Bone char

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Bone char (Latin: carbo animalis), also known as bone black, ivory black, animal charcoal, or abaiser, is a granular material produced by charring animal bones. To prevent the spread of Creutzfeldt–Jakob disease, the skull and spine are never used.[1] The bones are heated to high temperatures—in the range of 400 to 500 °C (752 to 932 °F)— in an oxygen-depleted atmosphere to control the quality of the product as related to its adsorption capacity for applications such as defluoridation of water and removal of heavy metals from aqueous solutions. The quality of the bone char can be easily determined by its color. Black charcoals are usually undercharred bones that still contain organic impurities which may impart undesired odor and color to treated waters. White bone chars are overcharred bones that present low fluoride removal capacity.[citation needed] Grey-brownish bone char are the best quality chars for absorption applications. The quality of the bone chars is usually controlled by the amount of oxygen present in the charring atmosphere. It consists mainly of tricalcium phosphate and a small amount of carbon. Bone chars usually have lower surface areas than activated carbons, but present high adsorptive capacities for copper, zinc, and cadmium.[2][3][4] Charred pig bones can effectively absorb cobalt; however this process is inhibited by copper and zinc; which have a greater affinity for bone char. [5]

Uses

  • Calcium triphosphate is used to remove fluoride from water and to filter aquarium water.[6]
  • Tricalcium phosphate is used in powdered spices as an anticaking agent.
  • Calcium phosphate is also a raising agent (food additive) E341. It is also used in cheese products.
  • It is often used in the sugar refining industry for decolorizing[7] (a process patented by Louis Constant in 1812).[8]
  • It is used to refine crude oil in the production of petroleum jelly.
  • In the 18th and 19th century, bone char mixed with tallow or wax (or both) were used by soldiers in the field to impregnate military leather equipment, both to increase its lifespan and as the simplest way to obtain pigment for black leatherwares.
  • Bone char is also used as a black pigment. It is sometimes used for artist's paint, printmaking, calligraphic and drawing inks as well as other artistic applications because of its deepness. Ivory black is an artists' pigment formerly made by grinding charred ivory in oil. Today it is considered a synonym for bone char. 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.

In popular culture

  • The production of bone char was featured on the Discovery Channel's TV series Dirty Jobs, on episode 24 of season 4, "Bone Black", originally broadcast on 9 February 2010.[1]
  • Human bone char, referred to as "bone charcoal," is mentioned in Thomas Pynchon's novel The Crying of Lot 49. The bones come from US soldiers who died in combat during WWII and were buried in a lake in Italy, and the char is used for filters in cigarettes.

References

  1. ↑ 1.0 1.1 "Dirty Jobs: Episode Guide"
  2. ↑ Huan Jing Ke Xue (February 2007). Chemical fixation of metals in soil using bone char and assessment of the soil genotoxicity (in Chinese) 28 (2). pp. 232–7. PMID 17489175. 
  3. ↑ Wilson, J.A., Pulford, I.D. and Thomas, S. (2003). Sorption of Cu and Zn by bone charcoal 25. Environmental Geochemistry and Health. pp. 51–56. 
  4. ↑ Choy, K.K.H. and McKay, G. (2005). Sorption of metal ions from aqueous solution using bone char 31. Environment International. pp. 845–854. 
  5. ↑ Xiangliang, Pan; Jianlong, Wang; Daoyong, Zhang (January 2009). "Sorption of cobalt to bone char: Kinetics, competitive sorption and mechanism". Salination 249: 609–614. 
  6. ↑ Ellin, Abby (Sept. 3, 2012). "The Seven Dirtiest Jobs". ABC News. Retrieved 29 January 2014. 
  7. ↑ Yacoubou, MS, Jeanne (2007). "Is Your Sugar Vegan? An Update on Sugar Processing Practices" (PDF). Vegetarian Journal (Baltimore, MD: The Vegetarian Resource Group) 26 (4): 16–20. Retrieved 2007-04-04. 
  8. ↑ Thorpe, Thomas Edward (1912). A dictionary of applied chemistry, volume 1. Longmans, Green and Co. p. 264. 

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