This study assessed the applicability of seafood waste, Patinopecten yessoensis shells (PY), for fluoride removal. PY was modified by calcination to improve its fluoride removal capacity, and 800°C was the optimum calcination temperature its modification as a fluoride adsorbent. Fluoride adsorption by PY-800 was confirmed due to the formation of fluorite (CaF2) through X-ray diffraction analysis. The fluorine adsorption to PY-800 reached equilibrium within 2 h at an initial fluoride concentration of 50 mg/L, and a reaction time of 36 h was required to reach equilibrium at 200 mg/L. Both the pseudo-first-order and pseudo-second-order models described the kinetic adsorption data well. In isotherm studies, the fluoride adsorption of PY-800 was best suited to the Langmuir model. The enthalpy change of fluoride adsorption was 45.49 kJ/mol, ranging in the boundary between physical and chemical adsorption. Fluoride adsorption decreased from 113.13 to 86.01 mg/g as the pH increased from 3 to 11. Anions in the solution inhibited fluoride adsorption, and impacted other ions in the following order: chloride < sulfate < carbonate < phosphate. PY-800 has a higher adsorption capacity than other reported adsorbents, with a maximum of 159.62 mg/g. These results show that PY-800 recycled from food waste is highly efficient for fluoride removal.
