Efficient Removal of Thallium from Flue Gas Using Manganese-Based MOF Catalysts by Gas–Solid Phase Catalytic Oxidation and Adsorption

Abstract

Thallium (Tl) is known to be extremely toxic. However, thallium pollution from smelting tail gas has long been neglected as an environmental issue. This study aims to develop a gaseous thallium control technology based on manganese-based metal–organic framework (MOF) catalysts, using a manganese centered paddle wheel structure as a support. Tl removal testing showed that these catalysts were effective at both adsorbing and oxidizing Tl­(I), producing Tl­(III), which is less harmful. Details of the catalytic oxidation mechanism were investigated, which demonstrated that Tl­(I) loses electrons to Mn­(III), Mn­(IV), and O2, generating Tl2O3. Over 90% removal efficiency was maintained for 10 h by a MOF catalyst with 10% Mn loading, at 423 K with 10% O2 in the feed gas, which was determined to be the optimal level of O2. SO2 inhibited thallium removal in this system, while 10% CO2 had no significant effect. Regeneration through acid washing was found to be effective, with the catalyst maintaining thallium removal efficiency for five regeneration cycles. Molecular simulation of Tl removal is investigated, based on which the possible reaction path is found.

Impregnation Synthesized Cu@MIL‐101(Cr) Catalyzes the Oxidation of Styrene to Benzaldehyde with TBHP**

“…MOF, namely metal‐organic framework, is a category of novel materials formed from inorganic metallic constituents and organic ligands, which exhibit high surface area, tunable cavities, component diversification, modifiable functionality and porosity, promising for applications in various areas, especially in catalysis [20–26] . MOFs combine the advantages of organic and inorganic catalysts, not merely possess high stability and recyclable applicability, but have abundant and designable catalytic sites [27–29] .…”

Kinetics of Thallium(I) Oxidation by Free Chlorine in Bromide-Containing Waters: Insights into the Reactivity with Bromine Species

“…Furthermore, Tl­(III) is prone to form Tl­(III) (hydr)­oxide precipitates, that is, Tl 2 O 3 with low solubility from 10 –5.8 M at pH 7 to 10 –11.7 M at pH 9 at Eh 0.55 V . Because Tl­(III) is less mobile and more easily separated from aqueous solutions in the form of (hydr)­oxide precipitates, − the oxidation of Tl­(I) to Tl­(III) is considered as a practical way for Tl removal in water and wastewater (WW) treatment . Tl­(I) oxidation to form Tl­(III) needs strong oxidizing conditions, ,− and chlorine (HOCl) was able to efficiently oxidize Tl­(I) over a wide pH range. ,, The oxidation kinetics of Tl­(I) by HOCl was highly dependent on solution pH.…”