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Cobalt

DESIGNATIONS

CAS No.: 7440-48-4
Registry name: Cobalt
Chemical name: Cobalt
Synonyms, Trade names: Cobalt
Chemical name (German): Cobalt
Chemical name (French): Cobalt
Appearance: steel-grey, shiny, ferromagnetic metal

BASIC CHEMICAL AND PHYSICAL DATA

Chemical symbol: Co
Rel. atomic mass: 58.93 g
Density: 8.85 g/cm3 at 25C
Boiling point: 2800C +/- 50C
Melting point: 1495C
Vapour pressure: <10-5 Pa at 1250C, >105 Pa at 3200C
Solvolysis/solubility: readily soluble in diluted, oxidising acids

ORIGIN AND USE

Usage:
Dyeing of glass, ceramics and enamel by Co compounds. Production of temperature-resistant, abrasion-proof and non-corroding alloys (stellite). The synthetic radioactive isotope 60Co is used in nuclear engineering and nuclear medicine (treatment of tumours) as well as in other countries to preserve foodstuffs. Co is used in the chemical industry in homogeneous and heterogeneous catalysis to synthesise fuels (Fischer-Tropsch method) as well as alcohols and aldehydes (hydroformylation). A further use is found in the cemented carbides.

Origin/derivation:
Co makes up 0.0023% of the Earth's crust and is found together with Cu, Ni and Fe ores. In most cobalt-containing ores, arsenic is present, too. Co is manufactured by the partial roasting of sulphide ores in the presence of fluxing agents. The resulting raw material contains Cu, Ni and Co sulphides and arsenides at higher concentrations. Further processing then involves heating the raw material in the presence of NaCl.

Production figures:
In 1980: 32,700 t (worldwide) [ULLMANN, 1986]

Toxicity

Mammals:
Rat LD50 1750 mg/kg, (Co oxide) acc. Ullmann, 1986
Rat LD50 821 mg/kg, (Co acetate) acc. Ullmann, 1986
Rat LD50 766 mg/kg, (Co chloride) acc. Ullmann, 1986
Rat LD50 691 mg/kg, (Co nitrate) acc. Ullmann, 1986
Rat LD50 630 mg/kg, (Co carbonate) acc. Ullmann, 1986
Rat LDLo 1500 mg/kg, oral acc. UBA, 1986
Rat LDLo 100 mg/kg, intravenous acc. UBA, 1986
Rabbit LDLo 20 mg/kg, oral acc. UBA, 1986
Rabbit LDLo 100 mg/kg, intravenous acc. UBA, 1986
Aquatic organisms:
Daphnia 1-9 mg/l = critical level, (Co chloride) acc. LAU-BW, 1989

Characteristic effects:

Humans/mammals: Overdoses reduce the activity of the thyroid gland and can cause the formation of goitres. The number of erythrocytes in the blood increases (polycythemia), the blood vessels are temporally enlarged and blood coagulation is impaired. The nervous system is also frequently affected. Heart damage and pulmonary fibrosis (chron.) may occur. The most important aspect in toxicological terms is the inhalation of Co dust (proven carcinogenic effect; ROTH, 1989) and the hazard of sensitisation (ROTH, 1989). In addition, there is corrosion of the throat and the gastrointestinal tract if cobalt dusts have been inhaled. Poisoning causes disfunctions of the liver and kidneys.

Plants: A surplus of Co results in an Fe and Cu deficit (toxic effect = displacement effect). There is an increase in the number of chlorotic leaves which become necrotic and then die off.

ENVIRONMENTAL BEHAVIOUR

Air:
Cobalt is stable at normal temperatures in air. When heated, it oxidises and burns at white heat to form Co3O4.

Soil:
The average Co content is 8 mg/kg. The solubility depends on the pH. There is more elution in acid soils. Cobalt is bonded above all to Mn and Fe oxides with the result that only small quantities are available and thus mobile.

Degradation, decomposition products, half-life:
Renal discharge of inhaled cobalt: majority with a half-life of 10 days, remainder with half-life of 90 days (MERIAN, 1984).

Food chain:
The absorption of cobalt in drinking water is insignificant. Generally, the atmosphere is likewise only contaminated by traces of cobalt. Humans absorb approx. 140 - 580 m g of cobalt per day. Between 20% and 95% are resorbed. However, most of the Co absorbed does not take the form of the necessary vitamin B12, but is encountered rather as inorganic Co bonded to foodstuff constituents. The absorption of inorganic Co is linked to that of iron.

