Sol–gel synthesis of Tb-doped hydroxyapatite with high performance as photocatalyst for 2, 4 dichlorophenoxyacetic acid mineralization

BACKGROUND: Tb³⁺doped hydroxyapatite was synthetized by the sol–gel technique, using amounts of the dopant source ranging from 2 to 12 wt%, with respect to the calcium former material. The solids were analyzed using several techniques in order to determine their structural, textural and optical properties. The photoactivity of the materials was tested in the degradation of 2,4-dichlorophenoxyacetic acid, under UV irradiation. RESULTS: The analysis of the samples by X-ray diffraction, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy indicates the formation of hydroxyapatite with calcium deficiency, with a stoichiometry close to the ideal in the sample doped with 10 wt% of terbium. The highest photoluminescence emission, production of •OH radicals under UV in the terephtalic acid reaction, as well as photocatalytic activity in the photodegradation of 2,4-dichlorophenoxyacetic acid (2,4-D) was found in the sample doped with 10 wt% of terbium, reaching almost total degradation and 95% of mineralization of the organic molecule, after 240 min irradiation. CONCLUSION: Terbium doping during the synthesis of hydroxyapatite significantly improves its efficiency as photocatalyst.