The Fenton reaction is a chemical transition with hydrogen peroxide (H.2Ö2) and the iron (iron) ion, which acts as a catalyst. This process is used to destroy hazardous pollutants in wastewater through oxidation. In the atmosphere, a similar reaction or “Fenton-like” reaction takes place continuously with iron (III) oxalate ([Fe(III)(C2O4)3]3-) and aerosols suspended in the air. This is the most common chemical reaction that occurs in the atmosphere. The ability of a particle to oxidize is directly related to its phase, either gaseous or aqueous, which has an important influence on the formation of secondary organic aerosols (SOA). Hence, research is needed not only to evaluate the contribution of this Fenton-like reaction to atmospheric oxidation, but also to improve the consistency of model-simulated and field-observed SOA budgets.
“It is widely believed that the contribution of the Fenton reaction to atmospheric oxidation comes from the generation of hydroxyl radicals,” said Prof. Wenbo Dong of the Department of Environmental Science & Engineering at Fudan University. “Scientists have not dealt often with the role of superoxide radicals, which are widely believed to be the source of hydrogen peroxide and hydroxyl radicals.”
Methacrolein (CH2= C (CH3) CHO) is the primary oxidation product of isoprene (CH2= C (CH3) CH = CH2), which is the most abundant volatile organic compound (VOC) in the atmosphere. It can react directly with superoxide radicals to create SOAs. While this is a common reaction, this process shows that other avenues for VOC oxidation exist.
“Previous studies believed that superoxide radicals do not react with most organic compounds,” noted Prof. Dong.
Some VOCs in the atmosphere, like methacrolein, can react with superoxide radicals. However, the SOA production potential of any VOC with accompanying superoxide radicals and hydroxyl radicals is different from the methacrolein reaction. The researchers focused on the oxidation process of organic pollutants caused by these free radicals. They found that the oxidation process is related to the reaction mechanism of the organic matter that accompanies these free radicals.
Previous studies have shown that the change in the absorption of aqueous aerosols is due to the formation of brown carbon. In the photo-oxidation of methacrolein with iron (III) oxalate, however, Prof. Dong’s group found a clear increase in aerosol absorption without the formation of brown carbon. For more analysis, see her research article entitled “Photooxidation of Methacrolein in Fe (III) Oxalate Aqueous System and Its Atmospheric Implication,” published in. has been published Advances in Atmospheric Sciences.
“When the Fenton-like reaction occurs with a high concentration of iron, the absorption of the solution changes significantly, with the solution turning yellow,” said Prof. Dong. “This may not be the only situation with methacrolein, as it can lead to the Fenton-like reaction of other organic compounds.”
Prof. Dong continued: “The formation of insoluble or colloidal iron hydroxide increases the absorption of atmospheric aerosols and affects the radiative forcing that has long been overlooked.”