CICEET Progress Report for the period 9/15/04 Through 3/15/05

Project Title: A System for Remediation of Polychlorinated Biphenyl in Sediments
Principal Investigator(s): Kevin H. Gardner, Warren Chesner, James Melrose
Additional Investigator(s): Emese Hadnagy, Irina Calante, Jean M. Spear
Project Start Date: 09/01/03

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- Run experiments with Mg/Pd in pure solvent system spiked with PCB to study congener-specific degradation pathways, relative resistance of positional isomers, changes in dioxin-like toxicity, and the reaction endpoints.

- Investigate biphenyl degradation in the same pure solvent system.

- Conduct experiments to determine the relative degradation potential of various PCB congeners by Mg/Pd and set up a model equation based on the reduction efficiency and the lowest unoccupied molecular orbital (LUMO) energy of selected PCB congeners. Yak et al. (2000) established a similar equation for PCB dechlorination by ZVI under subcritical water conditions.

- Study the catalytic effects of Pd in the dechlorination reactions.

- Complete data processing for the desorption experiments.

- Study the effect of surfactants and solvents on PCB availability in actual contaminated sediments and compare findings with results from the desorption experiments. Investigate, how all these factors influence PCB dechlorination in the sediment matrix.

- Work on the optimization of PCB dechlorination in sediments by Mg/Pd by varying the reaction times and the mass of the Mg/Pd added.

- Publish at least one research article.

Tasks to meet objectives
- Run batch experiments with various contaminated sediments and different types of surfactants and solvents to investigate both PCB availability and degradation.

- Run batch experiments in pure solvent systems spiked with a single PCB congener to investigate dechlorination pathways with palladium-coated magnesium (Mg/Pd, from NASA). Compare the relative degradation capability of several PCB congeners.

- Run batch experiments with Mg/Pd to investigate the catalytic effect of Pd ­ What makes Pd a good catalyst? For how long is Mg/Pd effective in pure and in sediment systems?

- Conduct literature search on PCB dechlorination by Mg/Pd in various matrices.

- Extract samples with Ultrasonic Extraction (EPA Method 3550B) and analyze them with a Varian Saturn 2200 Ion Trap Gas Chromatograph and Mass Spectrometer (GC/MS) following the manufacturer’s method (“Analysis of Semi-volatile Organic Compounds with Ion-Trap GC/MS”, developed based on EPA methods and requirements ­ Methods 8000B, modified 8270C, and 8290). Establish a calibration curve for congener-specific PCB analysis on GC/MS.

Progress on Tasks
Characterization of NASA Mg/Pd:
Samples of the Mg/Pd powder were sent to Case Western Reserve, Cleveland, OH for Scanning Electron Micrograph (SEM) analysis. Examples of the resulting photographs are shown in Figure 1.

Batch Experiments in Pure Solvent:
- All pure solvent experiments were conducted in a 10% methanol solution (in distilled water).

- At the end of the previous reporting period preliminary batch runs were run to investigate the PCB dechlorination capability of the NASA Mg/Pd (99.9%/0.1% by weight; 4 µm Mg particle size). The 10% methanol solution was spiked with either BZ 197 or BZ 170. More than 90% of the initial PCB was removed in 10 to 25 minutes (Figure 2). No degradation byproduct was observed in these experiments. The results were in good agreement with findings from NASA. Their researchers suggested that even biphenyl, the expected reaction end product, was completely broken down at the end of the dechlorination process.

- To investigate the above hypothesis, batch experiments were conducted in pure solvent with biphenyl and the addition of NASA Mg/Pd. More than 95% degradation of the initial biphenyl present was observed in 10 min (Figure 3).

- Next, batch experiments were run with biphenyl, BZ 170, and BZ 188, to study the effect of “aging” the Mg/Pd powder in water before exposing it to PCBs. In these experiments magnesium was kept in water for 3 to 5 min before spiking biphenyl or PCBs into the solution. The purpose of these experiments was to investigate the degradation efficiency of Mg/Pd under conditions with less hydrogen gas generation. Less than 10% PCB degradation was observed in 3 to 8 min. However, one batch prepared with Mg/Pd that was not “aged” previously also showed low PCB degradation, therefore the aspect of “aging” of Mg/Pd and its effectiveness afterwards still needs to be further investigated. [See below]

