Cockle (Anadara granosa) shells-based hydroxyapatite and its potential for defluoridation of drinking water

• DOI: 10.1016/j.rineng.2022.100379
• Publication Date: 2022-03-03T02:07:26Z
• Authors: Stanslaus G. Mtav...; Wilson Mahene; Revocatus L. Mach...; Bart van der Bruggen; Karoli N. Njau
• Keywords: BET theory; Langmuir adsorption model; Chemisorption; Specific surface area

The present study describes the synthesis and characterization of a hydroxyapatite (HAp)-based adsorbent derived from biogenic cockle (Anadara granosa) shells for defluoridation drinking water. raw synthesized HAp were characterized by X-ray fluorescence spectroscopy (XRF), attenuated total reflection-Fourier transform infrared (ATR-FTIR), diffraction (XRD), Field emission scanning electron microscopes-energy dispersive (FESEM-EDX) Brunauer-Emmett-Teller (BET) surface area analysis. As demonstrated FTIR, found to be composed calcium carbonate (97.4%), an aragonite polymorphous type mineral. XRD SEM analysis supported formation nanocrystalline with average crystal size 19.08 nm 57.1 nm, respectively, 105.8 m2/g pore 5.6 as depicted BET. Batch adsorption experiments conducted using Box-Behnken design (BBD) five input parameters: dose (2–10 g/L), initial fluoride concentration (10–80 mg/L), contact time (0.5–24 h), reaction temperature (303–333 K), pH. (3–11). BBD revealed following optimum conditions: (6 (45 period 12.25 h, (303 pH 3. Experimentally, on fitted well non-linear Langmuir isotherm linear pseudo-second order kinetics, signifying chemisorption process. A maximum capacity (qm) 15.374 mg/g, which is closer experimental value 14.053 was presented isotherm. Thermodynamically, process spontaneous, endothermic, stable in nature. mechanism through electrostatic attraction, ion exchange, hydrogen bonding, precipitation. Furthermore, bone char used examine their efficacy defluoridating field water: performed better at natural pH, where treated water met WHO TBS standards, whereas had insufficient removal, especially high levels. result, this suggests that Anadara granosa could viable