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TERRACAP™ Additives Technology Profile
TEPCO, a pioneer in this area, has a patent on a revolutionary microencapsulation technology for hydrocarbons, chemicals or heavy metals.
The process is a two-step microencapsulation system that encloses contaminants on a molecular level in an inert amorphous silica matrix
as envisioned in Figure 1.
The first step in this unique approach is to surround small quantities of the organic contaminant with an aqueous, silica-surfactant
system to form a micelle with the TERRACAP silica additive (3000 series). The surfactant orients itself with the hydrophobic portion
toward the hydrocarbon and the hydrophilic portion toward the polar sites of the hydrophilic silica (Figure 1). The second additive
is a curing agent. TERRACAP curing additives (4000 series) are slightly acidic, aqueous, polymeric materials
that react with the alkaline TERRACAP silica to speed up the microencapsulation process. Within minutes, microencapsulation is observed
to occur in the form of precipitated agglomerates of wet silica containing the contaminant species in the micelle trapped inside the
silica matrix. The pH of the microencapsulated material is approximately neutral.
Characterization results suggest the resulting silica matrix is not very permeable or leachable and is resistant to environmental or
chemical reactions. Examples of supportive research experiments with the TERRACAP additive process are described below:
Bulk Oil Samples - A sample of used 10W-30 motor oil was microencapsulated with the TERRACAP additives and allowed
to dry. A TCLP extraction (EPA 1311) followed by analysis for TPH (EPA 8015m) indicated less than 1 ppm extractable TPH from the
microencapsulated sample. A similar experiment was conducted with standard Type F hydraulic oil. The TPH leachable portion of the
microencapsulated hydraulic oil was 7 ppm using the same EPA test procedures. The concentrations of the neat oils were 20 percent
by volume.
Oil Contaminated Soil - Soil contaminated with 4015 ppm of crude oil was microencapsulated using the TERRACAP
additives. A TCLP extraction (EPA 1311) of the treated product, followed by analysis for TPH using EPA 8015m indicated the
leachable TPH was reduced to 1.23 ppm. This suggests a high level of success is possible in remediating crude oil contaminated
soil with TEPCO’s microencapsulation technology.
Oil/Halocarbon/Lead Contaminated Soil - Soil contaminated with 1590 ppm crude oil, 115 ppm lead and 32
ppm 1,1,1-trichloroethane was treated with TERRACAP additives. TCLP extraction (EPA 1311) of the treated product, followed by
analysis for TPH using EPA 8015m, SW846-8010 for halocarbons and SW846-6010 for lead indicated leachable TPH was reduced to 154
ppm, 1,1,1-trichloroethane was reduced to <10 ppm and lead was reduced to <0.10 ppm.
These three examples support the conceptual use of the TERRACAP microencapsulation technology to remediate hazardous waste to
within most regulatory guidelines. Morphological results from Optical Microscopy, Scanning Electron Microscopy (SEM), Energy
Dispersive X-Ray Analysis (EDXA), X-Ray Diffraction and Mass Spectroscopy provide evidence that suggests microencapsulation
has long-term stability associated with the micro silica cell matrix.
Morphological Characterization - Fluorescence, Optical Microscopy Photos, Scanning Electron Microscopy (SEM), Energy
Dispersive X- Ray Analysis (EDXA), X-Ray Diffraction and Mass Spectroscopy Research were used to characterize the morphology
of the microencapsulation silica cell matrix. Twenty volume percent of a neat crude oil sample, known to fluoresce under ultra
violet (UV) light, was microencapsulated and allowed to air dry. The sample was examined using several analytical procedures.
The crude oil was observed to be present in the microencapsulated sample under plane polarized light due to the presence of an
oil stain on the silica cells as shown in Figure 2.The same sample was then examined under UV light as shown in Figure 3. The
sample did not fluoresce as expected attributed to the crude oil in the microencapsulated sample. The oil stain was absent in
the control sample without crude oil.
SEM, coupled with EDXA, shows the silica morphology has many cavernous chambers and pockets at 2,000-fold magnification as shown
in Figure 4. X-Ray Diffraction indicates the silica cell is largely amorphous silicon dioxide (silica). Amorphous structures are
random in nature, and are known to be very stable as opposed to a highly ordered crystalline structure. The crude oil is said to
be microencapsulated, meaning it is molecularly bound by physical forces in the micelles and trapped in the fine pores of the
silica matrix. The electron micrograph RS 970546 shown in Figure 5 indicates fine structure at the edge reflected by dark and
light contrasting of the order of 0.05 to 1 m m or less (500 to 1000 Å or less). This suggests that the porosity and
characteristics of the silica aggregates have dimensions over a very broad range (tens of Ås to m
m size). The TERRACAP technologies ability to microencapsulate a high volume of oil (10 - 30 %) on a gram of
encapsued material per gram of silica basis is linked to a very small pore size (ca. 50 - 100 Å ) as indicated by the fine
structure on the micrograph shown in Figure 5.
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| Figure 4. SEM Showing Silica Morphology With Cavernous Chambers at 2,000 Fold Magnification |
Figure 5. SEM Showing the Fine STructure on the Order of 500-1000 Å Suggests the Porosity Characteristics of the Silica Aggregates Has Dimensions Over a Very Broad Range |
Mass Spectroscopic Analysis - The mass spectroscopy (MS) procedure is a technique to study volatiles in fluid
inclusions of ores and oil inclusions in rock core samples. In this example, it is used to demonstrate the stability of
microencapsulated product. The MS parameters are 125C at 10-7 torr. The procedure involves crushing a rock
sample in a mass spectrometer and observing all possible organic fragments between 60 and 120 atomic mass units resulting
from the organic species released from the sample at these severe conditions. In the control experiment (Figure 6a), a
background scan (without crushing) mass spectrum of a sample of crude oil included in rock was obtained. The spectrum shows
isolated peaks of modest intensity. The sample was crushed internally in the mass spectrometer according to the procedure.
Immediately, the spectra in Figure 6b shows a complete range of fragments with atomic mass units between 60 and 120 are
detected, as the crude oil components are set free from inclusions in the core sample.
a)
Atomic mass Units
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b)
Atomic mass Units
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c)
Atomic mass Units
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d)
Atomic mass Units
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Figure 6: Mass Spectra of the Following: a) Core Sample, Background Scan; b) Crushed Core Sample;
c) Microencapsulated Crude Sample, Background Scan; d) Crushed Microencapsulated Crude Sample |
Microencapsulated crude oil was placed in the mass spectrometer in a second experiment. The background scan (Figure 6c)
shows isolated peaks of modest intensity as expected similar to the results shown in Figure 6a. The microencapsulated
crude oil sample was subsequently crushed. Immediately, the spectra (Figure 6d) still showed only isolated peaks of
modest intensity and not the substantial increase in amu and intensity found in Figure 6b. The crude oil is present
in the microencapsulated sample, but under these aggressive conditions, it does not show appreciable release of the
oil for detection in the mass spectrometer. The mass spectroscopy experiment suggests the microencapsulated crude
oil sample is very stable to physical force as compared to the crude oil that is not irreversibly included in a rock.
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