Adsorptive removal of fluoride from water using hydroxyapatite synthesized from marine shell waste
Shantanu Singh, Gokulakrishnan Murugesan, Ramesh Vinayagam, Thivaharan Varadavenkatesan, Raja Selvaraj
Abstract
Abstract Fluoride contamination in groundwater threatens human health and ecological systems, necessitating cost-effective and efficient remediation strategies. This study synthesized hydroxyapatite (MRS-HAp) from Marcia recens shells through chemical precipitation to serve as a potential adsorbent for the removal of fluoride. The prepared MRS-HAp exhibited a specific surface area of 100.42 m 2 /g. FESEM analysis revealed an irregular, closely packed structure with a mean diameter of 28.89 nm. EDS determined a Ca/P molar ratio of 1.6, while XRD analysis confirmed a hexagonal crystalline lattice with a crystallite diameter of 32.18 nm. XPS identified a fluoride peak at 684.58 eV, confirming adsorption. The adsorption dataset obeyed pseudo-second-order kinetics and Langmuir isotherm, pointing to chemisorption and monolayer coverage, with a maximum adsorption capacity of 19.19 mg/g. Spiked water experiments demonstrated robust fluoride removal efficiencies across diverse real-world water matrices. MRS-HAp showed reasonable regeneration potential for fluoride removal, retaining significant adsorption capacity over four cycles. These results position MRS-HAp as a cost-effective and sustainable adsorbent for fluoride removal in water treatment applications.