Underwater microplasma bubbles for efficient and simultaneous degradation of mixed dye pollutants

Renwu Zhou; Tianqi Zhang; Rusen Zhou; Anne Mai-Prochnow; Sri Balaji Ponraj; Zhi Fang; Hassan Masood; John Kananagh; Dale McClure; David Alam; Kostya Ken Ostrikov; Patrick J Cullen

doi:10.1016/j.scitotenv.2020.142295

Underwater microplasma bubbles for efficient and simultaneous degradation of mixed dye pollutants

Sci Total Environ. 2021 Jan 1:750:142295. doi: 10.1016/j.scitotenv.2020.142295. Epub 2020 Sep 12.

Authors

Affiliations

¹ School of Chemical and Biomolecular Engineering, The University of Sydney, NSW 2006, Australia.
² School of Chemical and Biomolecular Engineering, The University of Sydney, NSW 2006, Australia; School of Chemistry and Physics, Centre for Materials Science, Queensland University of Technology, Brisbane, QLD 4000, Australia. Electronic address: zhourusen2008@gmail.com.
³ College of Electrical Engineering and Control Science, Nanjing Tech University, Nanjing 211816, Jiangsu, China.
⁴ Particle and Catalysis Research Group, School of Chemical Engineering, University of New South Wales, NSW 2052, Australia.
⁵ School of Chemistry and Physics, Centre for Materials Science, Queensland University of Technology, Brisbane, QLD 4000, Australia.

PMID: 33182177
DOI: 10.1016/j.scitotenv.2020.142295

Abstract

Complete degradation of mixtures of organic pollutants is a major challenge due to their diverse degradation pathways. In this work, a novel microplasma bubble (MPB) reactor was developed to generate plasma discharges inside small forming bubbles as an effective mean of delivering reactive species for the degradation of the target organic contaminants. The results show that the integration of plasma and bubbles resulted in efficient degradation for all azo, heterocyclic, and cationic dyes, evidenced by the outstanding energy efficiency of 13.0, 18.1 and 22.1 g/kWh with 3 min of processing, in degrading alizarin yellow (AY), orange II (Orng-II) and methylene blue (MB), individually. The MPB treatment also effectively and simultaneously degraded the dyes in their mixtures such as AY + Orng-II, AY + MB and AY + Orng-II + MB. Scavenger assays revealed that the short-lived reactive species, including the hydroxyl (OH) and superoxide anion (O₂^-) radicals, played the dominant role in the degradation of the pollutants. Possible degradation pathways were proposed based on the intermediate products detected during the degradation process. The feasibility of this proposed strategy was further evaluated using other common water pollutants. Reduced toxicity was confirmed by the observed increases in human cell viability for the treated water. This work could support the future development of high performance- and energy-efficient wastewater abatement technologies.

Keywords: Organic dyes; Plasma-liquid interaction; Reactive oxygen species; Underwater microplasma bubbles.