Adsorption behaviour of modified fish scales as an emerging fluoride adsorbent

This study explores the use of acid-activated, thermally treated Tilapia fish scales as an eco-friendly and cost-effective adsorbent to remove fluoride from water. The chemical structure, surface properties, and microstructure of the adsorbent were analysed using the Fourier transform infrared spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, and Barrett–Joyner–Halenda methods. Optimal fluoride adsorption was achieved at pH 6, 6 g/l adsorbent dose, 240 min contact time, and 10 mg/l fluoride concentration. The Freundlich model (R² = 0.9274) described multilayer adsorption, and the pseudo-second-order model (R² = 0.9921) provided a comprehensive insight into F⁻ adsorption kinetics. The thermodynamic examination confirmed that the adsorption rate of F⁻ on modified fish scale exhibited exothermic behaviour, driven mainly by the physical interaction mode. In the context of regeneration studies, it was discovered that the adsorbent exhibited the potential for reusability in fluoride sorption for up to five cycles.