Degradation of methylene blue by a continuous microfluidic plasma process

Abstract

Plasma degradation of organic pollutants serves as a promising alternative to conventional water treatment methods. This study develops a dielectric barrier discharge microfluidic plasma system that synergizes microfluidic technology with plasma to achieve the continuous and efficient degradation of methylene blue. Systematic investigation of processing parameters revealed that methylene blue degradation efficiency is enhanced by increasing the residence time or plasma power, or by decreasing the initial methylene blue concentration. Notably, complete degradation (100%) of a 100 mg∙L^–1 methylene blue solution was achieved at a residence time of merely 15.95 s and a plasma power of 17.3 W. Kinetic analysis revealed that degradation process follows a pseudo-first-order reaction model. Radical quenching experiments identified hydroxyl radicals as the pivotal oxidative species driving the reaction. On this basis, reaction mechanisms as well as the scale-up strategy of the plasma-driven methylene blue degradation process were discussed. Energy yield is further used to evaluate energy efficiency of the microfluidic plasma system, highlighting its potential for practical applications. This work establishes microfluidic plasma processing as an intensified, efficient, and continuous strategy for the treatment of organic pollutants in water.

Graphical abstract

Keywords

microfluidic plasma / plasma degradation / process intensification / water treatment / methylene blue

References

[1] Khan I , Saeed K , Zekker I , Zhang B , Hendi A H , Ahmad A , Ahmad S , Zada N , Ahmad H , Shah L A . et al. Review on methylene blue: its properties, uses, toxicity, and photodegradation. Water, 2022, 14(2): 242

[2] Kumar K , Kumar H , Singh D P . Silver nanoparticle synthesis on silicon substrate by electrodeposition technique and their SERS application for detection of melamine and methylene blue pollutants. Surfaces and Interfaces, 2025, 72: 106993

[3] Jang D H , Nelson L S , Hoffman R S . Methylene blue for distributive shock: a potential new use of an old antidote. Journal of Medical Toxicology, 2013, 9(3): 242–249

[4] Khader E H , Muslim S A , Saady N M C , Ali N S , Salih I K , Mohammed T J , Albayati T M , Zendehboudi S . Recent advances in photocatalytic advanced oxidation processes for organic compound degradation: a review. Desalination and Water Treatment, 2024, 318: 100384

[5] Hegazy S , Ibrahim H H , Weckman T , Hu T , Tuomikoski S , Lassi U , Honkala K , Srivastava V . Synergistic pyrolysis of cellulose/Fe-MOF composite: a combined experimental and DFT study on dye removal. Chemical Engineering Journal, 2025, 504: 158654

[6] Nguyet P N , Watari T , Hirakata Y , Hatamoto M , Yamaguchi T . Adsorption and biodegradation removal of methylene blue in a down-flow hanging filter reactor incorporating natural adsorbent. Environmental Technology, 2021, 42(3): 410–418

[7] Rashad M , Mahfoz Kotb H , Helali S , Ahmad M M , Albalawi A E , Alatawi N S , Al-Faqiri B , Alsharari A M , Abd-Elnaiem A M . Structural analysis and photocatalytic degradation towards methylene blue using (Nb_0.5Si_0.5)_xTi_1−xO₂ nanocomposites. Ceramics International, 2024, 50(1): 512–525

[8] Mebed A M , Alshammari K , Ezzeldien M , Al-Ghamdi S A , Abd-Elnaiem A M , El-Aal M A , Hamad D . Enhancement of the photodegradation performance towards methylene blue and rhodamine B using Ag_xSn_1–xO₂ nanocomposites. Journal of Alloys and Compounds, 2024, 1009: 176977

[9] Ramutshatsha-Makhwedzha D , Mavhungu A , Moropeng M L , Mbaya R . Activated carbon derived from waste orange and lemon peels for the adsorption of methyl orange and methylene blue dyes from wastewater. Heliyon, 2022, 8(8): e09930

[10] Liu C , Yang B , Chen J , Jia F , Song S . Synergetic degradation of methylene blue through photocatalysis and Fenton reaction on two-dimensional molybdenite-Fe. Journal of Environmental Sciences, 2022, 111: 11–23

[11] Panizza M , Barbucci A , Ricotti R , Cerisola G . Electrochemical degradation of methylene blue. Separation and Purification Technology, 2007, 54(3): 382–387

[12] Din M I , Khalid R , Najeeb J , Hussain Z . Fundamentals and photocatalysis of methylene blue dye using various nanocatalytic assemblies-a critical review. Journal of Cleaner Production, 2021, 298: 126567

[13] Zhu W , Wu Z , Zhao S , Lv F , Zhang Y , Guo S . Selective adsorption and separation of methylene blue from wastewater by self-standing polyvinylpyrrolidone and SiO₂ electrospun membranes. Chemical Engineering Science, 2023, 280: 119009

[14] Xie W , Zhang X , Xi D , Zhou R , Yang S , Cullen P , Zhou R . Power-to-chemicals: sustainable liquefaction of food waste with plasma-electrolysis. Frontiers of Chemical Science and Engineering, 2023, 17(5): 594–605

[15] Lin L , Xu H , Gao H , Zhu X , Hessel V . Plasma-assisted nitrogen fixation in nanomaterials: fabrication, characterization, and application. Journal of Physics D: Applied Physics, 2020, 53(13): 133001

[16] Bruggeman P , Bogaerts A , Pouvesle J M , Robert E , Szili E . Plasma-liquid interactions. Journal of Applied Physics, 2021, 130(20): 200401

[17] Lin L , Li X , Gao H , Xu H , Starostin S A , Ostrikov K K , Hessel V . Microfluidic plasma-based continuous and tunable synthesis of Ag-Au nanoparticles and their SERS properties. Industrial & Engineering Chemistry Research, 2022, 61(5): 2183–2194

