Bi3+ and Fe3+ Co-doped nanohydroxyapatite as an effective photocatalyst driven by visible light for methyl orange degradation

One of the major issues facing the world today is water contamination. The substitution of metal ions in the hydroxyapatite structure enhances its application for water treatment. Thus, this work applied Bi³⁺ and Fe³⁺ co-doped hydroxyapatite nanomaterials for the investigation of methyl orange dye photocatalytic degradation. Incorporations of Bi³⁺ and Fe³⁺ ions in the HA structure dramatically changed the light absorption property and the optical bandgap, due to the occurrence of the different electronic transitions of the dopant ions. In addition, the modification brings change in crystallite as well as particle size of HA nanomaterial. Elemental composition analysis inferred that the Ca/P ratio decreased as the dopants were introduced in the crystal system, which confirms direct replacement of Ca²⁺ ions. The co-doped HA nanomaterials showed better photocatalytic degradation of MO dye over the pristine HA due to the synergistic roles of Fe³⁺ and Bi³⁺ ions. It was observed that 98.57% methyl orange was degraded at 180 min of irradiation time using 0.6 g/L of the nanomaterial. Thus, Bi³⁺ and Fe³⁺ co-doped HA nanomaterials can be considered competent heterogeneous photocatalysts for the degradation of azo dyes.