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Composite sorbents based on Fe3O4 and Zn-Al-LDH with different weight ratios of magnetic and sorbing phases were obtained by the precipitation method. The optimal weight ratio of Zn/Fe was 16, which resulted in a 62% increase in hydromechanical strength. The maximum sorption exchange capacity towards U(VI) was 268.65 ± 22.22 mg/g. The efficiency of U(VI) adsorption was not affected by the presence of Cl−, SO42−, NO3− and Na+, Ca2+. The distribution coefficient in a groundwater model solution was Kd(U(VI) = 0.5–3 × 105 mL/g. The materials possess high exchange capacity and selectivity, which makes them suitable sorbents for U(VI) removal. [ABSTRACT FROM AUTHOR]

A series of sorption materials based on layered double hydroxides (Co-Fe LDH, Ni-Fe LDH, and Zn-Ti LDH) were obtained by a facile and environmentally friendly method of coprecipitation. A low particle size of no more than 10 µm was achieved. The use of transition metals makes it possible to obtain compounds that are mechanically and chemically stable in aggressive environments. XRD analysis revealed that the compounds have a highly organized crystalline structure. Using SEM, it was determined that Co-Fe LDH and Ni-Fe LDH had a loose, highly dispersed surface structure, while Zn-Ti LDH had a monolithic surface structure. U(VI) adsorption on the obtained materials in solutions containing Na2CO3, Na2SO4, KNO3, NaCl, K3PO4, and NaHCO3, was studied in batch mode. The degree of purification in the presence of these salts reached 99.9%, while the distribution coefficient Kd reached 105 mL/g. Sorption capacity qmax and equilibrium adsorption constants Kf and KL for U(VI) adsorption in batch mode (for 24 h) from distilled and seawater were determined using the Freundlich and Langmuir equations. The highest sorption capacity of 101.6 mg/g in seawater and 114.1 mg/g in distilled water was registered for Co-Fe-LDH. The presence of competing ions in seawater can reduce sorption efficiency by up to 40%. The provided research allowed us to conclude that the obtained materials, Co-Fe LDH, Ni-Fe LDH, and Zn-Ti LDH are promising for the sorption removal of U(VI) from aqueous media of medium salinity. [ABSTRACT FROM AUTHOR]

An original method was proposed for manufacturing sorption composite materials based on K-Ni and K-Zn mixed-metal ferrocyanides (FCs) formulated with siloxane–acrylate emulsion and polyethylene. The originality of the method consists in the hydrophobization of the material via the incorporation of polyethylene fibers into the FC structure. The surface morphology and structure of the manufactured sorbents were studied by scanning electron microscopy, X-ray powder diffraction, and low-temperature nitrogen adsorption. The specifics of the batch extraction of micro- and macroconcentrations of Cs+ and 137Cs radionuclides from seawater were studied. The experimental sorption values were fitted by the Langmuir and Freundlich equations, and the limiting sorption Gmax and adsorption equilibrium constants Kl were calculated. The sorbents comprising polyethylene (PE) have the best sorption characteristics, providing up to 99% cleaning of seawater from cesium ions. The cesium distribution ratio in seawater averages 3.7 × 104 mL/g at S : L = 1000 mL/g, which indicates the promise of these sorbents for use in cleaning seawater from radioactive cesium. [ABSTRACT FROM AUTHOR]