Biochar Breakthrough: New Method Removes Heavy Metals from Water

A team of researchers from Beihang University has developed a new method for removing heavy metals from wastewater, achieving a remarkable 99.5% copper removal rate. Their innovative approach utilizes ferromanganese oxide-modified biochar, known as FMBC-600, which effectively targets stable metal complexes in water, particularly those bound with organic agents like citric acid. This advancement, detailed in a study published on October 14, 2025, addresses a critical gap in traditional water treatment methods that often overlook these complex metal forms.

The study, led by Wenhong Fan, highlights the limitations of conventional techniques that primarily focus on free metal ions. Many industrial and municipal effluents contain metal complexes that are resistant to degradation, posing long-term environmental and health risks. Copper-citrate complexes, commonly found in industries such as electroplating and textile dyeing, exemplify this challenge. Traditional methods like precipitation and ion exchange have struggled to effectively remove these stable complexes.

FMBC-600 was synthesized through a process of impregnation and high-temperature calcination. The researchers meticulously characterized its structure and performance, revealing significant enhancements in adsorption capabilities. Scanning electron microscopy (FE-SEM) showed that the modification process transformed the smooth surface of pristine biochar into a rough texture, uniformly coated with 80-100 nanometer nanoparticles. Energy-dispersive X-ray spectroscopy (EDS) confirmed the successful incorporation of iron (Fe) and manganese (Mn) into the biochar matrix, as well as deposition of copper following adsorption.

The research team also conducted Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. These tests identified a variety of functional groups, including hydroxyl and metal-oxygen bonds, that facilitate the adsorption process. X-ray photoelectron spectroscopy (XPS) demonstrated the involvement of redox reactions in the adsorption mechanism, further supporting the efficiency of FMBC-600.

Optimizing the synthesis conditions revealed that the ideal iron to manganese ratio was 1:4, with a manganese concentration of 0.03 M and pyrolysis at 600 °C. Under these conditions, the biochar achieved its impressive copper removal rate of 99.5% and a total organic carbon reduction of 92.6%. Notably, the adsorption process was rapid, with significant results observed within just 30 minutes, and the material maintained effectiveness across a pH range of 4 to 10.

Even in the presence of competing ions such as sodium (Na+), calcium (Ca2+), chloride (Cl−), and sulfate (SO42−), FMBC-600 exhibited strong selectivity and resistance to interference, further highlighting its potential for real-world applications. Kinetic modeling indicated that chemisorption was the dominant mechanism, supported by a pseudo-second-order model with a high correlation coefficient (R2 > 0.99). The Freundlich isotherm analysis suggested heterogeneous multilayer adsorption, which is enhanced at higher temperatures.

Regeneration tests demonstrated that FMBC-600 retained approximately 80% of its efficiency after two cycles, underscoring its stability and reusability. This makes it a scalable and cost-effective solution for addressing persistent heavy metal contamination in wastewater.

The implications of this research extend beyond wastewater treatment. The technology could also be adapted for soil remediation, aiding in the reduction of heavy metal accumulation in agricultural lands. Compared to traditional adsorbents, FMBC-600 offers superior selectivity, stability, and reusability, making it a promising candidate for large-scale applications in various industries, particularly in electroplating, dyeing, and chemical sectors.

In summary, the advent of ferromanganese oxide-modified biochar marks a significant advancement in sustainable water treatment solutions. Its straightforward and low-cost production process, combined with its high efficiency, positions it as an essential tool in the global effort to minimize metal contamination and contribute to clean water and sustainability goals.

For more detailed findings, the study can be accessed via the following link: DOI: 10.48130/bchax-0025-0001.

This research was supported by the National Natural Science Foundation of China and several regional funding initiatives, reflecting a collaborative effort to advance environmental science.