Fe^II(EDTA)–NO Reduction by Mn Powder in Wet Flue Gas Denitrification Technology Coupled with Mn²⁺ Recycling: Performance, Kinetics, and Mechanism

Abstract

Fe II (EDTA) solution has been considered an efficient option in wet flue gas denitrification, whereas the generated Fe II (EDTA)−NO restricts its wide application, suggesting that Fe II (EDTA)−NO reduction is the key to this process. This work investigated the performance, kinetics, and mechanism of Fe II (EDTA)−NO reduction by Mn powder coupled with manganese ion (Mn 2+ ) recovery. We initially studied the performance of Fe II (EDTA)−NO reduction with respect to the major influencing factors (i.e., the particle size of Mn powder, initial Fe II (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 Fe II (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 Mn 2+ recovery. Results indicated that the pseudo-second-order model could precisely describe the kinetics of Mn 2+ recovery. Finally, according to Arrhenius and Eyring−Polanyi equations, the reaction activation energy, enthalpy of activation, and entropy of activation for Mn 2+ recovery were calculated as 17.25 kJ mol −1 , 14.55 kJ mol −1 , and 252.07 J (k mol) −1 , respectively.

Pilot Plant Evaluation of NOx Removal by Cobalt Ethylenediamine Solution

“…Over the years, wet denitrification of flue gas has been extensively investigated by various researchers, leading to significant achievements [26][27][28][29][30]. It has many advantages such as simple process equipment, short equipment operation cycle, low operating temperature, low energy consumption, good removal effect, and low treatment cost [26].…”

“…Over the years, wet denitrification of flue gas has been extensively investigated by various researchers, leading to significant achievements [26][27][28][29][30]. It has many advantages such as simple process equipment, short equipment operation cycle, low operating temperature, low energy consumption, good removal effect, and low treatment cost [26]. In particular, the complexation absorption method is a promising research field among many wet denitrification technologies and opens a new chapter of wet combined desulfurization and denitrification [27].…”

Membrane-less Paired Electrolysis for Cooperative Conversion of Complex NO in a Complexing Absorption System

“…Complex NO can be chemically reduced by a series of reducing agents, including sulfites, bisulfite, urea, reductive metals (Fe, Mn, Zn), − sodium hydrosulfite, coal pyrite, and sulfide . These reduction processes usually generate byproducts that are difficult to recover, leading to secondary pollution challenges for the chemical method.…”

Resistive Oxidation Kinetics of Iron(II) Thiochelate used as a Nitric Oxide Absorbent in Flue Gas

“…Among many iron chelates, iron­(II) ethylenediaminetetraacetic acid (Fe­(II)­(EDTA)) has attracted much attention because of its high NO absorption capacity ( K = 1.5 × 10 6 M –1 at 25 °C) and kinetics ( k = 1.7 × 10 8 M –1 s –1 at 25 °C). ,− However, the initial high NOx removal efficiency could not be maintained in the presence of O 2 (typically 4–7% in the flue gas) because Fe­(II)­EDTA is easily oxidized by O 2 , and the resultant Fe­(III)­EDTA has little binding affinity toward NO. ,, To solve this critical problem, iron­(II) thiochelates, notably Fe­(II)­(DMPS) 2 , in which DMPS denotes 2,3-bis­(sulfanyl)­propane-1-sulfonic acid (otherwise called 2,3-dimercaptopropane-1-sulfonic acid), have emerged as less O 2 -sensitive alternatives. − In the previous study, Fe­(II)­(DMPS) 2 showed a prolonged high NO removal efficiency in comparison to Fe­(II)­EDTA on account of high O 2 resistance . Besides, this iron­(II) thiochelate has a higher equilibrium constant for the nitrosylation reaction (eq ) than other iron­(II) chelates and thus has a greater NO absorption capacity …”