多相可控的超分子多孔吸附剂对污染物的吸附和分离功能的探索

Phase Controllable Supramolecular Porous Adsorbent for Pollutants Adsorption and Separation

快速吸附和有效分离是去除污染物的关键技术.其中,均相吸附剂能与吸附质充分碰撞,在快速吸附方面具备一定优势,但难以从介质中有效去除.非均相吸附剂容易从体系中分离,但与污染物的作用力较弱,容易引起二次污染.为此,基于V形两亲性嵌段共聚物的动态组装,构筑了可以实现均相和非均相吸附功能的超分子多孔吸附剂.120°折叠的芳香性嵌段通过自组装形成疏水性空腔捕获有机污染物,骨架外围的聚乙二醇嵌段具有良好的亲水效应,可助溶多孔吸附剂,使多孔材料具有均相吸附的特征,60 min内实现对双酚A和炔雌醇的高效吸附,其吸附容量分别达到126.5和95.4 mg/g.受到聚乙二醇的最低临界溶解温度(LCST)效应影响,升温使均相吸附剂转化为非均相吸附剂,促使多孔材料和水相的分离,易于从水体中去除.基于超分子多孔吸附剂的温度响应行为,在室温下对水污染物进行高效吸附,通过升温实现了与水环境的有效分离,多次吸附—解吸循环实验表明移除效率能够维持在84%以上.这种结合均相吸附和非均相吸附优势的构筑方法,为净化水体提供了一种新的方案.

Adsorption is an effective method for removing pollutants from water.Among them,homogeneous adsorbents can capture the adsorbates in the medium by effective collision.However,there are some difficulties in effectively removing themd from water.Compared with homogeneous adsorbents,heterogeneous adsorbents are easily separated from the system,but the interaction with pollutants is relatively weak,which may cause secondary pollution.Here,a thermos-responsive tubular adsorbent was presented by dynamic assembly of V-shaped aromatic amphiphiles.The tubular wall based on the assembly of 120-degree folded aromatic segment is very suited for the trap of organic pollutants.In addition,the aromatic pores have excellent water solubility for the surrounding of hydrophilic ethylene oxide segments,showing remarkable removal capacity as well as fast sorption kinetics with homogeneous adsorbent characteristics.The removal capacity is found to be 126.5 mg/g for bisphenol A(BPA)and 95.4 mg/g for ethinyl estradiol(Eo),respectively,due to the formation of hydrophobic tubular pores in aqueous environment.In addition,the equilibrium time of tubular adsorbents were just 60 min for BPA and 50 min for Eo to achieve complete removal efficiency,which is attributable to the existence of preferable collision with pollutant in aqueous environment for its spherical topology with an efficient hydrophilic surface.Due to the lower critical solution temperature(LCST)effect of ethylene oxide segment,the surface of adsorbent became hydrophobic by thermal triggers,resulting in a phase separation between water and adsorbent.Thus,the removed pollutants as well as adsorbents are easily separated from water through a simple centrifugation.Therefore,a new sewage treatment route is proposed based on the temperature responsive behaviour of supramolecular porous adsorbent.At room temperature,the tubular adsorbent with homogenous characteristics can be used to rapidly trap organic pollutants in water.Then,the adsorbent and adsorbate complexes are converted into solid phase by raising the temperature up to 65℃,which can be effectively separated by centrifugation.By further dialysis by water,the absorbent can be recovered and used for next utilization.During five adsorption and desorption cycles,the removal efficiency of supramolecular porous adsorbent was maintained,demonstrating excellent performance in sewage treatment.The strategy combined advantages of homogeneous and heterogeneous adsorption provides a new insight for water purification.