An efficient removal of methyl violet from aqueous solution by an AC-Bi/ZnO nanocomposite material

Abstract

An activated charcoal (AC) supported bismuth (Bi)-doped zinc oxide (ZnO) nanocomposite material was synthesized by a precipitation method. The obtained material was characterized by high resolution-scanning electron microscopy (HR-SEM) with energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Fourier transform-Raman spectroscopy (FT-RAMAN), photoluminescence spectroscopy (PL), UV-visible diffuse reflectance spectroscopy (UV-Vis-DRS), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) analysis. The BET surface area, pore radius and pore volume of the materials were calculated by applying the BET equation to the sorption isotherms. The cyclic voltammetry (CV) analysis suggested an electrochemical redox reaction. The production of hydroxyl radicals (˙OH) on the surface of the UV-irradiated photocatalysts was detected by a photoluminescence technique using coumarin as a probe molecule. The photocatalytic activity of the AC-Bi/ZnO material is demonstrated through the photodegradation of methyl violet (MV) under UV-light irradiation. AC-Bi/ZnO has an increased absorption in the UV region; moreover, it shows excellent UV-light driven photocatalytic performance. The photocatalyst of AC-Bi/ZnO reveals enhanced photocatalytic activities as compared to ZnO and Bi/ZnO for the degradation of harmful MV dyes. The enhanced photocatalytic activity of AC-Bi/ZnO is attributed to the low recombination rates of photoinduced electron hole pairs, caused by the transfer of electrons and holes between ZnO and AC supported Bi³⁺ ions. The mechanism of the photocatalytic effect of the AC-Bi/ZnO nanocomposite material has been discussed. The proposed use of AC-Bi/ZnO in water purification technique is promising.