Despite their excellent capabilities, wide implementation of membranes for oil/water emulsion separation is limited due to severe fouling. To date, microscale dynamics of the oil–water–membrane system are poorly understood. The present study uses confocal microscopy at unprecedented resolution for direct observation of oil droplet deposition, deformation, and detachment during separation and cleaning, respectively. The 3D shape of the droplets was imaged as a function of the permeation rate, J, droplet radius, R, membrane permeance, k, water viscosity, μ, and the water/oil interfacial tension coefficient, σ. These parameters yield a modified capillary number, = μVR^1/2/σk^1/2, which accounts for the extra viscous “suction” at close proximity to the membrane surface. A clear correlation was observed between the degree of droplet deformation and an increasing . Furthermore, the reversibility of droplet deposition and membrane performance were assessed through microscopic surface coverage and flux recovery analysis. In general, operation at a low flux (3.9 μm/s) yields spherical droplets that are easily removed by crossflow cleaning, whereas a high flux (85 μm/s) leads to significant deformation and mostly irreversible deposition. These results shed important new insight on the influence of hydrodynamic conditions on fouling reversibility during emulsion separation, and may guide better design of surface-modified membranes.

中文翻译：

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膜表面油滴的微观动力学：变形，可逆性和结垢的影响

尽管它们具有出色的功能，但由于严重的结垢，限制了膜在油/水乳化液分离中的广泛应用。迄今为止，人们对油-水-膜系统的微观动力学还知之甚少。本研究使用共聚焦显微镜以前所未有的分辨率分别观察分离和清洁过程中油滴的沉积，变形和分离。将液滴的3D形状成像为渗透率J，液滴半径R，膜渗透率k，水粘度μ和水/油界面张力系数σ的函数。这些参数产生修改后的毛细管数= μVR1 ^/2 / σk1 ^/2，这是在膜表面附近产生额外粘性“吸力”的原因。观察到液滴变形程度和增大程度之间有明显的相关性。此外，通过微观表面覆盖和通量回收率分析评估了液滴沉积和膜性能的可逆性。通常，在低通量（3.9μm/ s）下运行会产生易于通过错流清洗去除的球形液滴，而高通量（85μm/ s）则导致明显的变形和大部分不可逆的沉积。这些结果为流体动力学条件对乳液分离过程中结垢可逆性的影响提供了重要的新见解，并可能指导表面改性膜的更好设计。