HEAVY METAL CONTENT AND LEACHING POTENTIAL OF RECYCLED GLASS BEADS USED IN PAVEMENT MARKINGS

Transcription

1 HEAVY METAL CONTENT A LEACHING POTENTIAL OF RECYCLED GLASS BEADS USED IN PAVEMENT MARKINGS by Bryan Boulanger, Ph.D. Assistant Professor Environmental & Water Resources Engineering Division Zachry Department of Civil Engineering Texas A&M University Aditya Babu Raut Desai, Ph.D. Post-Doctoral Research Associate Environmental & Water Resources Engineering Division Zachry Department of Civil Engineering Texas A&M University and Paul Carlson, Ph.D., P.E. Research Engineer Texas Transportation Institute Project Title: Heavy Metal Content and Leaching Potential of Recycled Glass Beads Used in Pavement Markings April 1, 2011 TEXAS TRANSPORTATION INSTITUTE The Texas A&M University System College Station, Texas

2 DISCLAIMER The contents of this report reflect the research conducted by the authors who are responsible for the facts and the accuracy of the presented data. This report does not constitute a standard, specification, or regulation. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use. The researcher in charge of the project covered in this report was Dr. Bryan Boulanger of Texas A&M University s Zachry Department of Civil Engineering. ii

3 ACKNOWLEDGMENTS Completion of this research would not have been possible without the following individuals whom we gratefully acknowledge. Dr. William James from the Center for Chemical Characterization at Texas A&M University (TAMU) for helping with X-Ray Fluorescence. Tom Stephens from TAMU s Microscopy and Imaging Center for assistance with the scanning electron microscope. Brad Beless, Dr. Pranav Nagarnaik, and Ishan Desai from the Boulanger Research Group for their help and advice in research design, data acquisition, and data interpretation. All the support staff at the Texas Transportation Institute and the Zachry Department of Civil Engineering for their help in project administration. iii

4 TABLE OF CONTENTS Page List of Figures... vi List of Tables... viii List of Units... xv 1. Project Introduction Materials, Analytical Methods, and Experimental Procedures Recycled Glass Beads Reagents X-Ray Fluorescence (XRF) Sample Analysis Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) Sample Analysis Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) Sample Analysis Potassium Hydroxide Fusion Procedure Bead Rinsing Procedure Column Experimental Procedure Ultraviolet (UV) Light Bead Exposure Procedure Bead Temperature Exposure Procedure Bead Abrasion Procedure Quality Assurance/Quality Control Data Analysis and Presentation Results and Discussion QA/QC Experiment 1: Evaluation of Heavy Metal Composition in Bulk Bead Samples Experiment 2: Effect of Solution ph on Metal Leaching from Recycled Glass Beads Experiment 3: Effect of UV Light Exposure on Metal Leaching from Recycled Glass Beads Experiment 4: Effect of Temperature on Metal Leaching from Recycled Glass Beads Experiment 5: Effect of Abrasion on Metal Leaching from Recycled Glass Beads Conclusions and Recommendations References iv

5 Appendix A: QA/QC Reviewed Data Used to Determine Method Detection Limits Appendix B: Surface Visualization and Bulk Composition using SEM-EDS Appendix C: Rinsing Study QA/QC Reviewed data Appendix D: Column Study QA/QC Reviewed Data v

6 LIST OF FIGURES Page Figure 2.1. Experimental setup for upflow column leaching system Figure 3.1. Mean arsenic and Σ(heavy metals) content in sponsor provided recycled glass beads Figure 3.2. Characteristic leaching profile observed during column study Figure 3.3. ph Effect on mean arsenic and (heavy metals) leaching from Batch 1 beads Figure 3.4. ph effect on mean arsenic and (heavy metals) leaching from Batch 3 beads Figure 3.5. UV exposure effect on mean arsenic and (heavy metals) leaching from Batch 1 beads Figure 3.6. UV exposure effect on mean arsenic and (heavy metals) leaching from Batch 3 beads Figure 3.7. Temperature exposure effect on mean arsenic and (heavy metals) leaching from Batch 1 beads Figure 3.8. Temperature exposure effect on mean arsenic and (heavy metals) leaching from Batch 3 beads Figure 3.9. Effect of abrasion on mean arsenic and Σ(heavy metals) leaching from Batch 1 beads Figure Effect of abrasion on mean arsenic and Σ(heavy metals) leaching from Batch 3 beads Figure 4.1. Mean heavy metal content in sponsor supplied recycled glass bead Figure 4.2. Mean heavy metal content leached into rinsing solution Figure 4.3. Mean heavy metal content released into ph 7 solution during the 48 hour column leaching studies vi

7 Figure B.1. SEM image of slide with glass beads (Batch 1) Figure B.2. SEM image of three black-colored imputrities (Batch 1) Figure B.3. SEM image identifying location of impurities on surface of bead (Batch 1) Figure B.4. SEM image and EDS spectrum of surface impurity on glass bead (Batch 1) Figure B.5. SEM image and EDS spectrum of black-colored impurity (1):Figure B Figure B.6. SEM image and EDS spectrum of black-colored impurity (2):Figure B Figure B.7. SEM image and EDS spectrum of black-colored impurity (3: Figure B Figure B.8. SEM image of slide with glass beads (Batch 2) Figure B.9. SEM image of impurity attached to glass bead (Batch 2) Figure B.10. SEM image of fused glass beads (Batch 2) Figure B.11. SEM imageof surface impurities on a glass bead (Batch 2) Figure B.12. SEM image and EDS spectrum of surface impurity (1) on Batch 2 bead Figure B.13. SEM image and EDS spectrum of surface impurity (2) of bead (Batch 2) Figure B.14. SEM image and EDS spectrum surface impurity on glass bead (Batch 2) Figure B.15. SEM image and EDS spectrum of area around surface impurity (Batch 2) Figure B.16. SEM image and EDS spectrumof surface impurity on glass bead (Batch 2) Figure B.17. SEM image of slide with glass beads (Batch 3) Figure B.18. SEM image of impurity attached to glass bead (Batch 3) Figure B.19. SEM image of fused glass beads (Batch 3) Figure B.20. SEM image of crystalline needle-shaped glass (Batch 3) Figure B.21. SEM image of fused glass beads (Batch 3) vii

