Synthesis of iron-substituted hydroxyapatite nanomaterials by co-precipitation method for defluoridation

Abstract

The consumption of too much fluoride ions through drinking water can seriously harm human health. Thus fluoride ions need to be removed by the novel and efficient nanomaterials materials synthesized via eco-friendly method. The pure and iron-doped hydroxyapatites were synthesized using a simple co-precipitation technique for the removal of fluoride from water. The synthesized materials were characterized by advanced technical tools. The point of zero charge of the materials was determined by the salt addition method. Crystallite size and degree of crystallinity were observed to decrease with the substitution of calcium. However, the surface area and pore volume were found to have enhanced with modification of iron in the apatite. Batch adsorption experimental data were well fitted to pseudo-second order and Langmuir models, which implied that the sorption process is chemisorption through a monolayer on a homogenous surface. The maximum sorption capacities of HA and Fe-HA were found to be 40.46 and 83.86 mg g−1, respectively. The thermodynamic data revealed that the adsorption process is endothermic and spontaneous. The regeneration and reuse analysis insured that the materials have good potential for reuse. The adsorption mechanism was inferred as chemisorption through electrostatic interaction and ion exchange. The modification of hydroxyapatite using iron considered as a competent sorbent for the removal of fluoride ions.