The material, covered with 100-nanometer Mn₃O₄ and (FeO)₀.₀₉₉(MnO)₀.₉₀₁ nanoparticles, demonstrated a remarkable copper removal rate of 99.5% and 92.6% total organic carbon reduction. Its adsorption mechanism combines chemical bonding with oxygen-containing functional groups and physical adsorption through the biochar's porous structure.
Freshwater scarcity has intensified the need to recycle and treat wastewater. However, conventional treatment methods focus mainly on free metal ions, overlooking the metal complexes that dominate industrial and municipal effluents. These complexes, often bound with citric acid or other organic agents, resist degradation, migrate easily, and pose long-term ecological and health risks. Copper–citrate complexes are particularly common in electroplating, textile dyeing, and household applications. Conventional precipitation and ion exchange techniques often fail to remove these stable complexes effectively. Biochar, an inexpensive and eco-friendly adsorbent, offers promise, yet its limited active sites and poor selectivity have constrained its efficiency. Addressing these challenges requires designing modified biochars with enhanced adsorption capability and stability.
A study (DOI: 10.48130/bchax-0025-0001) published in Biochar X on 14 October 2025 by Wenhong Fan's team, Beihang University, highlights an efficient, low-cost, and environmentally sustainable approach for addressing persistent metal–organic pollutants in aquatic environments.
The researchers synthesized ferromanganese oxide-modified biochar (FMBC-600) via impregnation and high-temperature calcination and systematically characterized its structure and performance in removing CuCA complexes from water. FE-SEM revealed that the modification transformed smooth pristine biochar into a rough surface uniformly coated with 80–100 nm nanoparticles, while EDS confirmed Fe and Mn incorporation and post-adsorption Cu deposition. FTIR and XRD analyses verified abundant hydroxyl, aromatic, and metal–oxygen functional groups, along with crystalline Mn₃O₄ and (FeO)₀.₀₉₉(MnO)₀.₉₀₁ phases. XPS further demonstrated Fe and Mn redox involvement in adsorption through electron transfer and surface complex formation. Nitrogen adsorption–desorption indicated an increased pore volume that facilitated adsorption, and process optimization identified the best conditions as an Fe:Mn ratio of 1:4, Mn = 0.03 M, and pyrolysis at 600 °C. Under these settings, Cu removal reached 99.5% and total organic carbon removal 92.6%, with adsorption occurring rapidly within 30 minutes and remaining stable across pH 4–10. Even in the presence of competing ions such as Na⁺, Ca²⁺, Cl⁻, and SO₄²⁻, FMBC-600 maintained high performance, indicating strong selectivity and resistance to interference. Kinetic modeling fit a pseudo-second-order equation (R² > 0.99), suggesting chemisorption as the dominant process, while the Freundlich isotherm described heterogeneous multilayer adsorption enhanced at higher temperatures. Regeneration tests showed about 80% retained efficiency after two cycles. Overall, the uniformly structured FMBC-600 exhibits excellent stability, reusability, and adsorption efficiency, making it a scalable and cost-effective material for removing persistent heavy metal complexes from wastewater.
The ferromanganese oxide-modified biochar represents a major advance in sustainable water treatment. Its simple, low-cost production process and high efficiency make it suitable for large-scale applications in industrial effluent management, especially in electroplating, dyeing, and chemical industries. Beyond wastewater, the technology could be adapted for soil remediation, helping reduce heavy metal accumulation in agricultural lands. Compared to conventional adsorbents, it offers superior selectivity, stability, and reusability. Importantly, the material performs effectively under varying pH and ionic conditions, making it practical for real-world systems where water chemistry is complex. Its integration into wastewater treatment frameworks could substantially reduce metal contamination and contribute to achieving global clean water and sustainability goals.
