In-situ bioprocessing of bacterial cellulose aerogel with covalent organic frameworks for enhanced uranium extraction

Abstract

Developing efficient and cost-effective uranium adsorbents remain a significant challenge due to the complex composition of seawater. Herein, this study for the first time utilized an in-situ spray gel-assisted biosynthesis strategy to homogeneously incorporate the covalent organic frameworks (COF) into the three-dimensional pores of bacterial cellulose (BC) hydrogel during the culture of K. sucrofermentans. The BCCOF-SO3NH4 aerogel was fabricated through ammoniating modification of BC/COF (BCCOF-SO3H) hydrogel and freeze-drying processes. The BCCOF-SO3NH4 aerogels are characterized by the in-situ entanglement of COF within the three-dimensional network of BC, resulting in enhanced mechanical strength and groups interactions. The experimental maximum adsorption capacity of BCCOF-SO3NH4 aerogel reached 883.44 mg g−1, demonstrating exceptional uranium adsorption capacity compared with most of the reported adsorbents. The adsorption process follows the pseudo-second-order model and Langmuir isotherm. Throughout seven adsorption–desorption cycles, BCCOF-SO3NH4 maintained a stable adsorption capacity and desorption efficiency. The adsorption mechanism is verified by experiments and DFT calculations, which involves not only the ion exchange between uranyl and NH4+, but also the strong coordination interaction between the active groups (sulfonic acid group, hydroxyl group) and uranium. The in-situ biosynthesis strategy of composites shows a great application prospect in the preparation of high adsorption performance materials.