Hybrid porous magnetic bentonite-chitosan beads for selective removal of radioactive cesium in water

Easy-to-obtain magnetic bentonite-chitosan hybrid beads (Bn-CTS) were prepared by immobilizing bentonite within a porous structure of chitosan beads to achieve a hybrid adsorption effect for the removal of cesium ion (Cs⁺) from water. The hybrid adsorbent, which had a porous structure and abundant binding sites contributed by both chitosan and bentonite, ensured superb adsorption characteristics. The paramagnetic character of the beads enabled their facile separation for recycling. The chitosan/bentonite ratio, pH and contact time were optimized to achieve the optimal Cs⁺ efficiency, and the adsorption kinetics and isotherms were thoroughly discussed. The adsorption kinetics obeyed the pseudo-second-order model, and the best fitted equation for equilibrium data was the Langmuir isotherm model. The maximum adsorption capacity of the bentonite-chitosan beads was 57.1 mg g⁻¹. The adsorbent had excellent selectivity towards Cs⁺ adsorption in the presence of abundant cations (Li⁺, Na⁺, K⁺ and Mg²⁺). The adsorbent was able to be recycled by treating the beads with 0.1 mol L⁻¹ of MgCl₂ to quantitatively desorb Cs⁺ from the beads. Overall, the magnetic bentonite-chitosan beads can be used as a highly efficient adsorbent for radioactive waste disposal and management.