Hyper‐Crosslinked Imidazole Polymers for High‐Efficiency Adsorption of Congo Red in Wastewater

The hyper-crosslinked imidazolium polymer adsorbent, synthesized through the Friedel-Crafts alkylation reaction, possesses high specific surface area, a porous structure, and is rich in phenyl and imidazole groups. This adsorbent exhibits high adsorption capacity and short equilibrium time for Congo Red. It has demonstrated remarkable adsorption performance in simulated textile wastewater treatment, underscoring its potential application in wastewater treatment.

Abstract

This study explores the synthesis and application of a hyper-crosslinked organic imidazole polymer, termed HCP-p-DCB, for the removal of Congo Red (CR) from dye wastewater. The HCP-p-DCB exhibits a high specific surface area, a porous structure, and abundant phenyl/imidazole functional groups. Univariate experiments were conducted to evaluate the effects of adsorbent dose, pH, shaking speed, contact time, temperature, and initial CR concentration. The results demonstrated that HCP-p-DCB achieved optimal CR adsorption under the following conditions: 15 mg adsorbent dosage, 40 min contact time, pH 8.7, 298 K temperature, and 150 rpm shaking speed, achieving a maximum adsorption capacity of 542.9 mg/g. Kinetic data align with a pseudo-second-order model (R ² = 0.9996), suggesting chemisorption dominance. Thermodynamic studies revealed that this process is spontaneous and endothermic. The Langmuir model indicated that the adsorption follows a monolayer mechanism. Additionally, the process fits well with the intra-particle diffusion kinetic model, indicating a three-step rate-controlling mechanism. In dynamic adsorption experiments, the breakthrough curves were better described by the Yan model. The adsorption mechanism of CR involves π─π interaction and π─π electron donor-acceptor interaction. Furthermore, the adsorbent exhibited good adsorption performance when treating simulated textile wastewater containing CR, highlighting its strong potential for removing CR from dye wastewater.

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