Research Highlight

Tea polyphenols-coated nanoparticles remove pollutant dye

doi:10.1038/nindia.2017.49 Published online 25 April 2017

Researchers have synthesized magnetic nanoparticles coated with green-tea polyphenols. They can remove methylene blue, a pollutant dye, making them potentially useful for treating industrial wastewater. 

Iron oxide nanoparticles exhibit magnetic properties which can be utilised in magnetic resonance imaging, cell separation and tissue repair. Their magnetism allows them to be separated and reused.

Scientists from the Indian Institute of Technology and Gauhati University in Assam wanted to tap into the potential. After they coated them with green tea polyphenols, the nanoparticles quickly adsorbed the dye. The rate slowed and reached equilibrium after 16 minutes. The dye adsorption increased with increases in temperature and dose. The adsorbent removed 95% of the dye at neutral pH; whereas dye removal decreased at acidic ph levels.

The presence of green tea polyphenols on the surface of the nanoparticles acts as a protecting agent that prevents oxidation, improving their stability. The coating also makes the nanoparticles negatively charged, allowing them to bind to positively charged methylene blue.

The nanoparticles can be easily separated using an external magnet. After four reaction cycles, they retained 87% of their original dye-removing efficiency.



1. Singh, K. K. et al. Synthesis of superparamagnetic Fe3O4 nanoparticles coated with green tea polyphenols and their use for removal of dye pollutant from aqueous solution. J. Environ. Chem. Eng. (2017) doi: 10.1016/j.jece.2017.04.022