ENVIRONMENTAL STANDARDS

Medium/ acceptor Sector Country/ organ. Status Value Cat. Remarks Source
Water: Surface D

G

0.05 mg/l   1) For A + B acc. LAU-BW, 1989
Groundw D

(G)

50 g/l   Investigation acc. LAU-BW, 1989
Groundw D

(G)

200 g/l   Rehabilitation acc. LAU-BW, 1989
Groundw NL

G

20 mg/l   Reference acc. TERRA TECH, 6/94
Groundw NL

L

100 mg/l   Intervention acc. TERRA TECH, 6/94
Waste water CH

(L)

0.05 mg/l     acc. LAU-BW, 1989
Waste water CH

(L)

0.50 mg/l   Direct/indirect introduction acc. LAU-BW, 1989
Irrigation D

G

0.20 mg/l   Field cultivation acc. LAU-BW, 1989
Irrigation D

G

0.20 mg/l   Cultivation under glass acc. LAU-BW, 1989
Irrigation USA

(L)

0.20 mg/l     acc. LAU-BW, 1989
Irrigation USA

(L)

10 mg/l   2) acc. LAU-BW, 1989
Soil:   CH

G

25 mg/kg     acc. LAU-BW, 1989
  D

(G)

50 mg/kg   Investigation acc. LAU-BW, 1989
  D

G

300 mg/kg   Rehabilitation acc. LAU-BW, 1989
  D

G

800 mg/kg     acc. HOCK, 1988
  NL

G

20 mg/kg   Reference acc. TERRA TECH, 6/94
  NL

L

240 mg/kg   Intervention acc. TERRA TECH, 6/94
  USA

G

8000 mg/kg   TTLC acc. DVGW, 1988
  USA

G

80 mg/kg   STLC acc. DVGW, 1988
Sewage sludge CH

L

100 mg/kg     acc. LAU-BW, 1989
Air: Emiss. D

L

1 mg/m3   mass flow > 5 g/h3) acc. TA Luft, 1986
Workp AUS

L

0.1 mg/m3     acc. MERIAN, 1984
Workp B

L

0.01 mg/m3     acc. MERIAN, 1984
Workp BG

L

0.5 mg/m3     acc. MERIAN, 1984
Workp CH

L

0.1 mg/m3     acc. MERIAN, 1984
Workp CS

L

0.1 mg/m3   Mean value acc. MERIAN, 1984
Workp CS

L

0.3 mg/m3   Short-time value acc. MERIAN, 1984
Workp D

L

0.5 mg/m3 TRK use of powders acc. LAU-BW, 1994
Workp D

L

0.1 mg/m3 TRK all other uses DFG, 1994
Workp DDR

L

0.1 mg/m3   Mean value acc. MERIAN, 1984
Workp DDR

L

0.1 mg/m3   Short-time value acc. MERIAN, 1984
Workp SF

L

0.1 mg/m3     acc. MERIAN, 1984
Workp I

L

0.1 mg/m3   C, S acc. MERIAN, 1984
Workp NL

L

0.1 mg/m3     acc. MERIAN, 1984
Workp PL

L

0.5 mg/m3     acc. MERIAN, 1984
Workp RO

L

0.2 mg/m3   Mean value acc. MERIAN, 1984
Workp RO

L

0.2 mg/m3   Short-time value acc. MERIAN, 1984
Workp S

L

0.1 mg/m3     acc. MERIAN, 1984
Workp SU

L

0.5 mg/m3     acc. MERIAN, 1984
Workp USA

(L)

0.1 mg/m3 TWA Emission class 3 acc. LAU-BW, 1989
Workp YU

L

0.1 mg/m3      

Notes:

1) For drinking water treatment in each case: A = impact limits up to which drinking water can be produced solely by natural methods; B = impact limits up to which drinking water can be produced with the aid of currently tried-and-tested chemophysical methods
2) Only suitable for short-term irrigation on certain soils.
3) Dustlike/aerosolic Co and its compounds in respirable forms, stated as Co

Comparison/reference values

Medium/origin Country Value Source
Water:
Lake Constance D < 0.2 g/l acc. DVGW, 1988
Rhine (Mainz): D 6-12 g/l acc. DVGW, 1988
Ruhr (Duisburg): D < 1 g/l acc. DVGW, 1988
Seawater   0.1 g/l acc. DVGW, 1988
Sediment:
Lake Constance D 5.7-18.9 mg/kg acc. DVGW, 1988
Rhine (Wiesbaden): D 20 mg/kg acc. DVGW, 1988
Ruhr (Wetter): D 25 mg/kg acc. DVGW, 1988
Fly ash (coal) USA 5-73 mg/kg acc. HOCK, 1988
Plants   0.3-0.5 mg/kg acc. HOCK, 1988

Assessment/comments

Cobalt is the central atom in vitamin B12 and is an important trace element. The hazards emanating from cobalt compounds are slight when compared to other heavy metals. From the toxicological point of view it is important to avoid the inhalation of cobalt dusts.


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