Remediation Technologies Screening Matrix, Version 4.0 4.15 Chemical Extraction
(Ex Situ Soil Remediation Technology)
  Description Synonyms Applicability Limitations Site Information Points of Contact
Data Needs Performance Cost References Vendor Info. Health & Safety
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>>3.5 Ex Situ Physical/Chemical Treatment (assuming excavation)

      >>4.15 Chemical Extraction
Introduction>> Waste contaminated soil and extractant are mixed in an extractor, thereby dissolving the contaminants. The extracted solution is then placed in a separator, where the contaminants and extractant are separated for treatment and further use.

Description:

Figure 4-15
Typical Chemical Extraction Process
 

Chemical extraction does not destroy wastes but is a means of separating hazardous contaminants from soils, sludges, and sediments, thereby reducing the volume of the hazardous waste that must be treated. The technology uses an extracting chemical and differs from soil washing, which generally uses water or water with wash-improving additives. Commercial-scale units are in operation. They vary in regard to the chemical employed, type of equipment used, and mode of operation.

Physical separation steps are often used before chemical extraction to grade the soil into coarse and fine fractions, with the assumption that the fines contain most of the contamination. Physical separation can also enhance the kinetics of extraction by separating out particulate heavy metals, if these are present in the soil.

Acid Extraction

Acid can also be used as the extractant. Acid extraction uses hydrochloric acid to extract heavy metal contaminants from soils. In this process, soils are first screened to remove coarse solids. Hydrochloric acid is then introduced into the soil in the extraction unit. The residence time in the unit varies depending on the soil type, contaminants, and contaminant concentrations, but generally ranges between 10 and 40 minutes. The soil-extractant mixture is continuously pumped out of the mixing tank, and the soil and extractant are separated using hydrocyclones.

When extraction is complete, the solids are transferred to the rinse system. The soils are rinsed with water to remove entrained acid and metals. The extraction solution and rinse waters are regenerated using comercially available precipitants, such as sodium hydroxide, lime, or other proprietary formulations, along with a flocculent that removes the metals and reforms the acid. The heavy metals are concentrated in a form potentially suitable for recovery. During the final step, the soils are dewatered and mixed with lime and fertilizer to neutralize any residual acid.

Solvent Extraction

Solvent extraction is a common form of chemical extraction using organic solvent as the extractant. It is commonly used in combination with other technologies, such as solidification/stabilization, incineration, or soil washing, depending upon site-specific conditions. Solvent extraction also can be used as a stand alone technology in some instances. Organically bound metals can be extracted along with the target organic contaminants, thereby creating residuals with special handling requirements. Traces of solvent may remain within the treated soil matrix, so the toxicity of the solvent is an important consideration. The treated media are usually returned to the site after having met Best Demonstrated Available Technology (BDAT) and other standards.

The duration of operations and maintenance for chemical extraction is medium-term.

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Synonyms:

DSERTS Codes:

N16 (Acid Extraction)
N17 (Solvent Extraction)

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Applicability:

Solvent extraction has been shown to be effective in treating sediments, sludges, and soils containing primarily organic contaminants such as PCBs, VOCs, halogenated solvents, and petroleum wastes. The process has been shown to be applicable for the separation of the organic contaminants in paint wastes, synthetic rubber process wastes, coal tar wastes, drilling muds, wood-treating wastes, separation sludges, pesticide/insecticide wastes, and petroleum refinery oily wastes.

Acid extraction is suitable to treat sediments, sludges, and soils contaminated by heavy metals.

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Limitations:

Factors that may limit the applicability and effectiveness of the process include:
  • Some soil types and moisture content levels will adversely impact process performance.
  • Higher clay content may reduce extraction efficiency and require longer contact times.
  • Organically bound metals can be extracted along with the target organic pollutants, which restricts handling of the residuals.
  • The presence of detergents and emulsifiers can unfavorably influence the extraction performance.
  • Traces of solvent may remain in the treated solids; the toxicity of the solvent is an important consideration.
  • Solvent extraction is generally least effective on very high molecular weight organic and very hydrophilic substances.
  • After acid extraction, any residual acid in treated soil needs to be neutralized.
  • Capital costs can be relatively high and the technology may be more economical at larger sites.
  • Meeting highly stringent heavy metals criteria (e.g., passing the California WET test) may prove uneconomical.

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Data Needs:

A detailed discussion of these data elements is provided in Subsection 2.2.1 (Data Requirements for Soil, Sediment, and Sludge). It is important to determine whether mass transfer or equilibrium will be controlling. The controlling factor is critical to the design of the unit and to the determination of whether the technology is appropriate for the waste.

Soil properties that should be determined include particle size; pH; partition coefficient; cation exchange capacity; organic content; TCLP; moisture content; and the presence of metals, volatiles, clays, and complex waste mixtures.

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Performance Data:

The performance data currently available are mostly from Resource Conservation Company (RCC). The ability of RCC's full-scale B.E.S.T.TM process to separate oily feedstock into product fractions was evaluated by EPA at the General Refining Superfund site near Savannah, Georgia, in February 1987. The treated soils from this unit were backfilled to the site, product oil was recycled as a fuel oil blend, and the recovered water was pH-adjusted and transported to a local industrial wastewater treatment facility.

