Revealing the interaction forms between Hg(II) and group types (–Cl, –CN, –NH2, –OH, –COOH) in functionalized Poly(pyrrole methane)s for efficient mercury removal

Abstract

To explore the impact of different functional groups on Hg(II) adsorption, a range of poly(pyrrole methane)s functionalized by –Cl, –CN, –NH2, –OH and –COOH were synthesized and applied to reveal the interaction between different functional groups and mercury ions in water, and the adsorption mechanism was revealed through combined FT-IR, XPS, and DFT calculations. The adsorption performance can be improved to varying degrees by the incorporation of functional groups. Among them, the oxygen-containing functional groups (–OH and –COOH) exhibit stronger affinity for Hg(II) and can increase the adsorption capacity from 180 mg g−1 to more than 1400 mg g−1 at 318 K, with distribution coefficient (Kd) exceeding 105 mL g−1. The variations in the capture and immobilization capabilities of functionalized poly(pyrrole methane)s predominantly stem from the unique interactions between their functional groups and mercury ions. In particular, oxygen-containing –OH and –COOH effectively capture Hg(OH)2 through hydrogen bonding, and further deprotonate to form the –O–Hg–OH and –COO–Hg–OH complexes which are more stable than those obtained from other functionalized groups. Finally, the ecological safety has been fully demonstrated through bactericidal and bacteriostatic experiments to prove the functionalized poly(pyrrole methane)s can be as an environmentally friendly adsorbent for purifying contaminated water.