Bio-inspired Catechol-based Hypercrosslinked Polymer for Iron (Fe) Removal from Water

Catechol, a structure widely found in nature with a strong interaction with iron (Fe) ions, was used as a monomer to prepare a hypercrosslinked polymer (HCP) as a solid adsorbent for Fe removal from water. The catechol-based HCP (Catechol-HCP) was synthesized via Friedel–Crafts alkylation and characterized by FT-IR spectroscopy, elemental analysis, and BET surface area analysis. The HCPs based on toluene, phenol, and hydroquinone monomers were also prepared to compare their Fe adsorption efficiency. Comparing to toluene-, phenol-, and hydroquinone-based HCPs, Catechol-HCP showed a significantly higher Fe adsorption indicating the important of the strong interaction of catechol unit to the Fe ion. Factors including adsorbent dose, contact time, initial solution concentration, and temperature were studied on their effects on the adsorption efficiency. The Catechol-HCP could remove Fe from water more than 40 mg g⁻¹ or 94%. The adsorption isotherm was fitted to the Langmuir model with the R_L value between 0 and 1 indicating the favorable adsorption. The kinetics study suggested the adsorption occurred as a pseudo-second-order mechanism. Moreover, the material showed a good reusability demonstrating the cost effectiveness of the material which would be beneficial for further practical utilizations.