Synthesis of amidoximated polyacrylonitrile nanoparticle/graphene composite hydrogel for selective uranium sorption from saline lake brine

Abstract In order to increase the selectivity of graphene hydrogel (GH) for uranium and ensure its possible application in uranium extraction from complicated systems, such as seawater and saline lake brines, GH with amidoxime groups needs to be prepared. However, it is not an easy task to grafting amidoxime groups on GH. At present work, an innovative method is used to fabricate the amidoximated graphene hydrogel, polyarylonitrile nanoparticle/graphene composite hydrogel (PAO/GH), through simultaneously encapsulating polyacrylonitrile (PAN) nanoparticles in hydrogel formation process and then amidoximation. The prepared adsorbent is characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and BET specific surface area analyses. All the results prove that PAO/GH with amidoxime groups is successfully obtained. The effects of initial solution pH, ionic strength, time and initial uranium concentration on uranium sorption by PAO/GH are studied systematically and compared with the blank graphene hydrogel (GH). The uranium selectivity of PAO/GH increases obviously after introducing amidoxime groups. Moreover, the mechanism of uranium sorption by PAO/GH is also explored with different characterization methods. Amidoxime groups are revealed to be the main functional groups involved in uranium sorption by PAO/GH and served as electron donor. Basis on the above results, uranium extraction from natural saline lake brine by PAO/GH is also performed and PAO/GH is testified to be a promising adsorbent for recovering uranium from complicated systems.