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NOX emitted from fixed/mobile sources (X = 1 or 2) is generally considered to be a harmful anthropogenic source of ultrafine particulate matter (PM2.5), because NOX can undergo a series of SO2-assisted photochemical conversion stages and eventually become PM2. 5. This is an air pollutant.

A research team from South Korea recently corrected the general idea of ​​NOX by proposing an interesting way to use NOX in a creative way (see above).

According to the Korea Institute of Science and Technology (KIST), the research team composed of the research team's chief researcher Dr. Jongsik Kim and Dr. Heon Phil Ha and the research team led by Professor Keunhong Jeong of the Korea Military Academy (KMA) are working together in low heat (≤ Under 150 °C), the chemical fusion between NOX and O2 will graft NO3− species onto the metal oxide.

The resulting supported NO3− substances can then be free-radicalized to produce NO3• analogs, which act as degradants for refractory organic substances in wastewater.

The waterborne stubborn compounds containing bisphenol A and phenols are usually removed from the water matrix through the precipitation process using a coagulant or by adding OH shuttle (such as H2O2, O3, etc.) to degrade into H2O and COY (Y = 1 or 2).

However, these methods require more stages to recover the coagulant, or have a short life and/or chemical volatility of •OH, H2O2 and O3, which greatly hinders the sustainability of the H2O purification process currently being commercialized.

As an alternative to •OH, NO3• is particularly attractive because it has a longer lifespan and/or better oxidation ability than •OH, •OOH or O2•-, so it is expected to increase the degradation of waterborne pollutants. efficient. The free radicals mentioned above.

However, the production of NO3• is not simple and has some limitations, such as exposure to radioactive elements or high-energy electrons in a strong acid environment.

Dr. Kim and his team have made it feasible in wastewater, including H2O2 and NO3− functionalized manganese oxides. These surface manganese species (Mn2+/Mn3+) mainly stimulate H2O2 to produce •OH, and •OH then triggers NO3 − Functionality It changes to NO3• (expressed as•OH → NO3•), all of which are proved by density functional calculation (DFT) methods and some control experiments.

Compared with traditional free radicals (•OH/•OOH/O2•-), the subsequent NO3• substances can increase the degradation efficiency of textile wastewater by 5 or 7 times. Importantly, the catalyst (NO3-functionalized manganese oxide) found here is about 30% cheaper than the traditional commercial catalyst (iron salt) and can be produced on a large scale.

Most importantly, the catalyst can be reused 10 times or more. This is in contrast to traditional catalysts, which can only decompose water pollutants through homogeneous H2O2 cracking (•OH generation).

•OH→NO3•Technology has been patented and sold to domestic companies (SAMSUNG BLUETECH). In view of the many advantages of catalysts modified with NO3− functional groups, we basically hope to install the catalysts in wastewater treatment plants as soon as possible.

Dr. Jongsik Kim, Chief Researcher, Korea Institute of Science and Technology

This research was funded by a grant from the National Research Foundation of Korea (NRF) provided by the government (Ministry of Science and Information and Communication Technology, Minister Lim Hye Suk) and a future research and development and young researcher grant from KIST.

Kim, J. et al. (2021) Decipher the evolutionary path of supported NO3 free radicals, and realize the oxidative degradation of water-based pollutants through free radical transfer from •OH free radicals to surface NO3− functions. JACS Au. doi.org/10.1021/jacsau.1c00124.

Source: https://eng.kist.re.kr/kist_eng/main/

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