Hydrothermal synthesis of cobalt substitute zinc-ferrite (Co1-xZnxFe2O4) nanodot, functionalised by polyaniline with enhanced photocatalytic activity under visible light irradiation

Fabrication and development of effective visible-light-responsive photocatalysts are required to tackle critical environmental issues. The aim of this study was to develop a nanocomposite material with improved photocatalytic activity for the degradation of industrial dyes such as Reactive Orange-16 (RO-16), Reactive Blue (RB-222), Reactive Yellow-145 (RY-145), and Disperse Red-1 (DR-1) without the need for a post-separation process after use. Here we report the hydrothermal synthesis of nanodots of Co1-xZnxFe2O4 (x = 0.3, 0.5 and 0.7), coated with polyaniline, by in situ polymerization. The Co1-xZnxFe2O4 nanodots, coated with polyaniline (PANI) nanograins, facilitated optical properties by easily capturing visible light. X-ray Diffraction (XRD) patterns and Scanning Electron Microscopy (SEM) images have confirmed the single-phase spinel structure of Co1-xZnxFe2O4 nanodot and nano-pore size of the Co1-xZnxFe2O4/PANI nanophotocatalyst. The specific surface area of the Brunauer–Emmett–Teller (BET) of the Co1-xZnxFe2O4/PANI photocatalyst was determined to be 24.50 m2/g by multipoint analysis. The final Co1-xZnxFe2O4/PANI (x = 0.5) nanophotocatalyst showed high efficiency in the catalytic degradation of toxic dyes (∼98% within 5 min), with good mechanical stability and recyclability under visible light irradiation. The nanophotocatalyst was re-used and its efficiency was largely maintained, even after seven cycles (∼82%) of degradation. The effects of various parameters, such as initial dye concentration, nanophotocatalyst concentration, initial pH of dye solution, and reaction kinetics were studied. According to the Pseudo-first-order kinetic model, photodegradation data followed the first-order reaction rate (R2 > 0.95) of degradation of dyes. In conclusion, a simple and low-cost synthesis process, speedy degradation and excellent stability of polyaniline-coated Co1-xZnxFe2O4 nanophotocatalyst could be used as a promising photocatalyst for dye-wastewater treatment.