Synthesis of hydroxyapatite-sodium metasilicate via double decomposition method: Characterization and application to the removal of methylene blue

Abstract

The current paper describes the chemical modification of hydroxyapatite surface by sodium metasilicate via double decomposition method at room temperature for the removal of methylene blue (MB) from aqueous solution. The physicochemical properties of the prepared adsorbents (CaHAp-MSi) were characterized by Fourier Transform InfraRed Spectroscopy (FT-IR), X-ray diffraction Diffraction (XRD), Brunauer–Emmett–Teller (BET), chemical analysis, Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). Batch adsorption experiments were carried out to study the effect of several parameters on the adsorption process such as initial MB concentration, contact time, pH value, and temperature. The maximum adsorption capacity for (CaHAp-MSi)15 composite achieved 163.4 mg/g and it was only 59.8 mg/g for unfunctionalized CaHAp. The adsorption of MB onto the studied adsorbents may have been controlled by both physisorption and chemisorption processes. Given the chemical structure of MB molecules and CaHAp–(MSi) composites, hydrogen bonding, and electrostatic interactions could be the major driving forces for an efficient adsorption. Thermodynamic investigation suggested that the adsorption of MB dye onto functionalized hydroxyapatite was non-spontaneous and exothermic. Overall, this study highlighted the possibility of developing CaHAp-MSi composites materials for an effective removal of cationic dyes from colored waters.