in Wiley Online Library (wileyonlinelibrary.com).Since heavy metals react with some components in bone, it can be surmized that these components would strongly fix heavy metals. Hydroxyapatite and a series of substituted-apatites that are likely to exist in bone were prepared under nearphysiological conditions with the aim of developing materials that are capable of effectively removing low concentrations of heavy-metal ions at near-neutral conditions. The obtained apatites were characterized by inductively coupled plasma optical emission spectroscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, thermogravimetric and differential thermal analysis, and field-emission scanning electron microscopy. They were also tested for their ability to remove Pb, Cd, Hg, Cr, and As. The carbonate-substituted apatite exhibited very strong fixation of Pb 2þ , Cd 2þ , and Cr 3þ , and moderately strong fixation of Hg 2þ . Based on a heavy-metal-fixing mechanism, a bone-like composite, with chitosan as the saccharide portion and a polyaspartyl polymer as the protein portion, was synthesized via co-precipitation. The biomimetic composite was excellent at removing Pb 2þ , Cd 2þ , Hg 2þ , and Cr 3þ , with removal percentages as high as 99.8% and residual concentrations as low as 0.01 mg/L. However, the composite had little fixation of Cr 2 O 7 2À , CrO 4 2À , or H 3 AsO 3 . When Cr(VI) was reduced to Cr(III), the percent removed increased greatly. *Amount of adsorbents ¼ 0.1 g, total volume of solution ¼ 50 mL, pH ¼ 6À7, exchange time ¼ 2 h, temperature ¼ 18 C, M ¼ Pb, Hg, Cd, Cr, or As † Initial concentration: c (Pb 2þ ) ¼ c (Cd 2þ ) ¼ c (Hg 2þ ) ¼ c (Cr 3þ ) ¼ c (Cr 6þ ) ¼ c (As 3þ ) ¼ 0.48 mmol/L, Cr 6þ and As 3þ were mainly in the form of Cr 2 O 7 2or CrO 4 2and H 3 AsO 3 /HAsO 2 , respectively. ‡ HAP and the substituted-apatites were unground, grain-sizes can be estimated from SEMs in Figure 4. § The grain-size was about 40À50 lm. *Amount of adsorbents ¼ 0.1 g, total volume of solution ¼ 50 mL, exchange time ¼ 2 h, temperature ¼ 19 C, M ¼ Pb, Hg, Cd, Cr, or As, pH 6À7. † Initial concentration: c (Pb 2þ ) ¼ c (Cd 2þ ) ¼ c (Hg 2þ ) ¼ c (Cr 3þ ) ¼ 0.1 mmol/L, c (As 3þ ) ¼ 30.99 mg/L. ‡ As 3þ was mainly in the form of H 3 AsO 3 /HAsO 2 .