Bone char

"Bone black" redirects here. For the memoir by Bell Hooks, see Bone Black.
Bone char

Pills of bone char
Names
Other names
  • bone charcoal
  • bone black
  • ivory black
  • animal charcoal
  • abaiser
  • Pigment black 9
  • CI 77267
Identifiers
8021-99-6
EC Number 232-421-2
Properties
Appearance black powder
Density 0.7 - 0.8 g/cm3
insoluble
Acidity (pKa) 8.5 - 10.0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Bone char (Latin: carbo animalis) is a porous, black, granular material produced by charring animal bones. Its composition varies depending on how it is made; however, it consists mainly of tricalcium phosphate (or hydroxylapatite) 57-80%, calcium carbonate 6-10% and activated carbon 7-10%.[1] It is primarily used for filtration and decolourisation.

Production

Bone char is primarily made from cow bones; however, to prevent the spread of Creutzfeldt–Jakob disease, the skull and spine are never used.[2] The bones are heated in a sealed vessel at up to 700 °C (1,292 °F); a low concentration of oxygen must be maintained while doing this, as it affects the quality of the product, particularly its adsorption capacity. Most of the organic material in the bones is driven off by heat, and was historically collected as Dippel's oil; that which is not driven off remains as activated carbon in the final product. Heating bones in an oxygen-rich atmosphere gives bone ash, which is chemically quite different.

Used bone char can be regenerated by washing with hot water to remove impurities, followed by heating to 500 °C (932 °F) in a kiln with a controlled amount of air.

Uses

Water treatment

The tricalcium phosphate in bone char can be used to remove fluoride[3] and metal ions from water, making it useful for the treatment of drinking supplies. Bone charcoal is the oldest known water defluoridation agent and was widely used in USA from the 1940s through to the 1960s.[4] As it can be generated cheaply and locally it is still used in certain developing countries, such as Tanzania.[5] Bone chars usually have lower surface areas than activated carbons, but present high adsorptive capacities for certain metals, particularly those from group 12 (copper, zinc, and cadmium).[6] Other highly toxic metal ions, such as those of arsenic[7] and lead[8] may also be removed.

Sugar refining

Sugars (clockwise from top-left): white refined, unrefined, brown, unprocessed cane

Historically, bone char was often used in sugar refining as a decolourising and deashing agent. Bone char possesses a low decolouration capacity and must be used in large quantities.[9] It has largely fallen out of use, particularly in the US and Europe, mainly for economic reasons but also due to the concerns of vegetarians and vegans, as well as various religious groups.

However, it is also able to remove various inorganic impurities; most importantly sulfates and the ions of magnesium and calcium. The removal of these is beneficial, as it reduces the level of scaling later in the refining process, when the sugar solution is concentrated.[10] Modern alternatives to bone char include activated carbon and ion-exchange resins.

Black pigment

Édouard Manet, 'Music in the Tuileries Gardens', 1862

Bone char is also used as a black pigment for artist's paint, printmaking, calligraphic and drawing inks as well as other artistic applications because of its deepness of color and excellent tinting strength. Bone black and ivory black are artists' pigments which are in use since historic times by painters such as Rembrandt and Velázquez but also more recently by Manet or Picasso. The black dresses and high hats of the gentlemen in Manet's 'Music in the Tuileries' are painted in ivory black.[11][12]

Ivory black was formerly made by grinding charred ivory in oil. Today ivory black is considered a synonym for bone black. Actual ivory is no longer used because of the expense and because animals who are natural sources of ivory are subject to international control as endangered species.

Niche uses

In popular culture

See also

References

  1. ↑ Fawell, John (2006). Fluoride in drinking-water (1st published. ed.). Geneva: WHO. p. 47. ISBN 9241563192.
  2. 1 2 "Dirty Jobs: Episode Guide"
  3. ↑ Medellin-Castillo, Nahum A.; Leyva-Ramos, Roberto; Ocampo-Perez, Raul; Garcia de la Cruz, Ramon F.; Aragon-Piña, Antonio; Martinez-Rosales, Jose M.; Guerrero-Coronado, Rosa M.; Fuentes-Rubio, Laura (December 2007). "Adsorption of Fluoride from Water Solution on Bone Char". Industrial & Engineering Chemistry Research 46 (26): 9205–9212. doi:10.1021/ie070023n.
  4. ↑ Horowitz, HS; Maier, FJ; Law, FE (Nov 1967). "Partial defluoridation of a community water supply and dental fluorosis.". Public health reports 82 (11): 965–72. doi:10.2307/4593174. PMC 1920070. PMID 4964678.
  5. ↑ Mjengera, H.; Mkongo, G. (January 2003). "Appropriate deflouridation technology for use in flourotic areas in Tanzania". Physics and Chemistry of the Earth, Parts A/B/C 28 (20-27): 1097–1104. doi:10.1016/j.pce.2003.08.030.
  6. ↑ Ko, Danny C.K.; Porter, John F.; McKay, Gordon (December 2000). "Optimised correlations for the fixed-bed adsorption of metal ions on bone char". Chemical Engineering Science 55 (23): 5819–5829. doi:10.1016/S0009-2509(00)00416-4.
  7. ↑ Chen, Yun-Nen; Chai, Li-Yuan; Shu, Yu-De (December 2008). "Study of arsenic(V) adsorption on bone char from aqueous solution". Journal of Hazardous Materials 160 (1): 168–172. doi:10.1016/j.jhazmat.2008.02.120.
  8. ↑ Deydier, Eric; Guilet, Richard; Sharrock, Patrick (July 2003). "Beneficial use of meat and bone meal combustion residue: "an efficient low cost material to remove lead from aqueous effluent"". Journal of Hazardous Materials 101 (1): 55–64. doi:10.1016/S0304-3894(03)00137-7.
  9. ↑ Asadi, Mosen (2006). Beet-Sugar Handbook. Hoboken: John Wiley & Sons. p. 333. ISBN 9780471790983.
  10. ↑ Chou, ed. by Chung Chi (2000). Handbook of sugar refining : a manual for the design and operation of sugar refining facilities. New York, NY [u.a.]: Wiley. pp. 368–369. ISBN 9780471183570.
  11. ↑ Bomford D, Kirby J, Leighton, J., Roy A., Art in the Making: Impressionism. National Gallery Publications, London, 1990, pp. 112-119
  12. ↑ Édouard Manet, 'Music in the Tuileries Gardens', ColourLex

External links

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