8 LIST OF TABLES Page Table 2.1. Particle size distribution and calculated specific surface area of abraded beads Table 2.2. Layout of the experimental design Table 3.1. Method Detection Limit for ICP-MS analysis Table 3.2. Mean ± standard deviation heavy metal content in sponsor provided recycled glass beads Table 3.3. Mean ± standard deviaiton heavy metal content in the neutral ph rinse solutions per mass of rinsed beads Table 3.4. Mean ± standard deviation mass of metals leached per mass of beads in ph 7 solution Table 4.1. Mean ± standard deviation arsenic content in bulk beads, the rinse solution, and the ph 7 leaching solution Table 4.2. Mean ± standard deviation cadmium content in bulk beads, the rinse solution, and the ph 7 leaching solution Table 4.3. Mean ± standard deviation chromium content in bulk beads, the rinse solution, and the ph 7 leaching solution Table 4.4. Mean ± standard deviation copper content in bulk beads, the rinse solution, and the ph 7 leaching solution Table 4.5. Mean ± standard deviation lead content in bulk beads, the rinse solution, and the ph 7 leaching solution Table 4.6. Mean ± standard deviation nickel content in bulk beads, the rinse solution, and the ph 7 leaching solution Table A.1. Determination of background instrument response for eight blanks Table A.2. Data used to determine Method Detection Limit (MDL) viii

9 Table C.1. Bead rinsing (Batch 1) Table C.2. Bead rinsing (Batch 2) Table C.3. Bead rinsing (Batch 3) Table D.1. Concentration of heavy metals in leachate from glass beads (Batch 1) at ph 4, Repetition Table D.2. Concentration of heavy metals in leachate from glass beads (Batch 1) at ph 4, Repetition Table D.3. Concentration of heavy metals in leachate from glass beads (Batch 1) at ph 4, Repetition Table D.4. Concentration of heavy metals in leachate from glass beads (Batch 1) at ph 7, Repetition Table D.5. Concentration of heavy metals in leachate from glass beads (Batch 1) at ph 7, Repetition Table D.6. Concentration of heavy metals in leachate from glass beads (Batch 1) at ph 7, Repetition Table D.7. Concentration of heavy metals in leachate from glass beads (Batch 1) at ph 10, Repetition Table D.8. Concentration of heavy metals in leachate from glass beads (Batch 1) at ph 10, Repetition Table D.9. Concentration of heavy metals in leachate from glass beads (Batch 1) at ph 10, Repetition Table D.10.Concentration of heavy metals in leachate from glass beads (Batch 1) kept at 100 F for 24 hours, Repetition Table D.11.Concentration of heavy metals in leachate from glass beads (Batch 1) kept at 100 F for 24 hours, Repetition Table D.12.Concentration of heavy metals in leachate from glass beads (Batch 1) kept at 100 F for 24 hours, Repetition ix

10 Table D.13.Concentration of heavy metals in leachate from glass beads (Batch 1) kept at 150 F for 24 hours, Repetition Table D.14.Concentration of heavy metals in leachate from glass beads (Batch 1) kept at 150 F for 24 hours, Repetition Table D.15.Concentration of heavy metals in leachate from glass beads (Batch 1) kept at 150 F for 24 hours, Repetition Table D.16.Concentration of heavy metals in leachate from glass beads (Batch 1) exposed to UV radiation for 12 hours, Repetition Table D.17.Concentration of heavy metals in leachate from glass beads (Batch 1) exposed to UV radiation for 12 hours, Repetition Table D.18.Concentration of heavy metals in leachate from glass beads (Batch 1) exposed to UV radiation for 12 hours, Repetition Table D.19.Concentration of heavy metals in leachate from glass beads (Batch 1) exposed to UV radiation for 24 hours, Repetition Table D.20.Concentration of heavy metals in leachate from glass beads (Batch 1) exposed to UV radiation for 24 hours, Repetition Table D.21.Concentration of heavy metals in leachate from glass beads (Batch 1) exposed to UV radiation for 24 hours, Repetition Table D.22.Concentration of heavy metals in leachate from glass beads (Batch 1) exposed to UV radiation for 48 hours, Repetition Table D.23.Concentration of heavy metals in leachate from glass beads (Batch 1) exposed to UV radiation for 48 hours, Repetition Table D.24.Concentration of heavy metals in leachate from glass beads (Batch 1) exposed to UV radiation for 48 hours, Repetition Table D.25.Concentration of heavy metals in leachate from glass beads (Batch 1) abraded to size between 149 and 250 micron, Repetition x

