Adsorption removal of amaranth by nanoparticles-composed Cu2O microspheres

Cuprous oxide nanoparticles-composed microspheres (Cu2O SPs) with rough surfaces and porous structures were prepared by a one-step reduction method at room temperature. The Cu2O SPs were characterized by SEM, XRD, EDS and XPS techniques, respectively. The adsorption removal of amaranth dye from aqueous solution by the as-prepared Cu2O SPs was studied. Kinetics and isotherms studies suggested that the adsorption process followed pseudo-second-order and Freundlich models. Dubinin-Radushkevich (D-R) model indicated that the adsorption was a physical process. The maximum adsorption capacity at 20 degrees C was estimated to be 7627 mg g(-1), which was the highest reported value so far for amaranth adsorption. The thermodynamic parameters (free energy change, Delta G degrees; enthalpy change, Delta H degrees and entropy change, Delta S degrees) for the adsorption have been estimated. The results showed that the adsorption of amaranth onto Cu2O SPs could be considered as a spontaneous, exothermic and mainly physical adsorption process. (C) 2018 Elsevier B.V. All rights reserved.