- Kinetic studies were performed for BZ 170 and BZ 3 in pure solvent systems using NASA Mg/Pd. Samples were taken at 1, 2, 3, 4, 5, 6, 8, 10, 15, 20, 30, and 60 min for both congeners. All batches were run in duplicates. The degradation of BZ 170 was rapid with more than 90% removal of the initial PCBs in 10 min (Figure 4). After that time no significant degradation was observed. The degradation of BZ 3 (a monochlorobiphenyl) occurred at an even faster rate than of BZ 170 (a heptachlorobiphenyl), confirming that the smaller the number of chlorines in the PCB compound the faster the degradation is. More than 90% of the initial PCBs was degraded in 1 min; after that time no significant degradation was observed (Figure 5).

- It was hypothesized that biphenyl was volatilized or adsorbed to the Mg/Pd surface. To test these hypotheses and as attempt to close the mass balance of the system, mass balance experiments are currently being run. Some of the batch runs had already been completed and the samples are waiting for GC analysis. In these experiments, an Aroclor 1260 standard stock solution (10 µg/mL in methanol) was spiked into 10% methanol and NASA Mg/Pd was added. The batch reactors were shaken on a rotary shaker for 1 hr at about 170 rpm. The reactors were completely covered and a glass column containing activated carbon (AC) was attached to a tube that ended in the headspace, creating a passage for volatiles trying to leave the vessel. After 1 hr, the solution was extracted for the dissolved PCB and biphenyl phase. Both the AC from the column and the filtered Mg/Pd were extracted to account for the volatile and the adsorbed compound phases, respectively. The Mg/Pd was separated from the solution using vacuum filtration and Whatman 0.7 mm GF/F filters. All extracts will be analyzed for both PCBs (congener specific) and biphenyl on the GC/MS in our laboratory. A portion of the solution of each batch was analyzed for chloride with a Cole-Parmer® 27502-13 Chloride Electrode using a VWR Scientific Products, Model 8100 pH/mV Meter. Samples were also taken for chloride measurements to be done by Ion Chromatography. These samples will be sent to an independent laboratory to verify the chloride measurements done at our laboratory.

(3) Desorption Experiments:
The analysis of the desorption experiment (conducted at the end of the previous reporting period) data was completed. Desorption experiments were performed to study the role of desorption kinetics of PCBs in sediments on the overall treatment efficacy. Two sediment types were investigated, New Bedford Harbor (NBH) and Housatonic River (Hous.). In the batch runs, the sediment was combined with distilled waster and 0.2 g of Tenax TA® resin beads in a beaker. All reactors were shaken on a rotary shaker. Triplicate beakers were set up for each of the sediments as well as a blank batch. Samples were taken on 1, 2, 5, 12, 19, 26, 33, and 50 days and at each sampling occasion the used Tenax beads were removed and replaced with fresh ones. Adsorbed PCBs were extracted from the Tenax beads by the Ultrasonic Extraction method and the extracts were analyzed by GC/MS.

In the more sandy Hous. sediment, PCB desorption occurred in two stages (Figure 6). The first stage was the fastest and it lasted 5 days with approximately 22% desorption. The second stage lasted for the remainder of the experiment (from day 5 to 50) with only approximately 3% PCB desorption. This 2-stage desorption behavior has been previously noted in literature. When compared to the control batch, the Hous. sediment had a 24.8% PCB desorption from an initial concentration of 3.2 ppm.

The NBH sediment had much lower PCB desorption rate than the Hous. with only 6.2% desorbed from an initial concentration of 114 ppm (Figure 6). There was only one stage in the desorption curve for this sediment. The higher clay and silt content, both of which retain PCBs stronger than sand, might be one of the reasons for the slower PCB desorption in the NBH sediment. Another reason is that the NBH sediment has a higher organic content of approximately 4.6%, compared with 2.4% in the Hous. River. Mineralogy, organic content and sediment aging have been attributed in literature to PCB desorption resistance to sediments.

