Thermally treated Mytilus coruscus shells for fluoride removal and their adsorption mechanism

We evaluated Mytilus coruscus shells (MCS) as an adsorbent for fluoride removal. Its removal efficiency was enhanced by thermal treatment and MCS at 800 °C (MCS-800) increased significantly its fluoride adsorption capacity from 0 to 12.28 mg/g. While raw MCS is mainly composed of calcium carbonate (...

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Bibliographic Details
Published in:Chemosphere (Oxford) 2021-01, Vol.263, p.128328, Article 128328
Main Authors: Lee, Jae-In, Kang, Jin-Kyu, Hong, Seung-Hee, Lee, Chang-Gu, Jeong, Sanghyun, Park, Seong-Jik
Format: Article
Language:English
Subjects:
adsorbents
Adsorption
Adsorption mechanism
Animals
calcium
calcium carbonate
calcium hydroxide
chlorides
enthalpy
Fluoride removal
Fluorides
Gibbs free energy
heat treatment
Hydrogen-Ion Concentration
Kinetics
Mussel shell
Mytilus
Mytilus coruscus
phosphates
sorption isotherms
sulfates
surface area
Thermal treatment
Water Pollutants, Chemical
Water Purification
X-ray diffraction
X-ray photoelectron spectroscopy
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Summary:We evaluated Mytilus coruscus shells (MCS) as an adsorbent for fluoride removal. Its removal efficiency was enhanced by thermal treatment and MCS at 800 °C (MCS-800) increased significantly its fluoride adsorption capacity from 0 to 12.28 mg/g. While raw MCS is mainly composed of calcium carbonate (CaCO3), MCS-800 consisted of 56.9% of CaCO3 and 43.1% of calcium hydroxide (Ca(OH)2). The superior adsorption capacity of MCS-800 compared to untreated MCS can be also explained by its larger specific surface area and less negative charge after the thermal treatment. X-ray photoelectron spectroscopy and X-ray diffraction analysis revealed that the fluoride adsorption of MCS-800 occurred via the formation of calcium fluorite (CaF2). Fluoride adsorption of MCS-800 approached equilibrium within 6 h and this kinetic adsorption was well-described by a pseudo-second-order model. The Langmuir model was suitable for describing the fluoride adsorption of MCS-800 under different initial concentrations. The maximum fluoride adsorption amount of MCS-800 was 82.93 mg/g, which was superior to those of other adsorbents derived from industrial byproducts. The enthalpy change of fluoride adsorption was 78.75 kJ/mol and the negative sign of free energy indicated that this phenomenon was spontaneous. The increase of pH from 3.0 to 11.0 slightly decreased the fluoride adsorption capacity of MCS-800. The adsorption was inhibited in the presence of anions and their impact increased with following trend: chloride 
ISSN:0045-6535
1879-1298
DOI:10.1016/j.chemosphere.2020.128328