Environmental Engineering Reference
In-Depth Information
2.3.2
Stability of KMnO
4
In this study, KMnO
4
was tested for reactivity with the biodegradable polymers
and polymer blends. One concern for shell material is to ensure the oxidant was
not reactive with the polymer. If the KMnO
4
is reactive with the shell, visible evi-
dence would be a brown discoloration caused by manganese oxide formation or
visible degradation of the shell material. To determine the stability, KMnO
4
was
encapsulated in biodegradable polymer shells and mounted on a glass slide. Photos
at 40x and 100x were taken of the pellets using a digital microscope to observe
any reactions or discoloration of the shell. Little to no reactivity was seen in the
biodegradable polymers used to produce the CRBP prototypes. Figure 2.2 shows a
photo spanning the initial encapsulation and 7 months after of encapsulation. The
KMnO
4
in the polymer appears to be stable and non-reactive for the polymer pro-
totypes. Little to no reaction appears between the polymer material and the KMnO
4
demonstrating the shell is inert and able to stabilize the oxidant.
Scale
=
50.8 Microns
Scale
=
50.8 Microns
(a) Polymer with oxidant immediately
following encapsulation
(b) Polymer with oxidant after 7 months
Fig. 2.2
Photo of polymer with KMnO
4
7 months after encapsulation
2.3.3
Release Studies for Encapsulated KMnO
4
Biphasic KMnO
4
release was observed from the encapsulated oxidant pellets. This
is consistent with the observations seen in previous studies using wax and chlo-
rinated polymers [16, 18]. Figure 2.3 shows the polymer pellets and the oxidant
diffusing from the shell. The speed for diffusion of the oxidant across the pellet
surface was controlled by the polymer blend. A rapid release of KMnO
4
occurred
during the initial 1-3 days followed by a controlled and slower release of KMnO
4
.
Oxidant release was delayed by increasing the ratio of hydrophobic Polymer A
