Efficient removal of perchlorate by a quaternary ammonium-functionalized hydrogel: Performance and mechanisms

Perchlorate (ClO 4 ⁻) is a persistent and hazardous water pollutant that disrupts thyroid function. Hydrogels, with their tunable functionality and high capacity, offer a promising alternative, but their application for perchlorate removal remains largely unexplored. A novel hydrogel was synthesized via free-radical copolymerization of methacryloxyethyl trimonium chloride (MTAC) and N, N’-methylenebis (acrylamide) (MBA). The material was characterized using SEM, EDS, FTIR, XRD, and XPS. The MTAC hydrogel exhibited a high adsorption capacity for ClO 4 ⁻, with experimental data best fitted by the Langmuir isotherm, showing a maximum capacity of 425.22 mg/g at 298 K. The adsorption process is primarily driven by strong electrostatic interactions from quaternary amine groups, supplemented by ion exchange and hydrogen bonding. The adsorption energy reached −3.59 eV. The adsorption process was fast, spontaneous, and exothermic, remaining effective over a wide pH range (5–9) and in the presence of common competing anions. The hydrogel demonstrated excellent regenerability over five cycles. MTAC/Sodium alginate (SA) beads were used in fixed bed packing, which achieved a treatment capacity of 5346 bed volumes, reducing ClO 4 ⁻ from 500 μg/L to below the drinking water standard (70 μg/L). Furthermore, the column facilitated easy regeneration and exhibited an enrichment factor as high as 122.9 fold. This work successfully developed a MTAC-based hydrogel for the removal of ClO 4 ⁻. The hydrogel demonstrated high capacity and regenerability in real water samples and column experiments, making it an ideal candidate material for practical end-of-pipe water treatment applications. • A novel quaternary ammonium-functionalized hydrogel (MTAC) is synthesized for perchlorate adsorption. • The MTAC exhibits a high capacity (425.22 mg/g) and stable performance across pH 5–9. • The adsorption mechanism is elucidated as synergistic electrostatic attraction, ion exchange, and hydrogen bonding. • The MTAC shows excellent regenerability and high practical potential in fixed-bed columns (5346 bed volumes treated). • MTAC/alginate beads enable efficient point-of-use application with a high enrichment factor (122.9) upon regeneration.