Fabrication of 3D Macroscopic Graphene Oxide Composites Supported by Montmorillonite for Efficient U(VI) Wastewater Purification

In this work, montmorillonite (MMT) was intercalated into a sheet of GO and then cross-linked by agar, realizing the 3D macroscopic composites of agar-MMT-GO. Agar-MMT-GO composites were characterized by SEM, TEM, FTIR, TGA, and XPS techniques. Fabricated agar-MMT-GO composites were tough and lightweight materials with a multichannel structure. The heat stability of agar-MMT-GO composites were enhanced relative to GO, as demonstrated by TGA results. FTIR analysis testified to no chemical bond between GO and MMT component, suggesting that agar scaffold mainly caused the formation of agar-MMT-GO composites. Agar-MMT-GO composites exhibited a good performance in U(VI) sorption (Q(max) of 147 mg/g at pH 4.5) and in recycling tests. The rate-limiting sorption step was the diffusion of U(VI) from liquid solution to the surface sites of agar-MMT-GO composites. XPS analysis demonstrated that U(VI) sorption on agar-MMT-GO was mainly attributed to cation exchange and inner-sphere complexation in low and high pH regions, respectively. Briefly, our work here provides new insights in designing GO composites with a solid skeleton to promote its large-scale application in wastewater remediation.