Magnetic biochar from plant waste offers a new solution for toxic water pollutants

Using hydrothermal carbonization combined with iron doping, the team produced hydrochars with high adsorption efficiency, magnetic recoverability, and excellent reusability. The magnetic hydrochars removed up to 95% of PCP under optimal conditions and maintained structural stability over multiple cycles, presenting a promising pathway for low-cost, circular-economy water treatment technologies.

Increasing population growth, urbanization, and industrial activity have sharply raised global water demand while simultaneously generating wastewater rich in persistent organic contaminants. Pentachlorophenol, widely used in pesticides, wood preservation, and industrial processes, frequently enters rivers, soils, and even drinking water sources, posing significant ecological and human-health risks. While various remediation methods exist, many are energy-intensive, expensive, or generate secondary pollution. Adsorption remains a practical alternative, yet conventional activated carbon is costly and difficult to recover after use. Biomass-derived biosorbents offer a sustainable solution by valorizing waste materials, reducing landfill burden, and supporting circular economic systems. Against these challenges, the new study seeks to develop efficient, regenerable, and magnetically recoverable biosorbents.

A study (DOI: 10.48130/scm-0025-0003) published in Sustainable Carbon Materials on 27 October 2025 by Quan (Sophia) He’s team, Dalhousie University, provides a scalable and cost-effective strategy for converting abundant lignocellulosic residues into functional adsorbents for industrial wastewater purification.

Using a suite of advanced analytical techniques, the study characterized the structural, chemical, magnetic, and adsorption properties of iron-doped hydrochars produced from flax shives (FS-Fe-HC) and eucalyptus sawdust (ES-Fe-HC). FTIR was used to identify surface functional groups, XRD to determine crystalline phases, and XPS to analyze elemental composition and chemical states. Vibrating sample magnetometry (VSM) assessed magnetic behavior relevant for post-treatment recovery, while BET analysis quantified changes in surface area, pore volume, and pore structure. SEM-EDS provided complementary evidence of morphological changes introduced by iron incorporation. Batch adsorption experiments—evaluating adsorbent dosage, initial pollutant concentration, pH, and contact time—were coupled with kinetic and isotherm modeling to determine adsorption mechanisms, capacity, and stability. FTIR revealed abundant –OH, C=O, –COOH, C–O–C, and Si–O–Si groups in both materials, with Fe–O vibrations confirming successful iron doping while preserving native functionalities. XRD showed graphitic carbon, turbostratic carbon, Fe₂O₃, and zero-valent iron, with patterns remaining stable after reuse. XPS confirmed mixed-valence Fe²⁺/Fe³⁺ species and strong metal–oxygen interactions, while nitrogen groups indicated additional active sites. VSM demonstrated low remanence and rapid magnetic separability despite moderate magnetization values. BET results showed major improvements in porosity, with surface areas rising from <5 m²/g in raw hydrochars to 87–118 m²/g after iron modification, reflecting the formation of well-developed mesopores. SEM-EDS further confirmed porous surfaces decorated with iron-rich microspheres. Adsorption tests showed high PCP removal efficiencies—95% for FS-Fe-HC and 88% for ES-Fe-HC—under optimal conditions. Removal performance depended on dosage, pollutant concentration, pH-dependent surface charge, and contact time. Nonlinear kinetic modeling supported pseudo-first-order behavior, while Temkin isotherms indicated heterogeneous physisorption. Reusability remained substantial over six cycles, and ICP analysis confirmed no iron leaching, demonstrating excellent environmental safety and operational durability.

By enabling magnetic recovery, the hydrochars address a long-standing limitation of traditional activated carbon—difficult separation and regeneration—while maintaining strong adsorption efficiencies. Their high stability, minimal metal leaching, and repeated usability make them suitable for continuous or batch-based treatment systems. Moreover, the approach supports green manufacturing and waste valorization practices, aligning with circular-economy frameworks. Beyond PCP, such magnetic bio-adsorbents can potentially be adapted to remove dyes, pharmaceuticals, pesticides, and heavy metals from diverse wastewater streams.

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References

DOI

10.48130/scm-0025-0003

Original Source URL

https://doi.org/10.48130/scm-0025-0003

Funding information

The authors gratefully acknowledge funding from the Mitacs Globalink Research Internship program (ID: 129423), a Mitacs Elevate postdoctoral fellowship in partnership with Stella-Jones Inc. (NS-ISED IT34874), and funding from SSHRC-funded Sustainable Agriculture Research Initiative (1013-2024-0001).

About Sustainable Carbon Materials

Sustainable Carbon Materials is a multidisciplinary platform for communicating advances in fundamental and applied research on carbon-based materials. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon materials around the world to deliver findings from this rapidly expanding field of science. It is a peer-reviewed, open-access journal that publishes review, original research, invited review, rapid report, perspective, commentary and correspondence papers.