Industrial activities, such as textile manufacturing, paper production, leather processing, and food processing, can generate wastewater containing synthetic dyes. Because many synthetic dyes are chemically stable, difficult to biodegrade, and environmentally persistent, their release into water bodies can pose risks to aquatic ecosystems and human health.
To address this challenge, researchers at Doshisha University, Japan, devised a single-step co-pyrolysis strategy to valorize agricultural waste into an amphoteric adsorbent that can effectively remove synthetic dye contaminants. This ‘green’ solution to the synthetic dye-driven ecological crises was put forward by Mr. Asif Ali, PhD Student (MEXT Scholar); Professor Michiaki Matsumoto; and Professor Yoshiro Tahara at the Department of Applied Chemistry, Graduate School of Science and Engineering, Doshisha University. This study was made available online on August 19, 2026, and was published in Volume 14, Issue 5 of the Journal of Environmental Chemical Engineering on October 01, 2026.
Sharing their motivation for this study, the first author Mr. Asif Ali says, “ An alarming 20% of toxic, recalcitrant textile wastewater is discharged untreated causing severe damage to aquatic life and human health. So far, no single wastewater treatment method is universally suitable. ” Conventional treatment methods, including membrane separation and advanced oxidation, can be constrained by high energy requirements, secondary products, fouling, maintenance, and operational costs. Activated carbon provides an effective alternative for dye removal; however, commercial activated carbon can require costly production and regeneration, while some metal-modification approaches require additional chemical reducing agents.
To overcome these technical and environmental hurdles, the research team used bullrush agricultural waste as the sustainable carbonaceous precursor, while copper (II) nitrate trihydrate and potassium hydroxide (KOH) facilitated the in-situ growth of zero-valent copper nanoparticles (Cu 0 ) within a mesoporous framework. In a single-step co-pyrolysis strategy, by harnessing the biomass's own in-situ volatile reducing gases (CO and H 2 ) to reduce copper precursors, they fabricated a zero-valent copper nanoparticle-enhanced bullrush activated carbon composite, namely ZVCu@BAC, without using secondary chemical reductants.
To comprehensively characterize the composite, the team used advanced imaging techniques like SEM, TEM, EDX mapping, FTIR, BET, and XRD. They found that unlike the unmodified BAC, which formed an amorphous, highly porous structure, the ZVCu@BAC composite, with a high surface area of 984.5 m 2 /g and a total pore volume of 0.615 cm³/g, exhibited a mesoporous architecture, achieved a uniform, non-agglomerated distribution of needle-like Cu 0 structures securely anchored across the carbon matrix. The characterization also included TGA/DTA.
Next, the research team conducted comparative batch adsorption experiments to evaluate the removal profiles of cationic Methylene Blue (MB) alongside anionic Methyl Orange (MO) and Sunset Yellow (SY). Benefiting from an amphoteric interface (pH pzc ≈9.0), the ZVCu@BAC composite achieved superior broad-spectrum removal for both cationic (MB, q m = 62.31 mg/g) and anionic dyes (MO, q m = 56.37 mg/g; SY, q m = 35.76 mg/g). The equilibrium data were best described by the Langmuir isotherm, while pseudo-second-order kinetics indicated that chemisorption played a major role in the rate-controlling process. Thermodynamic evaluations established that the adsorption processes were highly spontaneous (Δ G ∘ < 0) and fundamentally exothermic (Δ H ∘ < 0). The adsorption was supported by a multi-pathway mechanism involving electrostatic attraction, π─π stacking, pore-filling, and coordinate bonding with metallic Cu 0 sites.
Further characterization showed that the composite exhibited excellent structural integrity and durability, retaining 90.6% MB removal efficiency and 88.0% MO removal efficiency after six regeneration cycles using a simple 0.1 M KOH/acetone eluent. Taken together with an estimated production cost of only ~¥1800 JPY/kg, these insights position the bullrush-derived ZVCu@BAC composite as a highly cost-effective, sustainable, and scalable candidate for industrial wastewater treatment.
This composite could potentially be explored for simultaneous mixed-dye removal during industrial wastewater remediation, with the wide operational pH tolerance expanding its applicability. Further, solvent-based cyclic regeneration capability may help reduce composite replacement requirements.
Emphasizing the significance of their findings, Prof. Matsumoto says, “ Our study findings present the opportunity to advance a circular economy: valorizing invasive, zero-cost bullrush weed biomass into a functional carbon framework through an ecofriendly, single-step co-pyrolysis route. ”
This study brings us one step closer to keeping rivers and streams clean, protecting our valuable water resource.
About Dr. Asif Ali from Doshisha University, Japan
Dr. Asif Ali received his PhD degree in Engineering from Doshisha University in September 2026. He was a MEXT Scholar at the Graduate School of Science and Engineering, Doshisha University. His research focuses on the development of advanced functional materials for removal of pollutants in water through adsorption, and for use in energy storage applications such as batteries and super capacitors. Dr. Ali’s research expertise in environmental chemistry has led to publication of 14 research articles.
About Professor Michiaki Matsumoto from Doshisha University, Japan
Dr. Michiaki Matsumoto is Professor at the Department of Applied Chemistry, Doshisha University. He received his Master of Engineering from the Department of Synthetic Chemistry, School of Engineering, Kyushu University in 1980. Soon after, in 1982, he received his Doctor of Engineering degree from the same department at Kyushu University. Professor Matsumoto joined Doshisha University in 2008, and has established his expertise in bioreaction engineering, separation technology, extraction, and membrane separation. He has published over 230 research articles and has received awards for his achievements.
Media contact:
Organization for Research Innovation
Doshisha University
Kyotanabe, Kyoto 610-0394, JAPAN
E-mail： jt-ura@mail.doshisha.ac.jp
Experimental study
Not applicable
Journal of Environmental Chemical Engineering
1-Oct-2026
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.