COBALT AND ITS COMPOUNDS

COBALT AND ITS COMPOUNDS

N. Angelescu, Cristiana Rizescu

“Valahia” University of Targoviste


Abstract

Cobalt is a compound that occurs in nature. It occurs in many different chemical forms. Pure cobalt is a steel-gray, shiny, hard metal. Cobalt used in industry is imported or obtained by recycling scrap metal that contains cobalt. It is used to make alloys (mixtures of metals), colored pigments, and as a drier for paint and porcelain enamel used on steel bathroom fixtures, large appliances, and kitchenwares. Small amounts naturally occur in food. Vitamin B12 is a cobalt-containing compound that is essential for good health.. Some natural sources of cobalt in the environment are soil, dust, and seawater. Cobalt is also released from burning coal and oil, and from car and truck exhaust. Cobalt enters the environment from natural sources and from the burning of coal and oil. Cobalt stays in the air for a few days. Pure cobalt does not dissolve in water, but some of its compounds do.
Everyone is exposed to cobalt at low levels in air, water, and food. People who live near hazardous waste sites containing cobalt may be exposed to higher levels of this chemical. Food is another source of exposure to cobalt.

Key words: cobalt, air, water, soil, food

Introduction

Cobalt is a brittle, hard metal, resembling iron and nickel in appearance. It has a metallic permeability of about two thirds that of iron. Cobalt tends to exist as a mixture of two allotropes over a wide temperature range. The transformation is sluggish and accounts in part for the wide variation in reported data on physical properties of cobalt.
Cobalt has also been used as a treatment for anemia, as it causes red blood cell production

Cobalt can stay for years in water and soil. It can move from the soil to underground water. Plants take up cobalt from the soil. OSHA exposure limit: 0.1 0.1mg/m³ for cobalt in workplace air for an 8-hour workday, 40-hour work week. American Conference on General and Industrial Hygiene (ACGIH) occupational exposure limit: 0.02 mg/m³ for cobalt for an 8-hour workday, 40-hour workweek. National Institute for Occupational Safety and Health (NIOSH) occupational exposure limit: 0.05 mg/m³ for cobalt for a 10-hour workday, 40-hour workweek.

Cobalt does not occur naturally as a base metal, but is a component of more than 70 naturally occurring minerals, including various sulfides, arsenides, sulfoarsenides, hydrates, and oxides. The most common cobalt minerals are the arsenide CoAs2–3 (smeltite), the arsenosulfide CoAsS (cobaltine), and the sulfide Co3S4 (linneite) (IARC, 1991).
Sources of environmental cobalt are both natural and anthropogenic (Barceloux, 1999). Natural sources include erosion (wind-blown continental dusts), weathering of rocks and soil, seawater spray, volcanoes, forest fires, extraction by plants, and continental and marine biogenic emissions. The worldwide estimate for atmospheric cobalt emissions is 5350–6170 tonnes per year (Lantzy & Mackenzie, 1979; Nriagu, 1989). Cobalt compounds have been found to occur naturally in seawater, surface water, spring water, and groundwater (Smith & Carson, 1981).

Cobalt is normally associated with copper or nickel; mined ore often contains only 0.1% elemental cobalt. About 44% of world production of cobalt comes from nickel ores. Cobalt is extracted from the metals in the ore by both flotation (sulfide ores) and gravity (arsenide ores); roasting or acid leaching is necessary to concentrate the cobalt (Barceloux, 1999). Cobalt is also extracted from the ore and concentrated by pyrometallurgical, hydrometallurgical, and electrolytic processes alone or in combination (Donaldson et al., 1986).

It is alloyed with iron, nickel and other metals to make Alnico, an alloy of unusual magnetic strength with many important uses. Stellite alloys, containing cobalt, chromium, and tungsten, are used for high-speed, heavy-duty, high temperature cutting tools, and for dies (Cobalt Development Institute, 2004).
Cobalt is also used in other magnetic steels and stainless steels, and in alloys used in jet turbines and gas turbine generators. The metal is used in electroplating because of its appearance, hardness, and resistance to oxidation.

