Redox reactions between chromium(VI) and hydroquinone: Alternative pathways for polymerization of organic molecules. (June 2020)

• Record Type: Journal Article
• Authors: Tzou, Yu-Min; Chen, Kai-Yue; Cheng, Ching-Yun; Lee, Way-Zen; Teah, Heng Yi; Liu, Yu-Ting
• Is Part Of: Environmental pollution. Volume 261(2020)
• Publication Date: 2020-06
• Subjects: Chromium(VI) -- Hydroquinone -- Oxidative polymerization; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2020.114024
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Chromium (VI) reduction by organic compounds is one of the major pathways to alleviate the toxicity and mobility of Cr(VI) in the environment. However, oxidative products of organic molecules receive less scientific concerns. In this study, hydroquinone (H2 Q) was used as a representative organic compound to determine the redox reactions with Cr(VI) and the concomitant oxidative products. Spectroscopic analyses showed that Cr(III) hydroxides dominated the precipitates produced during redox reactions of Cr(VI) and H2 Q. For the separated filtrates, the acidification induced the oxidative polymerization of organic molecules, accompanied with the complexation with Cr(III). The aromatic domains dominated the chemical structures of the black and fluffy organic polymers, which was different to the natural humic acids due to the shortage of aliphatic chains. Results of linear combination fitting (LCF) for Cr K-edge X-ray absorption near edge structure (XANES) spectra demonstrated that up to 90.4% of Cr inventory in precipitates derived after the acidification of filtrates was Cr(III) complexed with humic-like polymers, suggesting that Cr(III) possibly acted as a linkage among organic molecules during the polymerization processes of H2 Q. This study demonstrated that Cr(VI) may lead to the polymerization of organic molecules in an acidic solution, and thus, it could raise scientific awareness that the oxidative decomposition of organic molecules may not be the only pathway while interacting with the strong oxidant of Cr(VI). Graphical abstract: Image 1 Highlights: Cr(III) hydroxides dominated the precipitates produced during redox reactions. Acidification for separated filtrates induced further flocculation. Cr(III) complexed with humic-like polymers dominated acidified precipitates. Aromatic domains dominated the chemical structures in organic polymers. Cr(III) acted as linkages for organic molecules during polymerization processes. Abstract : This study addresses the oxidative polymerization of hydroquinone by Cr(VI) in an acidic solution and Cr(III) acts as linkages of organic molecules during polymerization process.