Adsorption of 2,4,6-trinitrotoluene by indole-based porous organic polymer with suitable three-dimensional space size via physisorption and chemisorption

An indole-based porous organic polymer (PTIM) with antibacterial activity was prepared by Friedel-Crafts alkylation and supercritical drying from the self-made tri(1H-indol-3-yl)methane (TIM). The adsorption of 2,4,6-trinitrotoluene (TNT) by PTIM involved physisorption followed by chemisorption, and the mechanism was verified by theoretical simulation and experiment. The physisorption and chemisorption between PTIM and TNT as well as the suitable three-dimensional space size of cross-linked network in PTIM enabled PTIM to have an unprecedented adsorption capacity for TNT (399.2 mg/g). Meanwhile, the removal efficiency of PTIM for TNT was also very high, and it could reach more than 85% of the maximum adsorption capacity after only 1 h of adsorption. Furthermore, the adsorption capacity of PTIM to TNT in actual water samples was slightly less than that in the laboratory, while the adsorption equilibrium time (4 h) was much shorter than the laboratory data (13.75 h). As a result, PTIM could not only achieve primary purification of TNT wastewater from high concentration to low concentration, but also advanced purification from low concentration to standard discharge concentration. In addition, PTIM possessed excellent recycling performance, and the maximum adsorption capacity was still 97% of the initial capacity after five adsorption-desorption cycles Unexpectedly, PTIM also had good antibacterial activity, preventing bacteria from adhering to or covering the pores, and ensuring excellent adsorption capacity and recycling performance. These results showed that PTIM was a promising TNT adsorbent.