Synthesis of Hydroxyapatite NPs for Removal of Fluoride from Aqueous Solution

Hydroxyapatite (Ca10(PO4)6(OH)2, calcium phosphate is a robust and viable magnetic material for the treatment of polluted air, water, and soil. Because of its unique structure and appealing properties such as high adsorption capabilities, acid-base adaptability, ion-exchange capability, and thermal stability, hydroxyapatite (HAp) has a lot of potential in the field of environmental management. An aqueous extract of Monoon Longifoliium leaves was used for the preparation of hydroxyapatite non-particles as adsorbent for fluoride ion removal from aqueous solution in this work, resulting in bio-based hydroxyapatite nanoparticles. The prepared adsorbent was characterized by using instrumental techniques such as TGA/DTA, XRD, AAS, FTIR, UV-Vis spectroscopy as well as SEM. The batch adsorption approach was used to determine the optimum adsorption efficiency of HAp NPs under various experimental conditions. As a result, the best removal efficiency corresponds to 0.75 g HAp NPs, 15 mg/L, and pH 7 at 50 minutes (96%). The equilibrium adsorption data were better fitted into the Freundlich isotherms (R2 = 0.99) and the pseudo-second-order kinetics model was found to be suitable (R2 = 0.99) for the kinetic model. Fluoride ion adsorption on HAp NPs is spontaneous, endothermic, and possible at temperatures over 318 K, according to thermodynamic calculations. The results hint at a conclusion concluded that the synthesized HAp NPs were an efficient adsorbent for the removal of fluoride ions and the overall process can be an economical choice for scaled-up water treatment processes.