Color-mixing effects of photosensitive organic dyes initiated by superoxide anion radicals under visible-light irradiati
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ORIGINAL PAPER
Color‑mixing effects of photosensitive organic dyes initiated by superoxide anion radicals under visible‑light irradiation Jin Yang1 · Yan Cao1 · Naidong Zhang1,2 Received: 13 March 2020 / Accepted: 23 June 2020 © Springer Nature Switzerland AG 2020
Abstract Water pollution by dyes is a major health and environmental issue. Photosensitive organic dyes produce hydrated electrons, eaq−, singlet oxygen, 1O2, and superoxide anion radicals, O 2·−. O2·− catalyzes H 2O2 transformation into hydroxyl radicals ·OH, which can be used to degrade wastewater under sunlight. Here, we measured eaq−, 1O2, O2·− and ·OH generated under visible light irradiation of photosensitive organic dyes in the presence of the auxiliary F e3+, the 1,5-diphenylcarbazide molecular probe, the N H2OH molecular probe and the dimethyl sulphoxide probe. Results show that single photosensitive organic dyes are not degraded in the visible light/H2O2 system. However, they were degraded when mixed in a certain proportion to produce a brown coloration, a phenomenon named the ‘color-mixing effect.’ Likewise, the average yields of O2·− in single photosensitive organic dye solutions were lower, of 0.015 (ΔA510), than that in mixed brown solutions, of 0.113. The colormixing effect is explained mainly by higher ·OH generation from increased O2·− production. Findings imply that sunlight irradiation is a promising way to clean colorful and dye-containing wastewater. Keywords Photosensitive organic dyes · Visible light · Hydrated electron · Singlet oxygen · Superoxide anion radical · Hydroxyl radical
Introduction Water pollution is a major environmental issue of worldwide concern (Ali et al. 2005, 2013; Basheer 2018a, b). Many countries and governmental organizations have formulated policies and measures regarding water pollution (Alharbi et al. 2018; Basheer 2018a, b). In addition, many chemical, physical and biological water treatment methods Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10311-020-01043-4) contains supplementary material, which is available to authorized users. * Naidong Zhang [email protected] Jin Yang [email protected] Yan Cao [email protected] 1
College of Environmental Science and Engineering, Dalian Maritime University, Dalian 116026, China
State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China
2
have been studied for wastewater treatment (Ali et al. 2016, 2017, 2018; Burakova et al. 2018). Organic dye pollutants in wastewater have always been one of the most serious water pollution problems (Shanker et al. 2017; Mashkoor et al. 2020). Chromophoric dissolved organic matters are an important light-absorbing substance in water and include photosensitive organic dyes as an important component of colored and dye-containing wastewater (Nie and Xiao 2020). Chromophoric dissolved organic matters are the major factor dominating ultraviolet light and visible light penetration in
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