Facile synthesis and highly efficient Congo red adsorption of a novel hierarchical ZnO nanorod/NiCo2O4 nanosheet composite nanomaterials

Hierarchical ZnO/NiCo2O4 nanocomposites have been successfully prepared via a simple hydrothermal approach. The synthesized ZnO/NiCo2O4 composite nanomaterials consist of NiCo2O4 nanosheets supported by ZnO nanorods, the unique hierarchical microstructure provides a high specific surface area (137.13 m(2) g(-1)) and exhibits an excellent adsorption ability towards Congo red (CR). The adsorption of CR onto ZnO/NiCo2O4 is in compliance with pseudo-second-order kinetic model and Langmuir isothermal model, indicating a monolayer adsorption of dye molecules on the surface of nanomaterials. Its maximum adsorption capacity towards CR in aqueous solution can reach to 653.59 mg g(-1), which is much higher than that of pure ZnO and pure NiCo2O4. The high adsorption capacity of ZnO/NiCo2O4 can be ascribed to its high specific surface area and unique network structure. The results suggest that the as-prepared hierarchical ZnO/NiCo2O4 nanocomposites are promising adsorbents for wastewater treatment.