Co-sorption of Sr²⁺ and SeO₄²⁻ as the surrogate of radionuclide by alginate-encapsulated graphene oxide-layered double hydroxide beads

Graphene oxides (GO) and layered double hydroxides (LDHs) were applied to produce alginate beads for the remove of ⁹⁰Sr²⁺ and ⁷⁹SeO₄²⁻. The Freundlich isotherm indicated that the Sr²⁺ sorptions were based on the energetically heterogeneous multilayer surfaces. In contrast, the sorption behavior of SeO₄²⁻ fitted to the Langmuir adsorption isotherm models, indicating that the removal of SeO₄²⁻ was caused by the ion-exchange of LDHs. The synthesized LDH/GO alginates beads were also applied for setting up small-bore adsorption columns with loading synthetic SeO₄²⁻ and Sr²⁺ contaminated wastewater. Based on the water chemistry, the adsorbed amount of Sr²⁺ significantly increased after using alginates beads, which was attributed to the functional groups of either GO or alginic acid. The incorporated SeO₄²⁻ was highly depended on the contents of fabricated LDHs in alginate beads. Specifically, the adsorption capacity of Sr²⁺ (0.85–0.91 mmol/g) on GO slightly increased after alginates fabrication. Therefore, it was deduced that this layered material was partially exfoliated during the manufacture and thus increased the sorption sites. Applications of LDH/GO alginates beads in the removal of both Sr²⁺ and SeO₄²⁻ in water and soil treatment have a significant impact on the environmental remediation.