United States
                        Environmental Protection
                                              Office of
                                              Solid Waste and
                                              Emergency Response
                                                  March 1992
                 A  Citizen's  Guide  To
                 Solvent  Extraction
Technology Innovation Office.
                                                               .Technology Fact Sheet
 What Is Solvent

 How Doss ft Work?

 Why Consider Solvent

 What Contaminant*
 Can It Treat?

 Will ft Work At
 Every Site?

 Where l* Solvent
 Extraction Being

 For More Information



What Is Solvent Extraction?

Solvent extraction is a treatment
technology that uses a solvent (a fluid
that can dissolve another substance) to
separate or remove hazardous organic
contaminants from sludges, sediments,
or soil. (Sludge is a mud-like material
produced from industrial or sewage
waste and sediment is fine-grained rock
and mineral fragments which have
settled to the bottom of a water body
such as a river or lake.)  Solvent
extraction does not destroy
contaminants.  It concentrates them so
they can be recycled or destroyed. It is
used in combination with other
technologies to destroy the separated
concentrated contaminants.

When the soil enters an extractor (a
tank where the contaminated soil is
mixed with the solvent), the soil is
separated into three components, or
fractions: solvent with dissolved
contaminants, solids, and water.
Contaminants are concentrated into
each of these fractions. For example,
PCBs (polychlorinated biphenyls)
concentrate in the contaminated solvent
mixture, while metals are left behind in
the solids and water. Each fraction can
then be individually treated or disposed
of more cost effectively. A simplified
drawing of the solvent extraction
process is illustrated in Figure 1 on page
2. The solvent extraction process
involves five steps:

•  Preparation (screening the contami-
   nated material)

•  Extraction

•  Separation of concentrated contami-
   nants from solvent

   Removal of residual solvent

•  Contaminant recovery, recycling, or
   further treatment

These are explained in the following
                             Solvent Extraction Profile

Separates contaminants so they may be treated Individually.

Is a transportable technology that can be brought to the site.

Reduces volume of contaminated material.

Processes from 24 to over 100 tons of waste per day.

)s designed to operate without air emissions.
                                                       04, Environmental Protection Agency
                                                       Region 5, Library (PM2J)
 Produced by the
 Superfund Program
                                            Printed on Recycled Paper

How Does It Work?

Treatment of contaminated soil will be discussed in this
guide, but the method would be essentially the same for
treatment of sludges or sediments.

The process begins by digging up the contaminated soil and
moving it to a staging area (a place where contaminated
material is prepared for treatment). The soil is then sifted to
remove debris and large objects, such as rocks. The soil
may be processed in either a batch, a semi-batch, or a
continuous mode. In the semi-batch mode, the material is
cycled through the extraction unit in increments.  If the soil
is processed continuously, it may need to be made more
fluid so it can move easily through the process by pumping.
This is accomplished by adding water or, in the case of oily
sludges, adding solvents to the material.

The soil is placed in the extractor. Extractors can vary in
size. Some process 24 tons per day while others may treat
over 100 tons daily. The larger systems may require a set
up area of more than 4,000 square feet. This is about the
size of a tennis court. The solvent is poured into the
extractor, and the soil and solvent are mixed together.
Consequently, the organic contaminants dissolve into the
    A number of factors control the speed with which
    contaminants are dissolved from the soil. Some of these
    controlling factors include temperature, moisture content,
    and the level of contamination. Each is critical to the design
    of the treatment.  Treatability studies performed in a
    laboratory are required to determine how much solvent is
    needed and how long the material must remain in the
    extractor in order to assure maximum effectiveness.  Since
    some solids may contain contaminants that require more
    than one cycle in the extractor for the solids to become
    nonhazardous, this step of the process may require

    The extraction process produces three fractions:

    •    The contaminated solvent mixture, which is removed
        from the mixing tank and passed to a separation tank;

    •    The treated soil or sludge (Depending on the
        concentrations of contaminants present in the solids, the
        solids may require a repeat cycle or further treatment by
        some other technique);

        The water, which must be analyzed to determine if
        further treatment is necessary before discharge to either
        a publicly-owned treatment plant or other approved
        discharge area.
                                                    Figure 1
                                       Solvent Extraction Process Flow
      Ť• *f *f ff -V if *V •.
 ^ ifif'f 'f 'f-f-Sif'f'f-S • i
      Contaminated Soil
                              Again If
                                                Recycled Solvent

                                                Solvent with
                                                  Organic    ťJ
                                                                                             (Further Treatment
                                                                                                or Disposal)
                                    Treated Solids
       Oversized Rejects
      (Boulders, Logs, Etc.)
   To OtherTreatment/Disposal

The separation process occurs next The contaminated
solvent mixture flows to the separation tank.  Here, the
pressure and temperature are changed, causing the organic
contaminants to separate from the solvent or the solvent is
extracted with another solvent At the completion of this
step, concentrated contaminants result Concentrated
contaminants are removed from the separation tank, and the
solvent is sent to  the mixing tank for reuse. These
contaminants are then analyzed to determine their suitability
for recycle/reuse, or need for further treatment before

Solvent extraction units are designed to operate without air
emissions. However, at some sites volatile air emissions
could occur during excavation or preparation of
contaminated soil. If air emissions exceed applicable
regulatory standards, then waste preparation and handling
procedures must be modified to meet the standards.

