Bone Char

Bone char, 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 mad-cow disease, the skull and spine are never used. 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. 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 calcium 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.