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

Abstract

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.

Generation of hydroxyl radicals by Fe-polyphenol-activated CaO2 as a potential treatment for soil-borne diseases

“…In previous experiments, the results of an XPS survey revealed that both ferric iron (Fe 3+ ) and ferrous iron (Fe 2+ ) were present in the Fe-polyphenol catalyst but no zerovalent iron (nZVI) was present. Iron was present in the forms of Fe 2 O 3 /FeCl 2 and FeCl 3 14 . On the other hand, more than 98% of the iron released from the Fe-polyphenol catalyst was in the Fe 2+ form as detected by the phenanthroline method 15 .…”

“…On the other hand, more than 98% of the iron released from the Fe-polyphenol catalyst was in the Fe 2+ form as detected by the phenanthroline method 15 . The results of in vitro experiments showed that the Fe-polyphenol catalyst can be used to supply iron to leaf vegetables 12 and rice 13 , and in vitro experiments under laboratory conditions showed that when applied in conjunction with liquid H 2 O 2 , this catalyst could disinfect pathogens such as Escherichia coli 14 and Ralstonia solanacearum (see Supplementary Figs S2 , S3 , and S4 ) or remove methylene blue from water systems 15 . We proposed a mechanism involving the generation of hydroxyl radicals by the reaction between the iron catalyst and H 2 O 2 .…”

“…Recently, we developed an Fe-polyphenol catalyst using coffee grounds as a raw material, and in a previous study, we demonstrated that this catalyst can be used as an iron fertilizer in agriculture 12 , 13 and in the Fenton process to disinfect pathogens such as E . coli 14 or to remove methylene blue from water systems 15 . In those works, we proposed that the generation of hydroxyl radicals was responsible for the desired effects.…”

Current Use of Fenton Reaction in Drugs and Food

“…Shi et al developed the Fenton reaction-assisted photodynamic inactivation method, a simple system that combines calcinated melamine sponges and Fe 2+ to inactivate Salmonella under light illumination [ 107 ]. Morikawa et al developed two “green” iron catalysts with reducing and chelating ability using tea leaves and coffee grounds [ 108 ]. This system with the catalytic Fenton reaction enhanced the degradation of the contaminants into harmless compounds and disinfection of Escherichia coli.…”