Despite advances in real-time monitoring, smart water systems still struggle with delayed feedback and uneven chemical distribution. In large-scale or decentralized operations, these issues can reduce the effectiveness of treatment or, worse, lead to dangerous byproducts such as cyanide volatilization. The Fenton reaction—renowned for generating potent oxidants—remains sensitive to pH changes, limiting its applicability in variable environments. Traditional solutions attempt to broaden the pH range through chemical adjustments, but often at the expense of safety or sensitivity. These challenges highlight the urgent need for self-regulating chemical systems that can autonomously respond to environmental signals, especially pH fluctuations.
In response to these challenges, scientists from Xiamen University and partnering institutions have unveiled a pH-responsive Fenton system that activates only under optimal alkaline conditions. Published (DOI: 10.1016/j.ese.2025.100566) on May 13, 2025, in Environmental Science and Ecotechnology, the study demonstrates how specific iron–ligand complexes enable a self-limiting oxidation process precisely tuned to real-time pH levels. By doing so, the researchers have introduced a "smart Fenton" platform that improves safety, reactivity, and adaptability in water purification—particularly in scenarios involving hazardous or pH-sensitive waste.
At the core of this innovation is a modified Fenton reaction incorporating hydroxylamine (HA) and EDTA. Unlike conventional acidic systems, this configuration generates hydroxyl radicals only when the solution pH is between 7.0 and 10.0. Using benzoic acid as a probe and electron spin resonance (ESR) for detection, the team confirmed up to 69% degradation at pH 9.0. Further computational modeling revealed that changes in pH influence the structure—and thus the reactivity—of iron–EDTA complexes. Specifically, [Fe²⁺–EDTA]2− is most effective in activating hydrogen peroxide, while [Fe³⁺–OH–EDTA]2− is more easily reduced by HA. These complementary species coexist only within the defined pH range, enabling controlled radical production. Importantly, once the pH drifts out of range, the reaction self-terminates—offering a built-in safety mechanism that avoids harmful byproducts or equipment wear. A multiple-dosing strategy for HA further improves radical stability and extends •OH half-life, enhancing overall system performance in dynamic water environments.
This pH-responsive Fenton system introduces a paradigm shift in oxidation-based water treatment, said Dr. Huabin Zeng, corresponding author of the study. Rather than simply expanding the effective pH range, we've designed a process that senses and adapts in real time. It offers built-in safeguards for delicate applications, such as cyanide-containing wastewater, and brings us closer to truly intelligent chemistry in environmental engineering.
The implications of this work are far-reaching for next-generation water management. The system's automatic shutdown in acidic conditions prevents accidental cyanide volatilization, a major risk in industrial wastewater treatment. It also minimizes chemical overuse and reduces reliance on energy-intensive mixing or pH correction methods. With its intelligent control, environmental safety, and operational efficiency, the technology paves the way for a new class of self-regulating chemical processes designed for complex, real-world challenges in sustainable water infrastructure.
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References
DOI
10.1016/j.ese.2025.100566
Original Source URL
https://doi.org/10.1016/j.ese.2025.100566
Funding information
The authors would like to thank Professor Ranwen Ou and Yinzhou Luo for their invaluable assistance during the revision process. This work was supported by the National Natural Science Foundation of China (No. 52400097), the Open Project of State Key Laboratory of Urban Water Resource and Environment from Harbin Institute of Technology (No. QA202446), and the Nanqiang Young Talents Supporting Program from Xiamen University.
About Environmental Science and Ecotechnology
Environmental Science and Ecotechnology (ISSN 2666-4984) is an international, peer-reviewed, and open-access journal published by Elsevier. The journal publishes significant views and research across the full spectrum of ecology and environmental sciences, such as climate change, sustainability, biodiversity conservation, environment & health, green catalysis/processing for pollution control, and AI-driven environmental engineering. The latest impact factor of ESE is 14, according to the Journal Citation ReportTM 2024.