Efficient and stable photocatalytic reduction of aqueous hexavalent chromium ions by polyaniline surface-hybridized ZnO nanosheets

ZnO/PNAI nanocomposites were obtained via a simple two-step method, in which a hierarchically flower-like ZnO, assembled from nanosheets, was first synthesized by low temperature (80 degrees C) solution method without surfactant/template and then, an in-situ polymerization of aniline onto the ZnO nanosheets was carried out. The characterization was actualized on the synthesized nanocomposite using XRD, Raman, TG-DSC, IJV-vis-DRS, PL, XPS, SEM, TEM and N-2 adsorption-desorption analysis. An efficient and stable photocatalytic activity was exhibited by the synergistic ZnO/PNAI nanocomposites on the reduction of toxic Cr(VI) to benign Cr(III) in comparison with the pristine ZnO and other semiconductor/PANI materials reported. The influence of parameters such as solution pH, initial Cr(VI) concentration and the addition of organic sacrifices on the Cr(VI) removal efficiency was investigated. It was found that the Cr(VI) removal was strongly pH-dependent and the optimum pH range was 4-7 for ZnO/PANI composite catalyst. The Langmuir-Hinshelwood kinetic examination showed that the surface photoreaction was the rate-determining step to compare the adsorption equilibrium. The organic additives such as EDTA and citric acid can promote the photocatalytic efficiency and the solution of EDTA/HCI can well restore the photoreduction ability of ZnO/PANI catalyst. Moreover, the reusability of photocatalyst was also tested to estimate the practicability. (C) 2019 Elsevier B.V. All rights reserved.