The salts have been used for centuries to producte brilliant and permanent blue colors in porcelain, glass, pottery, tiles, and enamels. It is the principal ingredient in Sevre's and Thenard's blue. A solution of the chloride is used as a sympathetic ink. Cobalt carefully used in the form of the chloride, sulfate, acetate, or nitrate has been found effective in correcting a certain mineral deficiency disease in animals.
Soils should contain 0.13 to 0.30 ppm of cobalt for proper animal nutrition.
Cobalt-60, an artificial isotope, is an important gamma ray source, and is extensively used as a tracer and a radiotherapeutic agent.

Cobalt metal has three major uses in the petrochemical and plastic industries as both heterogeneous and homogeneous catalysts: (1) hydro-treating and desulfurization catalysts for oil and gas; these catalysts are typically 3–5% cobalt oxide (Co3O4), 14% manganese trioxide (MnO3), and the balance aluminium oxide (Al2O3); (2) mixed cobalt acetate/manganese–sodium bromide homogeneous catalyst for the production of terephthalic acid and dimethyl terephthalate; and (3) cobalt catalyst in the oxo synthesis (hydroformylation) for the production of alcohols and aldehydes for plastic and detergent production, employing freshly reduced cobalt metal, carbonyls, or cobalt salts (transformed in situ to carbonyl) (Cobalt Development Institute, undated b; USGS, 2005).

Everyone is exposed to cobalt at low levels in air, water, and food. People who live near hazardous waste sites containing cobalt may be exposed to higher levels of this chemical. Food is another source of exposure to cobalt.
Workers may be exposed to cobalt in industries that process it or make products containing cobalt. Acute toxicity of cobalt may be observed as effects on the lungs, including asthma, pneumonia, and wheezing, that have been found in workers who breathed high levels of cobalt in the air. In the 1960s, some breweries added cobalt to beer to stabilize the foam. Some people who drank large quantities of the beer experienced nausea, vomiting, and serious effects on the heart. However, effects on the heart were not seen in people with anemia or pregnant women treated with cobalt. Animal studies have found problems with the development of the fetus in animals exposed to high concentrations of cobalt during pregnancy. However, cobalt is also essential for the growth and development of certain animals. The International Agency for Research on Cancer (USA) has determined that cobalt is a possible carcinogen to humans. Studies in animals have shown that cobalt causes cancer when placed directly into the muscle or under the skin. Cobalt did not cause cancer in animals that were exposed to it in the air, in food, or in drinking water. Human studies are inconclusive regarding cobalt and cancer. Tests for urine and blood level detection - accurate for up to a few days after exposure because cobalt leaves the body fairly quickly. Special equipment needed for detection is usually not available in doctors’ offices.

This CICAD - Concise International Chemical Assessment Document 69 - (This report contains the collective views of an international group of experts and does not necessarily represent the decisions or the stated policy of the United Nations Environment Programme, the International Labour Organization, or the World Health Organization) on cobalt and inorganic cobalt compounds was prepared by Sciences International, Inc. in the United States and the Centre for Ecology and Hydrology in the United Kingdom and was based on reviews prepared by the Agency for Toxic Substances and Disease Registry (ATSDR, 2004) and the International Agency for Research on Cancer (IARC, 2005). This CICAD was considered and approved as an international assessment at a meeting of the Final Review Board held in Nagpur, India, on 31 October – 3 November 2005. International Chemical Safety Cards for cobalt, cobalt(II) oxide, cobalt(III) oxide, cobalt(II) sulfide, cobalt(II) chloride, cobalt(II) sulfate, cobalt(II) sulfate heptahydrate, cobalt(II) nitrate, cobalt(II) nitrate hexahydrate, cobalt(II) acetate tetrahydrate, cobalt naphthenate, and cobalt carbonyl, produced by the International Programme on Chemical Safety (IPCS, 2000, 2001a–e, 2004a–f).

Cobalt (CAS No. 7440-48-4) is a silvery grey solid at room temperature. It is the 33rd most abundant element and has been found in a variety of media, including air, surface water, leachate from hazardous waste sites, groundwater, soil, and sediment. Sources of exposure to cobalt and inorganic cobalt compounds are both natural and anthropogenic. Natural sources include wind-blown dust, seawater spray, volcanoes, forest fires, and continental and marine biogenic emissions. Anthropogenic sources include the burning of fossil fuels, sewage sludge, phosphate fertilizers, mining and smelting of cobalt ores, processing of cobalt alloys, and industries that use or process cobalt compounds.

