Sustainable lotus petiole-derived adsorbents: Synergistic activation, high surface area, and efficient persistent organic contaminant removal.

Abstract

The emerging contaminant perfluorooctanoic acid and the traditional pollutant methylene blue-derived water pollution has driven the development of cost-effective, high-performance, and sustainable adsorbents. In this work, waste lotus petiole was used as raw materials to systematically explore the effects of single chemical activation (KOH/H3PO4) and sequential double chemical activation (H3PO4-KOH/KOH-H3PO4) on the material structure and adsorption performance. The KOH-H3PO4-activated sample (AC-KP) possessed a high specific surface area (2108 m2/g) and pore volume (1.14 cm3/g), which were significantly higher than those obtained via other activation methods. This enhancement may be attributed to the synergistic effect of KOH-induced micropore formation and H3PO4-mediated pore expansion. AC-KP presented optimal performance for methylene blue and perfluorooctanoic acid elimination, with maximum adsorption capacities reaching 748 mg/g and 515 mg/g, respectively. Additionally, AC-KP exhibited regenerability after adsorbing these organic pollutants. Its adsorption behavior was found to conform to the Elovich model and the Langmuir model. Combined experimental findings and density functional theory model calculations revealed that the adsorption mechanism was dominated by pore filling, coordination, hydrogen bonding, and electrostatic interactions. This work not only provides a new approach for the high-value utilization of waste lotus petiole but also offers theoretical insights for optimizing adsorbent activation processes and treating persistent organic pollutant-contaminated water.

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