NO Removal with Efficient Recovery of N2O by Using Recyclable Fe^sub 3^O^sub 4^@EDTA@Fe(II) Complex: A Novel Approach toward Resource Recovery from Flue Gas

Traditional technologies for handling nitrogen oxides (NOx) from flue gas commonly entail the formation of harmless nitrogen gas (N2), while less effort has been made to recover the N-containing chemicals produced. In this work, we developed a novel nanomagnetic adsorbent, Fe3O4@EDTA@Fe(II) (MEFe(II)), for NO removal. The NO adsorbed by MEFe(II) was then selectively converted to N2O, a valuable compound in many industries, by using sulfite (a product from desulfurization in flue gas treatment) as the reductant for the regeneration of MEFe(II). Because of the magnetic and solid properties of MEFe(II), the processes of NO adsorption and N2O recovery can be readily carried out under their optimal pH conditions in separate systems. In addition, the produced N2O is easily handled without unwanted release to the atmosphere. At the optimal pH (7.5 and 8.0 for NO adsorption and N2O recovery, respectively), the maximum NO adsorption capacity of MEFe(II) was measured as 0.303 ± 0.037 mmol·g–1, over 90% of which was converted to N2O during the recovery process. Moreover, MEFe(II) exhibited good five consecutive cycles. All of above reactions were performed at room temperature. These findings indicate MEFe(II) may hold great potential for application to NO removal from flue gas with the benefits of resource recovery, decreased chemical use, and low energy consumption.