Layered Co–Fe, Ni–Fe, Zn–Ti double hydroxides for sorptive extraction of u(vi) from aqueous media of medium salinity

This work presents the synthesis of a series of sorption materials based on layered Co–Fe, Ni–Fe and Zn–Ti double hydroxides obtained by the most reproducible and environmentally friendly method of homogeneous coprecipitation. This method allows to achieve dispersibility of materials with particle size not more than 10 μm and crystallite size up to 10 nm for Co–Fe and Ni–Fe systems. Application of such a combination of transition metals provides obtaining compounds that have mechanical and chemical stability in aggressive media and actively participate in redox reactions in the liquid phase. The physicochemical and sorption properties of the obtained materials have been investigated with respect to the recovery of uranyl ions U(VI) from aqueous solutions including salt solutions such as Na2CO3, Na2SO4, KNO3, NaCl, K3PO4 and NaHCO3 containing competing ions. The recovery rate of uranyl ions from the salt solutions reaches 99% and the Kd distribution coefficients are up to 105 mL/g, indicating high selectivity towards the extracted component. The Co–Fe SDG sample shows the highest value of limiting sorption (Gmax) equal to 101.6 mg/g in seawater and 114.1 mg/g in distilled water. The graphical dependences of residual uranyl ions content after sorption on the total volume of initial solution passed through the column are presented, which show the curve plateauing for Co–Fe and Fe-Ni SDG samples, which is caused by the ultimate saturation of the material with the extracted component. It was determined that the indices of the total dynamic sorption capacity for the studied sorption materials based on SDG can reach 101.4 mg/g for the SDG Co–Fe sample, but for the SDG Zn–Ti sample this index is much lower than 40.2 mg/g. The presented studies allow us to conclude that the obtained materials based on layered double hydroxides Co–Fe, Ni–Fe and Zn–Ti have a significant potential for sorption extraction of uranyl U(VI) from aqueous media of medium salinity.