Removal of Eu³⁺, Ce³⁺, Sr²⁺, and Cs⁺ ions from radioactive waste solutions by modified activated carbon prepared from coconut shells

ABSTRACT

As a biomass agricultural waste material, coconut shells were used for the preparation of high-quality modified activated carbon. Chemical modification of the surface of the prepared activated carbon is done by oxidation using H₂O₂ and HNO₃, respectively. The surface area and pore volume of the coconut shells activated carbon are increased by the chemical modification, and followingly the removal of the metals is improved. The structural morphology and composition of the modified activated carbon coconut shells (MACCS) were evaluated by Fourier transform infrared (FTIR) spectra, thermogravimetric analysis–differential thermal analysis (TGA-DTA), scanning electron microscope (SEM), X-ray diffraction (XRD), surface area analysis (SAA), X-ray fluorescence (XRF), and carbon, hydrogen, nitrogen, and sulfur (CHNS) elemental analysis. The prepared MACCS has reasonably good chemical stability. The influence of solution pH, contact time, adsorbent dosage, adsorption temperature, initial metal concentrations, and interfering ions on the adsorption performance of the investigated ions onto the prepared sorbent was examined by a batch method. The selectivity sequence for sorption of Eu³⁺, Ce³⁺, Sr²⁺, and Cs⁺ ions on MACCS was found to be Eu³⁺> Ce³⁺> Sr²⁺> Cs⁺. The saturation capacities of MACCS for the studied metal ions were found to be 136.84, 85.55, 69.85, and 60.00 mg g⁻¹ for Eu³⁺, Ce³⁺, Sr²⁺, and Cs⁺ ions, respectively. The thermodynamic parameters, ΔH°, ΔS°, and ΔG° were also evaluated.

KEYWORDS:

• Coconut shells
• modified activated carbon
• adsorption
• radionuclides
• waste solutions
• thermodynamic parameters

Acknowledgement

The authors would like to thank Prof. Dr Nabil Belacy, prof. of Physical Chemistry, Atomic Energy Authority, Cairo, Egypt, for his carefully reviewing this article to be in an acceptable form.

Disclosure statement

No potential conflict of interest was reported by the authors.