Cosorption Characteristics of SeO₄ ^2- and Sr²⁺ Radioactive Surrogates Using 2D/2D Graphene Oxide-Layered Double Hydroxide Nanocomposites

Cosorption of anionic and cationic radioactive nuclides is highly desired toward the total cleaning of radioactive contaminated wastewater. A 2D/2D multifunctional nanocomposite of MgAl-LDH/graphene oxide (GO) was fabricated using coagulation and applied for the cosorption of Sr²⁺ and SeO₄ ^2- from aqueous solution. The cosorption was synergetically enhanced with the copresence of each species and showed a maximum Sr²⁺ removal of 2.435 mmol/g of GO. The synergetic effect occurs only in the MgAl-LDH/GO nanocomposite because of the synchronized effect of MgAl-LDH, GO, and alkaline cations, which were not present in pure GO. The SeO₄ ^2- removal occurred by the interchange of the NO₃ ^- anion from the LDH, while the removal of Sr²⁺ occurred through coordination with carboxyl/alkoxy (âCOO^-/-CO^-) groups in GO by the ring opening of epoxides. The cosorption efficiencies of Sr²⁺ and SeO₄ ^2- were stable in the wide pH range of 4-10. The binary (Na₂SeO₄ + SrCl₂) and ternary (Na₂SeO₄ + SrCl₂ + M⁺/M²⁺ = other metal ions or A^n- = other negative ions) systems enhanced the cosorption of Sr²⁺ and SeO₄ ^2- in the presence of other alkali and alkali earth metals and other anions compared with the single system. The Sr²⁺ and SeO₄ ^2- sorption densities were superior to previously reported values. The combined multifunctional ability and environmentally benign nature of the MgAl-LDH/GO composite is promising as a sustainable material for the total remediation of Sr²⁺ and SeO₄ ^2- radioactive surrogates and can also be extended to wide combinations of divalent anions and cations.