Environmental Engineering Reference
In-Depth Information
Fig. 2.3
Time series photos of pellet with oxidant diffusing from shell
to hydrophilic polymer B in the polymer blend. Prototype blends were identified
as PAB-50, PAB-60, PAB-90, and PAB-100 contained 50, 60, 90, and 100% of
Polymer A to Polymer B, respectively. Therefore PAB-50 represented a 1:1 ratio
of Polymer A to Polymer B. Figure 2.4 shows a graph comparing the release rate
for the polymer blends. PAB-50 was observed to release KMnO
4
at a faster rate
than PAB-60, PAB-90 and PAB-100. PAB-60 and PAB-90 appeared to exhibit sim-
ilar release rates for KMnO
4
with PAB-90 releasing the oxidant slower during the
first 20-min. PAB-100 demonstrated the slowest release of the oxidant. Uniform
mixing of the polymers and oxidant proved to be important to ensure diffusion of
the oxidant from the shell at a controlled rate because the hydrophilic polymer will
readily dissolve in water leaving pores in the hydrophobic shell. For example, an
excess amount of hydrophilic polymer on the pellet surface led to rapid diffusion of
the oxidant from the polymer. Pellets designed with only the hydrophobic polymer
demonstrated the slowest rate of oxidant diffusion.
0.1 g of KMnO
4
encapsulated in select polymer blends
25
20
15
PAB-50
PAB-60
PAB-90
PAB-100
10
5
0
0
10
20
30
40
50
60
Minutes
Fig. 2.4
Prototype KMnO4 release for the hydrophilic and hydrophobic polymer blends