[18] Wu L , Xie Q , Lv Y , Wu Z , Liang X , Lu M , Nie Y . Degradation of methylene blue via dielectric barrier discharge plasma treatment. Water, 2019, 11(9): 1818

[19] García M C , Mora M , Esquivel D , Foster J E , Rodero A , Jiménez-Sanchidrián C , Romero-Salguero F J . Microwave atmospheric pressure plasma jets for wastewater treatment: degradation of methylene blue as a model dye. Chemosphere, 2017, 180: 239–246

[20] Li X , Wang W , Dong W , Zhang X , Xu H , Lin L . Plasma-liquid synthesized carbon-supported platinum nanoparticles as active electrocatalysts. Journal of the Taiwan Institute of Chemical Engineers, 2022, 133: 104234

[21] Lin L , Quoc Pho H , Zong L , Li S , Pourali N , Rebrov E , Nghiep Tran N , Ostrikov K , Hessel V . Microfluidic plasmas: novel technique for chemistry and chemical engineering. Chemical Engineering Journal, 2021, 417: 129355

[22] Lin L , Zhang Z , Min Y . Microfluidic plasma: novel process intensification strategy. Green Processing and Synthesis, 2022, 11(1): 1064–1071

[23] Mariotti D , Sankaran R M . Microplasmas for nanomaterials synthesis. Journal of Physics D: Applied Physics, 2010, 43(32): 323001

[24] Iervolino G , Vaiano V , Pepe G , Campiglia P , Palma V . Degradation of acid orange 7 azo dye in aqueous solution by acatalytic-assisted, non-thermal plasma process. Catalysts, 2020, 10(8): 888

[25] Lin L , Li S , Hessel V , Starostin S A , Lavrijsen R , Zhang W . Synthesis of Ni nanoparticles with controllable magnetic properties by atmospheric pressure microplasma assisted process. AIChE Journal, 2018, 64(5): 1540–1549

[26] Devi S , Aarushi S . Porous zinc-discs as nanocatalysts for methylene blue dye treatment in water: sensing, adsorption, and photocatalytic degradation. RSC Advances, 2022, 12(54): 34951–34961

[27] Poorsajadi F , Sayadi M , Hajiani M , Rezaei M . Synthesis of CuO/Bi₂O₃ nanocomposite for efficient and recycling photodegradation of methylene blue dye. International Journal of Environmental Analytical Chemistry, 2020, 102: 1–14

[28] Lin L , Ma X , Li S , Wouters M , Hessel V . Plasma-electrochemical synthesis of europium doped cerium oxide nanoparticles. Frontiers of Chemical Science and Engineering, 2019, 13(3): 501–510

[29] Li X , Zhao C X , Lin L . Plasma-based instant synthesis of functionalized gold nanoparticles for colorimetric detection of lead ions. Chemical Engineering Science, 2022, 260: 117849

[30] Zhang Z , Wang F , Hessel V , Ostrikov K , Wang W , Zhang X , Lin L . Microplasma-printed Au-based SERS sensing platform for ultra-sensitive chemical analyte detection. Reaction Chemistry & Engineering, 2024, 9(6): 1541–1549

[31] González S , Jaramillo-Fierro X . Density functional theory study of methylene blue demethylation as a key step in degradation mediated by reactive oxygen species. International Journal of Molecular Sciences, 2025, 26(4): 1756

[32] Wang B , Dong B , Xu M , Chi C , Wang C . Degradation of methylene blue using double-chamber dielectric barrier discharge reactor under different carrier gases. Chemical Engineering Science, 2017, 168: 90–100

[33] Wu L , Xie Q , Lv Y , Zhang Z , Wu Z , Liang X , Lu M , Nie Y . Degradation of methylene blue by dielectric barrier discharge plasma coupled with activated carbon supported on polyurethane foam. RSC Advances, 2019, 9(45): 25967–25975

[34] Huang F , Chen L , Wang H , Yan Z . Analysis of the degradation mechanism of methylene blue by atmospheric pressure dielectric barrier discharge plasma. Chemical Engineering Journal, 2010, 162(1): 250–256

[35] Krosuri A , Wu S , Bashir M A , Walquist M . Efficient degradation and mineralization of methylene blue via continuous-flow electrohydraulic plasma discharge. Journal of Water Process Engineering, 2021, 40: 101926

[36] Kim J D , Choi H C . Photocatalytic degradation of methylene blue on RuO₂-CNT. Bulletin of the Korean Chemical Society, 2019, 40(4): 385–388

[37] Hama Aziz K H , Mahyar A , Miessner H , Mueller S , Kalass D , Moeller D , Khorshid I , Rashid M A M . Application of a planar falling film reactor for decomposition and mineralization of methylene blue in the aqueous media via ozonation, Fenton, photocatalysis, and non-thermal plasma: a comparative study. Process Safety and Environmental Protection, 2018, 113: 319–329

[38] Benetoli L , Cadorin B , Postiglione C , Souza I , Debacher N . Effect of temperature on methylene blue decolorization in aqueous medium in electrical discharge plasma reactor. Journal of the Brazilian Chemical Society, 2011, 22(9): 1669–1678

[39] Chandana L , Manoj K R P , Subrahmanyam C . Atmospheric pressure non-thermal plasma jet for the degradation of methylene blue in aqueous medium. Chemical Engineering Journal, 2015, 282: 116–122

[40] Magureanu M , Bradu C , Piroi D , Mandache N B , Parvulescu V . Pulsed corona discharge for degradation of methylene blue in water. Plasma Chemistry and Plasma Processing, 2013, 33(1): 51–64

RIGHTS & PERMISSIONS

Higher Education Press