posted on 2020-04-01, 15:36authored byZhenyuan Bai, Qi Liu, Hongsen Zhang, Jing Yu, Rongrong Chen, Jingyuan Liu, Dalei Song, Rumin Li, Jun Wang
Metal–organic
frameworks (MOFs) are diffusely defined as
a promising class of porous material for uranium extraction from seawater,
but there are still challenges in their stability and anti-biofouling
performance. Herein, a water-stable and anti-biofouling ZIF-67/SAP0.45 composite hydrogel was reported by the sequential processes
of electrostatic interactions between the oppositely charged polymer,
ionic gelation, and template growth of ZIF-67 crystals. Entanglement
of positively charged polyethyleneimine (PEI) and negatively charged
sodium alginate (SA) polymer chains provided external porosities,
anti-biofouling properties, and mechanical support for the hydrogels
and further reduced the possibility of ZIF-67 aggregation. The neutral
composite hydrogel possessed the least Nitzschia on the surface after
7 days contact, which endows the adsorbent with a high uranium uptake
capacity of 2107.87 ± 41.64 μg g–1 at
1 mg L–1 uranium-containing seawater with 8.6 ×
105 mL–1 Nitzschia. Additionally, this
adsorbent showed water stability with an uranium uptake capacity of
232.88 ± 8.02 mg g–1 even after five adsorption–desorption
cycles because of the excellent preparation method. Benefitting from
the distinctive hierarchical structure and large accessible surface
area, the resultant adsorbent achieved a high uranium capacity of
6.99 ± 0.26 mg g–1 in real seawater. This flexible
and scalable approach made the MOF/SAP composite hydrogel a highly
desirable uranium adsorbent.