Cobalt and inorganic cobalt compounds are non-volatile and released into the atmosphere in particulate form. Anthropogenic cobalt from combustion sources is assumed to be primarily in the form of oxides. Sulfide and arsenide forms are also released into the atmosphere during ore extraction and refining processes.

Factors affecting the speciation and fate of cobalt in water, sediments, and soil include organic ligands such as humic acids, anions, pH, and redox potential. The soil mobility of cobalt is inversely related to the strength of adsorption by soil constituents. Although plants may take up cobalt from the soil, the translocation of cobalt from the roots to other parts of the plant is not significant.

Measured atmospheric concentrations of cobalt are about 1 ng/m3 or less in non-source areas and generally less than 10 ng/m3 in source areas, although higher concentrations in source areas have been reported. Surface water and groundwater concentrations of cobalt are low, below 1 µg/l in pristine areas and 1–10 µg/l in populated areas. Surface water and groundwater concentrations can be much higher in mining and agricultural areas — as much as several hundred milligrams per litre. Mean cobalt concentrations in seawater have been reported to be less than 1 µg/l. Cobalt concentrations in drinking-water are generally <1–2 µg/l. In rainwater, mean concentrations are 0.3–1.7 µg/l. The earth’s crust contains an average cobalt concentration of 20–25 mg/kg. Near some anthropogenic sources, the concentration of cobalt in soil may be several hundred milligrams per kilogram.

The largest source of exposure to cobalt for the general population is the food supply. The estimated intake from food is 5–40 µg/day, most of which is inorganic cobalt. Occupational exposure to cobalt occurs in several industries. Levels of cobalt in tobacco range from <0.3 to 2.3 µg/g dry weight, and approximately 0.5% of this cobalt is present in mainstream smoke. Cobalt concentrations in coal, crude oil, fuel oil, and gasoline in the United States were found to be 5 mg/kg, 0.001–10 mg/kg, 0.03–0.3 mg/kg, and <0.1 mg/kg, respectively.
Inhalation of cobalt particles results in deposition in the upper and lower respiratory tract, where they can be retained or absorbed into the blood after dissolution or mechanically transferred to the gastrointestinal tract by mucociliary action and swallowing. Approximately 50% of the cobalt that enters the gastrointestinal tract will be absorbed. Cobalt absorption is increased among individuals who are iron deficient. Water-soluble forms are better absorbed than insoluble forms. Total body burden is estimated as 1.1–1.5 mg, with 0.11 mg in the liver.
No studies describe the distribution of cobalt in humans following ingestion, but animal studies indicate that cobalt is retained primarily in the liver. In a controlled human aerosol exposure study, 40% of the initial lung burden of cobalt oxide was retained at 6 months after exposure.

Atmospheric cobalt is associated with particulate matter principally to the extent to which particles of soil are dispersed by the wind. At unpolluted sites, mean cobalt levels are typically <1–2 ng/m3 (Smith & Carson, 1981; Hamilton, 1994). At the South Pole, the concentration of cobalt was 0.000 49 ± 0.000 15 ng/m3 in 1974–1975 (Maenhaut et al., 1979). In open-ocean environments, mean cobalt concentrations ranged from 0.0004 to 0.08 ng/m3 (Chester et al., 1991). As examples of cobalt concentrations in urban areas, the annual average cobalt concentration at Nahant, Massachusetts (near Boston), USA, in 1992–1993 was 1.7 ng/m3 (Golomb et al., 1997), whereas in Seville, Spain, during 1996 it was 0.5 ng/m3 (Espinosa et al., 2001). In southern Norway, the mean cobalt level was 0.10 ng/m3 in 1985–1986 (Amundsen et al., 1992). In source areas, cobalt concentrations may exceed 10 ng/m3. The highest average atmospheric cobalt concentration was recorded near a nickel refinery in Wales, at 48 ng/m3 (Smith & Carson, 1981).

Cobalt is a metal found naturally in soil, dust, and seawater. It is usually found in association with nickel. Cobalt and its salts have many uses, the table below shows some of the many sources of cobalt and where or how we may come into contact with them either at home or at work.

