三聚氰胺功能化多孔有机聚合物的合成及其对甲基橙的吸附性能

Preparation of melamine-functionalized porous organic polymer and its adsorption properties for methyl orange

首先以对三联苯(TP)和对苯二甲酰氯(TC)为单体合成了酮基聚合物前体(TP-TC),而后基于席夫碱反应将三聚氰胺(MA)与之交联得到胺功能化的多孔有机聚合物TP-TC-MA。通过扫描电镜(SEM)、透射电镜(TEM)、傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)、氮气吸附-脱附(BET)以及零电荷点(pHpzc)的测定等手段对合成的多孔有机聚合物进行表征。以染料废水中典型的阴离子染料甲基橙为研究对象,研究了TP-TC-MA对其吸附行为,并探讨了吸附机制。利用紫外-可见分光光度计(UV-Vis)得出目标污染物的紫外吸收光谱标准曲线,标准曲线拟合相关系数(R2)为0.999。结果表明,TP-TC-MA由于具有高比表面积(708.5 m^(2)/g)和总孔体积(0.556 cm^(3)/g)以及丰富的含氮基团,对阴离子染料甲基橙表现出优异的吸附性能。TP-TC-MA对水中甲基橙的吸附动力学符合准二级动力学方程,吸附平衡数据可以采用Langmuir等温吸附模型描述。经由Langmuir等温吸附模型计算得到的理论最大吸附容量为156.3 mg/g。选择性实验结果表明,TP-TC-MA对阴离子染料甲基橙具有更强的吸附作用,吸附作用机理可归结为静电相互作用、氢键和π-π相互作用等。在重复使用5次之后,TP-TC-MA对甲基橙仍保持90%以上的去除率,表明材料具有良好的稳定性和重复利用性,在染料废水处理中具有很好的应用前景。

In this work,a polymer precursor was first synthesized using p-terphenyl(TP)and terephthaloyl chloride(TC)as monomers.Then,cross-linking was realized by means of a Schiff base reaction with melamine(MA)as a modifier to obtain an amine-functionalized porous organic polymer TP-TC-MA.The synthesized polymers were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared(FT-IR)spectroscopy,X-ray diffraction(XRD),and point of zero charge(pHpzc)measurements,as well as on the basis of nitrogen adsorption-desorption isotherms.Adsorption experiments were carried out to evaluate the adsorption properties of TP-TC-MA for methyl orange(MO),a typical anionic azo dye that has widespread industrial application.The amount of MO adsorbed on TP-TC-MA was evaluated by ultraviolet-visible(UV-Vis)spectroscopy at a wavelength of 463 nm.Microscopic analysis revealed that the as-synthesized polymer had an aggregated particle-shaped structure.XRD spectra confirmed that TP-TC-MA was an amorphous polymer,consistent with the results of high-resolution TEM experiments.The Brunauer-Emmett-Teller(BET)specific surface area and total pore volume of TP-TC-MA were determined as 708.5 m^(2)/g and 0.556 cm^(3)/g,respectively.The measured pHpzc of TP-TC-MA was 4.0,probably because of the abundant nitrogen-containing groups provided by MA.The factors affecting adsorption,such as pH,adsorbent dosage,contact time,initial pollutant concentration,and ionic strength,were investigated.Because of the protonation of the N-atom in TP-TC-MA,the pH had a strong impact on the adsorption of MO.The removal efficiency could be maximized at the optimized pH of 3.0.The adsorption equilibrium isotherm,measured at 25℃and a concentration of 50-500 mg/L,showed that the MO adsorption over TP-TC-MA followed the Langmuir isotherm,with a maximum adsorption capacity of 156.3 mg/g.The modeling of the experimental adsorption data was consistent with the pseudo-second-order kinetic model,which indicated fast adsorption and chemisorption as the dominant mechanism.With increasing ionic strength,the adsorption of MO slightly decreased,suggesting a partial antagonistic ion effect.Results of the selectivity study revealed that TP-TC-MA was more selective toward MO than methylene blue(MB),which indicated that electrostatic interactions played a significant role during the adsorption progress.Five adsorption-desorption cycles showed that TP-TC-MA could be regenerated without significant deterioration of its adsorption efficiency,indicating that it has good stability and reusability.The observed adsorption performance indicated that this MA-modified porous organic polymer offers prospects for further research and application in the treatment of dye-containing wastewaters.