Treatability Study of Mixed Waste Using Ion Exchange Resins

Ilham AlMahamid

Brian M. Smith

Lawrence Berkeley National Laboratory

EIChroM Users’ Group Workshop, Pleasanton, CA, May 25, 1999

Experimental Objective

By employing innovative treatment technology, meet Land Disposal Restriction waste treatment standards and provide a disposal option for 105 gallons of mixed waste generated by neutralization and consolidation of corrosive mixed wastes from past LBNL research.

Waste Description

Multiphase (solid, organic and aqueous) Presence of regulated metals such as chromium, lead

and mercury at concentrations that render the waste “combustion prohibited”.

Presence of regulated solvents such as chloroform, acetone, and methylene chloride that make combustion the appropriate treatment method.

Waste Characterization, R12

Waste Characterization, R12

Waste Characterization, R13

Waste Characterization for R13

Waste Characterization, R21

Waste Characterization, R21

Experimental Approach

Conduct a treatability study to reduce the concentrations of regulated metals to levels that would remove any combustion prohibition.

Chromium 2.77 mg/L Note: Chromium target in

Mercury 0.15 mg/L R12 is 1,350 mg/L because Lead 0.69 mg/L only half of the 2,700

mg/L

Silver 0.43 mg/L is combustion prohibited.

METHODS

Separate the organic layer (scrape off top)

Separate the sludge (vacuum filtration)

Treat the aqueous phase (resin exchange)

Treatment of the Aqueous Phase

Literature review of resins used to remove actinides and heavy metals from wastes

Diphonix, Radaway, and apatite were selected for further testing

Bench-Scale Studies

Diphonix resin, Radaway slurry, and apatite were added to aliquots of the waste.

Resin to waste ratio was 5 g / 50 mL. Vials were placed on a shaking table (100 rpm) for 24

hours at room temperature. Solutions were filtered and analyzed for actinides and

metals.

Diphonix had high uptake and was easy to handle.

Treatment of R12

Chromium (2,700 mg/L) was determined to be in two forms: Cr(III) and Cr(VI) as chromate from chromic acid

Precipitate chromate by addition of BaCl2. Reduced Cr concentration to ~400 mg/Liter Solution turned from orange to very light yellow. Filtered to remove solids (barium chromate+ barium sulfate).

Passage through the ion-exchange columns.

Semi-Pilot Scale Treatment

The set-up consists of:

– peristaltic pump– on-line filter– series of six columns, three containing diphonix resin

(cationic exchanger) and three containing anionic exchanger.

Results

R12 R13 R213 passes 1 pass 2 passes

Chromium 98.3% 96.0% 37.5%Mercury 99.6% >99.9% 99.9%Lead >50% >87.5% >50%Silver >89.2% >87.5% n.d.

Am-241 86.7% 95.0% 97.4%Np-237 98.9% 99.6% 99.5%Pa-233 98.8% 99.5% 99.2%Pu-239 82.6% n.d. n.d.

Metal and Actinide Removal

Results (continued)

R12 R13 R213 passes 1 pass 2 passes

Antimony 97.5%Copper 93.0% >83%Molybdenum 94.0%Nickel 25.0%Thallium 92.9%Zinc 88.9% 78.0%

Removal of other Metals

Conclusions

The treatment study removed regulated metals to allow combustion as a disposal option for 105 gallons of aqueous mixed waste.

Diphonix is useful in removal of metals and

actinides from aqueous radioactive wastes.

Small amounts of organics such as acetone did not diminish the efficiency of the resin.