Hexavalent Chromium Reduction by Water-Soluble Antioxidants
Coffee and black tea, two common beverages, were investigated as potential electron donors to reduce Cr(VI) to Cr(III). Antioxidant capacity experiments showed that both coffee and black tea are strong antioxidants that provide electrons. When 2 grams of either fresh coffee or black tea were applied to 25 mL of 20 mg/L Cr(VI) solution, all of the Cr(VI) disappeared within 10 minutes. When, instead of using fresh coffee and black tea, residue collected after brewing was applied to the Cr(VI) solution, most of the Cr(VI) disappeared with the used black tea within 3 hours, and approximately 75% of the Cr(VI) was removed with the used coffee within the 8-hour reaction period. The research confirmed that coffee and black tea are excellent, ecofriendly natural electron donors to remediate Cr(VI)-contaminated water without any harmful chemicals. Used coffee and black tea can also be recycled as potential electron providers for Cr(VI) detoxification technology.