Synergistic Heavy Metal Remediation Using LDH-Modified Magnetic Biochar and Resistant Microorganisms: A Comprehensive Review

Abstract

The water and soil contamination by heavy metals such as Cu, Cd, Pb, As and Cr leads to major environmental problems due to their toxic effects, persistent and accumulation in the environment. Traditional removal methods are limited due to high costs, low efficiency of metal removal and generation of secondary sludge. The development of Zn – Al and Mg – Fe LDH-coated magnetic biochar has shown higher efficiency to treat the metal pollutants. Their method of synthesis, structural properties and adsorption mechanisms are discussed. LDH – biochar hybrids perform surface precipitation, surface complexation, ion exchange, and electrostatic interaction to show higher removal efficiency through their synergistic mechanisms. Studies reported the adsorption capacity of Pb (II) and Cd (II) are high as 448-476 mg g^-1. Magnetic functionalization enables rapid solid–liquid separation and reusability, while LDH layers enhance stability and enable simultaneous removal of cationic and anionic metal species. The review further highlights the emerging integration of LDH–biochar composites with heavy metal-resistant microorganisms, where biochar provides a protective microbial habitat and LDHs act as nano-bridges to improve metal immobilization, redox transformation, and long-term soil stability. Key challenges related to acidic stability, metal leaching, scalability, and field-level validation are discussed. Overall, LDH-modified magnetic biochar–microbe systems represent a promising, low-carbon approach for efficient and sustainable heavy metal remediation.

Keywords: Metal contamination, Magnetic biochar, LDH Composite, Bioremediation.