(4) Batch Experiments in Sediments:
- Experiments were run in Hous. sediment with NASA Mg/Pd and various solvents. The solvents used were: methanol, ethanol, isopropyl alcohol (IA), acetone, hexane, and methylene chloride (MC). Batch reactors were run for each solvent added in both 10 and 30 % solution (in distilled water) to the sediment. Control batches (no Mg/Pd added) were prepared with sediment and pure distilled water. The use of solvents was studied to see if the addition of any of these chemicals would enhance PCB availability from sediments. The total PCB mass reduction after 5 days and relative to the control, in the presence of 10% hexane, MC, methanol, or IA is shown in Figure 7. In the presence of stronger solvents, there was more PCB degradation occurring. Samples for experiments with ethanol and acetone are yet to be run and analyzed by the GC/MS.

- Further experiments were run in Hous. sediment with the addition of only distilled water. Controls were prepared with sediment and pure distilled water. There were a total of 3 control and 3 treated batch runs. Two of the control and one treated sample were sent for extraction to an independent laboratory, Analytics Environmental Laboratory LLC in Portsmouth, NH, where these samples were extracted using the Accelerated Solvent Extraction method. The extracts were sent back to UNH where the concentration step and the GC analysis were performed. The rest of the samples were extracted (with ultrasonic extraction) and analyzed entirely at UNH. The results showed 98% PCB removal in 5 days (Figure 8 and Figure 9) for the samples extracted in both laboratories confirming the accuracy of the extraction method used at UNH. (Note: The initial PCB concentration in the last experiment was much higher than in the former runs with the addition of various solvents. The experiments were conducted on sediment from the same bucket, but sampled as different batches. The higher initial PCB concentration clearly indicates a “hot spot” (the expected average total PCB concentration in the Hous. sediment is 55 ppm), despite the manual mixing of the sediment in the bucket before the batch sampling. Therefore, results of the two experiments cannot be directly compared. Further testing of the role of various solvents in PCB availability and degradation is necessary to be able to draw more detailed conclusions.

- Experiments were conducted with Hunter’s Point (HP) sediment varying the following parameters: the mass of NASA Mg/Pd (0.1-0.5 g), the pre-treatment of Mg/Pd before addition (“aged” in distilled water for 20 to 30 min or added without “aging”), and the sampling time (2 or 4 days). One control batch was sampled at time zero, the rest at 4 days. The “aged” Mg/Pd showed about 28% PCB reduction after 4 days with 0.1 g Mg/Pd while no reduction with 0.2 g Mg/Pd (Figure 10). About 10% PCB degradation was observed both with 0.2 g and 0.5 g of the regular Mg/Pd over 2 days. No degradation was observed with 0.1 g Mg/Pd over 4 days, while the initial PCBs were reduced by about 28% with 0.2 g. Both the 2-day and the 4-day regular Mg/Pd samples showed higher PCB reduction with 0.2 g Mg/Pd than the “aged” Mg/Pd at 4 days. In general, higher maximum degradation was achieved over 4 days than 2 days.

- Batch experiments were also run with NBH sediment and 0.2 g NASA Mg/Pd. The total PCB degradation observed relative to the control was 22% over 4 days (Figure 11).

- To show that dechlorination was not desorption limited batch runs were conducted with Hudson River (HR) and NBH sediments with a high concentration of Mg/Pd (10% by weight). Total 5 g of Mg/Pd was added to 50 g dry weight of sediment. Batches were sampled at 1, 2, 4, 24 and 96 hours (Figure 12). The 24 and 96-hour samples are pending analysis on the GC/MS and will be added to the graph once the results are computed.

(5) GC/MS Analysis:
- The calibration curve for congener-specific PCB analysis was rerun and reedited after major interventions in the GC/MS, following the procedures described by the manufacturer.

- Routine analysis of samples described above.

(6) Literature Review:
Literature search was conducted on PCB dechlorination by Mg and Mg/Pd in various matrices. The fate of biphenyl in dechlorination reactions was also researched.

Accomplishments
Two calibration curves were established during the reporting period for the GC/MS for congener-specific PCB analysis. All QA/QC requirements were sufficiently met regarding the operation of the instrument. A total of 79 batches were run with a pure solvent (10% methanol in distilled water) system spiked with purchased PCB standards and 44 reactors with various contaminated sediments. Replicate samples were taken from the batches as required. Some of the samples are still to be analyzed by the GC/MS.

