RWTH Aachen University, AVT - Chemical Process Engineering, Forckenbeckstraße 51, 52074, Aachen, Germany.
DWI - Leibniz Institute for Interactive Materials, Forckenbeckstraße 50, 52074, Aachen, Germany.
Sci Rep. 2020 Nov 18;10(1):20043. doi: 10.1038/s41598-020-76970-x.
The filtration performance of soft colloid suspensions suffers from the agglomeration of the colloids on the membrane surface as filter cakes. Backflushing of fluid through the membrane and cross-flow flushing across the membrane are widely used methods to temporally remove the filter cake and restore the flux through the membrane. However, the phenomena occurring during the recovery of the filtration performance are not yet fully described. In this study, we filtrate poly(N-isopropylacrylamide) microgels and analyze the filter cake in terms of its composition and its dynamic mobility during removal using on-line laser scanning confocal microscopy. First, we observe uniform cake build-up that displays highly ordered and amorphous regions in the cake layer. Second, backflushing removes the cake in coherent pieces and their sizes depend on the previous cake build-up. And third, cross-flow flushing along the cake induces a pattern of longitudinal ridges on the cake surface, which depends on the cross-flow velocity and accelerates cake removal. These observations give insight into soft colloid filter cake arrangement and reveal the cake's unique behaviour exposed to shear-stress.
软胶体悬浮液的过滤性能会受到胶体在膜表面聚结形成滤饼的影响。通过膜的反冲洗和跨膜的错流冲洗是常用的临时去除滤饼并恢复膜通量的方法。然而，过滤性能恢复过程中发生的现象尚未得到充分描述。在这项研究中，我们过滤聚（N-异丙基丙烯酰胺）微凝胶，并使用在线激光扫描共聚焦显微镜分析滤饼的组成及其在去除过程中的动态迁移。首先，我们观察到均匀的滤饼形成，在饼层中显示出高度有序和无定形的区域。其次，反冲洗以整块的方式去除滤饼，其大小取决于之前的滤饼形成。第三，沿滤饼的错流冲洗会在滤饼表面诱导出纵向脊的图案，这取决于错流速度，并加速滤饼的去除。这些观察结果深入了解了软胶体滤饼的排列，并揭示了在剪切应力作用下滤饼的独特行为。
