Industrial & Engineering Chemistry Research, Vol.59, No.29, 12955-12963, 2020
Efficient Removal of Thallium from Flue Gas Using Manganese-Based MOF Catalysts by Gas-Solid Phase Catalytic Oxidation and Adsorption
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 O-2, generating Tl2O3. Over 90% removal efficiency was maintained for 10 h by a MOF catalyst with 10% Mn loading, at 423 K with 10% O-2 in the feed gas, which was determined to be the optimal level of O-2. 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.