Straw Biochar‐Loaded MgFe Layered Double Hydroxides Composite for Efficient and Regenerable Copper Ion Removal From Aqueous Solutions

ABSTRACT Efficient removal of copper ions (Cu 2+ ) remains a key challenge in water pollution control. Traditional adsorbents often suffer from complex synthesis, secondary pollution risks, and poor regeneration. This study presents an innovative solution by converting agricultural straw waste into biochar through high‐temperature pyrolysis and enhancing it with in situ loaded magnesium‐iron layered double hydroxide (MgFe‐LDH) via coprecipitation. The resulting BC‐MgFeLDH composite exhibits a high specific surface area (193.40 m 2 /g), abundant oxygen‐containing functional groups, and a hierarchical porous structure. Under optimal conditions, the composite achieved a 99.86% removal efficiency for Cu 2+ and a maximum adsorption capacity of 37.425 mg/g—nearly 10 times higher than raw biochar. Kinetic and isothermal studies revealed that the adsorption process follows a pseudo‐second‐order model and fits the Langmuir isotherm well, indicating dominant chemisorption and monolayer adsorption. Mechanistic analysis via XPS and FTIR confirmed that interlayer anion exchange, surface hydroxyl complexation, and electrostatic interactions are key to Cu 2+ removal. Furthermore, the material still maintains a removal rate of over 60% after five reuse cycles, fully demonstrating its excellent regenerative capacity and stability. This work highlights the dual benefits of waste biomass utilization and functional material innovation, offering a promising pathway for cost‐effective, sustainable heavy metal removal from water.