Simultaneous Removal of Elemental Mercury and Arsine from a Reducing Atmosphere Using Chloride and Cerium Modified Activated Carbon

Abstract

With the goal of simultaneous removal of elemental mercury and arsine from simulated yellow phosphorus off-gas, a series of Cl–Ce modified activated carbon samples were prepared via an impregnation method and investigated. The Cl3–Ce10/AC exhibited the best performance at 150 °C, with an Hg0 removal efficiency of 92.2%, and the reaction time of AsH3 removal efficiency greater than 90% was 15.5 h. The presence of Hg0 had little impact on AsH3 removal, but conversely AsH3 significantly reduced Hg0 removal efficiency. The effects of individual flue gas components on the simultaneous removal of Hg0 and AsH3 were also studied. O2 clearly promoted the simultaneous removal of Hg0 and AsH3 and CO had almost no influence, while H2S and water vapor inhibited the removal process. The physicochemical properties of the samples were characterized using BET, FESEM-EDS, XRD, and XPS. By combining experimental results with physical and chemical characterization, a mechanism for simultaneous removal of Hg0 and AsH3 was proposed. It was found that chemical adsorption and catalytic oxidation occurred on the surface of the samples, due to the presence of chlorine covalent bonds and cerium oxides, and that the presence of cerium makes it easier for mercury to combine with chlorine. The main products in the used samples were found to be HgCl2, HgO, and As2O3.

Simultaneous catalytic oxidation of elemental mercury and arsine over CeO2(111) surface: A density functional theory study

“…In our previous experimental study, we found that HgO is formed on the catalyst surface, suggesting that lattice oxygen in the catalyst plays an important role in the heterogeneous oxidation process, crucially, the consumed lattice oxygen is replenished by gas phase oxygen [5]. Therefore, we next discuss the possible…”

“…Zhao et al reported the modi cation of a commercial selective catalytic oxidation (SCR) catalyst with a series of metal oxides and found that CeO 2 -modi ed SCR catalyst showed the highest Hg 0 oxidation capacity [29]. In addition, in our previous work, we found that CeO 2 can oxidize Hg 0 and AsH 3 in a reducing atmosphere [5,28]. Speci cally, the removal e ciency was better than 90% at a low reaction temperature of 150 ℃.…”

“…Speci cally, the removal e ciency was better than 90% at a low reaction temperature of 150 ℃. X-ray photoelectron spectroscopy (XPS) measurements showed that Hg 0 and AsH 3 are converted to HgO, elemental As, and As 2 O 3 on the catalyst surface, suggesting that Hg 0 and AsH 3 are oxidized to these species by the lattice oxygen on the surface of the catalyst, and the mechanism of heterogeneous Hg 0 and AsH 3 oxidation should follow the Mars-Maessen mechanism [5].…”

“…To comply with these increasingly stringent requirements, several puri cation and resource utilization technologies have been developed to treat yellow phosphorus off-gas, and the removal of Hg 0 and AsH 3 has received particular attention because of their high toxicity, volatility, and persistence in the environment [3,4]. In addition to the health risks, the presence of Hg 0 and AsH 3 in yellow phosphorus off-gas limits its use as a raw material in other processes [5]. Therefore, Hg 0 and AsH 3 removal technology is urgently needed.…”

“…However, Hg 0 is di cult to dissolve in water or adsorb on solid surfaces because of its high vapor pressure and low water solubility [10]. In contrast, arsenic can be dispersed in the gas phase as oxidized (As 2 O 5 , As 2 O 3 , and arsenate) and reduced (AsH 3 ) species [5]. In yellow phosphorus off-gas, which is a highly reducing mixture, mercury mainly exists as Hg 0 , whereas arsenic mainly exists as AsH 3 [11].…”