ZnO tetrapods and activated carbon based hybrid composite: Adsorbents for enhanced decontamination of hexavalent chromium from aqueous solution

Owing to its acute toxicity and mobility, the hexavalent chromium [Cr(VI)] in water and wastewater is an immense risk to the environment. Herein, ZnO-tetrapods/activated carbon (ZnO-T/AC) nanocomposite was synthesized as an adsorbent for an efficient decontamination of Cr(VI) from an aqueous medium. The tetrapodal ZnO was synthesized by flame transport synthesis (FTS) approach. The utilized activated carbon (AC) was successfully prepared from sugarcane bagasse with sodium hydroxide (NaOH) impregnation, followed by carbonization. Finally the ZnO-T/AC nanocomposite was synthesized by the hydrothermal method. The structural and chemical properties of the obtained nanocomposite (NC) were systematically characterized using X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and Brunauer-Emmett-Teller (BET) analysis. Batch experiments were performed with the AC, ZnO-T and ZnO-T/AC to study their maximum adsorption efficiency for the Cr(VI). The effect of operational parameters such as contact time, pH and adsorbent dosage on the removal of Cr(VI) were also investigated. Different kinetic models were employed to comprehend the adsorption mechanism. The removal efficiency (97%) of Cr(VI) using ZnO-T/AC adsorbent was achieved at pH 2. The synthesized nanocomposite showed significant potential for the decontamination of Cr(VI) and can be further explored at a large scale for the efficient removal of hazardous heavy metal ions from the industrial contaminates.