A team of researchers in China has developed a new low-cost biochar material that can efficiently remove persistent metal complexes from water, offering a promising tool for improving water quality and environmental safety.
The study, published in Biochar X, describes how ferromanganese oxide-modified biochar can capture copper–citrate complexes, which are difficult to remove using conventional water treatment methods. These metal–organic complexes are common in industrial wastewater and pose serious environmental and health concerns due to their stability and tendency to accumulate in ecosystems.
"Unlike free metal ions, metal complexes such as copper–citrate are very stable and resistant to natural degradation," said Wenhong Fan of Beihang University, the corresponding author of the study. "Our goal was to design a simple, efficient, and reusable adsorbent that could tackle these stubborn contaminants."
The research team produced the new material by combining coconut shell biochar with iron and manganese oxides through a heat-based process. The resulting biochar was covered with nanosized particles that created abundant active sites for adsorption. Under optimal conditions, one gram of the modified biochar removed nearly all copper from a 10-milligram-per-liter solution within hours, achieving 99.5 percent copper removal and 92.6 percent total organic carbon reduction.
Microscopic and chemical analyses revealed that copper was captured through both chemical and physical adsorption processes. The modified biochar's porous structure allowed pollutants to diffuse into the material, while oxygen-containing functional groups and metal oxides on the surface bound the copper–citrate complexes tightly. The material also showed strong performance across a wide range of pH levels and remained stable even in the presence of other ions commonly found in wastewater.
"Efficient removal, simple preparation, and good chemical stability make this biochar a strong candidate for large-scale applications," said Ying Zhu, the study's first author. "It could be used not only for treating industrial wastewater but also for preventing metal pollution in natural water and soil systems."
The researchers note that further studies will explore how the material can be regenerated and reused over longer cycles and how its adsorption behavior might apply to other metal–organic contaminants.
This new biochar represents a practical step toward sustainable, low-cost technologies for water purification and environmental remediation.
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Journal reference: Zhu Y, Lei X, Liu J, Li Y, Fan W. 2025. Enhanced adsorption of copper citrate complexes by ferromanganese oxide biochar from water: performance and mechanism. Biochar X 1: e004 https://www.maxapress.com/article/doi/10.48130/bchax-0025-0001
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About the Journal:
Biochar X is an open access, online-only journal aims to transcend traditional disciplinary boundaries by providing a multidisciplinary platform for the exchange of cutting-edge research in both fundamental and applied aspects of biochar. The journal is dedicated to supporting the global biochar research community by offering an innovative, efficient, and professional outlet for sharing new findings and perspectives. Its core focus lies in the discovery of novel insights and the development of emerging applications in the rapidly growing field of biochar science.
