Low-gradient magnetic separation (LGMS) of magnetic nanoparticles (MNPs) has been proven as one of the techniques with great potential for biomedical and environmental applications. Recently, the underlying principle of particle capture by LGMS, through a process known as magnetophoresis, under the influence of hydrodynamic effect has been widely studied and illustrated. Even though the hydrodynamic effect is very substantial for batch processes, its impact on LGMS operated at continuous flow (CF) condition remained largely unknown. Hence, in this study, the dynamical behaviour of LGMS process operated under CF was being studied. First, the LGMS experiments using poly(sodium 4-styrenesulfonate)-functionalized-MNP as modelled particle system were performed through batchwise (BW) and CF modes at different operating conditions. Here BW operation was used as a comparative study to elucidate the transport mechanism of MNP under the similar environment of CF-LGMS process, and it was found out that the convection induced by magnetophoresis (timescale effective is ∼1200 s) is only significant at far-from-magnet region. Hence, it can be deduced that forced convection is more dominant on influencing the transport behaviour of CF-LGMS (with resident time ≤240 s). Moreover, we found that the separation efficiency of CF-LGMS process can be boosted by the higher number of magnets, the higher MNP concentration and the lower flowrate of MNP solution. To better illustrate the underlying dynamical behaviour of LGMS process, a mathematical model was developed to predict its kinetic profile and separation efficiency (with average error of ∼2.6% compared to the experimental results).

中文翻译：

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连续流下磁性纳米粒子的低梯度磁分离：实验研究、传输机制和数学建模

磁性纳米粒子 (MNP) 的低梯度磁分离 (LGMS) 已被证明是具有巨大生物医学和环境应用潜力的技术之一。最近，在流体动力学效应的影响下，LGMS 通过称为磁泳的过程捕获粒子的基本原理得到了广泛研究和说明。尽管流体动力学效应对于批处理过程非常重要，但它对在连续流 (CF) 条件下运行的 LGMS 的影响在很大程度上仍然未知。因此，在本研究中，研究了在 CF 下运行的 LGMS 过程的动力学行为。首先，使用聚（4-苯乙烯磺酸钠）-功能化-MNP 作为模拟粒子系统的 LGMS 实验通过分批 (BW) 和 CF 模式在不同的操作条件下进行。这里使用 BW 操作作为比较研究来阐明 MNP 在 CF-LGMS 过程的相似环境下的传输机制，并且发现磁泳引起的对流（时间尺度有效为~1200 s）仅在远距离显着-来自磁铁区域。因此，可以推断，强制对流对影响 CF-LGMS 的传输行为（停留时间≤240 秒）更占主导地位。此外，我们发现，CF-LGMS 过程的分离效率可以通过更多的磁铁数量、更高的 MNP 浓度和更低的 MNP 溶液流速来提高。为了更好地说明 LGMS 过程的潜在动力学行为，开发了一个数学模型来预测其动力学曲线和分离效率（与实验结果相比，平均误差为 ~2.6%）。