Home/personal sources Work sources
• Cobalt blue pigment in porcelain, glass, pottery, ceramics and enamels
• Cobalt blue in blue and green water colour paints and crayons
• Metal-plated objects
• Buckles
• Buttons
• Zippers
• Snaps
• Costume jewellery
• Utensils
• Tools
• Medical uses
• Vitamin B12 preparations for the treatment of anaemia
• Metal prostheses
• Dental plates
• Hair dyes; cobalt pigment produces light brown shades of hair
• Antiperspirant preparations
• Cobalt used as binding agent in hard metals to create drills, cutting tools, mechanical parts
• Cobalt naphthenate is a common catalyst in the manufacture of polyester resins
• Manufacture of cobalt-containing alloys
• As an oxidizing agent in automobile exhaust controls, in the rubber tire industry and in electroplating
• Cement industry; cement contains cobalt oxides
• Cobalt siccatives or driers are found in certain paints and varnishes
• Binding agent in the carbide industry
• Wet clay containing cobalt used by pottery workers

Reactions to contact with cobalt in an allergic individual include allergic contact dermatitis and irritant dermatitis. Vitamin B12 injections administered to allergic individuals may produce a red, tender and itchy area around the site of the injection. Oral ingestion of vitamin B12 is known to cause intractable hand eczema is some patients.
In many cases, allergic reactions are not caused solely by cobalt sensitisation. For example, metal objects almost always also contain nickel and in the cement industry nickel and chromium are present. Nickel and chromium are also potent sensitisers therefore; allergic reactions may not be due solely to cobalt but also to simultaneous specific allergy to nickel and chromium.

Nickel and cobalt are always found together in alloys and salts because it is too costly and impracticable to separate these two metals. Thus patch testing should always include both cobalt and nickel. Unfortunately, patch test results with cobalt and nickel can be confusing as it is extremely difficult to obtain pure solutions of each individual metal.

Intradermal testing with cobalt may also be performed to diagnose cobalt sensitivity.
Where avoidance is not achievable, several methods can be used to try to minimize exposure. Brief contact with metal devices is usually not a problem except in highly sensitive individuals.

In the workplace try to avoid exposure to cobalt, however this may not be practicable thus use measures to minimize exposure as described above. Identify potential sources of exposure using Material Safety Data Sheets; these are required for all chemicals and substances that you may come into contact with in the workplace. If you must use products that contain cobalt, wear gloves or other protective clothing to avoid contact with your skin.
Outside of the workplace, the best way to avoid cobalt allergy is by being aware of the possible sources of cobalt. Read product labels and do not use any that contain cobalt or any of its alternative names. If unsure ask your pharmacist for advice or a suitable alternative. Only use cosmetics, antiperspirants and hair dyes that you know do not contain cobalt. Avoid metallic costume jewellery. Sterling silver and platinum jewellery is usually tolerated.
Alert your doctor or dentist to the fact that you have an allergy to cobalt. Your dermatologist may have further specific advice, particularly if you are highly sensitive to cobalt.

Sources of Exposure to Cobalt
• Alloys
• Buttons
• Buckles
• Carbide
• Ceramics
• Cement
• Clay
• Cosmetics
• Costume jewellery
• Cutting tools
• Dental plates
• Detergents
• Flypapers
• Glass
• Hair dye
• Kitchen utensils
• Metal prostheses
• Oils
• Paints
• Pottery
• Polyester resin
• Printing inks
• Rock drills
• Rubber tires
• Tools
• Vitamin B12
• Zippers

Cobalt and its salts have high acute (short-term) toxicity on aquatic life. It also has high chronic (long-term) toxicity on aquatic life. There is not sufficient data to determine the acute or chronic toxicity of cobalt and its compounds on plants, birds or land animals. Cobalt and its compounds are highly persistent in water and the environment. Cobalt will bioaccumulate or concentrate in the tissues of fish.

Industrial emissions of cobalt and or cobalt compounds can produce elevated, but still low level concentrations in the atmosphere around the source. Because of its short life expectancy in the atmosphere cobalt and or cobalt compounds is expected to be confined to the local area within which it is emitted.
Cobalt and its compounds are expected to act like other particles in the atmosphere. The way they deposit in the local area will depend on the local wind and rain. They are expected to remain in the atmosphere from 5 to 15 days.
No national guidelines.

