Regulating the hydrophilicity and complexation of poly(pyrrole methane) by phenolic hydroxyl groups for efficient Mercury(II) capture

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The hydrophilicity and complexation ability of organic adsorbents are key factors affecting their adsorption performance for heavy metal ions in water. Herein, a series of polyphenols with different number and relative position of hydroxyl groups were employed to regulate the hydrophilicity and mercury(II) complexation ability of poly(pyrrole methane)s (PPDHBAs). It is found that increasing the number of –OH groups or extending their distance from the molecular skeleton can enhance the hydrophilicity and mercury(II) complexation ability of poly(pyrrole methane) more significantly. Notably, adjacent –OH groups demonstrate more effective improvement in hydrophilicity and mercury(II) complexation ability, thereby facilitating the mass transfer and synergistic chelation of mercury(II), resulting in ultra-fast adsorption kinetics (achieving equilibrium within 10 min), high capacities of up to 3000 mg·g−1 and distribution coefficients of approximately 105 mL·g−1. Furthermore, PPDHBAs functionalized with two adjacent –OH groups also exhibit remarkable practical application potential, demonstrating stable physicochemical properties, wide pH applicability (4–11), minimal decline in adsorption performance after 20 cycles and effectively achieving the removal of trace amounts of mercury(II) below the WHO limits of 1 μg·L-1. This research highlights the potential of polyphenol functionalized poly(pyrrole methane)s as efficient adsorbents for mercury(II) removal in water, and it also presents a straightforward approach for constructing functionalized adsorbents to remediate water contaminated with other heavy metal ions.