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Reduction of Hexavalent Chromium by Green Tea Polyphenols and Green Tea Nano Zero-Valent Iron (GT-nZVI)


This study reports on the direct reduction of hexavalent chromium [Cr(VI)] by green tea polyphenols, including a green tea solution and pure epigallocatechin gallate (EGCG) solution. A linear trend was observed between the amount of reduced Cr(VI) and the amount of added polyphenols. The green tea solution showed a continued decrease in the observed stoichiometry with increasing pH, from a maximum of 1.4 mol per gallic acid equivalent (GAE) of green tea at pH 2.5, to 0.2 mol/GAE at pH 8.8. The EGCG solution exhibited different behavior, with a maximum stoichiometry of 2 at pH 7 and minimum of 1.6 at pH 4.4 and 8.9. When green tea was used to first react with Fe3+ and form GT-nZVI, the amount of Cr(VI) reduced by a certain volume of GT-nZVI was double compared to green tea, and 6 times as high considering that GT-nZVI only contains 33 % green tea.

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The authors wish to thank Miko Kempton, Claudia Szerakowski and Kerry Harrigan for assistance in conducting the laboratory experiments.

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Correspondence to M. Chrysochoou.

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Chrysochoou, M., Reeves, K. Reduction of Hexavalent Chromium by Green Tea Polyphenols and Green Tea Nano Zero-Valent Iron (GT-nZVI). Bull Environ Contam Toxicol 98, 353–358 (2017).

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  • Green tea
  • Hexavalent chromium
  • Polyphenols
  • EGCG
  • Nano zero-valent iron