Grantee Research Project Results

2004 Progress Report: Arsenic Removal and Stabilization with Synthesized Pyrite

EPA Grant Number: R831276C002
Subproject: this is subproject number 002 , established and managed by the Center Director under grant CR831276
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Organotypic Culture Models For Predictive Toxicology Center
Center Director: Rusyn, Ivan
Title: Arsenic Removal and Stabilization with Synthesized Pyrite
Investigators: Batchelor, Bill
Institution: Texas A & M University
EPA Project Officer: Aja, Hayley
Project Period: December 1, 2003 through November 30, 2004
Project Period Covered by this Report: December 1, 2003 through November 30, 2004
Project Amount: Refer to main center abstract for funding details.
RFA: Gulf Coast Hazardous Substance Research Center (Lamar University) (1996) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , Targeted Research

Objective:

Arsenic is the second most commonly found contaminant of concern both at sites on the National Priority List (NPL) and at sites under U.S. Department of Energy control. Furthermore, tighter regulations on allowable levels of arsenic may make remediation more difficult and costly. Improved techniques for removal of arsenic from contaminated media that produce more stable residuals are needed. Pyrite is a compound that can remove arsenic and produce residuals that are stable under anaerobic conditions found in landfills. Recent research has demonstrated how to produce micro- and nano-sized pyrite crystals, which have high specific surface areas that lead to high capacities to adsorb arsenic. Although the initial removal mechanism would be adsorption, chemical reactions have been reported to form more stable surface phases that are similar to arsenopyrite (FeAsS). This compound is stable for geologic time periods and is very insoluble under reducing conditions. The objective of this research project is to develop a novel treatment method for removal of arsenic from water and stabilization of arsenic contaminated soils, sediments, and sludges based on application of micro- and nanosized synthesized pyrite.

Progress Summary:

The Quality Assurance Project Plan for the project was developed and submitted to the Center in December 2003. A companion project has been initiated with funding from the Texas Advanced Technology Program with a goal of developing contacting methods for applying synthesized pyrite in treatment technologies for removal of arsenic from drinking water. As such, it will complement the work on the current project.

A graduate research assistant (Mr. Jinkun Song) has been hired to conduct the laboratory research on this project. He has conducted a literature review covering methods of analyzing arsenic species, methods of quantitative analysis of pyrite, and methods of synthesizing pyrite. He has demonstrated his ability to analyze arsenic using the hydride generation atomic absorption (HGAA) spectrometry method. Review of the literature indicated that a simple procedure could be used to measure concentrations of pyrite in a mixture of iron sulfides. The procedure is based on the observation that iron sulfides are soluble in HCl, whereas pyrite is not. Pyrite, however, can be dissolved in HNO3, and the iron released can be measured easily by colorimetric procedures. Therefore, the HCl-insoluble iron can be measured and used to quantify pyrite. This procedure was developed and tested. It showed reasonable accuracy (90% recovery) and good precision (1% relative standard deviation) when applied to mineral pyrite obtained from commercial sources. Recoveries below 100 percent probably are the result of impurities in the mined pyrite. A source of mined pyrite with well defined purity has been identified and will be used to document the accuracy of the method.

The procedure of Wei and Osseo-Asare (1996) was applied to synthesize pyrite. Equal volumes (5 mL) of FeCl3 (0.033 M) and NaHS (0.067 M) were mixed and allowed to react in an anaerobic chamber. The products were analyzed for pyrite-iron and the presence of pyrite was confirmed by X-ray diffractometry (XRD). Recoveries of pyrite-iron and total iron were measured as a function of pH and approached 100 percent around pH 4. XRD analysis confirmed that pyrite was formed in the pH range from 3 to 6, with an optimum near pH 4. The effect of aging time on pyrite formation at pH 4.5 was investigated. Pyrite was produced after 2 days with 25 percent of the maximum theoretical yield. More than 80 percent of maximum theoretical yield, however, was achieved in 4 days. The effect of reaction temperature on pyrite formation was evaluated to develop a more rapid method to produce pyrite. Pyrite yields near the theoretical maximum were obtained in less than 1 day when the reaction was allowed to proceed at 67°C. This compares very favorably to 80 percent of maximum yield in 6 days at room temperature. Scanning electron micrography determined that the pyrite particles were around 1 mm in size. Adsorption isotherm tests were conducted with synthesized pyrite and indicate lower capacity than expected. Further characterization of the pyrite is underway.

