Novel preparation of sludge-based spontaneous magnetic biochar combination with red mud for the removal of Cu2+ from wastewater

In this study, municipal sludge and red mud were used as raw materials to prepare spontaneous magnetic biochar (SRMC-750) for the adsorption of Cu2+ from wastewater. The experimental findings demonstrated that the maximum actual adsorption capacity was 242.62 mg/g at 25 °C and pH 5. The adsorption process followed the pseudo-second-order kinetic model and the Freundlich isotherm model. The potential adsorption mechanisms were electrostatic attraction, complexation, cation-exchange, and “cation-π”. After five adsorption cycles, SRMBC-750 still had 75% removal efficiency for Cu2+. Overall, SRMBC-750 provides a potential pathway for the removal of Cu2+ from wastewater.