Feasibility studies on fluoride removal by thermally treated adsorbent developed from the waste snail shells

The utilization of waste materials to develop adsorbents for fluoride removal is gaining vast interest to help waste minimization and sustainable water treatment. The current research investigated the feasibility of a new biosorbent developed by thermal treatment from waste snail shells for water defluoridation. The maximum adsorbate removal efficiency of 92.60% with an uptake capacity of 11.610 mg/g was obtained at optimized process variables, i.e., pH: 7, adsorbate concentration: 15 mg/L, agitation speed: 150 rpm, temperature: 313 K, contact period: 60 min, and snail shell dose: 12 g/L. The isotherm and kinetic constants indicate the Freundlich and second-order models as best fitted for fluoride sorption onto snail shell sorbent. Thermodynamic constants such as ∆H = 56.189 kJ/mol, and ∆S = 0.286 kJ/mol.K indicates the spontaneous and endothermic sorption for snail shell sorbent. The morphological characteristics of snail shell sorbent were obtained from SEM and EDAX analysis, while the functional groups participated for fluoride sorption were acquired from the FTIR analysis. The desorption study with 0.1 N NaOH indicates the reusability up to 4 cycles for the exhausted waste snail shell sorbent. The practical feasibility of the snail shell sorbent was also performed for fluoride removal from the ground water samples and found potentially quite feasible.