A Calix[4]arene-crosslinked polymer for rapid adsorption of cationic dyes in water

Dyes are indispensable in the textile industry and are very difficult to degrade due to the presence of two or more benzene rings in their structures. However, the purification of water resources is currently an urgent issue. In this study, a trichlorotriazine-derived calix[4]arene and 1,3,5-tris(4-aminophenyl) benzene were crosslinked to generate a calix[4]arene crosslinked polymer that can serve as a highly efficient adsorbent for separating cationic dyes from water. This research provides evidence for the efficiency of the polymer to adsorb various organic micropollutants in water via batch adsorption experiments. In particular, this polymer exhibited a removal efficiency over 99.6% and 99.4% for methylene blue and toluidine blue within 5 min, respectively. The kinetic results showed that the adsorption process of this polymer for organic dyes could be described with quasi-second-order models, and Langmuir isotherm adsorption models demonstrated that the maximum equilibrium adsorption capacity for methylene blue and toluidine blue was reached to 1806.82 and 2161.32 mg g(-1), respectively. These observations suggest that the adsorption is mainly dependent on the electrostatic interactions, pi-pi interactions, and hydrogen bonding between the polymer and the organic dyes. Furthermore, the adsorption capacities of the adsorbent were maintained at high levels after five cycles. Its excellent adsorption capability and recyclability make this polymer a promising candidate for potential applications in water purification.