11 Table D.26.Concentration of heavy metals in leachate from glass beads (Batch 1) abraded to size between 149 and 250 micron, Repetition Table D.27.Concentration of heavy metals in leachate from glass beads (Batch 1) abraded to size between 149 and 250 micron, Repetition Table D.28.Concentration of heavy metals in leachate from glass beads (Batch 1) abraded to size less than 149 micron, Repetition Table D.29.Concentration of heavy metals in leachate from glass beads (Batch 1) abraded to size less than 149 micron, Repetition Table D.30.Concentration of heavy metals in leachate from glass beads (Batch 1) abraded to size less than 149 micron, Repetition Table D.31.Concentration of heavy metals in leachate from glass beads (Batch 2) at ph 4, Repetition Table D.32.Concentration of heavy metals in leachate from glass beads (Batch 2) at ph 4, Repetition Table D.33.Concentration of heavy metals in leachate from glass beads (Batch 2) at ph 7, Repetition Table D.34.Concentration of heavy metals in leachate from glass beads (Batch 2) at ph 7, Repetition Table D.35.Concentration of heavy metals in leachate from glass beads (Batch 2) at ph 7, Repetition Table D.36.Concentration of heavy metals in leachate from glass beads (Batch 2) at ph 10, Repetition Table D.37.Concentration of heavy metals in leachate from glass beads (Batch 2) at ph 10, Repetition Table D.38.Concentration of heavy metals in leachate from glass beads (Batch 2) at ph 10, Repetition xi

12 Table D.39.Concentration of heavy metals in leachate from glass beads (Batch 3) at ph 4, Repetition Table D.40.Concentration of heavy metals in leachate from glass beads (Batch 3) at ph 4, Repetition Table D.41.Concentration of heavy metals in leachate from glass beads (Batch 3) at ph 7, Repetition Table D.42.Concentration of heavy metals in leachate from glass beads (Batch 3) at ph 7, Repetition Table D.43.Concentration of heavy metals in leachate from glass beads (Batch 3) at ph 7, Repetition Table D.44.Concentration of heavy metals in leachate from glass beads (Batch 3) at ph 10, Repetition Table D.45.Concentration of heavy metals in leachate from glass beads (Batch 3) at ph 10, Repetition Table D.46.Concentration of heavy metals in leachate from glass beads (Batch 3) at ph 10, Repetition Table D.47.Concentration of heavy metals in leachate from glass beads (Batch 3) kept at 100 F for 24 hours, Repetition Table D.48.Concentration of heavy metals in leachate from glass beads (Batch 3) kept at 100 F for 24 hours, Repetition Table D.49.Concentration of heavy metals in leachate from glass beads (Batch 3) kept at 100 F for 24 hours, Repetition Table D.50.Concentration of heavy metals in leachate from glass beads (Batch 3) kept at 150 F for 24 hours, Repetition Table D.51.Concentration of heavy metals in leachate from glass beads (Batch 3) kept at 150 F for 24 hours, Repetition xii

13 Table D.52.Concentration of heavy metals in leachate from glass beads (Batch 3) kept at 150 F for 24 hours, Repetition Table D.53.Concentration of heavy metals in leachate from glass beads (Batch 3) exposed to UV radiation for 12 hours, Repetition Table D.54.Concentration of heavy metals in leachate from glass beads (Batch 3) exposed to UV radiation for 12 hours, Repetition Table D.55.Concentration of heavy metals in leachate from glass beads (Batch 3) exposed to UV radiation for 12 hours, Repetition Table D.56.Concentration of heavy metals in leachate from glass beads (Batch 3) exposed to UV radiation for 24 hours, Repetition Table D.57.Concentration of heavy metals in leachate from glass beads (Batch 3) exposed to UV radiation for 24 hours, Repetition Table D.58.Concentration of heavy metals in leachate from glass beads (Batch 3) exposed to UV radiation for 24 hours, Repetition Table D.59.Concentration of heavy metals in leachate from glass beads (Batch 3) exposed to UV radiation for 48 hours, Repetition Table D.60.Concentration of heavy metals in leachate from glass beads (Batch 3) exposed to UV radiation for 48 hours, Repetition Table D.61.Concentration of heavy metals in leachate from glass beads (Batch 3) exposed to UV radiation for 48 hours, Repetition Table D.62.Concentration of heavy metals in leachate from glass beads (Batch 3) abraded to size between 149 and 250 micron, Repetition Table D.63.Concentration of heavy metals in leachate from glass beads (Batch 3) abraded to size between 149 and 250 micron, Repetition Table D.64.Concentration of heavy metals in leachate from glass beads (Batch 3) abraded to size between 149 and 250 micron, Repetition xiii

14 Table D.65.Concentration of heavy metals in leachate from glass beads (Batch 3) abraded to size less than 149 micron, Repetition Table D.66.Concentration of heavy metals in leachate from glass beads (Batch 3) abraded to size less than 149 micron, Repetition Table D.67.Concentration of heavy metals in leachate from glass beads (Batch 3) abraded to size less than 149 micron, Repetition xiv

15 LIST OF UNITS cm mm μm nm in g lb(s) L ml hr(s) mw cm 2 m 2 centimeter millimeters micron or micrometer nanometer inch gram pound(s) liter milliliter hour(s) milliwatt square centimeter square meter C degree Celsius F degree Fahrenheit xv

16 1. PROJECT INTRODUCTION This project was carried out for the American Glass Bead Manufacturers Association (AGBMA) with Dr. Ufuk Senturk as the primary point of contact. The AGBMA produces recycled glass beads for use in pavement marking systems. The recycled glass beads incorporated into pavement marking systems retroreflect vehicle headlights and improve nighttime roadway delineation, marking visibility, and safety. While the benefits of using recycled glass beads in pavement markings is well established, the AGBMA approached researchers at the Texas Transportation Institute (TTI) with concerns over the presence of heavy metals, including arsenic and lead, in recycled glass beads currently used in pavement marking systems. AGBMA is concerned that some recycled glass beads applied in pavement marking systems may release heavy metals to the environment posing a human and environmental health risk. Therefore, AGBMA asked the TTI project team to 1) determine the composition of heavy metals in samples of recycled glass beads provided by the sponsor, and 2) investigate the leaching potential of heavy metals from the provided recycled glass bead samples under laboratory conditions. In response to the sponsor s request and with the sponsor s input, the project team proposed a series of five experiments to complete the evaluation. These five experiments included: Experiment 1: Experiment 2: Experiment 3: Experiment 4: Experiment 5: Evaluation of heavy metal composition in bulk bead samples Effect of solution ph on metal leaching from recycled glass beads Effect of ultraviolet light exposure on metal leaching from recycled glass beads Effect of temperature on metal leaching from recycled glass beads Effect of abrasion on metal leaching from recycled glass beads 1

