Efficient Hg(Ⅱ) adsorption of polyphenol functionalized Poly(pyrrole methane)s: The role of acid doped ions

A series of doped and dedoped polyphenol functionalized poly(pyrrole methane)s (234HBAs) were designed to investigate the impact of various dopants on mercury adsorption in water. The adsorption performance of dedoped 234HBAs showed no significant difference (ranging from 2961 to 3004 mg·g⁻¹ at 318 K). However, the adsorption capacities of doped 234HBAs for mercury exhibited significant optimization and varied among different dopants (ranging from 3676 to 4103 mg·g⁻¹ at 318 K). In addition to ultra-high adsorption capacity, 234HBAs also exhibited broad working pH range (2–11), fast kinetics (adsorption equilibrium within 10 min), good anti-ion interference and selectivity (K_d > 7.1 × 10⁵ mL·g⁻¹), and excellent regeneration ability (little attenuation of adsorption capacity after 20 cycles). Furthermore, through characterization techniques (FT-IR, XPS) and the density functional theory (DFT) calculation, it was discovered that the presence of doped acid ions enhanced the capture and immobilization of mercury to varying extents besides the robust chelation binding of mercury by the adjacent phenolic hydroxyl groups. Among these ions, oxygen-containing citrate and sulfate exhibited a stronger ability to facilitate the removal of mercury compared with chloride ions. More importantly, this straightforward approach to fabricating functionalized adsorbents for the remediation of mercury-containing wastewater holds significant guiding implications for the treatment of other heavy metal and organic wastewater.