In an era marked by escalating freshwater scarcity, the challenge of treating industrial and municipal wastewater containing complex metal pollutants has become more urgent than ever. Traditional water treatment techniques largely target free metal ions, but they falter when addressing metal complexes that resist conventional removal methods. Among these, copper–citrate complexes are particularly problematic due to their stability and widespread presence in effluents from industries such as electroplating, textile dyeing, and everyday household products. These complexes exhibit robust resistance to degradation, ensuring persistent migration through aquatic environments, thereby posing significant ecological and human health threats over extended periods.
To tackle this pressing issue, a groundbreaking study recently published in the journal Biochar X on October 14, 2025, presents a novel, efficient, and cost-effective approach to adsorb these stubborn copper–citrate complexes from water. Led by Wenhong Fan and his team at Beihang University, the research introduces a ferromanganese oxide-modified biochar (FMBC-600), synthesized through a meticulous impregnation method followed by high-temperature calcination. This material represents a remarkable advancement in sustainable wastewater treatment science, combining simplicity in production with superior performance.
Detailed electron microscopy analyses reveal that the FMBC-600 biochar undergoes a dramatic morphological transformation upon modification. Pristine biochar, initially characterized by a smooth surface, gains a significantly roughened texture evenly coated with nanoparticles sized between 80 and 100 nanometers. These nanoparticles are composed predominantly of manganese oxide (Mn₃O₄) and a mixed ferromanganese oxide phase denoted as (FeO)₀.₀₉₉(MnO)₀.₉₀₁, evidenced by energy-dispersive spectroscopy (EDS) and confirmed through X-ray diffraction (XRD) patterns. This structural enhancement directly contributes to the material’s increased surface area and porosity, key factors enhancing its adsorptive capabilities.
Crucially, surface chemical analyses through Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) illuminate the functional underpinnings of FMBC-600’s effectiveness. The biochar’s surface is rich in oxygen-containing groups such as hydroxyls and aromatic moieties, which engage in chemical bonding interactions with copper ions. Simultaneously, the ferromanganese oxide phases introduce redox-active sites, enabling electron exchange processes that strengthen adsorption through surface complexation. This dual mechanism of chemisorption combined with physical adsorption within the biochar’s enhanced porous matrix results in rapid and highly selective sequestration of copper–citrate complexes.
Experimental tests conducted under optimized conditions — specifically, an iron to manganese molar ratio of 1:4, manganese ion concentration of 0.03 M during synthesis, and pyrolysis temperature maintained at 600 °C — demonstrated extraordinary removal efficiencies. The FMBC-600 biochar achieved a copper removal rate of 99.5% and a total organic carbon (TOC) reduction of 92.6% within a mere 30 minutes. Furthermore, these results held consistent across a wide pH spectrum ranging from 4 to 10, affirming the material’s versatility under varying water chemistries commonly encountered in industrial wastewater streams.
The material’s robustness against competing ions further underscores its suitability for real-world applications. In water matrices containing prevalent ions such as sodium (Na⁺), calcium (Ca²⁺), chloride (Cl⁻), and sulfate (SO₄²⁻), FMBC-600 maintained its high adsorption efficiency, illustrating its strong selectivity and resistance to interference by non-target substances. This resilience is critical, as industrial effluents often comprise complex and variable compositions that challenge many adsorbents’ stability and functionality.
Kinetic adsorption studies revealed that the process adheres closely to a pseudo-second-order model with a correlation coefficient exceeding 0.99. This suggests that the rate-limiting step revolves around chemisorption mechanisms involving valence electron sharing or transfer between the biochar surface and copper species, rather than mere physical adherence. Additionally, adsorption isotherms fitted to the Freundlich model affirm that the adsorption occurs as heterogeneous multilayer deposition, a phenomenon enhanced at elevated temperatures, pointing to the material’s potential efficacy in diverse climatic and operational conditions.
Beyond initial performance, the study highlights the practical aspect of adsorbent regeneration and reusability, indispensable traits for industrial-scale deployment. The FMBC-600 biochar exhibited commendable durability, retaining approximately 80% of its adsorption capacity after two successive operational cycles. This longevity not only reduces operational costs but also mitigates waste generation associated with spent adsorbent disposal, aligning with circular economy and sustainability paradigms.
The innovative ferromanganese oxide modification of biochar yields a multifunctional adsorbent demonstrating exemplary stability, selectivity, and efficiency in removing persistent heavy metal complexes from aqueous solutions. Its straightforward synthesis route, leveraging impregnation coupled with controlled high-temperature calcination, ensures scalability and economic feasibility. These attributes position FMBC-600 as a promising candidate to revolutionize industrial wastewater treatment, particularly for industries burdened with recalcitrant copper–citrate species.
Looking ahead, the potential applications of this technology extend beyond water remediation. The same principles underlying its performance could be adapted for soil decontamination, effectively immobilizing heavy metals to prevent bioaccumulation in agricultural ecosystems. Such expansion would contribute significantly to mitigating environmental pollution burdens, fostering safer food production, and protecting biodiversity. Moreover, the material’s robust performance across a range of challenging conditions further heightens its appeal as a versatile environmental engineering tool.
Importantly, this research addresses critical gaps left by traditional adsorption materials, especially in terms of overcoming limited active site availability and poor selectivity inherent in many biochars. By integrating redox-active metal oxides, the modified biochar not only captures metal complexes chemically but also stabilizes them physically, ensuring minimal leaching and enhanced longevity. This balanced hybrid adsorption mechanism embodies the cutting edge of materials science approaches toward sustainable pollution control.
The promising results obtained by Wenhong Fan’s team mark a significant stride toward realizing global clean water and environmental sustainability goals. The FMBC-600 biochar’s adaptability to real water matrices with complex ionic backgrounds, combined with its facile regeneration, points to practical integration into existing wastewater treatment infrastructures. Such integration could drastically reduce the environmental footprint of metal pollution worldwide, safeguarding aquatic health and human well-being for future generations.
As the water treatment landscape continues to evolve, advances like FMBC-600 offer a model framework where modifications at the nanoscale translate into macroscopic environmental benefits. Future studies may explore further optimization parameters, such as varying metal oxide compositions, exploring synergistic effects with other functional additives, or examining long-term field deployment outcomes. Nonetheless, this pioneering work firmly establishes ferromanganese oxide-modified biochar as a formidable weapon in the fight against persistent metal-organic pollutants.
Subject of Research:
Not applicable
Article Title:
Enhanced adsorption of copper citrate complexes by ferromanganese oxide biochar from water: performance and mechanism
News Publication Date:
14-October-2025
Web References:
https://www.maxapress.com/article/doi/10.48130/bchax-0025-0001
References:
10.48130/bchax-0025-0001
Keywords:
Technology, Biochemistry, Agriculture