17 Experiment 1 was designed to evaluate the total arsenic (As), mercury (Hg), lead (Pb), cadmium (Cd), chromium (Cr), nickel (Ni), copper (Cu), and zinc (Zn) content in bulk bead samples following dissolution of the beads in a controlled laboratory setting. Experiments 2 through 5 were designed to examine the amount of As, Hg, Pb, Cd, Cr, Ni, Cu, and Zn mass release from the recycled glass beads into leaching solutions under different laboratory conditions. The recycled glass beads used in each of the experiments were Type I AASHTO M247 recycled glass beads provided by the sponsor in three individual batches of approximately 50 lbs. TTI researchers were informed that the bead samples contained varying levels of heavy metals and were given a preliminary metals content evaluation for each of the batch samples. TTI project personnel had no previous or current knowledge pertaining to the origin of the beads at the time of this final report s release. Project research was started with receipt of the letter of agreement between AGBMA and TTI on the 12 th of April, 2010 and work was completed with the conclusion of Experiment 5 s data analysis and interpretation on the 10 th of February, The final report was written and edited between February 22 nd and March 31 st, 2011 and submitted to Dr. Ufuk Senturk on April 1 st,

18 2. MATERIALS, ANALYTICAL METHODS, A EXPERIMENTAL PROCEDURES 2.1. Recycled Glass Beads Three individual 50 lb samples of Type I AASHTO M247 beads were provided to the TTI project team by the AGBMA for this study. The beads, designated as Batch 1, Batch 2, and Batch 3, were received at TTI on April 28th, Each batch of beads was subsampled using a SP-50 1/16th sample reducer to ensure representative subsamples. Prior to reducing the samples, the sample reducer was rinsed with deionized (DI) water and analyzed to evaluate the potential for cross contamination of metals. The sample reducer rinse was found to be free of the heavy metals measured in this study. Additional rinses and analyses performed in between the subsampling of each bead batch were also found to be free from the heavy metals evaluated in this research. Approximately two lbs of each bead batch from the initial 50 lb samples were collected into individual pre-labeled Ziploc bags during the sample reducing process. The two lb subsamples were stored and used throughout the experiments Reagents DI water was produced in the laboratory using a Barnstead Nanopure DI water system. DI water was used for preparing reagents, generating standards, and conducting experiments. Specpure analytical standards for As, Hg, Pb, Cr, Cd, Ni, Cu, and Zn were purchased from Alfa Aesar. ACS grade nitric acid (HNO3), potassium nitrate (KNO3), potassium hydroxide (KOH) and sodium hydroxide (NaOH) were purchased through Fisher Scientific. Oxalic acid was purchased from VWR. 3

19 2.3. X-Ray Fluorescence (XRF) Sample Analysis A QuanX EC benchtop EDXRF analyzer housed in Texas A&M University s (TAMU s) Center for Chemical Characterization was used for conducting XRF analysis. Since standard glass beads with known concentrations of heavy metals were not available, this method was used solely as a qualitative measure to identify which heavy metals were observable within the recycled glass bead samples. Glass bead samples from each batch were put into a 42 mm diameter sampling cup and covered with a thin polypropylene foil approximately 5 µm thick. XRF analysis was completed by staff at the Center for Chemical Characterization following the centers standard operating procedure for the determination of metals in solid samples Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) Sample Analysis A FEI Quanta 600 FE-SEM housed at the TAMU Microscopy and Imaging Center was used to visualize the surface of the recycled glass beads to screen for impurities present in the bead samples. The SEM was operated by the Center staff and samples were analyzed with members of the TTI project team present. Samples were prepared for SEM analysis by mounting subsamples from each batch for received beads on 12.5 mm pin mounts using carbon conductive adhesive tabs. A 10 nm conductive layer of platinum was deposited onto each prepared sample to reduce charging effects. All SEM images are secondary electron images collected with an Everhart-Thornley detector and the spectra were obtained using an Oxford Instruments Inca EDS system. Scanning information relevant to each captured image, including accelerating voltage (HV), working distance (WD) and the type of detector, is provided at the bottom of the SEM images presented in Appendix B. 4

20 2.5. Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) Sample Analysis An ELAN DRC II ICP-MS housed within TAMU s Center for Chemical Characterization was used quantify the concentration of As, Cd, Cr, Cu, Pb, Hg, Ni, and Zn in solutions produced from digestion of the recycled glass beads and the leaching experiments. All samples were preserved with HNO3 (1% volume/volume) and stored at 4 C. Samples were allowed to come to room temperature before analysis. Analysis was carried out as described in EPA Method 6020A. The Method Detection Limit (MDL) for each of the eight heavy metals using ICP-MS was determined according to 40 CFR Appendix B to Part 136 Definition and Procedure for the Determination of the Method Detection Limit. The MDL is the minimum concentration of a substance that can be measured and reported with 99% confidence that the analyte concentration is greater than zero. The practical quantitation limit (PQL) was then set based upon the greater of the MDL or the lowest analyzed calibration standard. A four point calibration was used to quantitate analytes between a range of 1 to 100 µg/l. Samples where the analytes were present at concentrations above the highest calibration standard were diluted down to within the calibration range and reanalyzed Potassium Hydroxide Fusion Procedure The KOH fusion process (procedure number APSL-03) developed by the Pacific Northwest National Laboratory (Brinkley 1994 and Cerefice 1996) was used to dissolve a portion of the subsampled Batch 1, Batch 2, and Batch 3 beads for total bulk bead metals content analysis. In this procedure recycled glass beads from each batch were crushed using a porcelain mortar and pestle and passed through a #140 US mesh sieve (<100 μm) ± g of the crushed beads were weighed and transferred into a 7 ml carbon crucible. Approximately 1.8 ± 0.4 g of KOH and 0.2 ± 0.1 g of KNO3 were 5

