Silica-supported ionic liquid for efficient gaseous arsenic oxide removal through hydrogen bonding

The emission of highly-toxic gaseous As₂O₃ (As₂O₃ (g)) from nonferrous metal smelting poses environmental concerns. In this study, we prepared an adsorbent (S_MIL-X) by loading an ionic liquid (IL) ([HOEtMI]NTf₂) into MCM-41 through an impregnation-evaporation process and then applied it to adsorb As₂O₃ (g). S_MIL-20% exhibited an As₂O₃ (g) adsorption capacity of 35.48 mg/g at 400 °C, which was 490% times higher than that of neat MCM-41. Characterization of S_MIL-X indicated that the IL was mainly supported on MCM-41 through O-H…O bonds formed between the hydroxyl groups (-OH) and the silanol groups (Si-OH) and the O-H…F bonds formed between the C-F groups and the Si-OH groups. The hydrogen bonds significantly contributed to the adsorption of As₂O₃ (g), with -NH and -OH groups forming hydrogen bonds with As-O species (i.e., N-H…O and O-H…O). This showed superior performance to traditional adsorbents that rely on van der Waals forces and chemisorption. Moreover, after exposure to high concentrations of SO₂, the adsorption capacities remained at 76% of their initial values, demonstrating some sulfur resistance. This study presents an excellent adsorbent for the purification of As₂O₃ (g) and shows promising application potential for treating flue gas emitted by nonferrous metal smelting processes.