Selective Removal of Uranyl from Aqueous Solutions Containing a Mix of Toxic Metal Ions Using Core-Shell MFe2O4-TiO2 Nanoparticles of Montmorillonite Edge Sites

Usually, uranyl (UO22+) is competitively adsorbed by coexisting potentially toxic metal ions (Xn+: Rb+, Sr2+, Cr3+, Mn2+, Ni2+, Zn2+, Cd2+) that limit the adsorbent application. Here, the core shell MFe2O4-TiO2 (M = Mn, Fe, Zn, Co, or Ni) nanoparticles were synthesized on K-montmorillonite (MMT) edge sites and assessed as new selective adsorbents. The results revealed that UO22+ and Xn+ were simultaneously adsorbed on the TiO2(101) surfaces, MFe2O4(111)-TiO2(101)/MMT(100)-MFe2O4(111) interfaces, and MMT inner layers. Specifically, the Xn+ ions were mainly adsorbed on the TiO2(101) surfaces. We note that, according to Freundlich models, UO22+ and Cr-3 were selectively adsorbed on the MFe2O4(111) TiO2(101) interface. The high adsorption capacity of UO22+ was 109.11 mg g(-1) in the MMT Fe3O4(111) TiO2(101) interface. The interface electron gases transferred from MMT(100) MFe2O4(111) to MFe2O4(111) TiO2(101) prevent the Cr3+ oxidation-reduction reaction and further adsorption. Our results suggested that MMT MFe2O4 TiO2 is a suitable candidate of highly selective uranyl removal.