Abstract
Raw white clay was acidified with H<sub>2</sub>SO<sub>4</sub> (2 M) and then activated in a furnace for 2 h at 150<sup>o</sup>C. The resulting acid-activated clay product was used as an adsorbent for the removal of radioactive substances such as Cs<sup>+</sup>, Sr<sup>2+</sup> and Co<sup>2+</sup> ions in aqueous solution. The specific surface area and the pore volume of acid-activated clay were three times higher compared to raw white clay. At 100 mg L<sup>-</sup> of initial concentration and 1.0 g of dosage, removal efficiencies of Cs<sup>+</sup>, Sr<sup>2+</sup> and Co<sup>2+</sup> ions showed 60.0%, 27.3%, and 88.1%, respectively. It was found that the Langmuir isotherm was described well to the adsorption behavior of Cs<sup>+</sup>, Sr<sup>2+</sup> and Co<sup>2+</sup> ions on acid-activated clay rather than Freundlich isotherm. The Langmuir isotherm constant (Q) for Cs<sup>+</sup>, Sr<sup>2+</sup> and Co<sup>2+</sup> ions was found to be 8.81, 3.78 and 10.20 mg g<sup>-1</sup>, respectively. Compared to the pseudo-first-order kinetic model, the pseudo-second-order kinetic model was more suitable for adsorption of Cs<sup>+</sup>, Sr<sup>2+</sup> and Co<sup>2+</sup> ions in water/acid-activated clay medium owing to the higher correlation coefficient (<i>R</i><sup>2</sup>) and the more proximity value of the experimental value <i>q</i><sub>e,exp</sub> and the calculated value <i>q</i><sub>e,cal</sub>.
Funder
National Research Foundation of Korea
Ministry of Science and ICT
Publisher
Korean Society of Environmental Engineering