Fe<sup>II</sup>(EDTA)–NO Reduction by Mn Powder in Wet Flue Gas Denitrification Technology Coupled with Mn<sup>2+</sup> Recycling: Performance, Kinetics, and Mechanism
Jun Chen, Yi Chen, Dzmitry Hrynsphan, Yu Mei, Hua Pan, Jiali Wu, Jianmeng Chen, Jiachao Yao
Abstract
FeII(EDTA) solution has been considered an efficient option in wet flue gas denitrification, whereas the generated FeII(EDTA)–NO restricts its wide application, suggesting that FeII(EDTA)–NO reduction is the key to this process. This work investigated the performance, kinetics, and mechanism of FeII(EDTA)–NO reduction by Mn powder coupled with manganese ion (Mn2+) recovery. We initially studied the performance of FeII(EDTA)–NO reduction with respect to the major influencing factors (i.e., the particle size of Mn powder, initial FeII(EDTA)–NO concentration, Mn powder concentration, stirring speed, and temperature). Shrinking core model and Arrhenius law were applied to illustrate the kinetics and mechanism between FeII(EDTA)–NO solution and Mn powder, suggesting that the solid–liquid reaction was fitted on chemical reaction control, and the activation energy was calculated as 43.0 kJ mol–1. The effects of main operating parameters, such as precipitant concentration, pH value, and temperature, were studied on Mn2+ recovery. Results indicated that the pseudo-second-order model could precisely describe the kinetics of Mn2+ recovery. Finally, according to Arrhenius and Eyring–Polanyi equations, the reaction activation energy, enthalpy of activation, and entropy of activation for Mn2+ recovery were calculated as 17.25 kJ mol–1, 14.55 kJ mol–1, and 252.07 J (k mol)−1, respectively.