# Sedimentation of microparticles in Highly Concentrated Non-Newtonian Emulsions
## 3 Results
### Influence of Solid Parameters on the Sedimentation Process in Emulsion  
To determine the effect of solid particle size on the sedimentation process, glass microspheres with five different grain size fractions were selected (see Table 1). The sedimentation process was carried out according to the test procedure described earlier,  
Figure 3: Changes in the backscatter signal over time as a function of test sample height for a 70% concentration emulsion (D\({}_{1}\)), using 0.3 g/mL glass microspheres with diameter 300–400 \(\upmu\)m.  
which made it possible to obtain graphs of the dependence of the sediment layer growth h\({}_{\rm s}\) at time t. Applying Equation (1), it was also possible to calculate changes in velocity u during the process. The graphs of time dependence of h\({}_{\rm s}\) and u for sedimentation of 0.3 g/mL microspheres in 70% emulsion with average droplet diameter d\({}_{\rm e1}\) are presented in Figure 4a,b, respectively. By analyzing the change in sediment layer height over time (Figure 4a) for different grain size fractions, large differences in the alignment of experimental points can be observed. For the sedimentation of the smallest microspheres with a diameter range of 100-200 \(\mu\)m, the sediment layer growth is mild, and finally, the sediment layer height after 30 min h\({}_{\rm sk}\) was small and was about 2.5 mm. In addition, the sedimentation velocity for this fraction was small and relatively constant, as can be observed in Figure 4b. For larger microspheres, with a diameter range of 200-300 \(\mu\)m, it can be observed that the value of h\({}_{\rm s}\) varies more steeply over time, and eventually, the height of h\({}_{\rm sk}\) was higher (6.42 mm). This also corresponds to higher sedimentation velocities. For the sedimentation of microspheres with a fraction of 300-400 \(\mu\)m, the final height of the sediment h\({}_{\rm sk}\) was the highest with a value of 10.34 mm. However, the shape of the h\({}_{\rm s}\) versus t curve is not as steep as for smaller beads. For larger microspheres, with a diameter range of 400-600 \(\mu\)m, it can be seen that the final sediment layer height h\({}_{\rm sk}\) was slightly smaller than that recorded for the preceding fraction. Differences can also be noticed in the shape of the h\({}_{\rm s}\)(t) curve. It can be observed that at the beginning of the process, there was a rapid increase in the value of h\({}_{\rm s}\), while with the duration of the process, the increases were smaller and smaller. These results are also illustrated in the velocity vs. time plot (Figure 4b). It can be seen here that initially, the sedimentation velocities take on high values, but as the process continues, these values decrease and eventually take on a fixed value. The trends observed here are further enhanced for the sedimentation process of microspheres with a diameter range of 600-800 \(\mu\)m. Here, a rapid increase in the height of the sediment layer is more clearly observed in the first phase of the process, but smaller and smaller changes are observed over time. Finally, the height of the sediment layer was lower than in the previous case. To explain the observed trends, it is necessary to consider what happens to the phases in each case. It should be emphasized that we are dealing with sedimentation in a highly concentrated emulsion, where the packing of oil droplets is very high. Three cases can be distinguished here. The first refers to small particles, the second to medium particles, and the third to large particles. For each of these cases, the mechanism of movement of the microspheres will be different. To explain this, the diagram shown in Figure 5 is used. In this diagram, oil droplets are shown in yellow and solid microspheres in brown. Figure 4: Dependence plot of (**a**) sediment layer height and (**b**) sedimentation velocity during the process for the sedimentation of microspheres with a concentration of 0.3 g/mL in an emulsion with a concentration of 70%, d\({}_{\rm e1}\).