Abstract:
Organic dyes, especially the cationic dyes of methyl orange(MO) and acid green 25(AG25), have been emerged as harmful pollutants. Developing new materials for efficient adsorption and removal of organic dyes are thus of great significance. The design of porous organic polymers(POPs) with both good porosity and task-specific functionalization is still a critical challenge. In this work, an amino-containing imidazolium ionic liquid(IL-NH
2) 3-propylamine-1-methylimidazolium trifluoromethanesulfonimide salt was chemically grafted onto a triptycene-based porous polymer(TPP). The ionic liquid modified TPP(TPP-IL) was characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), Fourier transform infrared spectroscopy(FT-IR), thermo-gravimetric analysis(TGA), elemental analysis(EA),
13C-nuclear magnetic resonance(
13C-NMR) and nitrogen adsorption-desorption isotherms. The results showed that TPP-IL displayed a rough yet irregular morphology, and also was amorphous in nature. The novel polymer showed high Brunauer-Emmett-Teller surface area(of up to 781.1 m
2/g), porosity, and physicochemical stability. The resulting polymer materials were then used as solid adsorbent for removing organic dyes. It was found that TPP-IL showed higher adsorption capacity against the anionic dyes of AG25 and MO. The adsorption process could be described by a Langmuir isotherm adsorption model. Moreover, the experimental data fitted quasi-secondary kinetic model very well. At room temperature, the maximum adsorption capacities of TPP-IL against AG25 and MO were 571.7 mg/g and 501.9 mg/g, respectively, which were about 1.5 times as much as those of unmodified adsorbent TPP. Furthermore, TPP-IL exhibited an excellent recyclability. Theoretical calculations showed that TPP-IL adsorption of AG25 and MO mainly relied on electrostatic attraction, as well as hydrogen bonding interactions. Therefore, it is believed that TPP-IL with hierarchical porous structures, high surface areas, and physicochemical stability is a promising candidate for the purification and treatment of dyes in solutions.