In situ constructing of sulfur bedecked ZIF-67 with ultrahigh and selectivity UO22+ immobilization capability from seawater

Abstract

Uranium, a strategically significant resource, is estimated to contain approximately 4.5 billion tons of unconventional uranium in seawater, which can be extracted as a sustainable fuel source for nuclear power plants. In this work, a sulfur bedecked ZIF-67 (SF@ZIF-67) uranium adsorbent were successfully fabricated by employing a facile hydrothermal sulfur functionalization approach. Sequential batch experiment showed that the SF@ZIF-67 specimen displayed a broader pH response range, exceptional UO22+ harvesting efficiency (Uinitial = ∼5–10 ppm, ∼90.68 %–93.79 %) and ultra-high uranium capture capacity (qmax = 769.23 mg/g). Remarkably, due to the strong affinity between sulfur functional groups and uranyl, the SF@ZIF-67 sample exhibited exceptional selectivity with a Kd value exceeding 104 mL/g even in the presence of diverse interfering ions. Moreover, the SF@ZIF-67 specimen showed a sustained uptake efficiency of 66.61 % with close 104 KdU value in a 3000-fold VO43− system. In natural uranium spiked-seawater (Uinitial = ∼10–1000 μg/L), SF@ZIF-67 can capture ∼21–2484.5 μg/g uranium after 24 h contact. Mechanism analysis confirmed that excellent uranyl fixation ability is attributed to the coordination of sulfur and oxygen terminals with uranyl, as well as the redox processes of S2− and U6+. This hydrothermal functionalization technique offers novel insights into the potential application of MOF materials for uranium extraction from seawater.