Efficient adsorption of trinitrotoluene by isoxazoline-based porous polymers prepared from room-temperature stable bis(nitrile oxide)

Abstract

A novel isoxazoline-based porous adsorbent (PB-TTNO) is prepared by click polymerization and freeze-drying from a methyl-containing bis(nitrile oxide) stable at room temperature. The introduction of four methyl groups around the nitrile oxide group reduces the activity of the bis(nitrile oxide) and make it react more mildly with polybutadiene, resulting in PB-TTNO with a more uniform pore size. Meanwhile, the electron-donating methyl groups further increase the π–π interaction between the polymer benzene ring and the TNT benzene ring. The π–π interaction enables one benzene ring in the polymer to interact with two TNT molecules to form a sandwich structure, which further improves the adsorption capacity. The synergistic effect of dual π–π interactions and dipole-π interactions makes the maximum adsorption capacity of PB-TTNO reach 235.3 mg g−1 within 12 h at 25°C. The factors such as pH value, adsorbent dosage, contact time, initial TNT concentration, and temperature are also discussed. The adsorption kinetics fit well with the pseudo-second-order model, and the Langmuir model exhibits better correlation for equilibrium data analysis. In addition, the adsorption data of PB-TTNO in real water samples are similar to those in laboratory, and the maximum adsorption capacity decreases by only 15% after five adsorption–desorption cycles.