Inhibiting Mercury Re-emission and Enhancing Magnesia Recovery by Cobalt-Loaded Carbon Nanotubes in a Novel Magnesia Desulfurization Process

Abstract

Mercury re-emission, because of the reduction of Hg to form Hg by sulfite, has become a great concern in the desulfurization process. Lowering the concentrations of Hg and sulfite in the desulfurization slurry can retard the Hg formation and, thus, mitigate mercury re-emission. To that end, cobalt-based carbon nanotubes (Co-CNTs) were developed for the simultaneous Hg removal and sulfite oxidation in this work. Furthermore, the thermodynamics and kinetics of the Hg adsorption and effect of Hg adsorption on catalytic activity of Co-CNTs were investigated. Experimental results revealed that the Co-CNTs not only accelerated sulfite oxidation to enable the recovery of desulfurization by-products but also acted as an effective adsorbent of Hg removal. The Hg adsorption rate mainly depended on the structure of the adsorption material regardless of the cobalt loading and morphological distribution. The catalytic activity of the Co-CNTs for sulfite oxidation was not significantly affected due to the Hg adsorption. Additionally, the isothermal adsorption behavior was well-fitted to the Langmuir model with an adsorption capacity of 166.7 mg/g. The mercury mass balance analysis revealed that the Hg re-emission was decreased by 156% by adding 2.0 g/L of Co-CNTs. These results can be used as a reference for the simultaneous removal of multiple pollutants in the wet-desulfurization process.

Simultaneous Removal of SO2 and NO Using a Novel Method of Ultraviolet Irradiating Chlorite–Ammonia Complex

“…During the removal process, SO 2 and NO first diffused to the gas− liquid interface, and then, NH 4 OH absorbed SO 2 to form SO 3 2− (eq 32), along with oxidation by ClO 2 − /radicals to generate SO 4 2− (eq 33). The insoluble NO in the gas−liquid interface first reacted with ClO 2 − /radicals to produce soluble NO 3 − and NO 2 (eq 34), and then, the fate of NO 2 had three paths: (1) The NO removal refers to the conversion to NO 3 − . Because ClO 2 − , HO • , ClO • , and ClO 2 determine the NO oxidation, the chemical reaction rate equation of NO oxidation by the UV/ NaClO 2 −NH 4 OH system can be expressed as eq 36.…”

“…The simultaneous removal of sulfur dioxide (SO 2 ) and nitric oxide (NO) from flue gas is a hot topic in the field of air pollution control . The key is to effectively oxidize the insoluble NO to NO 3 – and reduce the production of NO 2 .…”

“…The simultaneous removal of sulfur dioxide (SO 2 ) and nitric oxide (NO) from flue gas is a hot topic in the field of air pollution control. 1 The key is to effectively oxidize the insoluble NO to NO 3 − and reduce the production of NO 2 . Extensively studied oxidation methods include gas−solid heterogeneous catalytic oxidation, liquid phase oxidation, and gas phase oxidation.…”

Simultaneous Catalysis of Sulfite Oxidation and Uptake of Heavy Metals by Bifunctional Activated Carbon Fiber in Magnesia Desulfurization

“…However, the tendency declines slightly after Co loading reaches 50 wt. %, which might be due to the fact that the excessive Co species has agglomerated on the surface of support [13,14,16,45,46]. Moreover, the catalysis performance of cobalt-based catalysts for sulfite oxidation, including Co-MS, Co-CNTs, Co-SBA-15, and Co-TiO 2 , are thoroughly compared in Figure S3, in which the active cobalt species are loaded onto the different supports.…”

Construction of Confined Bifunctional 2D Material for Efficient Sulfur Resource Recovery and Hg2+ Adsorption in Desulfurization

“…The impractical energy penalty up to 8.00 GJ/ton of this dehydration process inhibits the sustainable utilization of sulfur resources, thus the yellow mud byproduct (mainly MgSO 3 ) is mostly abandoned and not recycled . The effluent of magnesium sulfite slurry might reemit SO 2 and cause water pollution by consuming the dissolved oxygen. , Moreover, another environmental risk that was always neglected is the coexisting aqueous Hg 2+ in the slurry, which is difficult to remove by conventional alkaline precipitation owing to the presence of large amounts of soluble Mg 2+ . Particularly, Hg 2+ can be reduced to Hg 0 by the excess MgSO 3 to introduce extensive re-emission issues and damage the quality of product MgSO 4 . − …”