21 added to the crushed beads and the contents were mixed by swirling. The crucible and its contents were heated using a Bunsen burner until the mixture melted. The melted mixture was then allowed to cool to room temperature. Approximately 5 ml of DI water was added to dissolve the cake-like crystalline melt and the resulting solution was transferred to a 1000 ml volumetric flask. Additional 5 ml aliquots of DI water were repeatedly added to the crucible until all of the melt was dissolved. The solution in the flask was diluted to approximately 500 ml total volume using DI water and acidified using 25 ± 5 ml of concentrated HNO3 to dissolve any precipitate. 0.3 ± 0.1 g of oxalic acid crystals were also added to dissolve any additional observed precipitate that was not dissolved with the HNO3 addition. The flask contents were filled up to 1000 ml mark with DI water and stored at 4 C until ICP-MS analysis. Individual metals content of glass beads was calculated from the measured concentrations using the following formula Metal Content μg metal g bead = C M where, C mean concentration of metal in solution used to dissolve beads, volume of solution, L M mass of beads, g 2.7. Bead Rinsing Procedure A 500 ml Erlenmeyer vacuum flask with a Pall 300 ml polyphenylsulfone magnetic seal funnel was used to hold beads during rinsing. Pre-acid rinsed 934-AH Whatman glass microfiber filters were placed in the funnels to prevent smaller sized beads from passing through the apparatus. Fifteen g of recycled glass beads of each bead batch 6

22 were weighed and placed in the funnel over the filter. The beads were rinsed using 15 ml of ph neutral DI water applied under vacuum. The entire sample of rinse solution passed through the beads into a sampling tube within two minutes. The volume of water recovered was measured by weighing the extracted water. The bead rinse was conducted in triplicate for each of the three batches of glass beads and the rinse was analyzed for total metals content using ICP-MS Column Experimental Procedure The up flow column leaching system (shown in Figure 2.1) composed of two joined 20 ml BD syringes filled with 80 g of glass beads were used in triplicate to determine the mass release of heavy metals from each batch of glass beads. The up-flow reactors were 10.5 in. long and 1 in. in diameter and contained pre rinsed glass wool in the inlet and outlet to prevent the beads from leaving the column. ph adjusted DI water was passed through the columns using a peristaltic pump operated at a flow rate of 30 ml/hr. Observed variability on the flowrate was less than 5%. 10 ml samples of column effluent were collected from the outlet of the column at times 0, 1, 2, 4, 8, 16, 24, 36, and 48 hours. The samples were preserved with HNO3 (1% volume/volume) and refrigerated at 4 C until analysis using ICP-MS. 7

23 Figure 2.1. Experimental setup for upflow column leaching system. The measured concentrations of heavy metals in the leachate were converted to mass leached per mass of beads (mass per mass basis) using the formula; Total Mass Leached μg metal g bead 9 = C i + C i+1 (t 2 i+1 t i ) Q M i=1 where, C concentration of metal measured in column effluent, t time, hrs i sample interval number Q mean flow rate through column over duration of experiment, L/hr M - mass of beads in column, g 8

24 2.9. Ultraviolet (UV) Light Bead Exposure Procedure 500 g of Batch 1 beads and 500 g of Batch 3 beads were spread out on separate paper trays to ensure that the beads were exposed to the UV source in a single layer. The trays with the beads were placed in an enclosure that had a Bryant UVLB1LP UV lampwith an output of 105 mw/cm 2 (measured at a distance of one meter). The distance from the lamp to the trays was 10 cm. Based upon available literature, the estimated surface intensity at the beads was approximately 3.2 W/cm 2 (Scheir, R. and Fencl, F., 1996). However, the bead intensity was not directly measured. The beads were left in the enclosure with the lamps on for 12, 24, and 48 hours. The beads were removed from the enclosure and placed into the columns for testing Bead Temperature Exposure Procedure Two 500 g subsamples of Batch 1 beads and two 500 g subsamples of Batch 3 beads were spread out on separate paper trays to ensure that the beads were in a single layer. Trays filled with subsamples from each batch were placed in the laboratory oven set to 100 F and removed from the oven after 24 hrs. The temperature in the oven was raised to 150 F and the remaining trays were placed in the laboratory oven and removed after 24 hrs. All beads were allowed to cool in a desiccator and the cooled beads were placed into columns for testing Bead Abrasion Procedure Subsamples of Batch 1, 2, and 3 beads were sent to the sponsor and the sponsor mechanically abraded the beads and sieved the beads prior to shipping the abraded glass beads back to the TTI researchers. Beads were abraded with an International Equipment Company Fritszch planetary mill using zirconium oxide ceramic jars and balls. The milled beads were then sieved through +60, - 60/+100, and -100 US mesh sieves for collection of size fractions of <149, between 150 and 249, and > 250 μm. The 9