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Cost:

The key cost driver information and cost analysis was developed in 2006 using the Remedial Action Cost Engineering and Requirements (RACER) software.

Key Cost Drivers 

        Economy of Scale

o       Quantity of material treated has a large impact

        Moisture content in waste

o       Slight increase in costs between soil and sludge

Cost Analysis

The following table represents estimated costs (by common unit of measure) to apply chemical extraction technology at sites of varying size and complexity.   A more detailed cost estimate table which includes specific site characteristics and significant cost elements that contributed to the final costs can be viewed by clicking on the link below.

SOIL TECHNOLOGY:

Chemical Extraction

 

RACER PARAMETERS

Scenario A

Scenario B

Scenario C

Scenario D

Small Site

Large Site

Easy

Difficult

Easy

Difficult

 

 

 

 

 

COST PER CUBIC FOOT

$45

$49

$10

$10

COST PER CUBIC METER

$1,582

$1,717

$358

$361

COST PER CUBIC YARD

$1,202

$1,305

$272

$275

 Detailed Cost Estimate

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References:


Treatment Technologies for Site Cleanup: Annual Status Report (ASR), Tenth Edition, EPA 542-R-01-004

Innovative Remediation Technologies:  Field Scale Demonstration Project in North America, 2nd Edition

Remediation Technology Cost Compendium - Year 2000

Groundwater Cleanup: Overview of Operating Experience at 28 Sites, September 1999, EPA 542-R-99-006,

Potential Applicability of Assembled Chemical Weapons Assessment Technologies to RCRA Waste Streams and Contaminated Media, August 2000, EPA 542-R-00-004

Treatment Experiences at RCRA Corrective Actions, December 2000, EPA 542-F-00-020

Abstracts of Remediation Case Studies, Volume 4,  June, 2000, EPA 542-R-00-006

Guide to Documenting and Managing Cost and Performance Information for Remediation Projects - Revised Version, October, 1998, EPA 542-B-98-007

California Base Closure Environmental Committee (CBCEC), 1994. Treatment Technologies Applications Matrix for Base Closure Activities, Revision 1, Technology Matching Process Action Team, November, 1994.

DOE, April 1995. Technology Catalogue, Second Edition, Office of Environmental Management & Office of Technology Development, DOE/EM-0235.

EPA, 1988. Evaluation of the B.E.S.T.TM Solvent Extraction Sludge Treatment Technology Twenty-Four Hour Test, EPA/600/2-88/051.

EPA, 1988. Technology Screening Guide for Treatment of CERCLA Soils and Sludges Appendix B.1: Chemical Extraction, EPA, Washington, DC, EPA/540/2-88/004.

EPA, 1989. Innovative Technology: B.E.S.T.TM Solvent Extraction Process, OSWER Directive 9200.5-253FS.

EPA, 1990. CF Systems Organics Extraction Process New Bedford Harbor, MA, Applications Analysis Report, Superfund Innovative Technology Evaluation, Washington, DC, EPA/540/A5-90/002. Available from NTIS, Springfield, VA, Order No. PB91-1133845.

EPA, 1990. CF Systems Corp. Solvent Extraction, EPA RREL, series includes Technology Evaluation Vol. I, 540/5-90/001; Technology Evaluation Vol. II, EPA/540/5-90/002a, PB90-186503; Application Analysis, EPA/540/A5-90/002; and Technology Demonstration Summary, EPA/540/S5-90/002.

EPA, 1990. Solvent Extraction Treatment, Engineering Bulletin, EPA, OERR and ORD, Washington, DC, EPA/540/2-90/013.

EPA, 1993. Terra Kleen Solvent Extraction Technology Terra Kleen Response Group, Inc., EPA RREL, Demonstration Bulletin, EPA/540/MR-94/521.

Federal Remediation Technologies Roundtable, 1998. Remediation Case Studies: Ex Situ Soil Treatment Technologies (Bioremediation, Solvent Extraction, Thermal Desorption), EPA/542/R-98/011.

Raghavan, R., D.H. Dietz, and E. Coles, 1988. Cleaning Excavated Soil Using Extraction Agents: A State-of-the-Art Review, EPA Releases Control Branch, Edison, NJ, EPA Report EPA 600/2-89/034.

 

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Site Information:

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Points of Contact:

General FRTR Agency Contacts

Technology Specific Web Sites:

Non Government Web Sites

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Vendor Information:

A list of vendors offering Ex Situ Physical/Chemical Soil Treatment is available from EPA REACH IT which combines information from three established EPA databases, the Vendor Information System for Innovative Treatment Technologies (VISITT), the Vendor Field Analytical and Characterization Technologies System (Vendor FACTS), and the Innovative Treatment Technologies (ITT), to give users access to comprehensive information about treatment and characterization technologies and their applications.

Government Disclaimer

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Health and Safety:

Hazard Analysis

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