Ultrafast and selective uptake of Eu3+ from aqueous solutions by two layered sulfides

Efficient and selective capture of lanthanides from radioactive wastewater containing excessive diverse concentrated salts is challenging but urgently demanded for environmental protection and human health. Herein, we present an effective approach for Eu3+ uptake from complex aqueous solutions by using two layered sulfide adsorbents (Me2NH2)2(Ga2Sb2S7)center dot H2O (FJSM-GAS-1) and (Et2NH2)2(Ga2Sb2S7)center dot H2O (FJSM-GAS-2). Both adsorbents exhibit ultrafast kinetics (within 2 min) and high absorption capacities for Eu3+ (127.7 and 115.8 mg/ g for FJSM-GAS-1 and FJSM-GAS-2, respectively). The distribution coefficient (Kd) can be as high as 6.39 x 105 and 6.00 x 105 mL/g for FJSM-GAS-1 and FJSM-GAS-2, respectively, exceeding that of reported Eu3+ adsorbents. They still display high selectivity for Eu3+ in presence of excessive competitive cations (e.g., Na+ and K+). Particularly, high Kd values remain for Eu3+ removal from Eu3+-contaminated tap, lake and sea water, and lanthanides recovery from acidic industrial wastewater. Absorbed Eu3+ ions can be facilely eluted using a lowcost method. The adsorption mechanism, illuminated via DFT calculations coupled with characterizations of EA, Raman, XPS and EXAFS, is ion exchange between Eu3+ and interlayered cations owing to the strong interactions between Eu3+ and framework S2-. This work confirms that layered sulfides are promising adsorbents for efficient removal of lanthanides/actinides from wastewater for environmental remediation.