Bone char

This article is about bone char. For the memoir by bell hooks, see Bone Black: memories of girlhood.

Bone char, also known as bone black, ivory black, animal charcoal, or abaiser, is a granular material produced by charring animal bones: the bones are heated to high temperatures (in the range of 400 to 500 °C) 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. Grey-brownish bone char are the best quality chars for adsorption applications. The quality of the bone chars is usually controlled by the amount of oxygen present in the charring atmosphere. It consists mainly of calcium phosphate and a small amount of carbon. Bone chars usually have lower surface area than activated carbons, but presents high adsorptive capacities for copper, zinc, and cadmium

Uses

Bone char is used to remove fluoride from water and to filter aquarium water.

It is often used in the sugar refining industry for decolorizing (a process patented by Louis Constant in 1812).

It is used to refine crude oil in the production of petroleum jelly.

Bone char is also used as a black pigment. It is sometimes used for artistic painting because it is the deepest available black, though charcoal black is often satisfactory and is more often used. Ivory black is an artists' pigment formerly made by grinding charred ivory in oil. Today it is considered a synonym for bone char. 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.