Engineered Polymeric Microspheres with Synergistic Hydrogen-Bonding Nanotraps and Multisite Adsorption for Ultrafast Herbicide Decontamination

Abstract

The ultrafast removal of trace herbicides like paraquat (PQ) and diquat (DQ) from water is urgent yet challenging due to their highwater stability and strong-binding properties. Here, efficient PQ and DQ removal based on hydrogen-bonding nanotraps dominant multisite adsorption were developed. Two crosslinked polymeric microspheres, βCD-PF and γCD-PF, were synthesized from cyclodextrins (CDs) and hexafluorocyclotriphosphazene (HFP). The γCD-PF microsphere with sufficient hydrogen-bonding nanotraps on the pore surface prompts adsorption kinetics constants of PQ and DQ up to 127.09 and 192.64 g mg⁻¹ min⁻¹, achieving 99% removal efficiency for PQ and DQ within 5 s. γCD-PF exhibits exceptional selectivity for PQ and DQ over larger competing dyes. Importantly, trace PQ (1 ppm) can be effectively treated with γCD-PF to achieve a concentration far below the US Environmental Protection Agency (EPA) standard (0.003 ppm) within 30 s. The ultrafast adsorption is driven by a multisite mechanism: electrostatic and π–π interactions from HFP promote adsorbate accumulation on the CD surface, while the high-density hydrogen-bonding nanotraps in γCD-PF enhance hydrogen bond strength, enabling rapid capture. This work provides a valuable strategy for designing ultrafast adsorbents for effective herbicide removal from water.