Fine synthesis of hierarchical CuO/Cu(OH)2 urchin-like nanoparticles for efficient removal of Cr(Ⅵ).

• Urchin-liked nanoparticles were prepared by microwave-induced hydrolysis process. • Urchin-liked nanoparticles made up of CuO/Cu(OH) 2 substructure nanowires. • Urchin-liked nanoparticles present the porous structure with BET of 230.67 m2/g. • Maximum adsorption capacity for Cr(Ⅵ) on Cu-based nanoparticles is 357.25 mg/g. • The Cr(VI) adsorption was an endothermic and spontaneous process. The hierarchical CuO/Cu(OH) 2 urchin-like nanoparticles with branching nanowires were rationally constructed under the ultrasonic hydrolysis treatment based on the Cu-based hollow spheres by microwave treatment. Moreover, due to the novel hierarchical nanostructure with a high specific surface area (230.67 m2/g) and a porous structure (the average pore volume was 0.96 cm3/g), hierarchical CuO/Cu(OH) 2 urchin-like nanoparticles demonstrated an outstanding adsorbent properties for Cr(VI). The maximal adsorption proportion was 95.4% at 100 mg/L initial Cr(VI) concentrations, the maximum adsorption capacity at 298 K and pH 4.0 was 425.49 mg/g. [Display omitted] Hierarchical self-assembly nanomaterials with high spatial/angular precision have attracted intensive attention in the urgent research focus in industrial and environmental fields, such as the efficient removal of heavy metal ions from aqueous solution. Herein, we developed an facile microwave-induced ultrasonic hydrolysis approach for the fine synthesis of the hierarchical CuO/Cu(OH) 2 urchin-like nanoparticles, which is comprised by Cu-based substructure nanowires with an average diameter of ~5 nm. Benefiting from the high specific surface area of 230.67 m2/g, the urchin-like CuO/Cu(OH) 2 hierarchical nanoparticles demonstrated a high maximum adsorption capacity of 357.25 mg/g at pH = 6.0 and T = 298 K for Cr(VI). Furthermore, the corresponding removed approximately 95% can be achieved after the adsorption process for 30 min, suggesting the fast adsorption for Cr(VI). Thermodynamic and kinetic investigations revealed that the Cr(VI) adsorption on the urchin-like CuO/Cu(OH) 2 hierarchical nanoparticles was an endothermic and spontaneous process, which could be well fitted by the pseudo-second-order kinetic model. This approach provides new prospects for curbing heavy metal pollution in the environment based on the hierarchical self-assembly nanomaterials. [ABSTRACT FROM AUTHOR]