Polysiloxane Stabilization at Idaho National Engineering and Environmental Laboratory, Idaho Falls, Idaho

Site Name:

Idaho National Engineering and Environmental Laboratory


Idaho Falls, ID

Period of

1997 - 1998


Field demonstration


Dr. Steve Prewett
Orbit Technologies
Palomar Triad One
2011 Palomar Airport Road, Suite 100
Carlsbad, CA

Stabilization using polysiloxane
- Polysiloxane is a part inorganic part thermosetting polymer; for the demonstration, Orbit Technology's polysiloxane material was used
- The base chemicals (SiH and SiOH) are mixed with the waste and reacted in the presence of a platinum catalyst to form the desired thermosetting polymer and hydrogen gas
- A filler such as quartz can be added to strengthen the waste form
- The resultant vinyl-polydimethyl-siloxane product is gelled, and cured to form a solid waste form
- For the demonstration, the process was tested on three different salt surrogates - Pad-A salts from INEEL, one high chloride salt surrogate, and one high nitrate salt surrogate

Cleanup Authority:

Principal Investigator:
G.G. Loomis
Lockhead Martin
Idaho Technologies Company
P.O. Box 1625 (MS 3710)
Idaho Falls, ID 84315
MWFA Product Line Manager:
Vince Maio, Advisory Engineer
Mixed Waste Focus Area
Lockheed Martin
Idaho Technologies Company
Idaho National Engineering
and Environmental Laboratory
P.O. Box 1625
Idaho Falls, ID 83415
Telephone: 208-526-3696
Fax: 208-526-1061
E-mail: vmaio@inel.gov

Heavy Metals
- hexavalent chromium - 1.045 ppm in one surrogate waste
- oxides of lead, mercury, cadmium, and chromium at 1,000 ppm each in two surrogate wastes

Waste Source:
Salt-containing wastes designed to simulate wastes from DOE operations

Type/Quantity of Media Treated:
Process waste streams

Purpose/Significance of Application:
Demonstration of polysiloxane to encapsulate high-salt content wastes

Regulatory Requirements/Cleanup Goals:
RCRA Land Disposal Restriction (LDR) and DOT
- Target TCLP levels for RCRA heavy metals - cadmium (1.0 mg/L), hexavalent chromium (5.0 mg/L), lead (5.0 mg/L) and mercury (0.2 mg/L); also compared to RCRA universal treatment standards (UTS)
- DOT oxidizer test for nitrate salt wastes
- NRC recommended compressive strength of at least 60 psi

- INEEL Pad-A salt surrogate waste form - met the target TCLP levels; but did not meet the UTS standard for chromium; had a compressive strength of 637 psi
- Chloride salt surrogate waste form - met the target TCLP levels; did not meet the UTS standard for cadmium or chromium
- Nitrate salt surrogate waste form - met the target TCLP levels; did not meet the UTS for chromium or mercury; passed the DOT oxidizer test

Cost Factors:
- Cost for full-scale polysiloxzane treatment are about $8/lb or $573 per cubic foot of salt waste
- The cost for polysiloxane encapsulation is competitive with the baseline technology of Portland cement stabilization

The Mixed Waste Focus Area, a DOE Environmental Management (EM)-50 program, sponsored the development of five low-temperature stabilization methods as an alternative to cement grouting to stabilize salt-containing mixed waste. One of the alternative methods is stabilization using polysiloxane. A demonstration of Orbit Technology's polysiloxane encapsulation process for high-salt content wastes was performed at INEEL on three salt surrogates, representing wastes found at DOE facilities.

The results showed that the polysiloxane process produced a durable waste form for all three high-salt content surrogates. The waste forms met the target TCLP levels for heavy metals, and the more stringent UTS standards for several of the metals tested. The process is currently limited to nonaqueous solid materials. Treatability testing is recommended for specific wastes prior to use of this technology. In addition, long-term durability testing of the polysiloxane waste forms is needed.