Green and sustainable recycling of MnCo2O4/Mn3O4/Li(Mn0.75Ni0.25)2O4 mixed oxide from of spent Li-ion and Zn–MnO2 batteries and evaluation of its photocatalytic properties

Abstract

In this study, MnCo2O4/Mn3O4/Li(Mn0.75Ni0.25)2O4 spinel-like mixed oxide was synthesized by green recycling of spent Li-ion and Zn–MnO2 batteries. The first step consisted of leaching the cathode of Li-ion batteries and the cathode of Zn–MnO2 batteries with citric acid and glucose. Then, Li-ion cathode leachate was mixed with Zn–MnO2 cathode leachate. Leachate mixture received the addition of oxalic acid, yielding oxalate precursor material, which was calcined at 450 °C for 3 h to afford MnCo2O4/Mn3O4/Li(Mn0.75Ni0.25)2O4. Mixed oxide structure, composition, and morphology were determined by X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP OES), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The photocatalytic properties of mixed oxide were evaluated in the decolorization of a model dye (methylene blue) under UV radiation. System using UV radiation + H2O2 + catalyst reached decolorization efficiency >93% in 120 min of reaction. This study provides a possible solution for two environmental liabilities (batteries and wastewater), and the results reported here are of scientific, economic, environmental, and social interest.