Cosorption Characteristics of SeO42- 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 SeO42- 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 SeO42- removal occurred by the interchange of the NO3- anion from the LDH, while the removal of Sr2+ occurred through coordination with carboxyl/alkoxy (-COO-/-CO-) groups in GO by the ring opening of epoxides. The cosorption efficiencies of Sr2+ and SeO42- 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 SeO42- in the presence of other alkali and alkali earth metals and other anions compared with the single system. The Sr2+ and SeO42- 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 SeO42- radioactive surrogates and can also be extended to wide combinations of divalent anions and cations.