Preparation of biomimetic-bone materials and their application to the removal of heavy metals


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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 near-physiological 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 Pb2+, Cd2+, and Cr3+, and moderately strong fixation of Hg2+. 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 Pb2+, Cd2+, Hg2+, and Cr3+, 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 Cr2O72−, CrO42−, or H3AsO3. When Cr(VI) was reduced to Cr(III), the percent removed increased greatly. © 2012 American Institute of Chemical Engineers AIChE J, 59: 229–240, 2013