Fabrication of three-dimensional printed hybrid graphene oxide/calcium alginate network by 3D printing technology with outstanding U(VI) recycling capacity in acidic solution

Abstract

In this study, a 3D-printed graphene oxide (GO)/calcium alginate (CA) hybrid network (3D GO/CA) with excellent U(VI) adsorption performance was constructed using direct ink writing-based 3D printing technology and in situ calcium ion cross-linking technology. The GO and CA sheets in 3D GO/CA were stacked layer by layer. Meanwhile, the 3D multilayered pore structure with large-scale characteristics was constructed. Furthermore, the pore structure was orderly arranged, with abundant active adsorption sites (oxygen-containing functional groups/Ca2+ binding sites) exposed. The adsorption experiment results showed that 3D GO/CA exhibited a wide valid pH range (3–12) and excellent adsorption capacity for U(VI) in a strongly acidic solution (for example, at pH = 2.8, the adsorption capacity is 200.1 mg/g). In addition, 3D GO/CA exhibited high adsorption kinetic reaction rate (adsorption equilibrium could be reached within 30 min). In the simulated acidic wastewater (pH = 2.8), 3D GO/CA exhibited an excellent adsorption capacity of UO22+ and an adsorption ratio of approximately 99.7 %. The 3D GO/CA retained its original stable structure morphology after it was reused eight times. In addition, the stable structure of 3D GO/CA was retained after it was soaked in the strong acid solution at different concentrations (1.59 × 10−3–2 mol/L) for 48 h. With the aid of 3D printing technology and Ca2+ cross-linking technology, the structure of 3D GO/CA was optimized, and more oxygen-containing functional groups were retained at the edge of the GO sheet. Therefore, 3D GO/CA has a promising application prospect for removing and recovering U(VI) in acidic solutions.