Insight into performance and mechanism of tea polyphenols and ferric ions on reductive decolorization of malachite green cationic dye under moderate conditions

• Published in: Journal of environmental management 2020-05, Vol.261, p.110226-110226, Article 110226
• Main Authors: Xie, Yiqiao, Huang, Jiawei, Dong, Haojie, Wu, Tong, Yu, Ling, Liu, Guoqiang, Yu, Yang
• Format: Article
• Language: English
• Subjects: Cationic dye; Coloring Agents; Ferric ions; Hydrogen-Ion Concentration; Ions; Malachite green; Polyphenols; Reductive decolorization; Rosaniline Dyes; Tea; Tea polyphenols
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2020.110226

Dye decolorization is of crucial concern for effectively treating dye wastewater. In this study, rapid and effective decolorization of malachite green cationic dye was achieved by tea polyphenols and ferric ions under moderate conditions. Approximately 96.2% of decolorization efficiency could be obtained within the first 10 min at the initial dye concentration of 50 mg/L. The proposed method can perform excellently in a wide pH range of 5–9 and decolorization kinetics of malachite green under different solution pH were well fitted by the pseudo-second-order model. After the decolorization, only a slight reduction of tea polyphenols was observed, while the strength of peaks assigned to nitrogen-containing groups was significantly weakened, indicating that the N-demethylation reaction might occur during the decolorization process. The nucleophilic attack of deprotonated hydroxyl groups of tea polyphenols was proposed as the decolorization mechanism. The presence of ferric ions at an appropriate dosage could promote the deprotonation process and therefore enhance decolorization efficiency, while excess ferric ions in solution might compete with malachite green dye towards reductive sites on tea polyphenols. The findings from this study provided an economical and environmentally friendly technique for the effective decolorization of dye wastewater. [Display omitted] •Tea polyphenols can effectively decolorize malachite green dye under stirring.•96.2% of decolorization efficiency can be obtained in the first 10 min.•Deprotonated –OH groups of tea polyphenols were responsible for dye decolorization.•Fe(III) dosage is the key factor for improvement of the decolorization efficiency.