Department of Chemical & Biochemical Engineering, The University of Iowa, Iowa City, IA, USA.
Environ Sci Process Impacts. 2017 Nov 15;19(11):1445-1456. doi: 10.1039/c7em00289k.
We fabricated a suite of polymeric electrospun nanofiber mats (ENMs) and investigated their performance as next-generation passive sampler media for environmental monitoring of organic compounds. Electrospinning of common polymers [e.g., polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and polystyrene (PS), among others] yielded ENMs with reproducible control of nanofiber diameters (from 50 to 340 nm). The ENM performance was investigated initially with model hydrophilic (aniline and nitrobenzene) and hydrophobic (selected PCB congeners and dioxin) compounds, generally revealing fast chemical uptake into all of these ENMs, which was well described by a one compartment, first-order kinetic model. Typical times to reach 90% equilibrium (t) were ≤7 days under mixing conditions for all the ENMs and <0.5 days for the best performing materials under static (i.e., no mixing) conditions. Collectively, these short equilibrium timescales suggest that ENMs may be used in the field as an equilibrium-passive sampler, at least for our model compounds. Equilibrium partitioning coefficients (K, L kg) averaged 2 and 4.7 log units for the hydrophilic and hydrophobic analytes, respectively. PAN, PMMA and PS were prioritized for additional studies because they exhibited not only the greatest capacity for simultaneous uptake of the entire model suite (log K ∼1.5-6.2), but also fast uptake. For these optimized ENMs, the rates of uptake into PAN and PMMA were limited by aqueous phase diffusion to the nanofiber surface, and the rate-determining step for PS was analyte specific. Sorption isotherms also revealed that the environmental application of these optimized ENMs would occur within the linear uptake regime. We examined the ENM performance for the measurement of pore water concentrations from spiked soil and freshwater sediments. Soil and sediment studies not only yielded reproducible pore water concentrations and comparable values to other passive sampler materials, but also provided practical insights into ENM stability and fouling in such systems. Furthermore, fast uptake for a suite of structurally diverse hydrophilic and moderately hydrophobic compounds was obtained for PAN and PS, with t ranging from 0.01 to 4 days with mixing and K values ranging from 1.3 to 3.2 log units. Our findings show promise for the development and use of ENMs as equilibrium-passive samplers for a range of organic pollutants across soil/sediment and water systems.
我们制备了一系列聚合物静电纺纳米纤维垫（ENMs），并研究了它们作为下一代有机化合物环境监测用被动采样介质的性能。通过共纺常见聚合物[例如聚丙烯腈（PAN）、聚甲基丙烯酸甲酯（PMMA）和聚苯乙烯（PS）等]可以得到具有可重复控制的纳米纤维直径（50-340nm）的 ENMs。我们最初用模型亲水性（苯胺和硝基苯）和疏水性（选择的多氯联苯同系物和二恶英）化合物来研究 ENM 的性能，结果普遍表明所有这些 ENM 都能快速地进行化学吸收，这可以通过一个单室、一级动力学模型来很好地描述。对于所有的 ENMs，在混合条件下达到 90%平衡所需的典型时间（t）均≤7 天，而在静态（即无混合）条件下表现最好的材料则<0.5 天。总的来说，这些较短的平衡时间表明，ENMs 至少可以作为我们模型化合物的平衡-被动采样器在现场使用。亲水性分析物的平衡分配系数（K，L/kg）平均为 2 和 4.7 个对数单位，疏水性分析物的平衡分配系数（K，L/kg）平均为 2 和 4.7 个对数单位。由于 PAN、PMMA 和 PS 不仅表现出对整个模型化合物套件同时吸收的最大能力（log K∼1.5-6.2），而且吸收速度也很快，因此被优先用于进一步研究。对于这些优化的 ENMs，PAN 和 PMMA 中的吸收速率受到水相间扩散到纳米纤维表面的限制，而 PS 的速率决定步骤则是分析物特异性的。吸附等温线也表明，这些优化的 ENMs 将在环境中的线性吸收范围内使用。我们考察了 ENM 对添加到土壤和淡水沉积物中的孔隙水浓度的测量性能。土壤和沉积物研究不仅产生了可重现的孔隙水浓度和与其他被动采样材料相当的值，而且还提供了关于这些系统中 ENM 稳定性和污垢的实际见解。此外，PAN 和 PS 对一组结构多样的亲水性和中等疏水性化合物的快速吸收也得到了证明，混合时的 t 范围为 0.01 到 4 天，K 值范围为 1.3 到 3.2 个对数单位。我们的研究结果表明，在土壤/沉积物和水系统中，开发和使用 ENM 作为一系列有机污染物的平衡-被动采样器具有广阔的前景。
