Final Report: Chelating Extraction of Heavy Metals from Contaminated Soils

EPA Grant Number: R825549C052
Subproject: this is subproject number 052 , established and managed by the Center Director under grant R825549
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: HSRC (1989) - Great Plains/Rocky Mountain HSRC
Center Director: Erickson, Larry E.
Title: Chelating Extraction of Heavy Metals from Contaminated Soils
Investigators: Andrew Hong, P. K. , Banerji, Shankha K. , Okey, Robert W.
Institution: University of Utah , University of Missouri - Columbia
EPA Project Officer: Hahn, Intaek
Project Period: June 1, 1994 through September 26, 1997
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (1989) RFA Text |  Recipients Lists
Research Category: Heavy Metal Contamination of Soil/Water , Land and Waste Management


The goal of this project is to assess the full potential of chelating extraction technology in removing and/or recovering heavy metals from contaminated media, e.g., soils and mine tailings ponds. A large number of chelators will be examined, and those chelators which are suitable for selective removal or recovery of various heavy metals will be identified.

Summary/Accomplishments (Outputs/Outcomes):

Heavy metal contamination of soil is a common problem encountered at many hazardous waste sites. Lead, chromium, cadmium, copper, zinc, and mercury are among the most frequently observed metal contaminants. They are present at elevated concentrations at many National Priority List sites, are toxic to people, and threaten groundwater supplies. Once released into the soil matrix, most heavy metals are strongly retained and their adverse effects can last for a long time. Chelating extraction of heavy metals from contaminated soils is a relatively new treatment method. There exists a need to assess the full potential of this technology in removing and/or recovering heavy metals from contaminated media. A methodology is needed to examine a large number of chelators and identify those suitable for the selective removal or recovery of various heavy metals. Chelators that are identified, studied, and recommended as a result of this project could be used in on-site soil washing processes following excavation.

Investigators will assess the potential of extracting and recovering heavy metals from contaminated soils using chelators. Results of assessment of a large number of chelators will provide a guide to select suitable chelators for different metals. Equilibrium chemical modeling/calculation and connectivity index modeling will be performed to choose about ten chelators from the initial list for detailed experimental study. Study will be conducted on the extraction and recovery of the seven target metals from collected contaminated soils using ten selected chelators. Investigators will also demonstrate that through a proper choice of functional groups in a chelator, the selectivity of the chelator can be greatly enhanced and that through a proper choice of chelator, extracted mixed metals can be recovered separately through sequential treatment stages. Finally, stability of about six chelators will be evaluated with respect to biodegradation.

Characterization of soil samples was completed for two uncontaminated soil samples and seven samples contaminated with various types and amounts of metals. Chemical equilibrium modeling and connectivity index modeling were completed. The results of chemical equilibrium modeling, and the connectivity index modeling work have been published. Five target heavy metals were extracted using eight chelating agents. Investigators were able to separate and reuse the reclaimed chelating agents using only pH adjustment for those chelating agents of moderate strength. They were also able to effectively recover the strongest chelators using cationic and/or anionic precipitants. The mechanisms of loss of the chelators were investigated with ion chromatography. Optimal precipitant dosages to enhance recovery and minimize loss were studied. Investigators were able to recover a single metal at a time from mixed metals extraction solutions. The biodegradation of DTPA and ADA was evaluated.

The following chelators were tested for extraction and recovery of various metals from spiked and authentic contaminated soils:

a) N-(2-acetamindo)iminodiacetic acid (ADA) for Pb (spiked, authentic), Zn (spiked)
b) S-carboxymethyl-L-cysteine (SCMC) for Pb (spiked, authentic), Cu (spiked, authentic)
c) Pyridine-2,6-dicarboxylic acid (PDA) for Pb (spiked, authentic), Cd (spiked)

The results showed that 1) Pb, Cu, Cd, Zn can be extracted from contaminated soils using various chelating agents ADA, PDA, and SCMC; 2) the metals can be readily separated and recovered as metal precipitates by simply raising the solution pH; 3) the chelators that remained in solution after separation were successfully reused for further extraction during consecutive runs. The results suggest that ADA is particularly effective for extraction of Pb while SCMC is especially effective for Cu. The extent of extraction depends on contact time and chelator concentration, but does not depend on extraction pH or soil suspension. The extraction results have been consistent with equilibrium calculations using published thermodynamic constants.

