ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

An eco-friendly and low-cost methodology for fluoride adsorption using synthesized and characterized ceria-impregnated activated graphite (CIAG)

Sajitha Nair, Roopa Bose, Smeer Durani, and Pandurangappa Malingappa

Chemistry Laboratory, Department of Atomic Energy, Atomic Minerals Directorate for Exploration and Research, Nagarbhavi, Bangalore, India

E-mail: roopabose.amd@gov.in

Received: 26 August 2023  Accepted: 4 February 2024

Abstract:

Fluoride concentration greater than 1.5 mg/L in drinking water affects more than 748 million of the global population causing life-threatening diseases like fluorosis amongst many others. In the present study, activated graphite incorporated with ceria nanocrystals was synthesized by simple two step wet chemical route for fluoride removal and subsequently characterized to define its physical and chemical properties based on analytical tools like SEM–EDX, FTIR, XRD, XPS and BET. The sorption experiments were carried out in batch mode for analyte concentration of 5 mg/L, and the obtained optimized parameters were pH 3, stirring time 10 min followed by static contact time of 1 h and adsorbent dosage 0.1 g in total aqueous volume of 50 ml at ambient temperature. The maximum adsorption capacity of the adsorbent was 7.6 mg/g towards fluoride which was comparable with various other adsorbents suggested in the literature. Langmuir and Temkin isotherms were the best-suited models for the equilibrium data at room temperature, Freundlich being more favourable with increase in temperature suggesting initial monolayer adsorption followed by multilayer adsorption with rise in temperature. The kinetics of adsorption appeared to follow pseudo-second-order model with intraparticle diffusion and boundary mass transfer also significantly influencing the rate-limiting step. Thermodynamic studies showed the adsorption process to be exothermic and spontaneous. From the interference studies based on commonly occurring anions and cations, sulphate exhibited adverse effect on adsorption. The synthesized adsorbent could be used for fluoride removal studies on real samples over five cycles and was successfully regenerated for reuse. The scaling up possibilities of the present methodology for defluoridation application appear impressive based on features like efficiency, selectivity, environmentally benign nature and economic viability of the ceria-impregnated activated graphite composite.

Graphical Abstract

Keywords: Defluoridation; Adsorption isotherm; Fluoride; Regeneration; Ceria; Activated graphite

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-024-03360-2

Chemical Papers 78 (6) 3883–3906 (2024)