Three-dimensional-printed calcium alginate/graphene oxide porous adsorbent with super-high lead ion adsorption ability in aqueous solution

Using three-dimensional (3D) printing technology, a 3D calcium alginate/graphene oxide (3D CA/GO) adsorbent, with a hierarchical macroporous structure, was successfully constructed. Owing to the optimized construction process, the 3D CA/GO showed an enhanced adsorption capacity (490.2 mg/g at pH = 3.0) for lead (Pb(II)) in aqueous solution, which was two times higher than reported in the literature). Meanwhile, the selective adsorption ratio of 3D CA/GO for Pb(II) reached 99.8% when positive ions occurred. In addition, after eight adsorption–desorption cycles, the adsorption capacity did not experience a significant decrease and the structure remained stable. Meanwhile, the adsorbed Pb(II) could be eluted by hydrochloric acid. Moreover, through characterization analysis and Ca(II) releasing experiment, we confirmed that the adsorption mechanism of 3D CA/GO consisted of electrostatic interactions, ion exchange and chelation. According to the actual application experimental, the waste water of medical environment was chosen, and the 3D CA/GO was verified as capable of removing and recycling Pb(II). The immersion experiment using simulation wastewater solution containing heavy metal ions also indicated that 3D CA/GO could maintain structural stability and sustain its adsorption capacity. The excellent structural stability, strong adsorption capacity, and outstanding selective adsorption capacity for 3D CA/GO were attributed to the controllable construction and optimized structure of hierarchical macroporous materials by 3D printing technology.