Hydroxyapatite for colorimetric detection of nickel(II) ion

Abstract

Hydroxyapatite (HAp) coated with 1-(2-pyridylazo)-2-naphthol (PAN) was prepared for the use as a sensor for Ni²⁺ designated as HAp-PAN. HAp surface modification was performed by impregnation method and adsorption method. The materials were characterized by powder X-Ray diffraction spectrometer (Powder XRD), Zetasizer, and thermogravimetric analyzer (TGA). In impregnation method, HAp was modified with hexadecyltrimethylammonium bromide (CTAB) and further impregnated with PAN solution. HAp-PAN prepared by using 1.0 mM PAN solution could be used to detect 100 and 1000 μg/L Ni²⁺. The leaching of PAN from the obtained material was observed when tested with Ni²⁺ solution. In the adsorption method, HAp was modified by mixing HAp with PAN in CTAB solution. The obtained material was used in Ni²⁺ detection. The solid turned from pale yellow in the absence of Ni²⁺ to pink or purple in increasing Ni²⁺ concentration. The suitable condition to prepare HAp-PAN was by using a 1.2 mM PAN solution and 5 mins of adsorption time. The suitable pH for Ni²⁺ detection was pH 6. The HAp-PAN obtained by adsorption method could detect 300 and 700 μg/L Ni²⁺ by naked eyes.