Jan 31, 2008 · Fish bone, obtained from a natural Japanese sea bream, was heated at 600 °C for 24 h or 900 °C for 12 h, and then a removal test was conducted by adding the produced powder to nitrate solutions with aqueous chromium (Cr +3) concentration 3 × 10 −4 m. The mixture was stirred and soaked for 2 h, and then held for 6 days without stirring.