Mechanisms and Application Advances in the Synergistic Immobilization of Nitrate by Iron-Manganese Minerals and Biochar in Water

Nitrate pollution in water environment poses a serious threat to ecosystem security and human health. The existing remediation technologies generally have the limitations of high cost and easy to produce secondary pollution. It is urgent to develop efficient and sustainable nitrate treatment methods. The synergistic immobilization technology of iron-manganese minerals and biochar can significantly improve the removal efficiency of nitrate through multi-mechanism coupling, which has become a research hotspot in the field of water pollution control. This paper systematically reviews the synergistic mechanism of iron-manganese minerals and biochar composites, covering key processes such as surface adsorption, redox, ligand exchange and electrostatic attraction. The synergistic effects of temperature, pH, material dosage, metal ratio and coexisting ions on the immobilization effect were analyzed. The increase of temperature usually promoted the adsorption kinetics and capacity. Acidic conditions are conducive to the protonation of the material surface and enhance electrostatic attraction; the dosage needs to weigh the total removal rate and the unit adsorption efficiency; the optimization of metal ratios such as Fe/Mn can regulate the distribution of active sites and the reaction path. The coexisting ions produce complex interference through competitive adsorption or charge regulation. These factors are interrelated and jointly determine the suitability and effectiveness of the composite material in the actual water body. This paper further evaluates the application potential and existing limitations of this technology in actual water body restoration. Studies have shown that the iron-manganese mineral-biochar synergistic system has the advantages of high efficiency, stability and environmental friendliness in nitrate removal, but it still faces challenges such as insufficient adaptability to actual water bodies, lack of standardization in material preparation, and uncertainty in long-term stability. It is suggested that future research should focus on the optimization of material construction strategy, the in-depth analysis of reaction mechanism, and actively promote the demonstration of engineering application, so as to provide theoretical basis and technical scheme for the efficient and sustainable treatment of nitrate pollution.