Figure 4
From: Unravelling colloid filter cake motions in membrane cleaning procedures
Cake mobility experiment with photo-bleached section. The membrane position is indicated with a grey dashed line. (a) After cake formation by dead-end filtration a \(40 \times 40\,\upmu {}\hbox {m}\) area of the cake is irradiated with high energy laser light to bleach the microgels. (b) Cross-flow flushing without permeation shows a mobility of the cake on the lower part of the surface after the surface pattern appears. (c) After complete cake removal, only a irreversible microgel monolayer remains on the membrane. The low resolution makes the single microgels shine fuzzily by diffraction, such that the light cone appears larger than the microgels are. (d) The schematic drawing shows the zones of the cake while inducing shear by cross-flow flushing of the bulk: An immobile monolayer on the membrane surface, a fixed cake-zone in the center, and the mobile cake with pattern formation on the bulk-side of the cake. The microgels move from the valley to the ridge, where detachment and dissolution is accelerated.
