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

Abstract

• Two sulfides exhibit high adsorption capacities and ultrafast removal of Eu 3+ . • Selective Eu 3+ adsorption against interfering ions in natural water. • Lanthanides recovery from acidic industrial wastewaters is realized. • The adsorption mechanism is ion exchange between Eu 3+ and cations. • The soft Lewis basic and flexible layer is beneficial to selective Eu 3+ uptake. 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 Eu 3+ uptake from complex aqueous solutions by using two layered sulfide adsorbents (Me 2 NH 2 ) 2 (Ga 2 Sb 2 S 7 )·H 2 O ( FJSM-GAS-1 ) and (Et 2 NH 2 ) 2 (Ga 2 Sb 2 S 7 )·H 2 O ( FJSM-GAS-2 ). Both adsorbents exhibit ultrafast kinetics (within 2 min) and high absorption capacities for Eu 3+ (127.7 and 115.8 mg/g for FJSM-GAS-1 and FJSM-GAS-2 , respectively). The distribution coefficient ( K d ) can be as high as 6.39 × 10 5 and 6.00 × 10 5 mL/g for FJSM-GAS-1 and FJSM-GAS-2 , respectively, exceeding that of reported Eu 3+ adsorbents. They still display high selectivity for Eu 3+ in presence of excessive competitive cations (e.g., Na + and K + ). Particularly, high K d values remain for Eu 3+ removal from Eu 3+ -contaminated tap, lake and sea water, and lanthanides recovery from acidic industrial wastewater. Absorbed Eu 3+ ions can be facilely eluted using a low-cost method. The adsorption mechanism, illuminated via DFT calculations coupled with characterizations of EA, Raman, XPS and EXAFS, is ion exchange between Eu 3+ and interlayered cations owing to the strong interactions between Eu 3+ and framework S 2− . This work confirms that layered sulfides are promising adsorbents for efficient removal of lanthanides/actinides from wastewater for environmental remediation.