Robust reduced graphene oxide-PDA/ZIF-8 aerogel composite for cyclic, high-capacity dye adsorption

Hierarchical rGO-PDA/ZIF-8 aerogels with high surface areas and 3D porous structures were successfully fabricated via self-assembly and in-situ crystallization strategy. The aerogel exhibited excellent adsorption toward small dye molecules with good regeneration and cyclic performance, thus showing great potential for robust high-capacity dye removal from pharmaceutical effluents. [Display omitted] •Hierarchical porous hybrid aerogels combining rGO and ZIF nano-adsorbents.•The aerogel showed robust mechanical stability and unique surface properties.•Ultrahigh dye adsorption capacities that doubled the best-reported values were achieved.•The aerogel exhibited excellent long-term cyclic performance for dye removal. The contamination of nanosized organic dyes in the water bodies is of great concern as it adversely affects the marine ecosystem and biodiversity, leading to water-borne ailments. In recent years, designing sustainable, high-performance, and cost-effective composite adsorbents embedded with functional adsorbents for wastewater treatment has attracted immense attention. In this work, a new composite aerogel (rGO-PDA/ZIF-8) was prepared via self-assembling graphene oxide (GO) flakes to form a three-dimensional (3D) structure with functional polydopamine (PDA). Then, ZIF-8 crystals were decorated on the porous aerogel structure via the in-situ crystallization method. PDA-modified rGO aerogel provided abundant useful functional groups, such as –OH, –COOH, and –NH–, on the surface, while the incorporation of ZIF-8 nanocrystals further endowed composite aerogels with higher surface area and extra functional groups for enhanced organic dye adsorption. Our results revealed that the composite aerogel exhibited not only ultrahigh adsorption towards methylene blue (MB) with a maximum adsorption capacity of 1045 ± 2.9 mg g−1 (with a maximum rejection rate of > 99 %) but also excellent recyclability with a slightly decreased adsorption capacity of 897 ± 26.9 mg g−1 and a stable removal efficiency of > 92 % even after 10 cycles of adsorption. To the best of our knowledge, the obtained adsorption capacity almost doubled the best-reported values at similar conditions in the literature. The excellent adsorption performance is owing to strong π–π and electrostatic attractions between the dye molecules and the hierarchical porous composite structures with functional PDA coating and ZIF-8 nano-adsorbents. Therefore, the new composite rGO-PDA/ZIF-8 aerogel composite h