Preparation Of Isoxazoline-based Porous Material And The Adsorption For TNT In Water Under The Synergistic Action

2,4,6-trinitrotoluene(TNT)is one of the most widely used aromatic explosives.TNT is toxic and carcinogenic,and difficult to degrade naturally.It is a relatively economical and effective way to reduce the harm of TNT waste solution by adsorption,but the adsorption capacity of these reported adsorbents are weak and the adsorption efficiency is low.Therefore,the design and preparation of high efficiency adsorbent of TNT is still a subject worthy of study.In this work,three isoxazoline-based porous polymers were prepared via a click polymerization followed the freeze-drying.Efficient adsorption of TNT in water was achieved through the synergy between polymer and TNT(hydrophobic interaction,Lewis acid-base interaction,dipole-? interaction between N-O dipole in isoxazoline ring and benzene ring of TNT,?-? stacking effect between benzene rings of polymer and TNT,etc.).The result as follows:(1)Firstly,m-phenyldinitrileoxide was synthesized,and then a series of isoxazolinebased porous polymer materials were prepared via click polymerization between m-phenyldinitrileoxide and vinyl siloxane,and freeze drying was performed subsequently.The polymers consist of many macropores.With the increase of feed ratio,the average pore diameter and porosity of the polymer gradually decreased,while the hydrophobicity gradually increased.The adsorption capacity was the strongest when the feed ratio was 1:1,and the pH was around 6.The result of the adsorption kinetics displayed that the adsorption process conformed to a pseudo-second-order kinetic model,chemical adsorption was the rate-controlling step,and the adsorption equilibrium time was 3 h.Langmuir adsorption isotherm model can describe the isotherm adsorption process perfectly,which shows that is a monolayer adsorption.The maximum adsorption capacity at room temperature is 90.7 mg/g,which is the highest value among the similar silicon-containing adsorbents.The reason is mainly due to the hydrophobic interaction,Lewis acid-base interaction,and the synergistic effect between dipole-? and ?-? stacking.Thermodynamic studies show that the adsorption of TNT by the polymer is a spontaneous exothermic process,and the increase in temperature is not conducive to the adsorption.In addition,the polymer can be recycled.With acetone as the desorbent,after 5 adsorption-desorption cycles,the adsorption capacity of the polymer remains about 80%.(2)In order to increase the amount of action sites to further improve the adsorption capacity.A novel isoxazoline-based porous polymer material was prepared via click polymerization between isophthalonitrile oxide and polybutadiene,and then freeze drying was performed.The polymer has both micron-sized pores and nano-sized pores.The adsorption capacity was the strongest when the pH was around 6.The result of the adsorption kinetics displayed that the adsorption process conformed to a pseudo-second-order kinetic model,chemical adsorption was the rate-controlling step,and the adsorption equilibrium time was 4 h.Langmuir adsorption isotherm model can describe the isotherm adsorption process perfectly,which shows that is a monolayer adsorption.The maximum adsorption capacity at room temperature is 177.3 mg/g.It is a very high adsorption efficiency that has not been reported.And the high adsorption efficiency is due to the increase of the amount of active sites and the synergy between dipole-? and ?-? stacking.Thermodynamic studies show that the adsorption of TNT by the polymer is a spontaneous exothermic process,and the increase in temperature is not conducive to the adsorption.In addition,the polymer can be recycled.With acetone as the desorbent,after 5 adsorption-desorption cycles,the polymer still maintained an adsorption capacity of more than 85%.(3)In order to solve the problem of uneven reaction caused by high activity of isophthalonitrile oxide,a room temperature stable nitrile oxide was prepared.Then a new isoxazoline-based porous polymer was prepared via a click polymerization between the stable nitrile oxide and polybutadiene,and then freeze drying was performed.The adsorption capacity was the strongest when the pH was around 5.The result of the adsorption kinetics displayed that the adsorption process conformed to a pseudo-second-order kinetic model,chemical adsorption was the rate-controlling step,and the adsorption equilibrium time was 12 h.Langmuir adsorption isotherm model can describe the isotherm adsorption process perfectly,which shows that is a monolayer adsorption.The adsorption ability was enhanced due to the addition of the methyl groups result in the increases of the electron-rich properties of the polymer benzene ring.The maximum adsorption capacity at room temperature is 235.3 mg/g,which is higher than the reported TNT adsorption materials.Thermodynamic studies show that the adsorption of TNT by the polymer is a spontaneous exothermic process,and the increase in temperature is not conducive to the adsorption.In addition,the polymer can be recycled.With acetone as the desorbent,after 5 adsorption-desorption cycles,the polymer still maintained an adsorption capacity of more than 83.5%.