Tubular microreactor-based Fe(II)-driven advanced oxidation: comparative assessment of percarbonate and persulfate systems for toxic dye removal
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Slimane Merouani
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Leila Nemdili
Abstract
This study presents an intensified degradation strategy for azo dyes using a flow microreactor (6 m-length/1 mm-diameter)-integrated sulfate and hydroxyl radicals advanced oxidation processes (SO4 •−/•OH-AOPs) platform. Three systems were assessed: thermally activated persulfate (KPS), Fe(II)/KPS, and Fe(II)/sodium percarbonate (SPC), focusing on key parameters – bath temperature (20–70 °C), inlet dye concentration (5–20 µM), Fe(II) dosage (50–100 µM), pH (3–7), and oxidant flowrate (20–120 μL/s). Experiments were conducted with Basic Fuchsin (BF), a persistent dye of mutagenic and carcinogenic properties. Thermal KPS led to full dye conversion at 70 °C but negligible TOC removal at lower temperatures. Fe(II)/KPS and Fe(II)/SPC improved degradation across all temperatures. Fe(II)/KPS led to substantial mineralization (63 % TOC removal), while Fe(II)/SPC achieved only 33 %, and KPS alone 54 %. At 20 °C, Fe(II)/SPC showed slightly higher TOC removal than Fe(II)/KPS (18 % vs. 15 %). Performance was strongly influenced by Fe(II) speciation (pH-dependent) and radical scavenging by intermediates. Removal ratio analyses (Fe(II)/KPS to KPS: up to 5.0; Fe(II)/SPC to Fe(II)/KPS: up to 1.97) highlighted strong catalytic synergy, especially at low pH and low dye concentration. These findings demonstrate the potential of the microreactor-based SO4 •−/•OH-AOPs platform for scalable, energy-efficient, and high-throughput water treatment applications.
Acknowledgments
The authors gratefully acknowledge the financial support from the Ministry of Higher Education and Scientific Research of Algeria under project number A16N01UN250320220002, as well as the Directorate-General for Scientific Research and Technological Development (DGRSDT).
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Research ethics: Not applicable.
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Informed consent: All authors have given their consent for publication.
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Author contributions: Slimane Merouani: Investigation, conceptualizing, methodology, draft-writing and revising, and supervising the study. Leila Nemdili: Investigation. Marwa Derbal: Investigation. Aya E. Djidjekh: Investigation, Mostefa L. C. Benkara: Investigation.
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Use of Large Language Models, AI and Machine Learning Tools: AI tools were used solely for language enhancement purposes. Specifically, ChatGPT (OpenAI) was employed to improve the clarity, grammar, and flow of the English text. No content, data analysis, or scientific interpretation was generated by AI; all scientific content and conclusions are the original work of the authors.
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Conflict of interest: The authors declare no conflict of interest.
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Research funding: Not applicable.
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Data availability: Not applicable.
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