A research team has developed an iron-copper bimetallic activated hydrochar capable of removing methylene blue dye and treating wastewater from potato processing. Produced from sawdust, the porous carbon material achieved a maximum dye adsorption capacity of 1,635.28 mg/g under optimized conditions. Laboratory analyses showed that adsorption was driven mainly by pore filling and interactions between methylene blue and active sites containing iron, copper, and aromatic carbon structures. Fixed-bed experiments further demonstrated the material's ability to operate in a continuous treatment system. The findings provide a foundation for converting low-value forestry residues into efficient adsorbents for industrial wastewater purification and resource-efficient pollution control.
Water pollution from synthetic dyes remains a serious environmental concern as textile, printing, cosmetic, and other industries expand. Methylene blue is widely used but can restrict light penetration and photosynthesis when released into aquatic environments. Adsorption with activated carbon is relatively economical and easy to operate, while hydrothermal carbonization can convert wet biomass into carbon-rich materials without energy-intensive predrying. However, conventional hydrochar may be difficult to recover, and most previous adsorption studies have relied on simplified batch tests rather than continuous treatment of real wastewater. These limitations highlight the need to investigate recoverable, metal-modified hydrochars under both controlled laboratory conditions and realistic continuous-flow conditions.
A study (DOI: 10.48130/scm-0026-0014 ) published in Sustainable Carbon Materials on 08 April 2026 by Yulin Hu's team, University of Prince Edward Island, reports that sawdust-derived Fe-Cu activated hydrochar combines high dye adsorption capacity with continuous treatment potential for synthetic solutions and real industrial wastewater.
The researchers first converted sawdust into hydrochar through hydrothermal carbonization at 210 °C for four hours. The resulting material was activated with potassium hydroxide at 800 °C under nitrogen to develop its porous structure. Iron chloride and copper sulfate were then introduced, and the composite was carbonized at 300 °C to produce Fe-Cu bimetallic activated hydrochar, designated MAHC. Its physicochemical properties were examined using surface-area analysis, scanning electron microscopy, elemental analysis, infrared spectroscopy, thermogravimetric analysis, zeta-potential measurements, and X-ray photoelectron spectroscopy. MAHC exhibited a predominantly microporous structure, a specific surface area of 1,266.1 m²/g, and a total pore volume of 0.7394 cm³/g. Batch experiments evaluated the effects of pH, dye concentration, adsorbent dosage, temperature, and contact time. The highest adsorption capacity, 1,635.28 mg/g, occurred at pH 10 with 50 ppm methylene blue, 5 ppm MAHC, and a temperature of 44 °C. Adsorption increased with temperature, indicating an endothermic process, although the required heating may constrain practical applications. The Freundlich isotherm described the data better than the Langmuir and Temkin models, pointing to multilayer adsorption on a heterogeneous surface. Meanwhile, the pseudo-second-order kinetic model provided the best overall fit, suggesting that surface interactions contributed alongside physical adsorption. Intraparticle-diffusion analysis showed that higher temperatures reduced mass-transfer resistance and accelerated dye movement into the pores. After adsorption, MAHC's surface area fell from 1,266.1 to 97.0 m²/g, supporting pore filling as a major mechanism. Spectroscopic evidence also implicated Fe and Cu active sites and π-π interactions between the dye's aromatic rings and the carbon framework. Finally, a column packed with 1.5 g of MAHC reached breakthrough after 165 minutes for methylene blue solution and approximately 360 minutes for potato-processing wastewater.
Overall, the study demonstrates that combining hydrothermal carbonization, chemical activation, and bimetallic modification can transform sawdust into a high-capacity wastewater adsorbent. By testing MAHC in both batch and fixed-bed systems, the researchers moved beyond idealized dye-removal experiments toward more realistic industrial conditions. However, comparisons with commercial activated carbon, tests using other biomass feedstocks, and systematic assessments of stability, regeneration, and recyclability are still required before large-scale implementation. Future work should also determine whether strong adsorption performance can be maintained at lower temperatures and over repeated treatment cycles.
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References
DOI
Original Source URL
https://doi.org/10.48130/scm-0026-0014
Funding information
This work was financially supported by Discovery Grants (Grant numbers: RGPIN-2022-03203 and RGPIN-2020-05695) and the Mitacs Global link program (Project ID: 45224 and Project ID: 45223).
About Sustainable Carbon Materials
Sustainable Carbon Materials (e-ISSN 3070-3557) 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.
Sustainable Carbon Materials
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Adsorption of methylene blue dye and potato processing wastewater using bimetallic activated hydrochar: batch and fixed bed column experiments
8-Apr-2026
The authors declare that they have no competing interests.