Chelated Native Iron in Fenton-Like Oxidation of BTEX and PAHs in Soils
Andreas D. Jazdanian, Burns & McDonnell Engineering Company, Oak Brook, IL
Krishna R. Reddy, University of Illinois, Chicago, IL  

Treatment of PCB Contaminated Sediment by Persulfate Oxidation with Pozzolanic Reaction
Sharavan V. Govindan, University of Connecticut, Storrs, CT
George E. Hoag, University of Connecticut, Storrs, CT
Kun-Chang Huang, University of Connecticut, Storrs, CT  

The Adsorption of Chromium to Hydrous Manganese Oxides Produced during In-Situ Oxidation using Permanganate
Kelly A. Frasco, Carus Chemical Company, LaSalle, IL
Elizabeth L. Vlastnik, Carus Chemical Company, LaSalle, IL
Philip A. Vella, Carus Chemical Company, LaSalle, IL  

In-Situ Chemical Oxidation Misfires and Recent Innovative Improvements
Ron Adams, EBSI, Inc., Ponte Vedra, FL
Dr. Bill Mahaffey, Pelorus Labs
Dr. Bill Slack, FRx
Mark Vigneri, EBSI, Inc.

Chelated Native Iron in Fenton-Like Oxidation of BTEX and PAHs in Soils

Andreas D. Jazdanian, Burns & McDonnell Engineering Company, 2601 West 22^nd Street, Oak Brook, IL 60523, Tel: 630-990-0300, Fax: 630-990-0301, Email: ajazdanian@burnsmcd.com
Krishna R. Reddy, University of Illinois, Department of Civil and Materials Engineering, 843 West Taylor Street, Chicago, IL 60607, Tel: 312-996-4755,Fax: 312-996-2426, Email: kreddy@uic.edu

This paper presents the feasibility of using chelated native iron as catalyst in a Fenton-like oxidation of BTEX and PAHs in soils. The catalysts selected for the decomposition of hydrogen peroxide consist of iron-aminopolycarboxylate chelates, specifically iron-ethylene diamine tetraacetic acid (Fe-EDTA) and iron-diethylene triamine pentaacetic acid (Fe-DTPA). DTPA is a stronger chelating agent than EDTA consequently its metal-complexes have a higher stability in alkaline conditions. Carboxylate-ligand complexed iron decomposes hydrogen peroxide to free radicals that oxidize hydrocarbons and chlorinated hydrocarbons. The iron for the chelated-iron complexes (Fe-EDTA and Fe-DTPA) is extracted from the native soil using EDTA and DTPA. Chelate-extractable metals such as calcium (Ca) and magnesium (Mg) are also detached from mineral surfaces through dissolution and desorption. A series of batch tests are conducted using different BTEX and PAH impacted soils and aqueous solutions with various concentrations of EDTA and DTPA as well as various concentrations of hydrogen peroxide. To simulate groundwater in equilibrium with the soil, the aqueous phase is adjusted to the soil pH before it is mixed with the soil for approximately 24 hours. The final pH, conductivity, alkalinity, DOC, and Fe, Ca and Mg-concentrations are determined in the supernatant. The stability of Fe-EDTA and Fe-DTPA complexes is affected by pH and the Ca and Mg activity that develops as a result of the formation of anionic complexes with metal ions. The effectiveness of EDTA and DTPA to extract Fe and remain stable for the decomposition of hydrogen peroxide in circum-neutral solutions is evaluated. The effectiveness of hydroxyl radicals diminishes in the presence of free radical scavengers such as carbonate and bicarbonate that develop as a result of Ca, Mg-carbonate dissolution.  The effectiveness of Fe-EDTA and Fe-DTPA to generate a sufficient free radical activity for the oxidation of sorbed BTEX and PAHs in circum-neutral conditions is evaluated. A comparison of the conventional Fenton oxidation with the iron-chelate catalyzed Fenton-like oxidation in different soil compositional environments is also presented.

Sharavan V.Govindan, Environmental Research Institute, University of Connecticut, 270 Middle Turnpike, U-5210, Storrs, CT 06269, Tel: 486-6161, Fax: 486-5488 Email: sgovindan@eri.uconn.edu
George E. Hoag, Environmental Research Institute, University of Connecticut, 270 Middle Turnpike, U-5210, Storrs, CT 06269, Tel: 486-2001, Fax: 486-5488 Email: ghoag@eri.uconn.edu
Kun-Chang Huang, Environmental Research Institute, University of Connecticut, 270 Middle Turnpike, U-5210, Storrs, CT 06269, Tel: 486-5893, Fax: 486-5488 Email: khuang@eri.uconn

Cleaning up the environmentally persistent poly chlorinated biphenyl (PCB) contaminated sediment and further transforming them into a monolithic structure has been the motivation behind developing effective treatment technology. Highly reactive free radicals generated as a result of photolysis or heat decomposition of persulfate ions in aqueous phases have been found to be able to mineralize many organic compounds including PCBs.   In this study, we have investigated the feasibility of combining the chemical oxidation of sodium persulfate (N₂S₂O₈) and the stabilization/solidification by lime for the treatment of PCBs sediment and soils. 

