Functionalized biogenic hydroxyapatite with 5-aminosalicylic acid - Sorbent for efficient separation of Pb2+ and Cu2+ ions

The biogenic hydroxyapatite (BHAP), obtained by proper treatment of bovine bones, was functionalized with 5-aminosalicylic acid (5-ASA). The coordination of 5-ASA to the surface of BHAP leads to the charge transfer (CT) complex formation accompanied with absorption in visible spectral range. The sorption ability of surface-modified BHAP with 5-ASA (5-ASA/BHAP) for removal of Pb2+ and Cu2+ ions from single-and bi-component solutions was compared with unmodified BHAP. The thorough characterization of both sorbents, BHAP and 5-ASA/BHAP, was performed including X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms, as well as diffuse reflection spectroscopy. Sorption kinetics and equilibriums for both ions (Pb2+ and Cu2+) by as-prepared BHAP and 5-ASA/BHAP are quite different. Functionalized sorbent demonstrated faster sorption kinetic and higher maximum sorption capacity for Pb2+ ions from bi-component solutions. From equimolar Pb2+ and Cu2+ mixture with a total concentration of 10-2 mol/L, 66% of Pb2+ was recovered using BHAP, while 97% using 5-ASA/BHAP. These preliminary data indicate potential applicability of properly functionalized hydroxyapatite for selective removal of heavy metal ions from contaminated water.