RIGP-Induced Surface Modification of Cellulose for the Preparation of Amidoxime-Modified Cellulose/Graphite Oxide Composites with Enhanced Uranium Adsorption

Surface modification plays an important role in the design and fabrication of high-performance cellulose in many fields, especially in uranium adsorption. However, the high crystallinity of cellulose makes surface modification difficult to some extent, resulting in an impaired application performance. Herein, a radiation-initiated graft polymerization (RIGP) method is utilized to regulate the crystallinity of cellulose and improve the surface modification capability. To compensate for the weakening of the cellulose structure caused by the reduced crystallinity, graphite oxide (GO) powder is utilized as the scaffold, and the as-obtained amidoxime-modified cellulose/graphite oxide (Cel-AO/GO) composites are employed for U(VI) removal. The crystallinity of the cellulose can be effectively decreased by increasing irradiation doses, and the reduced crystallinity is proven to increase the amidoxime modification degree of cellulose. It is found that the sufficient surface amidoxime sites caused by the reduced crystallinity as well as the intrinsic carboxyl group of GO contribute synergistically to the efficient U(VI) adsorption performance. The maximum theoretical adsorption capacity of U(VI) can reach 237.5 mg·g–1 with ultrafast adsorption kinetics (90% removal in just 1 min). The adsorption process is well fitted by a pseudo-second-order and Langmuir isotherm. After eight adsorption–desorption cycles, the absorbent still retains 85% removal. These results indicate that the strategy of crystallinity-regulation by the RIGP method will be a valid way to develop high-performance cellulose-based U(VI) adsorbents.