Performance and Mechanism of MnO2/γ-Al2O3 for Gaseous Thallium Capture from Cement Kiln Flue Gas

• • Optimal Mn loading: 10 wt% MnO2 on γ-Al2O3 achieves the highest gaseous Tl capture capacity; increasing to 15 wt% reduces performance, indicating an optimal dispersion–activity trade-off. • • Redox mechanism: Mn species oxidize Tl+ to Tl3+, enhancing immobilization; H2-TPR and O2-TPD confirm improved redox properties of MnO2/γ-Al2O3 compared to bare γ-Al2O3. • • DFT insights: TlCl adsorption on MnO2/γ-Al2O3 involves stronger Mn–Cl bond formation and higher adsorption energy than Al–Cl on γ-Al2O3, with greater charge transfer, explaining enhanced capture. • • Industrial relevance: Placing 10MnO2/γ-Al2O3 upstream of SCR catalysts can intercept gaseous Tl, reducing Tl flux to the catalyst and mitigating poisoning, thereby extending catalyst lifetime and ensuring stable cement kiln operation.