Common uses

Cobalt is a metal that occurs naturally in many different forms. Small amounts of it are found in most rocks, soil, water, plants, and animals. Cobalt is a component of vitamin B12, which is required for good health. The largest use of cobalt metal is to make alloys, which retain strength even when very hot. It is also used to help paint dry quickly. Cobalt is also used to make artificial body parts such as hip and knee joints. Cobalt carbonate is used in ceramics and as an animal feed supplement in trace amounts. Cobalt chloride is used as a humidity and water indicator, in electroplating, in the manufacture of vitamin B12, as a fertilizer and feed additive in trace amounts. Cobalt oxide is used in pigments for ceramics and glass, in fast drying paints and varnishes, in semiconductors, in enamel coatings on steel, and again as an animal feed additive in trace amounts. Cobalt sulfate is used in electroplating, in batteries, as a drying agent in inks and varnishes, in enamels, and ceramics, and as a feed and fertilizer additive.

Sources of emissions

• Industry sources
• Diffuse sources, and industry sources included in diffuse emissions data
• Natural sources
• Transport sources
• Consumer product that may contain cobalt and compounds

Industry sources

Cobalt is mainly emitted from sources where it is used in the production of steel and other alloys. It may be emitted to air, land or water from these sources. Automotive repair shops may be significant emitters (to air) of cobalt. It will also be emitted to air, land and water during the mining or refining of nickel, copper, silver, lead and iron.

Diffuse sources, and industry sources included in diffuse emissions data
Cobalt may be emitted to air, land or water from the manufacture, use or disposal of paints and varnishes. It may also be emitted to air, land or water from the manufacture, use or disposal of ceramic, inks, and enamels.

Natural sources

Cobalt is found in soil, dust, seawater, volcanic emissions, and smoke from forest and bush fires.

Transport sources

Small amounts of cobalt have been found in motor vehicle exhaust.

Consumer products that may contain cobalt and its compounds
Consumer products containing cobalt and its compounds include: vitamin B12, animal feeds and fertilisers, paints, varnish, enamels and ceramics. It is in metals used at high temperatures (e.g. some car parts).

Management of cobalt allergy

Identifying possible sources of contact and avoiding them is the only long-term management strategy for cobalt allergy. Where avoidance is not achievable, several methods can be used to try to minimize exposure. Brief contact with metal devices is usually not a problem except in highly sensitive individuals.

IARC - The International Agency for Research on Cancer (2005) evaluated the carcinogenic hazards of cobalt and cobalt compounds and concluded that:
•There is limited evidence in humans for the carcinogenicity of cobalt metal with tungsten carbide.
•There is inadequate evidence in humans for the carcinogenicity of cobalt metal without tungsten carbide.
•There is sufficient evidence in experimental animals for the carcinogenicity of cobalt sulfate.
•There is sufficient evidence in experimental animals for the carcinogenicity of cobalt metal powder.
•There is limited evidence in experimental animals for the carcinogenicity of metal alloys containing cobalt.
•There is inadequate evidence in experimental animals for the carcinogenicity of cobalt–aluminium–chromium spinel.

The overall evaluation was that:

•Cobalt metal with tungsten carbide is probably carcinogenic to humans.
•Cobalt metal without tungsten carbide is possibly carcinogenic to humans.
•Cobalt sulfate and other soluble cobalt(II) salts are possibly carcinogenic to humans

Methods to minimize cobalt exposure

•Use metal instruments such as scissors, kitchen utensils and combs that have plastic or wooden handle grips.
• If necessary, wear vinyl or rubber gloves to avoid contact (however, do not use for wet work as moisture increases the penetration of cobalt into the skin).
• Items such as keys can be coated with several layer of clear nail polish.
In the workplace, wear protective clothing and employ no-touch techniques

Comparison to other substances

NPI rank - The National Pollutant Inventory – Australia - approximately 400 substances were considered for inclusion on the NPI reporting list. A ranking and total hazard score was given based on health and environmental hazards and human and environmental exposure to the substance.
Cobalt and its compounds was ranked as 27 out of 400.