The study was conducted by using two sets of laboratory scale experimental systems: completely mixed aqueous batch (containing PCBs, water and persulfate) and soil slurry batch (containing PCBs sediment and persulfate solution with/without lime).  The aqueous batch experiments conducted in 100-mL zero headspace syringe at 40°C resulted in 94% decrease in PCB concentration within 56 hrs, with a decrease in pH from 4.5 to 1.5 at a persulfate concentration of 10 g/L.  In the slurry phase experiments, desorption of PCBs from the organic layer was observed till 12 hours followed by a decrease in PCB concentration at 40°C and 50°C.  However, PCBs were not significantly degraded. More experiments were then conducted in a stirred tank reactor setup with excess persulfate and at a temperature of 80°C for a duration of 168 hrs with/without the presence of lime.   This resulted in a 95-99+% decrease in PCB concentration levels to as low as 1 PPB.  The control experiments showed the final concentration greater than that of the initial concentration. This indicated that the sorbed PCBs that were not otherwise detected were released from the organic layer in the sediment.

The study shows that heated persulfate effectively degraded PCBs in aqueous and soil slurry media under the experimental conditions.  Increase in degradation was observed at higher temperatures and also with the presence of lime.  Degradation can be improved by increasing persulfate concentration and duration of the reaction.

The Adsorption of Chromium to Hydrous Manganese Oxides Produced during In-Situ Oxidation using Permanganate

Kelly A. Frasco, Carus Chemical Company, 1500 Eighth St., LaSalle, IL 61301-3500, Tel: 815-224-6852, Fax: 815-224-6841
Elizabeth L. Vlastnik, Carus Chemical Company, 1500 Eighth St., LaSalle, IL 61301-3500, Tel: 815-224-6867, Fax: 815-224-6841
Philip A.Vella, Carus Chemical Company, 1500 Eighth St., LaSalle, IL 61301-3500, Tel: 815-224-6869, Fax: 815-224-6841  

Potassium permanganate (KMnO₄) is commonly used for in-situ oxidation at sites contaminated with chlorinated solvents such as trichloroethylene (TCE) and perchloroethylene (PCE).  Metal mobility is a concern at some sites where in-situ oxidation is employed.  Chromium can exist naturally in the trivalent form {Cr(III)} which is relatively insoluble.  However, Cr(III) can be oxidized by potassium permanganate or hydrous manganese oxides (HMOs) to hexavalent chromium {Cr(VI)}.  Cr(VI) is relatively soluble (and therefore mobile) and is a known toxin.  Since large amounts of HMOs are formed during the in-situ treatment of TCE/PCE contaminated sites, the interaction between HMOs and mobilized Cr(VI) is of interest.  The present study addresses the rate and extent of Cr(VI) adsorption to HMOs under representative remediation conditions.  Samples containing 0.25, 0.75, and 3.0 g of HMOs were exposed to 1 mg/L of Cr(VI) and monitored over a 21 day period.  This experiment was done in solutions adjusted to pH 6.5 and pH 8.5.  Results showed that aqueous chromium levels decreased significantly in the presence of HMOs for both pH values, with 3.0 g adsorbing the most chromium.  The most significant decreases in aqueous chromium levels occurred within the first 5 days.  An equilibrium experiment was also conducted in which 0.5 g of HMOs were exposed to chromium dosages ranging from 0.1-5.0 mg/L of Cr(VI) for 24 hours (ambient temperature, pH buffered to 7).  The equilibrium chromium levels were readily predicted using a Freundlich isotherm model.  The hydrous manganese oxides used in these experiments were carefully synthesized and treated so that they simulated what is formed at remediation sites.  The purpose of this work is to provide a quantitative basis for predicting subsurface chromium levels following in-situ permanganate oxidation.

In-Situ Chemical Oxidation Misfires and Recent Innovative Improvements

Ron Adams, P.E. – EBSI, Inc., Tel: 904-280-2596, Email: radams@ebsi-inc.com
Dr. Bill Mahaffey, Pelorus Labs
Dr. Bill Slack, FRx
Mark Vigneri, EBSI, Inc.

The paper presents an overview of ISCO projects gone bad with a review of recently developed methods to avoid mistakes of the past.  A brief overview of each project with pictures, where available, will be presented along with a discussion of the factors leading to failure.  In-situ chemical treatment of soil and groundwater at contaminated sites has become increasingly accepted as a feasible, cost-effective, and timely method of site remediation.  Laboratory-scale testing has clearly demonstrated the effectiveness of a wide-range of common, often times food-grade, chemicals in transforming or enhancing the transformation of many contaminants.  While lab results show success, field application is less predictable due to naturally occurring chemical interferences and site limitations due to the lithologic and hydrogeologic setting.  The key difficulty in implementing site treatment to achieve cleanup goals has been the ability to cost-effectively deliver treatment chemicals such that treatment chemicals come in contact with site contaminants prior to degrading or participating in un-wanted side reactions.  Projects to be discussed include: an explosion in Wisconsin, an explosion in North Carolina, and many examples of significant volumes of injected fluids exiting at surface grade, sometimes damaging property and harming personnel.  The paper is concluded with an overview of the steps that can be taken and the methods that can be used to safely and successfully apply ISCO for site remediation and in some cases, site closure.

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