Technologies for the stabilization of elemental mercury

Sven HagemannGRS

What is stabilization/ solidification?

• Reduces the mobility of contaminants in the media by physically binding them within stabilized mass mass or inducing chemical reactions (US EPA 2007)   

• Solidification: liquid solid by using additives lid) without changing the chemical properties of the wastes

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Types of stabilization technolgies

Chemical stabilization: Chemical transformation into more stable, less mobile chemical compound

Microencapsulation: Embedment of particles in impermeable matrix (e.g. cement)

Macroencapsulation: Coverage of waste material with impermeable material, e.g. polyethylene

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What is Stabilization of Mercury?

Conversion of liquid, elemental mercury into a much less hazardous solid, e.g. mercury sulphide

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Why stabilization?

• Solid, no risk of liquid spillage

• Mercury vapour pressure below occupational safety limits

• Mercury concentration in leachates below acceptance thresholds for disposal

• Lower commercial value (reduced risk of theft)

Benefits:

Easier and safer to manage, transport, store and dispose

Stabilization and Disposal Options for Mercury Wastes

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Waste contaminated with mercury(e.g. soil, debris)

Waste containing mercury(e.g. end of life products)

Stabilized elemental mercury

Permanent storage in underground mines

Specially engineered landfill

Extraction

Stabilized mercury waste

?

+ Hg free waste

Technologies for the stabilization of elemental mercury

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1. Stabilization as mercury sulphide (HgS) or mercury selenide

2. Stabilization as mercury sulphide in a sulphur / (polymer) / (cement) matrix

3. Stabilization as amalgam

Stabilization as mercury sulphide (HgS) or mercury selenide (HgSe)

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Hg + S HgS

Mercury + Sulfur Mercury sulphide

Identical process with selenium, but much more expensive

+Heat

Stabilization as mercury sulphide in a sulphur / (polymer) / (cement) matrix

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Two steps:

1. Reaction of mercury with sulphur

2. Mixing of mercury sulphide with liquid sulfur (and additives)

+Heat

+ +PolymerCement

PolyethyleneSand

Heat

Amalgam

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Reaction of mercury with another powdered metal (copper, zink)

+

Hg + Cu (Hg,Cu)

Mercury + Copper Copper amalgam

(an alloy)

Update on Stabilization Technologies

• Two new technologies developed by companies in Spain and Germany

• Different approaches, similarily stable products

• Products fulfil US and EU leaching criteria

• One in pilot stadium, another brought to full scale: licensed and commercially used

• Similar processes are under development by other companies

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New Stabilization Technologies -1

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Process developed by German company (2009-2010)

• Mixing of Hg + sulphur under vacuum at 250-350 °C

• Gas phase reaction: pure solid mercury sulphide (cinnabar)

• Full-scale plant in operation: up to 800 kg per batch/ up to 1000 t per year per plant

• Plant constructible as ‘mobile version’ bring plant to waste

Similar processes under development by companys in the USA and France

New Stabilization Technologies -1

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Process developed by German company (2009-2010)

• 200 t Hg already stabilized and disposed (May 2011)

• Cost: 2,000 EUR/ t ~2,800 USD/t (including final disposal)

Similar process under development by a US company

New Stabilization Technologies - 2

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US company (2008-2010)• Addition of Hg to sulphur under vacuum (450-

590°C) • Product: red mercury sulphide• Pilot: 50 kg per batch/ 275 kg per day,

scale-up to 200kg/ batch or higher envisaged• Product: pure red mercury sulphide• Reported cost: 11,000 – 13,000 EUR/ t

New Stabilization Technologies - 3

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Process developed by Spanish company (2009)

1) Stabilization as mercury sulphide by milling mercury with sulphur, then

2) encapsulation in liquid sulphur/ gravel/ sand/ polymer (< 150°C)

• Product: dark brown concrete like material of high physical and chemical durability

• Could be moulded in any form• 2 kg per batch (pilot apparatus),

larger plant under development (2.5 t/ day)

New Stabilization Technologies - 3

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Process developed by Spanish company (2009)

• Estimated costs: 3,500 – 4,500 EUR for full scale plant

Similar processes developed by

• 2 US companies (Mixing of elemental mercury, sulphur polymer and sulphides), one used to stabilize 10 t radioactive mercury

• Korean University (sulpur cement/ polyethylene matrix)

Stabilization Technologies: Amalgamation

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Many companies• Mixing of elemental mercury with metal

powder (e.g. zink or copper)• Well known physical process at room

temperature, no chemical reaction• Product: soft metallic solid• Recommended process for solidification of

radioactive mercury• mercury vapour pressure may be as high as of

elemental mercury (at least for zinc amalgam) not regarded as adequate of non-radioactive mercury

Stabilization Technologies: Conclusion

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1. Stabilization technologies (at least one) available at full-scale

2. Costs start at 2,800 USD/t

3. Product could be transported and stored in drums or big bags: avoid long-term storage of elemental mercury

4. Allows new concept: disposal after stabilization