Carbonated nanohydroxyapatite from bone waste and its potential as a super adsorbent for removal of toxic ions

The effective, low-cost decontamination of toxic metals is critical for addressing global health risks, reducing environmental pollution, and building a sustainable future. Here, we developed an eco-friendly hydroxyapatite nanocrystal adsorbent made from bone waste that can effectively capture 90Sr. Highly carbonated nanohydroxyapatite (C-NHAP) crystals with a negatively charged surface were obtained by simply immersing pig bone in an aqueous solution of sodium hydrogen carbonate (NaHCO3). Fourier transform infrared spectra showed that the C-NHAP was highly carbonated and that the amount of introduced carbonate ions (CO32−) increased with increasing NaHCO3concentration in the immersion solution. With increasing amount of CO32−ions introduced into the C-NHAP, it exhibited a greater ion-adsorption performance. The distribution coefficient (Kd=24,780 mL g−1) of the C-NHAP for Sr2+was approximately 20 and 250 times greater than those of clinoptilolite and untreated bone, respectively. The C-NHAP also exhibited high adsorption capacity (Qe=125 mg g−1) for Sr2+. The extended X-ray absorption fine structure spectra showed that the CO32−sites in C-NHAP played an important role in its high adsorption performance. The C-NHAP exhibited high adsorptivity for Cd2+, Pb2+, and Cu2+. The C-NHAP prepared from bone waste is an eco-friendly, high-performance, low-cost material that should be useful in environmental pollutant removal and food waste disposal.