Preparation and characterization of dendro biochar-hydroxyapatite composite: A potential material for defluoridation

Hydroxyapatite (HAP) is a recognized material for fluoride adsorption; however, dissolution in acidic pH is a disadvantage, while dendro biochar (DBC) is a byproduct from dendro power plants in Sri Lanka. The objective of this study was to synthesize dendro biochar-hydroxyapatite (DBC-HAP) composite to reduce HAP dissolution and improve biochar's capacity for fluoride removal. Then it was characterized toward an enhanced fluoride removal in water. DBC-HAP composite was synthesized by the co-precipitation method. Pristine and composite materials were characterized using point of zero charge (pHPZC), Fourier Transform Infrared spectroscopy (FTIR), X-ray Diffraction (XRD) and Thermogravimetric analysis (TGA) to understand its potential for fluoride removal. The pHPZC for DBC, HAP and DBC-HAP were 10.39, 6.82 and 8.52 respectively. The surface charge of DBC-HAP composite was reduced by a pH of 1.87 compared to DBC. FTIR bands confirmed mineralized functional groups such as Ca2+ and -OH in the composite, which can facilitate defluoridation. XRD analysis indicated enhanced crystalline properties of the composite compared to DBC. TGA results exhibited changes in thermal stability for the composite compared to HAP. Overall characterization results of the DBC-HAP composite indicated the features of a low-cost, easily synthesizable defluoridation material.