Preparation Of Indole-Based Porous Materials And Its Purification Of TNT Wastewater

2,4,6-trinitrotoluene（TNT）is a very stable and widely used high explosive,which will produce a large amount of wastewater in production,transportation,and use.TNT has strong toxicity,and these wastewaters are bound to pose a serious threat to the environment and life.Therefore,the treatment of TNT wastewater has become the focus of research.In this thesis tris（1H-indol-3-yl）methane（TIM）was synthesized by a simple method,and then triindole-based porous polymer（PTIM）with suitable three-dimensional structure was prepared by Friedel-Crafts alkylation reaction using TIM as raw material,and its adsorption behavior for TNT wastewater was studied.In addition,another triindole-based porous polymer（PTIMK）with better thermal stability was prepared by nucleophilic substitution reaction using TIM and 4,4’-difluorobenzophenone as raw materials,and its adsorption behavior for TNT wastewater was studied.Finally,using PTIMK as a carrier,the cation-πinteraction was used to drive and induce Ti⁴⁺to be uniformly dispersed around the indole plane of PTIMK,and the indole-based porous polymer/TiO₂composite（PTIMK/TiO₂-C）with good dispersion was prepared by in-situ reaction.Compared with the indole-based porous polymer/TiO₂composite（PTIMK/TiO₂-S）prepared by traditional sol-gel method,the photodegradation behavior of TNT wastewater by PTIMK/TiO₂-C was studied.The main work is as follows:（1）TIM was first synthesized from indole and indole-3-formaldehyde,and then crosslinked by Friedel-Crafts alkylation reaction.and PTIM was prepared by supercritical drying technology.TIM was first synthesized from indole and indole-3-formaldehyde,and then crosslinked by Friedel-Crafts alkylation reaction.Finally,PTIM was prepared by supercritical drying technology.The theoretical calculation and experimental results proved that the suitable three-dimensional space size was beneficial to the adsorption of TNT by PTIM.The pore size of PTIM was 3.63 nm,which allowed TNT to pass through and enter the pores of PTIM quickly,so that the adsorption sites of PTIM could fully play its role.Furthermore,the interactions（dual hydrogen bonds,dual dipole-πinteractions,and dualπ-πinteractions）between PTIM and TNT were simulated and calculated,and three dual interactions increased the adsorption capacity of PTIM to TNT.the suitable three-dimensional space size and three dual interactions made the adsorption capacity of PTIM to TNT reach an unprecedented 399.2 mg/g,and the adsorption equilibrium time was13.75 h.In addition,adsorption kinetics,isothermal adsorption model and adsorption thermodynamics showed that chemical adsorption and intraparticle diffusion were the rate-controlling steps of TNT adsorption by PTIM,and the adsorption was monolayer adsorption,and the adsorption was a spontaneous exothermic process.Finally,the adsorption capacity of PTIM for TNT in actual water samples decreased slightly,but the equilibrium time was greatly shortened to only 4 h.PTIM possessed excellent recycling characteristics,and the adsorption capacity of PTIM for TNT was still 97%of the initial capacity after five adsorption-desorption cycles.It should be pointed out that PTIM also had good antibacterial activity,preventing bacteria from adhering to or covering the pores,and ensuring excellent adsorption capacity and recycling performance.（2）PTIMK was prepared by nucleophilic substitution reaction and freeze-drying technology using TIM and 4,4-difluorobenzophenone as raw materials.PTIMK is porous,with a small number of micropores and a large number of mesopores.The simulation results show that there were also hydrogen bonding,π-πinteraction and dipole-πinteractions between the benzophenone unit and TNT in addition to the hydrogen bond,dipole-πinteraction andπ-πinteraction between the triindole group and TNT.The synergistic effect of these interactions made PTIMK have a good adsorption efficiency for TNT,that is,the adsorption capacity was285.4 mg/g,and the adsorption equilibrium time was 8.75 h.Chemical adsorption and intraparticle diffusion were also the rate-controlling steps of TNT adsorption by PTIM,and the adsorption was monolayer adsorption,and the adsorption was a spontaneous exothermic process.PTIMK also had good adsorption efficiency in actual water samples,PTIMK also has good adsorption efficiency in real water samples.Although the adsorption capacity was slightly reduced,the equilibrium time was greatly shortened to only 4 h.After five adsorption-desorption cycles,the adsorption capacity was still 90%of the initial capacity.It should be pointed out that PTIMK had good thermal stability,the initial weight loss temperature was 234°C and the temperature at 5%weight loss was 315°C,which could be used as a carrier for the preparation of indole-based porous polymer/TiO₂composites in the next chapter.（3）Using titanium tetrachloride as raw material,Ti⁴⁺was driven and induced to uniformly distribute around the indole plane of PTIMK by cation-πinteraction,and PTIMK/TiO₂-C composite with TiO₂uniformly loaded on PTIMK were prepared by in-situ reaction.Compared with PTIMK/TiO₂-S composite and TiO₂prepared by traditional sol-gel method,the effects of TiO₂content,removal time,TNT solution concentration,composite addition amount and solution p H on TNT removal rate were investigated,and the results showed that PTIMK/TiO₂-C had great photocatalytic activity on TNT.Due to the uniform dispersion of TiO₂,PTIMK/TiO₂-C could completely purify 50 mg/L TNT solution in 1.16 h and reduce the chemical oxygen demand of TNT solution to 18 mg/L within 6.50 h,reaching the national third-class water standard.