References

1. Abbasi SA, Nipaney PC, Soni R (1989) Environmental status of cobalt and its micro determination with 7-nitroso-8-hydroxyquinoline-5-sulfonic acid in waters, aquatic weeds and animal tissues. Analytical Letters, 22(1):225–235.
2. Abraham JL, Hunt A (1995) Environmental contamination by cobalt in the vicinity of a cemented tungsten carbide tool grinding plant. Environmental Research, 69:67–74.
3. ACGIH (1999) 1999 TLVs and BEIs. Threshold limit values for chemical substances and physical agents. Biological exposure indices. Cincinnati, OH, American Conference of Governmental Industrial Hygienists, 184 pp.
4. Adam C, Baudin JP, Garnier-Laplace J (2001) Kinetics of 110mAg, 60Co, 137Cs and 54Mn bioaccumulation from water and depuration by the crustacean Daphnia magna. Water, Air, and Soil Pollution, 125:171–188.
5. Adriano DC (1986) Trace elements in the terrestrial environment. New York, NY, Springer-Verlag.
6. Afeworki S, Chandravanshi BS (1987) Simultaneous determination of iron(III) and cobalt(II) with N-phenylcinnamohydroxamic acid and thiocyanate by extraction and spectrophotometry. Mikrochimica Acta, 92:143–152.
7. Ahluwalia AS, Kaur M (1988) Effect of some heavy metal compounds on growth and differentiation in a blue-green and a green alga. Microbios, 53:37–45.
8. Albrecht A (2003) Validating riverine transport and speciation models using nuclear reactor-derived radiocobalt. Journal of Environmental Radioactivity, 66:295–307.
9. Aldenberg T, Slob W (1993) Confidence limits for hazardous concentrations based on logistically distributed NOEC toxicity data. Ecotoxicology and Environmental Safety, 25:48–63.
10. Alexander CS (1969) Cobalt and the heart. Annals of Internal Medicine, 70:411–413.
11.International Programme on Chemical Safety (1994) Assessing human health risks of chemicals: derivation of guidance values for health-based exposure limits. Geneva, World Health Organization (Environmental Health Criteria 170) (also available at http://www.who.int/pcs/).
12.Hanna RGM (1992) The level of heavy metals in the Red Sea after 50 years. Science of the Total Environment, 125:417–448.
13. Gibbs RJ (1994) Metals in the sediments along the Hudson River estuary. Environment International, 20(4):507–516.
14. Gladstones JS, Loneragan JF, Goodchild NA (1977) Field responses to cobalt and molybdenum by different legume species, with inferences on the role of cobalt in legume growth. Australian Journal of Agricultural Research, 28(4):619–628.
15. Francis CW, Davis EC, Goyert JC (1985) Plant uptake of trace elements from coal gasification ashes. Journal of Environmental Quality, 14(4):561–569.
16. Donaldson JD (1986) Cobalt in the environment. In: Proceedings of the first congress on cobalt and the environment, Toronto, Ontario, 2–3 April 1986. Guildford, Surrey, Cobalt Development Institute, pp.1–21.
17. Donaldson JD, Clark SJ, Grimes SM (1986) Cobalt in medicine, agriculture and environment. Guildford, Surrey, Cobalt Development Institute.
18. Dalvi RR, Robbins TJ (1978) Comparative studies on the effect of cadmium, cobalt, lead, and selenium on hepatic microsomal monooxygenase enzymes and glutathione levels in mice. Journal of Environmental Pathology and Toxicology, 1:601–607.

Time for Exhibitions

Like every year once we start leaving winter time, Cevisama break into with the first exhibition of the year, after the first one a long list of ceramic exhibitions all around the world come to us.

In this blog as part of International Ceramic Industry we're going to share information about those exhibitions with our point of view for those ones that we're visiting or the point of friends that get the opportunity of being there. As you know we're here for giving as much information as possible from International Ceramic Industry and our objective is creating a blog useful for all of you.

UNICERA 2011

Unicera Estambul

Feria de cerámica, baño y cocina

Unicera es una organización internacional de cerámica, baño y cocina, donde justo la industria cerámica turca se reúne una vez al año en conjunto la promoción de los productos más nuevos y las tecnologías de la industria. Baldosas de cerámica, loza vitrificada, piscinas, saunas, grifería, baño y muebles de cocina y accesorios y publicaciones relativas a estos se exhiben. Unicera no es sólo un comercial, sino también como comunicación, información y una plataforma de transmisión de la cultura