Novel copper–aluminum oxide nanocomposites based on natural diatomite for efficient Cr6+ removal

Abstract

Removing hexavalent chromium (Cr⁶⁺) from wastewater is of great significance for the ecological environment, human health, and sustainable industrial development. In this work, Cu–Al₂O₃ nanopowders and Cu–Al₂O₃@AD nanocomposite were prepared by a coprecipitation method, which were used to adsorb Cr⁶⁺. The materials Cu–Al₂O₃@AD have ordered structures, and rich functional groups as verified by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy spectrum analysis (EDS), and field emission scanning electron microscopy (FESEM). Then, Cu–Al₂O₃@AD was used as adsorbents for fast and efficient removal of Cr⁶⁺ from aqueous solution by batch equilibrium experiments. The experimental results demonstrate that when the adsorbent dosage was 10 g L⁻¹, the pH value was 3, the initial concentration of Cr⁶⁺ was 2 μg mL⁻¹, and the reaction temperature was 30 °C, the adsorption performance of Cu–Al₂O₃@AD was the best, with a removal rate of up to 90%. The adsorption kinetics and isotherm data follow the pseudo-first-order equation and the Langmuir model, respectively. The adsorption mechanisms of Cr⁶⁺ are ascribed to monolayer adsorption.