Why Consider Solvent Extraction?

Solvent extraction is both an effective and cost efficient
process for separating hazardous contaminants from non-
hazardous materials and concentrating the hazardous
materials for further treatment Because the contaminants
are separated, the treatment selected can be targeted to the
contaminant.  As a result of solvent extraction, many of the
contaminants may be recycled or reused in manufacturing,
thus minimi/ing disposal requirements. The process has
been effective in removing organic contaminants from paint
wastes, synthetic  rubber process wastes, coal tar wastes,
drilling muds, wood treating wastes, pesticide/ insecticide
wastes, and oily wastes.

What Contaminants Can It Treat?

Solvent extraction has been shown to be effective in treating
sediments, sludges, and soils containing primarily organic
contaminants, such as polychlorinated biphenyls (PCBs),
volatile organic compounds (VOCs), halogenated solvents
(solvents containing halogens, which are bromine, chlorine,
or iodine), and petroleum wastes. These contaminants
typically come from metal degreasing, printed circuit board
cleaning, gasoline, and wood preserving manufacturing
processes. Table  1 lists the solvents that are used. This
technology is generally not used for removing inorganics
(i.e., acids, bases, salts, and heavy metals) as these materials
do not readily dissolve in most solvents. Other treatment
methods can be applied to these contaminants.

Will  It Work At Every Site?

Solvent extraction is effective at separating hazardous
organic contaminants from soils, sludges and sediments. It
does not reduce the toxicity of the contaminants and,
therefore, additional treatment techniques must be used
during the clean-up. Some of the limitations of this
technology include:

    •   If the waste contains detergents or strong acids or
        bases, solvent extraction may not be effective.
        Their presence can reduce the amount of
        contamination removed and inhibit the speed with
        which the contaminants can be removed.

    •   The presence of lead and other inorganics may
        interfere with the removal of organic materials.

    •   Implementation can require complex engineering
        considerations. For example, some systems
        include compressed butane and propane, which
        require strict management to prevent them from
        vaporizing and becoming flamable.
  ť_ťť~_Ťť^-—------••——-•—---•ť-•-—•-—--———-———i   m^
    What Is An Innovative Treatment

    Treatment technologies are processes applied
    to the treatment of hazardous waste or
    contaminated materials lo permanently after
    their condition through chemical, biological, or
    physical means. Technologies that have been
    tested, selected or used for treatment of
    hazardous waste or contaminated materials but
    lack well-documented cost and performance
    data under a variety of operating conditions are
    called innovative treatment technologies.
 •s^  	,>

Where Is Solvent Extraction Being

Solvent extraction has been selected as a treatment method
at several Superfund sites. Table 2 on page 4 lists some
sites, their locations, and the types of facilities.  In addition
to using this technology at Superfund sites, solvent
extraction is also commonly used by manufacturers in their
day-to-day operations.  Since solvents are expensive raw
materials that can be reused, manufacturers,  such as the
drycleaning and perfume industries, regularly recycle the
solvents used in their manufacturing processes.
                      Table 1
 Solvents Used In The Solvent Extraction Process
                Liquid Carbon Dioxide





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       77 West Jackson Boulevard, 12ih Floor
       Chicago, IL  60604-3590

                                                 Table 2
                       Site Locations Where Solvent Extraction Has Been Selected*
   Site                                   Location                          Type of Facility

   Norwood                              Massachusetts                     Industrial Waste Dumping

   O'Connoc                              Maine                             Salvage and Electrical
                                                                            Transformer Recycling

   Pinette's Salvage Yard                 Maine                             Salvage and Vehicle Repair

   Ewan Property                         New Jersey                        Industrial Waste Dumping

   General Refining                       Georgia                           Abandoned Waste Oil
                                                                            Recycling Facility

   Traband Warehouse                   Oklahoma                         Abandoned Storage
                                                                            Management Complex

   'All waste types and soil conditions are not similar. Each site must be individually investigated and tested. Engineer-
   ing and scientific judgment must be used to determine if a technology is appropriate for a site.
    For More information

    EPA prepared this fact sheet to provide basic Information on solvent extraction. Additional technical reports
    are listed below. The documents containing a "PB" designation are available by contacting the National
    Technical Information Service (NT1S) at 1-800-336-4700.  Mali orders can be sent to:

                              National Technical Information Service
                              Springfield, VA 22161

    Other documents may be obtained by contacting:

                              Center for Environmental Research Information
                              26 West Martin Luther King Drive
                              Cincinnati, OH 45268

    There may be a charge for these documents.

        •   Applications Analysis Report - CF Systems Organic Extraction System, New Bedford, MA, EPA/540/

        •   Evaluation of BEST Solvent Extraction Sludge Treatment Technology 24 Hour Test, PB88-245907.

        •   Innovative Technology: BEST Solvent Extraction Process, EPA/9200.5-253FS; PB90-274218.

        •   Engineering Bulletin, Solvent Extraction Treatment, September 1990, EPA/540/2-90/013.
NOTICE: This fact sheet is intended solely as general guidance and information. It is not intended, nor can it be relied upon, to create any rights enforceable by any
party in litigation with the United States. The Agency also reserves the right to change this guidance at any time without public notice.

                                                     4                    'U.S. Government Priming Office: 1992—648-080/60004