Aminoethanethiol-Grafted Porous Organic Polymer for Hg²⁺ Removal in Aqueous Solution

A highly porous organic polymer, CBAP-1, was synthesized from terephthaloyl chloride and 1,3,5-triphenylbenzene via the Friedel-Crafts reaction, and functionalized with either ethylenediamine (EDA) or 2-aminoethanethiol (AET) for Hg²⁺ removal from water. Both materials were characterized by X-ray diffraction, N₂ adsorption-desorption isotherms, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma and elemental analysis, and the stability of the porous polymers under different pH and temperature conditions was examined. The adsorption experiments were carried out by varying contact time, Hg²⁺ concentration, and system pH to study the adsorption equilibrium and kinetics. The Hg²⁺ ion-adsorption capacities of CBAP-1(EDA) and CBAP-1(AET) were 181 and 232 mg/g, respectively, at room temperature and pH 5, and the observed adsorption isotherms could be fitted well to the Langmuir model (correlation factor R² > 0.99). Under the optimum set of conditions, the adsorption equilibrium for CBAP-1(AET) was reached within a contact time of 10 min; CBAP-1(AET) exhibited an excellent distribution coefficient of greater than 2.41 × 10⁷ mL/g. The adsorption kinetics could be satisfactorily described by a pseudo-second-order model. Hg²⁺ recovery in the presence of commonly coexisting metal ions such as Na⁺, Ca²⁺, Mg²⁺, Pb²⁺, and Fe³⁺ was also investigated. CBAP-1(AET) showed high Hg²⁺ selectivity against other ions except Pb²⁺. CBAP-1(AET) was superior to CBAP-1(EDA) in terms of overall performance; it could efficiently remove >96% of Hg²⁺ ions in 2 min from a 100 ppm of Hg²⁺ solution. The material could be reused for 10 consecutive runs with negligible loss in adsorption capacity.