In a new study, Northwestern University researchers demonstrated that brewing tea naturally adsorbs heavy metals like lead and cadmium, effectively filtering dangerous contaminants out of drinks. Heavy metal ions stick to, or adsorb to, the surface of the tea leaves, where they stay trapped until the used tea bag is disposed of.
The study was published in the journal ACS Food Science & Technology.
“We’re not suggesting that everyone starts using tea leaves as a water filter,” said Northwestern’s Vinayak Dravid, the study’s senior author.
“For this study, our goal was to measure tea’s ability to adsorb heavy metals. By quantifying this effect, our work highlights the unrecognized potential for tea consumption to passively contribute to reduced heavy metal exposure in populations worldwide.”
“I’m not sure that there’s anything uniquely remarkable about tea leaves as a material,” said Benjamin Shindel, the study’s first author.
“They have a high active surface area, which is a useful property for an adsorbent material and what makes tea leaves good at releasing flavor chemicals rapidly into your water. But what is special is that tea happens to be the most consumed beverage in the world.
“You could crush up all kinds of materials to get a similar metal-remediating effect, but that wouldn’t necessarily be practical. With tea, people don’t need to do anything extra. Just put the leaves in your water and steep them, and they naturally remove metals.”
An expert on sorbent materials and sponge entrepreneur, Dravid is Abraham Harris Professor of Materials Science and Engineering at Northwestern’s McCormick School of Engineering.
Exploring different variables
To conduct the study, the Northwestern team explored how different types of tea, tea bags and brewing methods affect heavy metal adsorption …
