Polydopamine-coated magnetic montmorillonite immobilized with potassium copper hexacyanoferrate for selective removal of Cs+ and its facile recovery

To address the challenges in remediating cesium contaminated aqueous environments, a low-cost, magnetically recoverable and superior composite adsorbent was fabricated based on the concept of magnetizing montmorillonite and entrapping potassium copper hexacyanoferrate that offers excellent selectivity for Cs+. The facile, green and scalable synthesis route involved exchanging the interlayer ions of montmorillonite with ferrous ions before oxidizing to form magnetic montmorillonite using a low-temperature hydrothermal method. The composite was then coated with polydopamine to be complexed with copper ions and subsequently reacted with the hexacyanoferrate precursor to in situ grow potassium copper hexacyanoferrate nanoparticles, thus forming the composite, D-Mt-Mag-HCF. The adsorbent exhibited excellent Cs+ sorption capacity (~159.2 mg/g) and Cs+ selectivity greater than 8.2 × 104 mL g−1 in concentrated brine. Moreover, the magnetic properties (17.4 emu/g) of the adsorbent facilitated its separation from contaminated aqueous environments once the adsorbent had removed Cs+. The current study demonstrates a novel and scalable production of a composite adsorbent that can be readily used to remediate contaminated water.