Superb adsorption capacity of hydrothermally synthesized copper oxide and nickel oxide nanoflakes towards anionic and cationic dyes

The CuO and NiO nanoflakes were synthesized by a hydrothermal reaction. The secondary nucleation and growth of hydroxides resulted in the formation of flake like architectures as the prepared nanoparticles were used as an adsorbent for malachite green oxalate (MGO) and methyl orange (MO). The structure, morphology and surface properties of the nanoparticles were characterized by XRD, SEM and TEM. Effects of the experimental conditions on the adsorption behavior were studied by varying the contact time, initial concentration, initial pH and temperature. The adsorption of MGO increased with increase in the pH, while the MO adsorption showed an opposite trend. The adsorption kinetics was studied in terms of pseudo-first and second-order kinetics, the Langmuir and Freundlich models were also applied to the equilibrium adsorption data. The adsorption process was spontaneous and exothermic in nature and followed the pseudo-second-order kinetic model. Our study indicates that the CuO and NiO nanoflakes can be used as alternative adsorbents for the efficient removal of dyes from an aqueous solution.