Additional chelators were tested for extraction and recovery of 5 target metals including Pb, Cu, Cd, Ni, and Zn from spiked and authentic contaminated soils, which include:

d) thiazolidine-4-carboxylic acid (C4H7O2NS),
e) nitrilotris(methylene)triphosphonic acid (C3H12O9NP3),
f) triethylenetetraamine (C6H18N4),
g) 2-acryloylamido-2-methylpropanesulfonic acid (C7H13NO4S),
h) 1,3-diaminopropane-N,N,N',N'-tetraacetic acid (C11H18N2O8),
i) L-cystine (C6H12O4N2S2),
j) Ethylenediaminetetraacetic acid (EDTA, C10H16O8N2)
k) Diethylenetriamine-pentaacetic acid (DTPA, C14H23N3O10)

These chelators include those of high and moderate strength as well as those well-tested strong chelators EDTA and DTPA. Chelators d, e, and f demonstrated chelation ability similar to that of previously reported chelator SCMC, ADA, and PDA. Chelators g, h, and I showed strong preference for target metals rather than alkali cations, while chelators j and k show the strongest chelation ability as expected.

The recovery of chelating agents (d-k, above) was enhanced by the addition of cationic (e.g., Ca2+, Fe3+) or anionic precipitants (e.g., HS-/S2-, HCO32-, HPO42-/PO43-). The calcium and Fe3+ ions are proven to compete with the target heavy metals for the chelating agents, thus aiding the release of the metals as hydroxides during the recovery process. The sulfide is most effective in recovering the target metals while carbonated and phosphate is only marginally effective. The extraction and recovery of five target metals (Pb, Cu, Ni, Zn) were repeated for four to five times using the reclaimed chelating agents. The slight to moderate loss of chelating agents was characterized, the mechanism of loss was investigated using the ion chromatographic technique.

Dr. Banerji, Co-PI of this project, and his research group at the University of Missouri-Columbia studied the biodegradation of chelating agents EDTA, SCMC, and PDA under experimental conditions simulating intended soil extraction application. They found that different chelating agents displayed different levels of resistance to biodegradation. The ease of biodegradation followed this increasing order: EDTA<SCMC<PDA, with EDTA being most resistant to biodegradation. Biodegradation study for additional chelators including ADA and DTPA has also been conducted using acclimated cultures from Columbia wastewater. Results show that ADA is somewhat resistant to biodegradation and that DTPA can be degraded by 50% in about 10 days. Intensive studies have been conducted to determine the behavior of these compounds under different conditions.

This project has made significant advances in the field of soil remediation using chelation technology. Throughout the project period we have been communicating our findings to the technical community through traditional means including journal publications, workshop presentations, conference presentations, and publications of theses and reports.

In addition, we have contacted 150 public agencies and private companies through the University of Utah Technology Transfer Office on a related heavy metals recovery technology and thus established a database of potential users of this remediation technology. Three of those contacted responded with a strong interest in following the development and possible commercialization of the research results. SMC (Strohschen Management Consultants) has expressed a strong interest in the technology. However, the company and its clients would like to see more demonstration results at a larger scale than bench top.