25 particle size distribution and corresponding calculated surface area of each sample is provided in Table 2.2. Table 2.1. Particle size distribution (µm) and calculated specific surface area of abraded beads. Grade Screen Size (US Mesh) 10 (volume%) 50 (volume%) 90 (volume%) Mean size Specific Surface Area (m 2 /g) Batch 1 Batch 3-60/ / Quality Assurance/Quality Control QA/QC efforts focused on several areas including: preventing cross contamination; ensuring a representative subsampling from the initially provided batches of beads for additional testing; experimental controls and replicates; and instrumental QA/QC. Cross contamination prevention included controls on sample handling that involved marking the subsamples and storing the initially provided bulk samples outside of the laboratory testing environment. Any materials coming into contact with the glass beads during the experiments were also prescreened for their likelihood of cross contaminating the bead samples with the metals of interest. The sample reducer, glass fiber filters, sample trays, and labware were washed with DI water prior to their initial use and the wash from these laboratory components were evaluated for metals content. 10

26 The laboratory water used in the experiments and the acid mixtures were also evaluated for their background metals content. Care was also taken to ensure that the subsamples of the initially provided bead samples were representative of the original 50 lb batches. This was achieved through use of a sample reducer. Experiments were carried out in triplicate to produce data between experimental variables that could be compared using statistics. The mean ± standard deviation concentration (or mass content) of each triplicate evaluation was determined by taking the average metal concentration (or mass content) observed between individual replicates in Excel. Instrumental QA/QC followed the guidelines outlined in EPA Method 6020A and the MDL was determined as described in Section 2.5. Finally, it is important to point out that the initially provided samples did arrive with characterization data and labels marking each received bead batch as low, medium, and high. The labels were meant to reflect the extent of metals contamination within the beads provided by the sponsor. Upon receipt, subsamples of each bead batch used in the analysis were individually characterized for their metals composition and the labels used in the study were replaced with Batch 1, Batch 2, and Batch 3 to prevent potential bias. While this change was made, it is important to note that samples were not blinded to the researchers. However, every effort was made to put in place QA/QC measures to ensure non-biased experimental data and data evaluation Data Analysis and Presentation One-way Analysis of Variance (ANOVA) was used to statistically evaluate whether individual experimental variables (shown in Table 2.2) affected the mean mass release of metals from the recycled glass beads. The null hypothesis used in the evaluation assumed that individual experimental variables (including ph, UV exposure, 11

27 temperature exposure, and abrasion) did not impact the mean mass of metal released from the glass beads into the leaching solution during each experiment at the 95% confidence interval. When ANOVA results suggested rejection of the null hypothesis (when p < 0.05), Tukey multiple comparison testing was applied for pair-wise comparison of the resulting mean experimental data. Table 2.2. Layout of the experimental design. Experimental Variables Evaluated Values Evaluated Bead Batch Sampling Intervals Total Number of Samples ph 4, 7, 10 1,2,3 UV Temperature Particle Size 0, 12, 24, 48 hrs 70 (ambient), 100, 150 F < 149, , 1,3 1,3 1,3 0, 1, 2, 4, 8, 16, 24, 36, 48 hr(s) > 250 μm 243 Both parametric and non-parametric statistical tests were considered for evaluation of the data. The decision to utilize a parametric evaluation was based upon the assumption that the underlying data distribution for a larger data set would be normally distributed. We decided against evaluating the data with non-parametric statistics due to lower statistical power (compared to parametric approaches) when using non-parametric statistics on small datasets. We state our reasoning and assumptions to recommend a cautious interpretation of the presented statistical evaluation of the data. If the underlying statistical distribution of our data is nonnormal, the resulting p-value determined through our selected ANOVA approach may be an overestimate. 12

28 Finally, tabulated data is presented as mean ± one standard deviation wherever more than one replicate had measurable metal concentrations or content. Figures are presented with the mean value indicated in a bar chart with error bars representing one standard deviation about the mean. Metal concentrations in the rinse and leaching solutions are presented in the tables and figures in units of µg/l. Mass content in bulk samples, rinse solutions, and leaching solutions presented in the figures and tables are normalized to the mass of beads used in the evaluation. The normalized metal mass is reported in units of µgmetal/gbeads. 13

29 3. RESULTS A DISCUSSION The following sections discuss the results of the experiments conducted as part of this study QA/QC The MDLs for the analysis of each metal analyte are given in Table 3.1. Because the MDLs were lower than the lowest calibration standard (1 ), the lowest calibration standard became the PQL. All reported data presented in this report are based on measurements where the analyte concentrations were present at levels above the PQL. Analytes with a concentration between the PQL and the MDL are reported in the appendices as below the quantitation limit (BQL). Analytes detected below the MDL are reported as below the detection limit (BDL). Analytes with a no observable measured response are reported as non-detectable (). Table 3.1. Method Detection Limit for ICP-MS analysis. Arsenic Chromium Copper Mercury Zinc MDL Mercury and zinc analysis were excluded due to observed interferences. During the MDL and PQL determination, significant interferences were observed for Hg and Zn within the project samples. Efforts to remove the interferences from the samples were unsuccessful. Therefore, Hg and Zn were removed from the list of analytes included in the study. Interferences were not observed for the other analytes of interest. 14

