996).
<
Palladium(II)  nitrate: Palladium(II) nitrate is used as a catalyst in
organic  syntheses   and  in  the  separation  of  chlorine  and iodine
(NAS, 1977; Budavari et al., 1996).

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EHC 226: Palladium
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<
Palladium(II)   oxide:  Palladium(II) oxide is used as a hydrogen-
ation catalyst in the synthesis of organic compounds.
<
Hydrogen  tetrachloropalladate(II) :  The  solution of hydrogen
tetrachloropalladate(II) is an industrially important palladium prep-
aration.  It  is  the  starting  material for many other palladium
compounds, particularly catalysts (Renner, 1992).
<
Tetraammine  palladium  hydrogen  carbonate:  Tetraammine
palladium  hydrogen  carbonate is used as an intermediate in the
production  of  automobile catalysts (Lovell, Johnson Matthey plc,
personal communication, February 2000).
3.3
Emissions during production and use
Since palladium is a valuable metal, great care is taken to avoid
significant  loss  during  mining  and  refining  processes and during use
and disposal of palladium-containing objects. 
There are no data available concerning losses of palladium to the
atmosphere  and  potentially  to  aquatic sinks from the use of catalysts
in the chemical and petroleum industry. Used palladium catalysts can
be recovered with a loss of about 5–6% (Fishbein, 1976).
3.3.1
Emissions into air
3.3.1.1
Production and fabrication losses
There  are  three  major  categories of industrial point sources for
possible  emission  of  palladium  compounds:  mining  (where  no  infor-
mation is available), refining and processing.
Older  data  are  available  on  the  annual  amount  of palladium lost for
the  smelter stacks in Sudbury, Ontario (Canada). Palladium losses of 69
kg  were  reported  for  the  year  1971  (Smith et al., 1978). The data show
that  palladium  can  be  lost  in  particulate  and  gaseous  emissions during
smelting  of  copper, nickel and other base metal ores containing PGMs.
Other  data  on  emissions  of  palladium  during  production  are  not
available.

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Sources of Human and Environmental Exposure
39
Also,  during  the  use  of  stationary  palladium-containing  catalysts,
palladium  may  escape into the environment, but there is no measure-
ment available to support this assumption.
3.3.1.2
Losses from automotive exhaust emission control catalysts
Experimental  data  show  that  automobile  catalysts  are  likely  to  emit
palladium  into  the  environment.  These emissions may be due to
mechanical  and  thermal  impact.  Information  on  the  palladium emission
rate  of  cars  equipped  with  modern  monolithic  palladium/rhodium  three-
way catalysts is still scarce.
Moldovan  et  al.  (1999)  determined PGM concentrations in the raw
car  exhaust fumes released by two different types of fresh gasoline
catalytic  converters  (platinum/palladium/rhodium  and  palladium/rho-
dium),  a  diesel  catalyst (labelled as platinum only) and an 18 000-km
aged  platinum/palladium/rhodium  gasoline  catalyst. Palladium was the
main  noble metal in the three gasoline catalysts. Samples were col-
lected  following  91  441  urban  and  extra-urban  driving cycles for light-
duty  vehicle  testing. As shown in Table 10, the particulate palladium
released from the fresh catalysts is in the range of 3.7–108 ng/km.
Table 10. Particulate and soluble palladium emissions in exhaust fumes
from new catalysts
Emissions (ng/km)
Pt/Pd/Rh catalyst
Pd/Rh catalyst
Pt diesel
catalyst
Particulate
93–108
18.5–23.2
3.7–6.0
Soluble
12.3–14.1
4–7.8
not
detected
(% of
total)
(10.2–13.2)
(15.7–29.7)
–
Most  of  the  palladium  released  was  in  particulate form. The solu-
ble  fraction  represents  10–30%  of  the  total  released.  In  a preliminary
study   performed  on  the  aged  platinum/palladium/rhodium  catalyst, the
palladium  emission  was  lower  at  a  constant  speed  of  80  km/h  (1.2–
1.9  ng/km)  than  when  the  driving  cycle  was  applied  (2–24  ng/km).
Hence,  new  catalysts  seemed  to  release  more  particulate palladium than
older catalysts.

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