Journal Articles on this Report : 7 Displayed | Download in RIS Format

Other subproject views: All 28 publications 8 publications in selected types All 7 journal articles
Other center views: All 904 publications 230 publications in selected types All 182 journal articles
Type Citation Sub Project Document Sources
Journal Article Chen TC, Hong A. Chelating extraction of lead and copper from an authentic contaminated soil using N-(2-acetamido)iminodiacetic acid and S carboxymethyl-L-cysteine. Journal of Hazardous Materials 1995;41(2-3):147-160. R825549C052 (Final)
not available
Journal Article Chen TC, Macauley E, Hong A. Selection and test of effective chelators for removal of heavy metals from contaminated soils. Canadian Journal of Civil Engineering 1995;22(6):1185-1197. R825549C052 (Final)
not available
Journal Article Hong APK, Chen TC. Chelating extraction and recovery of cadmium from soil using pyridine-2,6-dicarboxylic acid. Water Air and Soil Pollution 1996;86(1-4):335-346. R825549C052 (Final)
not available
Journal Article Hong PKA, Li C, Banerji SK, Regmi T. Extraction, recovery, and biostability of EDTA for remediation of heavy metal-contaminated soil. Journal of Soil Contamination 1999;8(1):81-103 R825549C052 (Final)
not available
Journal Article A. Hong, C. Li, "Improved recovery of heavy metals and chelating agents following soil extraction." J. Environ. Eng., in revision. R825549C052 (Final)
not available
Journal Article Hong A, Chen TC, Okey RW. Chelating extraction of copper from soil using s-carboxymethylcysteine. Water Environment Research 1995;67(6):971-978. R825549C052 (Final)
not available
Journal Article Macauley E, Hong A. Chelation extraction of lead from soil using pyridine-2,6-dicarboxylic acid. Journal of Hazardous Materials 1995;40(3):257-270. R825549C052 (Final)
not available

Supplemental Keywords:

heavy metals, chelators, extraction, lead, copper., Scientific Discipline, Waste, Water, Contaminated Sediments, Remediation, Environmental Chemistry, Geochemistry, Analytical Chemistry, Ecology and Ecosystems, contaminant transport, contaminated sediment, hazardous waste, chelating extraction, soil washing, contaminated soil, mining waste, heavy metal contamination

Relevant Websites: Exit

Progress and Final Reports:

Original Abstract
  • 1994
  • 1995
  • 1996

  • Main Center Abstract and Reports:

