Magnetic hierarchical titanium ferrocyanide for the highly efficient and selective removal of radioactive cesium from...

Selective adsorption is the most suitable technique for eliminating trace amounts of ¹³⁷Cs from various volumes of ¹³⁷Cs-contaminated water, including seawater. Although various metal ferrocyanide (MFC)-functionalized magnetic adsorbents have been developed for the selective removal of ¹³⁷Cs and magnetic recovery of adsorbents, their adsorption capacity for Cs remains low. Here, magnetic hierarchical titanium ferrocyanide (mh-TiFC) was synthesized for the first time for enhanced Cs adsorption. Hierarchical TiFC, comprising 2-dimensional TiFC flakes, was synthesized on SiO₂-coated magnetic Fe₃O₄ particles using a sacrificial TiO₂ shell as a source of Ti⁴⁺ via a reaction with ferrocyanide under acidic conditions. The resultant mh-TiFC exhibited the highest maximum adsorption capacity (434.8 mg g^-1) and enhanced Cs selectivity with an excellent K_d value (6,850,000 mL g^-1) compared to those of previously reported magnetic Cs adsorbents. This enhancement was attributed to the hierarchical structure, which reduced intracrystalline diffusion and increased the surface area available for direct Cs adsorption. Additionally, mh-TiFC (0.1 g L^-1) demonstrated an excellent removal efficiency of ¹³⁷Cs exceeding 99.85% for groundwater and seawater containing approximately 22 ppt ¹³⁷Cs. Therefore, mh-TiFC offers promising applications for the treatment of ¹³⁷Cs-contaminated water.