Environmental applications of GO-ZnO nanocomposites in chromium removal from tannery wastewater: Green treatment and sustainable approach

Competing ions and organic matters may alter the surface charge or block active sites of the adsorbents in real tannery effluent and reduce their effectiveness compared to synthetic solutions. Thus, the purpose of this work was to use graphene oxide-zinc oxide (GO-ZnO) nanocomposite to remove Cr ions from real tannery wastewater. The solvothermal method was used in this work to create decorated zinc oxide (ZnO) nanoparticles on graphene oxide (GO) nanoparticles. Fourier Transform Infrared (FTIR), UV–visible, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDX) techniques were used to characterize the surface deposition of ZnO on GO. To assess the impact of operational parameters, equilibrium isotherm, adsorption kinetics, and thermodynamics, batch adsorption analysis was performed. As time and adsorbent dosage increase, so does the removal efficiency of Cr (III). The results indicated that the maximal adsorption capacity of Cr (III) reached 99.97% with the presence of 2.5 g/L GO-ZnO under 25 min of contact time at pH 8.0. The Cr (III) concentration and clarity of the effluent were ensured via atomic absorption spectrometry and UV–visible spectroscopic analyses. The adsorption of Cr (III) could be well described using the Freundlich equation, and obeyed the pseudo-second order kinetic expression. The thermodynamic spontaneity and viability of a chemical reaction mechanism are represented by the negative value of Gibbs’ Free Energy. The results of biodegradation and antibacterial tests suggested the GO-ZnO nanocomposite to be non-toxic and environmentally safe. This work could provide an effective reference for the application of GO-ZnO nanocomposite for the adsorption of Cr (III) from tannery wastewater.