Radioactive cesium removal from nuclear wastewater by novel inorganic and conjugate adsorbents

• Inorganic and conjugate adsorbent were performed for selective Cs uptake.
• Crown ether immobilized conjugate adsorbent was effective for Cs removal.
• Radioactive 137Cs can be efficiently removed even in the presence of Na and K.
• Both adsorbents are reversible and reusable without significant loss of performances.

This work was focused on the promising inorganic and ligand immobilized conjugate materials for selective and high capacity of radioactive cesium (Cs) removal from radioactive liquid waste in Fukushima after an accident at Daiichi Nuclear Power Plant hit by the Great East Japan Earthquake and tsunami on 11 March 2011. The conjugate adsorbent was prepared by direct immobilization of dibenzo-18-crown-6 ether onto mesoporous silica monoliths. The Cs sorption behavior was investigated using batch equilibrium technique. The applicability of the inorganic conjugate adsorbent for Cs removal from aqueous test solutions was assessed, and the effective parameters such as solution pH, contacting time, initial Cs concentration and ionic strength of Na and K ion concentrations were evaluated systematically. The effective pH range for high Cs capacity was possible within the pH range 5.5–7.0 and the maximum sorption capacities were 50.23 and 27.40 mg/g for conjugate adsorbent and inorganic adsorbent, respectively. The results clarified that conjugate adsorbent had the higher selectivity towards Cs even in the presence of high concentration of Na and K ions rather than the inorganic adsorbent due to strong Cs–π interaction of benzene ring. The conjugate adsorbent was efficiently decontaminated the radioactive Cs from waste solution with high sorption efficiency. The data also revealed that both adsorbents worked well for removing of dissolved radioactive Cs even in the presence of high concentration competing ions. The adsorbents were reused in several cycles after elution operation with a suitable eluent (0.20 M HCl). Therefore, the prepared adsorbents could be used as low-cost potential adsorbents for the selective radioactive Cs decontamination from Fukushima wastewater samples.

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