    R825549    HSRC (1989) - Great Plains/Rocky Mountain HSRC

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R825549C006 Fate of Trichloroethylene (TCE) in Plant/Soil Systems
    R825549C007 Experimental Study of Stabilization/Solidification of Hazardous Wastes
    R825549C008 Modeling Dissolved Oxygen, Nitrate and Pesticide Contamination in the Subsurface Environment
    R825549C009 Vadose Zone Decontamination by Air Venting
    R825549C010 Thermochemical Treatment of Hazardous Wastes
    R825549C011 Development, Characterization and Evaluation of Adsorbent Regeneration Processes for Treament of Hazardous Waste
    R825549C012 Computer Method to Estimate Safe Level Water Quality Concentrations for Organic Chemicals
    R825549C013 Removal of Nitrogenous Pesticides from Rural Well-Water Supplies by Enzymatic Ozonation Process
    R825549C014 The Characterization and Treatment of Hazardous Materials from Metal/Mineral Processing Wastes
    R825549C015 Adsorption of Hazardous Substances onto Soil Constituents
    R825549C016 Reclamation of Metal and Mining Contaminated Superfund Sites using Sewage Sludge/Fly Ash Amendment
    R825549C017 Metal Recovery and Reuse Using an Integrated Vermiculite Ion Exchange - Acid Recovery System
    R825549C018 Removal of Heavy Metals from Hazardous Wastes by Protein Complexation for their Ultimate Recovery and Reuse
    R825549C019 Development of In-situ Biodegradation Technology
    R825549C020 Migration and Biodegradation of Pentachlorophenol in Soil Environment
    R825549C021 Deep-Rooted Poplar Trees as an Innovative Treatment Technology for Pesticide and Toxic Organics Removal from Soil and Groundwater
    R825549C022 In-situ Soil and Aquifer Decontaminaiton using Hydrogen Peroxide and Fenton's Reagent
    R825549C023 Simulation of Three-Dimensional Transport of Hazardous Chemicals in Heterogeneous Soil Cores Using X-ray Computed Tomography
    R825549C024 The Response of Natural Groundwater Bacteria to Groundwater Contamination by Gasoline in a Karst Region
    R825549C025 An Electrochemical Method for Acid Mine Drainage Remediation and Metals Recovery
    R825549C026 Sulfide Size and Morphology Identificaiton for Remediation of Acid Producing Mine Wastes
    R825549C027 Heavy Metals Removal from Dilute Aqueous Solutions using Biopolymers
    R825549C028 Neutron Activation Analysis for Heavy Metal Contaminants in the Environment
    R825549C029 Reducing Heavy Metal Availability to Perennial Grasses and Row-Crops Grown on Contaminated Soils and Mine Spoils
    R825549C030 Alachlor and Atrazine Losses from Runoff and Erosion in the Blue River Basin
    R825549C031 Biodetoxification of Mixed Solid and Hazardous Wastes by Staged Anaerobic Fermentation Conducted at Separate Redox and pH Environments
    R825549C032 Time Dependent Movement of Dioxin and Related Compounds in Soil
    R825549C033 Impact of Soil Microflora on Revegetation Efforts in Southeast Kansas
    R825549C034 Modeling the use of Plants in Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances
    R825549C035 Development of Electrochemical Processes for Improved Treatment of Lead Wastes
    R825549C036 Innovative Treatment and Bank Stabilization of Metals-Contaminated Soils and Tailings along Whitewood Creek, South Dakota
    R825549C037 Formation and Transformation of Pesticide Degradation Products Under Various Electron Acceptor Conditions
    R825549C038 The Effect of Redox Conditions on Transformations of Carbon Tetrachloride
    R825549C039 Remediation of Soil Contaminated with an Organic Phase
    R825549C040 Intelligent Process Design and Control for the Minimization of Waste Production and Treatment of Hazardous Waste
    R825549C041 Heavy Metals Removal from Contaminated Water Solutions
    R825549C042 Metals Soil Pollution and Vegetative Remediation
    R825549C043 Fate and Transport of Munitions Residues in Contaminated Soil
    R825549C044 The Role of Metallic Iron in the Biotransformation of Chlorinated Xenobiotics
    R825549C045 Use of Vegetation to Enhance Bioremediation of Surface Soils Contaminated with Pesticide Wastes
    R825549C046 Fate and Transport of Heavy Metals and Radionuclides in Soil: The Impacts of Vegetation
    R825549C047 Vegetative Interceptor Zones for Containment of Heavy Metal Pollutants
    R825549C048 Acid-Producing Metalliferous Waste Reclamation by Material Reprocessing and Vegetative Stabilization
    R825549C049 Laboratory and Field Evaluation of Upward Mobilization and Photodegradation of Polychlorinated Dibenzo-P-Dioxins and Furans in Soil
    R825549C050 Evaluation of Biosparging Performance and Process Fundamentals for Site Remediation
    R825549C051 Field Scale Bioremediation: Relationship of Parent Compound Disappearance to Humification, Mineralization, Leaching, Volatilization of Transformaiton Intermediates
    R825549C052 Chelating Extraction of Heavy Metals from Contaminated Soils
    R825549C053 Application of Anaerobic and Multiple-Electron-Acceptor Bioremediation to Chlorinated Aliphatic Subsurface Contamination
    R825549C054 Application of PGNAA Remote Sensing Methods to Real-Time, Non-Intrusive Determination of Contaminant Profiles in Soils
    R825549C055 Design and Development of an Innovative Industrial Scale Process to Economically Treat Waste Zinc Residues
    R825549C056 Remediation of Soils Contaminated with Wood-Treatment Chemicals (PCP and Creosote)
    R825549C057 Effects of Surfactants on the Bioavailability and Biodegradation of Contaminants in Soils
    R825549C058 Contaminant Binding to the Humin Fraction of Soil Organic Matter
    R825549C059 Identifying Ground-Water Threats from Improperly Abandoned Boreholes
    R825549C060 Uptake of BTEX Compounds by Hybrid Poplar Trees in Hazardous Waste Remediation
    R825549C061 Biofilm Barriers for Waste Containment
    R825549C062 Plant Assisted Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances: Experimental and Modeling Studies
    R825549C063 Extension of Laboratory Validated Treatment and Remediation Technologies to Field Problems in Aquifer Soil and Water Contamination by Organic Waste Chemicals