30 For a subset of the ph 4 study samples, significant background concentrations of cadmium, chromium, copper, and lead were observed in the feed water used in the column experiments. When a concentration in the feed water was measured to be above the PQL, concentrations in the column effluent samples were determined by subtracting the background levels from the measured values Experiment 1: Evaluation of Heavy Metal Composition in Bulk Bead Samples Experiment 1 was conducted in three phases. Phase 1 involved a preliminary investigation using XRF to qualitatively confirm the presence of individual metals in the bulk bead samples. Phase 2 involved using SEM-EDS to visualize the bead surface to determine the bead shape and explore the presence of residual impurities. Phase 3 included determining the metals composition for the six analytes in the bulk beads. Phase 1: Preliminary Investigation Preliminary investigation was conducted using XRF according to Section 2.3. All three batches of glass beads included spectral signatures qualitatively identified as arsenic. Researchers also observed spectral signatures indicating the presence of lead and zinc in the beads from all three batches, but interferences in the signatures due to presence of titanium did not allow for qualitative confirmation of lead and zinc in the samples using XRF. Chromium, nickel, copper, cadmium, and mercury were not observed in bulk bead samples using XRF for any samples. Phase 2: Surface Visualization Surface characterization was carried out using SEM-EDS as explained in Section 2.4. SEM scans and EDS spectra are provided in Appendix B. The scans shows glass beads 15

31 of spherical shape with some fused beads. Irregularities on the glass bead surface and non-spherical black-colored impurities were visually observed as impurities in the glass bead samples. The EDS spectra of the examined surface irregularities and non-spherical impurities indicated that these impurities were also glass. Aluminum was observed within the EDS spectra in select samples and is believed to be caused either by background levels of aluminum in the bead samples or more likely due to the samples contact with the aluminum components of the sample reducer used to subsample the batches. Phase 3: Bulk Bead Heavy Metal Content The amount of heavy metals in the glass beads was determined following the KOH fusion procedure outlined in Section 2.6 and the resulting fusion solutions containing dissolved glass bead samples were analyzed using ICP-MS (Section 2.5). Table 3.2 summarizes the results of the Phase 3 experiment by presenting the concentration of all six individual metal analytes measured within each batch. Figure 3.1 graphically depicts the mass of arsenic compared to the mass summation of all six metal analytes measured in each of the three bead batches. Arsenic content in the beads accounted for between 45% of the total measured metals content of Batch 1 beads up to 79 % of the total measured metals content of Batch 3 beads. The lowest measured arsenic content (83 μg/g in Batch 1 beads) is higher than the metals content of any other metal analyte in all the measured samples. Only nickel in Batch 2 and lead in Batches 2 and 3 had contents measured above 50 μg/g. All other metal contents observed for the other analytes were below this level. 16

32 Table 3.2. Mean ± standard deviation heavy metal content (μgmetal/gbeads) in sponsor provided recycled glass beads. Batch 1 Batch 2 Batch 3 Arsenic 83.3 ± ± ± Chromium 35.8 ± Copper ± ± ± ± 4.17 Metals 186 ± ± ± 7.29 Two of the three replicate concentrations were Not Detected Statistical testing, as described in Section 2.13, between all three batches of beads indicated that the mean arsenic and mean total metals content is not statistically similar between any pair-wise group of bead batches (Batch 1 vs Batch 2, Batch 2 vs Batch 3, and Batch 1 vs Batch 3) at the 95% confidence interval. The mean arsenic and total metals content is lowest in Batch 1 beads and highest in Batch 3 beads. 17

33 Figure 3.1. Mean arsenic and Σ(heavy metals) content in sponsor provided recycled glass beads. Error bars indicate ± one standard deviation Experiment 2: Effect of Solution ph on Metal Leaching from Recycled Glass Beads The effect of ph on leaching of the six measured metals from each batch of beads was evaluated in two phases. Phase 1 involved rinsing the beads with a ph 7 solution as described in Section 2.7. Phase 2 was designed to evaluate the amount of metals leached from the glass beads over one week using the column set up presented in Section 2.8. With the exception of cadmium and copper in two of the three ph 4 experiments, ICP-MS analysis revealed that the measurable metal concentrations of all metals fell below the PQL or were non-detectable after 48 hours. 18

34 Phase 1: Bead Rinse The ph neutral rinse solutions from all three bead batches contained measurable concentrations of all six investigated metals. Table 3.3 summarizes the mass of the six metals leached into the rinse solution normalized to the mass of rinsed beads. For each of the bead batches, the mass of arsenic was the predominant mass of the six metals observed in the rinse solutions accounting for greater than 80% of the total observed metals content in the rinse. Rinsing demonstrated that metals are easily extracted from the bead batches with a neutral ph rinse solution. The rinse study results prompted the authors to examine the bead batch samples for signs of impurities on the surfaces of the beads. SEM-EDS analysis performed in Phase 2 of Experiment 1 was not able to visually identify surface impurities that had a metallic spectral signature. Instead, as previously reported, the observed impurities were noted to be glass. Therefore, the mass of metals observed in the rinse solutions is inferred to originate from the bead surface. Statistical testing (described in Section 2.13) indicated that the mean mass release of arsenic and total metals was not statistically similar between the pair-wise comparison of batches 1 vs 2 and 1 vs 3 beads, but was statistically similar between Batch 2 and 3 beads. The mean arsenic and mean total metals content released to the rinse solutions from the beads was highest for Batch 3 beads and lowest for Batch 1 beads; following the trend noted for the mean total metals and arsenic content in the bulk beads. 19

35 Table 3.3. Mean ± standard deviaiton heavy metal content in the neutral ph rinse solutions per mass of rinsed beads (μgmetal/gbeads). Batch 1 Batch 2 Batch 3 Arsenic ± ± ± Chromium ± ± ± Copper ± ± ± Metals ± ± ± Not Detected 20

36 Phase 2: Column Study Following the Phase 1 bead rinsing experiments, a series of column leaching studies were conducted to evaluate the impact of solution ph on leaching of metals from the bead samples. Figure 3.2 shows a characteristic leaching profile observed during the column studies. Throughout all of the column studies in Experiments 2, 3, 4, and 5, the highest observable metals in solution occurred at the start of the experiment. The high initial mass release was followed by a reduction in metal mass release during the course of the experiment. Figure 3.2. Characteristic leaching profile observed during column study. The presented figure is for the mean ± standard deviation arsenic concentration observed in ph 7 leaching solution for Experiment 2 Batch 1, 2, and 3 beads. Error bars represent ± one standard deviation. 21