A kinetic study was completed for both congener 170 and congener 3 in pure solvent. Batch experiments in pure solvent are still in progress to accomplish a closed mass balance. Significant PCB mass reduction was observed in various sediment types (Hous., NBH, HR, and HP) by NASA Mg/Pd. The reactions in the sediments occur much slower than in pure solvents ­ on the order of days instead of minutes ­ and generally lower % removal is achieved in the sediment system, although the reaction endpoints had not been determined yet. An exception was observed in one experiment with Hous. sediment where 98% of the initial PCBs were removed in 5 days. A factor that might have attributed to this “anomaly” was the higher initial PCB concentration of the sediment batch used for the runs, almost 200 ppm vs. the expected 55 ppm, therefore having a larger mass of PCBs available for reduction. When adding Mg/Pd in a high concentration to the batch (10% by dry weight), greater degradation was achieved faster in sediments as well. The total observed PCB reduction varied from 20 to 40 % in HR and from 13 to 30 % in NBH sediments for reaction times of 1 to 4 hours. Desorption curves were established for Hous. and NBH sediments.

Difficulties
In GC/MS Operation: Periodical difficulties were faced with GC/MS operation, including too low response in chromatograms and faulting of the Auto Sampler on a regular basis. The manufacturer’s (Varian) service representatives came out to service the instrument several times but some of the problems still persisted. These downtimes in the instrument operation caused a delay in the analysis of the experimental samples.

Project Objectives for Next Reporting Period

Objectives
- Complete the mass balance experiments and close the mass balance of the system.

- Complete processing pending samples on the GC/MS.

- Investigate the possibility of biphenyl degradation/complexation into organic molecules not detectable by the GC/MS.

- Further test the degradation potential of “aged” Mg/Pd.

- Continue PCB degradation experiments in pure solvents to identify congener-specific degradation pathways, relative resistance of positional isomers, changes in dioxin-like toxicity, and the reaction endpoints.

- Conduct experiments to determine the relative degradation potential of various PCB congeners by Mg/Pd

- Continue to study the effect of solvents on PCB availability in actual contaminated sediments and compare findings with results from the desorption experiments. In particular, evaluate the effect of two biodegradable, citrus derived solvents, d-Limonene and Citrus Burst® 2 (the latter solvent contains a surfactant as well) on PCB availability. Investigate how all these factors influence PCB dechlorination in the sediment matrix.

- Analyze whether better sediment homogenization improves replication of the results within the sediments.

- Publish research articles.

Tasks to Meet Objectives
- Run batch experiments in pure solvent systems with careful accounting for PCB dechlorination end products.

- Run batch experiments with contaminated sediment and solvents.

- Measure extraction efficiency of biodegradable, natural solvents.

- Make sure that GC/MS operation is continuous and all QA/QC requirements are met.

- Conduct continuous literature search in major environmental research journals.

- Communicate and collaborate with other researchers and attend scientific conferences and workshops.

- Conduct mixing tests using the laboratory scale mixing device and fluorescent microsphere beads to evaluate time of mixing required.

Anticipated Success in Meeting Project Objectives
It is anticipated that the above objectives will be successfully met over the next reporting period.

Overall Project Timeline Update
Project is anticipated to be completed by the original time proposed.

Preliminary Data
See Figures.

Dissemination
Conferences:
- Calante, I., E. Hadnagy, J.C. Spear, K.H. Gardner, "PCB Dechlorination by Palladized Magnesium: Role of Desorption Kinetics from Sediments in Overall Treatment Efficacy", Third International Conference on Remediation of Contaminated Sediments, New Orleans, Louisiana, Jan 24-27, 2005.

- Hadnagy, E., J.C. Spear, I. Calante, K.H. Gardner, “Pathways of Congener-Specific PCB Dechlorination by Palladized Magnesium”, Third International Conference on Remediation of Contaminated Sediments, New Orleans, Louisiana, Jan 24-27, 2005.

- Gardner, K.H., E.A. Stern, “Status of Ex-Situ and In-Situ Treatment Methods,” Addressing Uncertainty and Managing Risk at Contaminated Sediment Sites,” St. Louis, MO October 26 - 28, 2004.

Expenditures
Expenditures have been in the range anticipated for the work accomplished to date.

References
Yak, H.K., Q. Lang, and C.M. Wai. 2000. Relative Resistance of Positional Isomers of Polychlorinated Biphenyls toward Reductive Dechlorination by Zerovalent Iron in Subcritical Water. Environ. Sci. Technol., 34/13: 2792-2798.