Environmental Engineering Reference
In-Depth Information
Schwartz et al. [17] investigated use of wax encapsulated KMnO
4
as the active
component for a permeable reactive barrier. Controlled release KMnO
4
was manu-
factured by dispersing KMnO
4
in paraffin wax. The wax was cooled in cylindrical
molds at room temperature to produce candle shaped rods 2.5 cm in diameter
and 5 cm long. Each rod contained 70 g of KMnO
4
. The rods were inserted into
2.6 (i.d.)
10 cm long delivery wells used in the flow-tank experiments. Release
studies were performed in column tests where KMnO
4
concentrations were mea-
sured for flowing water (19-21 mL/min) through a 4.8
×
×
15 cm Chromaflex glass
column. Biphasic release of KMnO
4
was observed where a high concentration of
KMnO
4
was released followed by an extended release over 28 days of testing. In
the second part of the study by Schwartz, two delivery wells containing six KMnO
4
wax rods (2.5
10 cm) were inserted in the into a glass tank filled with silica
sand. Water was uniformly pumped into the tank at an inflow rate of 19.2 L/day.
Small multi-level wells were emplaced along the center of the tank to permanganate
samples from the tank. In the study, KMnO
4
delivery through the tank and remedia-
tion of water contaminated with trichloroethylene (TCE) were measured. The study
demonstrated that the controlled release method is capable of destroying dissolved
trichloroethylene (TCE) in a long-term, controlled manner. Incomplete destruction
of TCE was observed suggesting that placement of delivery wells to facilitate lateral
spreading and mixing of permanganate with the dissolved contaminated plume is
necessary.
Ross et al. [18] produced microcapsules ranging in size from 0.06 to 2 mm
using chlorine-based waxy polymers which released oxidants for up to 20 days
in an aqueous batch system. Potassium permanganate was encapsulated in blend
of Boler way, Piccolyte resin S115, Epolene C-16, and Clorez 700. Microcapsules
were fabricated by producing a slurry of KMnO
4
and wax by heating the material
above the melting point of the waxes. The wax and KMnO
4
were sonicated and
the slurry was formed into droplets using a spinning disk. The process produced
two types of microcapusles. The first prototype contained a single grain core (SGC)
of KMnO
4
encased in a polymer shell. The second prototype had 5-10 multiple
grains of KMnO
4
in the core (MGC). The grain size for SGC ranged from 0.06 to
1 mm and the MGC ranged from 0.06 to 2 mm. The mass ratio of KMnO
4
to shell
material ranged from 0.25 to 0.50. Ross et al. investigated the use of MGC micro-
capsules for TCE remediation in batch aqueous studies. TCE degradation using the
MGC demonstrated effective degradation of TCE in aqueous media over several
weeks.
The studies by Kang, Schwartz, and Ross et al. suggest the development of
encapsulated oxidants to create controlled release systems for remediation war-
rants further investigation. In particular, KMnO
4
solutions have been used in various
field studies and remediation projects to remediate TCE contamination. The reaction
between KMnO
4
and TCE involves cleavage of TCE to yield CO
2
, manganese diox-
ide (MnO
2
), potassium chloride (KCl), and hydrochloric acid (HCl). The reaction
is as follows
×
C
2
Cl
3
H
+
2KMnO
4
→
2CO
2(aq)
+
2MnO
2(s)
+
2KCl
+
HCl