Future Activities:

The effects of pH, pyrite dose, concentration of interfering ions, and arsenic type on adsorption will be investigated and a chemical equilibrium model developed. The stability of arsenic on the surface of pyrite will be investigated by desorption experiments over a range of pH. The ability of pyrite to stabilize arsenic-contaminated soils will be investigated.

Supplemental Keywords:

arsenite, arsenate, reduced sulfur, polysulfide, waste, ecological risk assessment, environmental engineering, hazardous waste, advanced treatment technologies, bioremediation, contaminated waste sites, groundwater contamination, petroleum contaminants, hydrocarbon,, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Water, Waste, POLLUTANTS/TOXICS, Hazardous, Environmental Chemistry, Engineering, Chemistry, & Physics, Contaminated Sediments, Hazardous Waste, Arsenic, Drinking Water, Environmental Engineering, Soil Contaminants, Water Pollutants, contaminated sediment, contaminant candidate list, hazardous waste treatment, contaminated groundwater, groundwater remediation, remediation, contaminated soil, pyrite, pyrite crystals, drinking water contaminants, groundwater, drinking water treatment, nanotechnology, nano sized pyrite crystals, synthesized pyrite, arsenic exposure, arsenic removal

Relevant Websites:

http://dept.lamar.edu/gchsrc/ Exit
http://phys4.harvard.edu/~wilson/arsenic/arsenic_project_links Exit

Progress and Final Reports:

Original Abstract

Final

Main Center Abstract and Reports:

CR831276    Organotypic Culture Models For Predictive Toxicology Center

Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R831276C001 DNAPL Source Control by Reductive Dechlorination with Fe(II)
R831276C002 Arsenic Removal and Stabilization with Synthesized Pyrite
R831276C003 A Large-Scale Experimental Investigation of the Impact of Ethanol on Groundwater Contamination
R831276C004 Visible-Light-Responsive Titania Modified with Aerogel/Ferroelectric Optical Materials for VOC Oxidation
R831276C005 Development of a Microwave-Induced On-Site Regeneration Technology for Advancing the Control of Mercury and VOC Emissions Employing Activated Carbon
R831276C006 Pollution Prevention through Functionality Tracking and Property Integration
R831276C007 Compact Nephelometer System for On-Line Monitoring of Particulate Matter Emissions
R831276C008 Effect of Pitting Corrosion Promoters on the Treatment of Waters Contaminated with a Nitroaromatic Compounds Using Integrated Reductive/Oxidative Processes
R831276C009 Linear Polymer Chain and Bioengineered Chelators for Metals Remediation
R831276C010 Treatment of Perchlorate Contaminated Water Using a Combined Biotic/Abiotic Process
R831276C011 Rapid Determination of Microbial Pathways for Pollutant Degradation
R831276C012 Simulations of the Emission, Transport, Chemistry and Deposition of Atmospheric Mercury in the Upper Gulf Coast Region
R831276C013 Reduction of Environmental Impact and Improvement of Intrinsic Security in Unsteady-state
R831276C014 Integrated Chemical Complex and Cogeneration Analysis System: Greenhouse Gas Management and Pollution Prevention Solutions
R831276C015 Improved Combustion Catalysts for NOx Emission Reduction
R831276C016 A Large-Scale Experimental Investigation of the Impact of Ethanol on Groundwater Contamination
R831276C017 Minimization of Hazardous Ion-Exchange Brine Waste by Biological Treatment of Perchlorate and Nitrate to Allow Brine Recycle
R831276C018 Integrated Chemical Complex and Cogeneration Analysis System: Greenhouse Gas Management and Pollution Prevention Solutions