Removal of Pb2+ from aqueous solution using an MgO nano-hybridized magnetic biochar from spent coffee grounds

Abstract

An MgO nano-hybridized magnetic biochar (MMB) was successfully prepared from spent coffee grounds to remove Pb2+ from aqueous solution. It was the first time that carbon-based MgO composites were prepared by hydrothermal synthesis. At 20 °C, the maximum adsorption capacity of MMB was 321.9 mg/g (pH 5). The adsorption kinetics followed Pseudo second-order kinetic model. The adsorption process of MMB was confirmed by the Langmuir isothermal model, indicating the adsorption reaction was a single-layer chemisorption on MMB surface. XPS, FTIR and XRD analyses indicated the adsorption mechanism included surface complexation, ion exchange reaction and surface precipitation, with surface precipitation playing the largest role.