A new green approach to Fenton's chemistry using tea dregs and coffee grounds as raw material

Abstract

Claudio Kendi Morikawa completed his graduate study at University of São Paulo State-UNESP Ilha Solteira Campus, Ilha Solteira, SP, Brazil, and in 1993, he completed his Master of Science study at Federal University of Lavras, Brazil. In 2003, he received his PhD in Environmental Bioremediation at the Tohoku University, Japan. From 2005 to 2007, he did his postdoctoral research at University of Tokyo, Japan. His research interests are in the fields of catalysis, human nutrition, plant protection and soil science and plant nutrition. He has more than 20 scientific and professional publications and five patents, and more than 20 oral and poster presentations at international conferences presenting his scientific work. Since 2008, he has been a researcher at the National Agriculture and Food Research Organization, National Institute of Tea and Vegetable Science, Japan. Fenton's chemistry has long been useful in industry because of the power of hydrogen peroxide (HP), in the presence of ferrous iron (Fe2+), to produce a highly reactive free radical species capable of oxidizing aqueous materials. However, its application has been limited due to the rapid oxidation of ferrous iron. The rapid oxidation of ferrous iron limits the production of free radicals necessary for a powerful reaction. We developed two 'green' iron catalysts using used tea leaves (tea dregs) or coffee grounds as raw material. The new 'green' iron catalysts contained iron in a reductive stable status for a Fenton catalyst. The study showed that the developed 'green' iron catalysts can be used as iron fertilizer and for the Fenton's reaction on the degradation of methylene blue (MB), and in the disinfection of Escherichia coli. The tea and coffee polyphenols were estimated to be responsible for the reductive stable state of the iron in the developed catalysts, due to their reducing power and chelating iron ability. The developed new 'green' iron catalysts are expected to diffuse in wide fields such as food, medicine, public health, agriculture, the environment, etc.