Fabrication of highly porous adsorbent templated by surfactant stabilized foams for photothermally assisted U(VI) capture

The adsorption of uranium (VI) from wastewater is vital for environment treatment and sustainable growth of the nuclear energy industry. The porous adsorbents with excellent adsorption capacity can be efficiently fabricated by the template from surfactant stabilized foams, but the template is rather susceptible and easily destabilized, resulting in the unsatisfactory performance for target materials. In this work, we proposed a cooperative method using Schiff base reaction combining with surfactant foaming for constructing stable porous templates. A surfactant, cocamidopropyl betaine (CAB), was applied to stabilize foams containing chitosan (CS), glutaraldehyde (GA), acrylamide (AAm) and acrylic acid (AA). The Schiff base reaction between CS and GA endowed the foams with superior stability due to the formation of 3D network in the fluid films. A secondary network generated by polymerizing acrylamide (AAm) and acrylic acid (AA) further reinforced the structure, yielding a highly porous adsorbent (89.5% porosity). The adsorbent, CGAA@NTs, achieved a high U(VI) uptake capacity of 826   mg·g -1 under light irradiation thanks to the incorporation of carboxylated carbon nanotubes (CCNTs), which conferred the adsorbent with excellent photothermal performance, creating a local heat environment to facilitate the U(VI) uptake under light irradiation. Meanwhile, in the complex environment of wastewater, the abundant functional groups (e.g., −NH 2 and −COOH) enabled rich interactions with U(VI) via electrostatic effect and metal-coordination, opening an avenue for exploiting highly porous adsorbents of U(VI) using stable foams as templates.