Engineered Biochar for Metal Recycling and Repurposed Applications

Heavy metal pollution is posing significant threats to the environment and human health. Engineered biochar, derived from various biomass sources through thermochemical processes, has emerged as a promising solution for metal pollutant remediation and metal recovery. This review explores the latest advancements in the preparation, characterization, and application of engineered biochar for metal adsorption, recycling, and utilization. It begins by discussing the significance of metal adsorption and providing an overview of biochar properties. The review examines the preparation and characterization techniques, emphasizing feedstock selection, thermochemical conversion methods, and surface modifications. Mechanisms of metal adsorption, such as physical and chemical adsorption, ion exchange, and surface complexation, are critically discussed. Moreover, factors influencing metal adsorption capacity, including biochar properties, metal characteristics, and environmental conditions, are critically analyzed. The efficacy of engineered biochar in adsorbing specific metals, including heavy metals, transition metals, and rare earth elements, is reviewed with recent studies and key findings. Furthermore, the recycling and regeneration of metal-loaded biochar are discussed, focusing on recycling and repurposed application techniques alongside challenges and economic considerations. Finally, future perspectives are provided for the enlightening of future research. This review is unique in addressing the potential of metal-adsorbed biochar as a novel precursor to produce catalytical and electrochemical materials.