Efficient and rapid adsorption of rare earth elements from water by magnetic Fe3O4/MnO2 decorated reduced graphene oxide

Considerable separation of rare earth elements ( REEs) from water is still a challenging problem due to their similar chemical and physical properties. In this work, a ternary magnetic Fe3O4/MnO2/rGO composite (FMG) was successfully fabricated by a facile two-step process and introduced to recycle rare earth cations (La3+ and Ce3+) from water. The physicochemical properties of FMG were studied by vibrating sample magnetometer, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer-EmmettTeller, and zeta potential. The effects of several factors on REEs adsorption were comprehensively evaluated, including pH value, contact time, REEs initial concentration, and temperature. Under the condition of 100 mg/L REEs concentration, 0.3 g/L FMG, time 60 min, and pH 7, the removal efficiency of REEs reached 99%. Furthermore, the maximum adsorption capacity of FMG for La3+ and Ce3+ reached 1016 and 981 mg/g, respectively. The experimental data were better followed with the Langmuir isotherm model and the pseudo-second-order kinetic model, indicating the adsorption process is mainly monolayer chemisorption. Furthermore, the Temkin model also predicted chemical adsorption. Thermodynamics studies demonstrated that the reaction is spontaneous, favorable, and endothermic. The FMG still maintained excellent removal efficiency (93%) for REEs after five adsorption-desorption cycles. Herein, the FMG exhibited its great potential in the retrieval of REEs from water via simultaneously utilizing its magnetic properties and high affinity for REEs. (C) 2020 Elsevier B.V. All rights reserved.