全氟辛酸(PFOA)是一种对自然环境有害的持久性污染物。这种持久性导致潜在的富集和渗透转移,会影响环境中的正常循环。PFOA对自然环境和人类健康都构成重大威胁。因此,成本效益的发展,高效,环保PFOA吸附剂是一项至关重要的努力。本文介绍了通过席夫碱缩合反应无催化剂一锅法合成氟化富氮多孔有机聚合物(POP-3F)。富氮化合物1,4-双(2,4-二氨基-1,3,5-三嗪)苯与对三氟甲基苯甲醛之间的反应得到POP-3F。富氮多孔有机聚合物中氟原子的引入增强了其疏水性,从而促进氟与PFOA的有利相互作用,因此,提高吸附剂的功效。扫描电子显微镜(SEM),傅里叶变换红外(FT-IR)光谱,X射线衍射(XRD)固态核磁共振(ssNMR)光谱,X射线光电子能谱(XPS),氮气吸附-解吸分析,和热重分析(TGA)用于确认POP-3F的成功合成和表征。液相色谱-串联质谱(LC-MS/MS)以负电喷雾电离(ESI)模式和多反应监测模式(MRM)进行。该仪器配备了AtlantisT3色谱柱(100毫米×2.1毫米,3μm),并使用外标法进行分析。多种因素对POP-3F吸附PFOA的影响,包括pH值,盐浓度,和腐殖酸的存在,被调查了。在pH为2时达到最高的PFOA去除率(98.6%),表明POP-3F可有效去除酸性工业废水中的PFOA。PFOA的去除率不受NaCl浓度增加的影响。该现象可归因于POP-3F中的质子化仲胺与去质子化PFOA之间的静电相互作用。加入NaCl后,在POP-3F表面上形成双电层,外层有Cl-离子,内层有Na+离子,削弱了这些相互作用。腐植酸与PFOA竞争吸附。然而,POP-3F即使在水中存在高腐殖酸浓度的情况下也表现出良好的去除率。在最佳pH下进行吸附等温线和动力学实验,以探索相关的吸附机理。结果表明,初始吸附速率较快,在5分钟内去除95.4%PFOA。在6h内达到最佳吸附平衡,24小时后,去除率仅下降了0.3%。这一发现表明,POP-3F对PFOA的去除表现出持续的功效。Langmuir拟合分析表明,POP-3F的理论最大吸附容量为191mg/g;该值超过了活性炭材料和大多数其他吸附剂的吸附容量。突出了POP-3F优越的PFOA吸附性能。此外,基体效应对POP-3F去除PFOA的影响最小,在模拟自然水中仅观察到轻微减少(0.1%)。在五个吸附-解吸循环中评估了POP-3F的可回收性。五个循环后,去除效率仅显示出0.67%的微小下降。这些结果证明了所提出的吸附剂的可回收性,这通过可重用性转化为成本降低。该特性使POP-3F成为在实际应用中经济有效地从废水中去除PFOA的有希望的候选物。
Perfluorooctanoic acid (PFOA) is a persistent contaminant with detrimental effects on the natural environment. This persistence leads to potential enrichment and osmotic transfer, which can affect normal circulation in the environment. PFOA poses significant threats to both the natural environment and human health. Therefore, the development of cost-effective, highly efficient, and environment-friendly PFOA adsorbents is a crucial endeavor. This paper presents the catalyst-free one-pot synthesis of fluorinated nitrogen-rich porous organic polymers (POP-3F) via a Schiff-base condensation reaction. The reaction between the nitrogen-rich compound 1,4-bis(2,4-diamino-1,3,5-triazine)benzene and p-trifluoromethylbenzaldehyde yielded POP-3F. The introduction of fluorine atoms into the nitrogen-rich porous organic polymer enhanced its hydrophobicity, thereby facilitating favorable fluoro-fluorine interactions with PFOA and, thus, improving the efficacy of the adsorbent. Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), solid-state nuclear magnetic resonance (ssNMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption analysis, and thermogravimetric analysis (TGA) were used to confirm the successful synthesis and characterization of POP-3F. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was conducted in negative electrospray ionization (ESI) mode coupled with multi-reaction monitoring mode (MRM). The instrument was equipped with an Atlantis T3 column (100 mm×2.1 mm, 3 μm), and analysis was conducted using an external standard method. The influences of various factors on PFOA adsorption by POP-3F, including pH, salt concentration, and humic acid presence, were investigated. The highest PFOA removal rate (98.6%) was achieved at a pH of 2, indicating the applicability of POP-3F for the effective removal of PFOA from acidic industrial wastewater. The removal rate of PFOA was unaffected by increases in NaCl concentration. This phenomenon can be attributed to electrostatic interactions between the protonated secondary amines in POP-3F and deprotonated PFOA. Upon the addition of NaCl, a double electric layer is formed on the POP-3F surface, with Cl- ions in the outer layer and Na+ ions in the inner layer, which weakened these interactions. Humic acid is competitively adsorbed with PFOA. However, POP-3F demonstrated good removal rates even in the presence of high humic acid concentrations in water. Adsorption isotherm and kinetics experiments were conducted at the optimal pH to explore the relevant adsorption mechanism. The results showed a rapid initial adsorption rate, with 95.4% PFOA removal within 5 min. Optimal adsorption equilibrium was achieved within 6 h, and the removal rate decreased by only 0.3% after 24 h. This finding indicates that POP-3F exhibits sustained efficacy for PFOA removal. Langmuir fitting analysis revealed a theoretical maximum adsorption capacity of 191 mg/g for POP-3F; this value surpasses those of activated carbon materials and most other adsorbents, highlighting the superior PFOA-adsorption performance of POP-3F. Additionally, matrix effects minimally affected the removal of PFOA by POP-3F, with only a slight reduction (0.1%) observed in simulated natural water. The recyclability of POP-3F was assessed over five adsorption-desorption cycles. The removal efficenecy exhibited a minor decrease of only 0.67% after five cycles. These results demonstrate the recyclability of the proposed adsorbent, which translates into cost reduction through reusability. This characteristic renders POP-3F a promising candidate for the economical and efficient removal of PFOA from wastewater in practical applications.