Stabilization Using Phosphate Bonded Ceramics at Argonne National Laboratory, Argonne, Illinois

Site Name:

Argonne National Laboratory

Location:

Argonne, IL

Period of
Operation:

Not identified

Cleanup
Type:

Development tests

Technology:
Stabilization using phosphate bonded ceramics
- 50/50 blend of magnesium oxide and monopotassium phosphate powder mixed with water, additives, and waste
- Mixed for 20-30 minutes; waste form set for 2 hours, then cured for 14 days
- Initial testing performed to determine effects of different test scenarios on waste forms conducted on surrogate salt solutions and on surrogate salt waste streams containing activated carbon and ion exchange resins
- alt solutions - saturated solutions of NaNO3 (50-wt%) and NaCl (10-wt%); RCRA metals (Cd, Cr, Pb, and Hg) added at 5,000 mg/kg each; additives included 50-wt% Class-F fly ash and 1-wt% K2S to tie up Hg
- Salt waste streams with activated carbon and ion exchange resins - mix included nitrate, sulfate, and chloride salts (30%), Na2CO3, and CsCl (to simulate a radioactive component)
- Based on results, additional tests were performed on two salt surrogates - one containing a high quantity of nitrate salts (58-wt%); the other high quantities of chloride and sulfates (70-wt%); RCRA metals (Cd, Cr, Pb, Hg, and Ni) added at 1,000 mg/kg each;
- Waste forms tested for density, compressive strength, and flammability (nitrate wastes)

Cleanup Authority:
RCRA and NRC

Principal Investigator:
Arun S. Wagh, Ph.D.
Argonne National Laboratory
9700 South Case Ave
Argonne, IL 60439
Telephone: 630-252-4295
Fax: 630-252-3604
E-mail: arun wagh@gmgate.anl.gov
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

Contaminants:
Metals
- Oxide forms of cadmium, chromium, lead, mercury, and nickel were added to the waste stream at concentrations of 1,000 mg/kg each

Waste Source:
Surrogate waste streams containing high levels of nitrate salts and chloride and sulfates similar to those found at DOE facilities

Type/Quantity of Media Treated:
Salt-containing waste streams

Purpose/Significance of Application:
Demonstration of phosphate-bonded ceramics to stabilize a variety of high salt-containing wastes

Regulatory Requirements/Cleanup Goals:
RCRA Land Disposal Restriction (LDR) standards and NRC guidelines
- Universal Treatment Standards (UTS) for metals
- NRC leach index of 6; compressive strength of 500 psi

Results:
Waste forms from salt solutions of NaNO3 (50-wt%) and NaCL (10-wt%):
- Densities of 1.8 g/cm3 and 1.72 g/cm3, respectively and compressive strengths of 1,800 psi and 3,500 psi, respectively
- Passed the UTS standards for metals, with the exception of Cd; attributed to the less acidic conditions of the test (pH 4) that slowed reaction of Cd with the phosphate; Cd was fully stabilized in subsequent tests at lower pH levels
- Marginally passed leach index criteria with leach levels of 6.86 and 6.7, respectively, indicating slow salt leaching; additional binding or coating techniques may be needed to prevent salt leaching from deteriorating the waste

Waste forms from salt solutions containing activated carbon and ion exchange resins:
- For the 60-wt% and 70-wt% loadings - had densities of 1.24 g/ml and 1.32 g/ml and compressive strengths of 2,224 psi and 5,809 psi, respectively
- Passed the UTS standards for metals

MWFA salt surrogates:
- Had densities in the range of 1.7-2.0 g/cm3 and compressive strength in the range of 1,400-1,900 psi
- Passed the UTS standards for metals
- Leach index results showed that process was only marginally successful in retaining NO3 and CL anions; modifications to the basic formulation for the process were made including adding fly ash to the binder and a polymer coating to the waste form, which increased the leach index to as high as 12.6

Cost Factors:
- Projected cost for full-scale stabilization using phosphate bonded ceramics are capital costs of about $2 million, including equipment design and development, and operating costs of about $6,510 per cubic meter of waste form, including labor and materials; disposal costs are estimated to be $2,836 per cubic meter of waste
- Compared to the baseline technology (basic Portland cement), the operating costs are higher ($6,510 versus $4,300 per cubic meter of waste form), but the disposal costs are lower ($2,836 versus $3,700 per cubic meter of waste)

Description:
A series of development tests were conducted at the Argonne National Laboratory to validate the stabilization of salt-containing wastes using a patented chemically bonded phosphate ceramics (CBPC) process. The low-temperature process uses magnesium oxide and monopotassium phosphate to form a low porosity, dense waste form consisting mainly of a ceramic magnesium potassium phosphate barrier. Various tests were performed using a number of mixed waste surrogates, including saturated salt solutions, salt surrogate containing activated carbon and ion exchange resin, and two MWFA recommended dry salt waste surrogates that represented actual wastes found at DOE facilities.

The results of the tests showed that the waste forms produced by the CBPC process met the RCRA UTS standards for metals and the NRC disposal criteria. Flammability test results showed the waste forms containing oxidizing salts (nitrates) to be stable and safe. Based on the results of the testing, additional testing of the salt waste form is recommended before full-scale deployment, such as the effects of salt anion leaching over time. For different waste streams, additional analytical and development work would be needed to qualify wastes for disposal and to verify the operating parameters for the specific wastes.