37 Table 3.4 shows the total individual mean metal mass leached from each bead batch during the ph studies. Figures 3.3 and 3.4 present the mean mass of arsenic and the mass of total metals leached from the bead batch subsamples for each evaluated ph. The observed measurable mass release that occurs within the first 48 hours infers that metal leaching occurs from the surface of the glass beads and not from the bead interior. This finding is in agreement with existing models describing the dissolution of the glass in the presence of water (Clark et al. 1979). If water penetrated the glass matrix, additional metal leaching from the bead would be expected. Statistical testing (described in Section 2.13) indicated that bead normalized mean arsenic content was not statistically similar in ph 7 and 10 leaching solutions, but was statistically similar in ph 4 and 7 and ph 4 and 10 leaching solutions. While the mean total metals content was observed to be ph dependent, statistical similarity of the pairwise groups trended differently for the summation of mean metals data. The amount of mean total metals content in ph 4 and 7 leaching solutions was statistically similar. However, the mean total metals content measured in ph 10 leaching solutions was lower and not statistically similar to the mean total metals contents measured in ph 4 and 7 leaching solutions. Based upon these results, we conclude that ph does effect the overall leaching of heavy metals from the glass beads. However, it is important to note that the underlying statistical relationships between the leaching of individual metal analytes under varying ph conditions may trend differently than the total amount of metals leached from the beads. 22

38 Table 3.4. Mean ± standard deviation mass of metals leached per mass of beads (μg/g) in ph 7 solution. Batch 1 Batch 2 Batch 3 Arsenic ± ± ± ± ± ± Chromium ± ± ± Copper ± ± ± ± ± ± ± Metals ± ± ± Not Detected Figure 3.3. ph Effect on mean arsenic and (heavy metals) leaching from Batch 1 beads. Error bars represent ± one standard deviation. 23

39 Figure 3.4. ph effect on mean arsenic and (heavy metals) leaching from Batch 3 beads. Error bars represent ± one standard deviation Experiment 3: Effect of UV Light Exposure on Metal Leaching from Recycled Glass Beads Following Experiment 2 s ph evaluation, a series of column leaching studies were conducted to evaluate the impact of short term exposure to high intensity UV light on the release of metals from the beads. The same column set up presented in Section 2.8 was followed, but the beads were exposed to high intensity UV light prior to placing the beads within the columns as described in Section 2.9. Because the measurable concentrations in the ph 7 experiments went below the PQL within 48 hours, the UV exposure experiments were only run for a total of 48 hours. Additionally, because the arsenic and total metals content of Batch 1 beads was lowest and Batch 3 beads was highest, Batch 2 beads were excluded from further testing in Experiments 3, 4, or 5. 24

40 Short term high intensity UV exposure durations did not impact the bead normalized mean arsenic or total metals content measured in the ph 7 leaching solution based upon the statistical analysis of the data (as described in Section 2.13). Figures 3.5 and 3.6 present the mean mass loss of arsenic and total metals for beads exposed to UV for a set duration compared to a non-uv exposure control. In all cases for both bead batches, the resulting mean heavy metals content leached into the column effluent solution (at ph 7) was statistically similar across UV exposure durations. Figure 3.5. UV exposure effect on mean arsenic and (heavy metals) leaching from Batch 1 beads. Error bars represent ± one standard deviation. 25

41 Figure 3.6. UV exposure effect on mean arsenic and (heavy metals) leaching from Batch 3 beads. Error bars represent ± one standard deviation Experiment 4: Effect of Temperature on Metal Leaching from Recycled Glass Beads A series of column leaching studies were also conducted to evaluate the impact of short term exposure to high temperatures on the release of metals from the beads. Beads evaluated for the effect of temperature were placed in an oven at 100 F or 150 F for 24 hours as described in Section 2.10 prior to being placed in the column set up (Section 2.8). The temperature effect leaching experiments were conducted for 48 hours and subsamples from Batch 1 and 3 were evaluated. Based upon the temperature effect experimental results, short term high temperature exposures did not impact the mean bead normalized total metals or arsenic content observed in ph 7 leaching solution as indicated from the statistical evaluation of the data (Section 2.13). Figures 3.7 and 3.8 present the mean arsenic and total metals 26

42 content in the ph 7 leaching solution at different temperatures for 24 hours compared to an ambient temperature control. Figure 3.7. Temperature exposure effect on mean arsenic and (heavy metals) leaching from Batch 1 beads. Error bars represent ± one standard deviation. 27

43 Figure 3.8. Temperature exposure effect on mean arsenic and (heavy metals) leaching from Batch 3 beads. Error bars represent ± one standard deviation Experiment 5: Effect of Abrasion on Metal Leaching from Recycled Glass Beads A final set of column leaching studies were conducted to evaluate the impact of abrasion on the release of metals from the beads during the column leaching study. Beads were abraded according to Section Batch 1 and Batch 3 beads from each abraded size fraction were placed into columns and the experiments were conducted according to Section 2.8 over 48 hours. Figures 3.9 and 3.10 graphically depict the release of arsenic and total metals based upon the different size fractions. Statistical testing (Section 2.13) indicated that the mean normalized mass release of arsenic and total metals were not statistically similar between the pair-wise comparison of the smallest particle fraction (<149 mm) and either 28

44 of the two larger fractions (150 to 249 beads and > 250). However, the mean arsenic and total metals content introduced into ph 7 leaching solutions from the two larger bead fractions were statistically similar. Based upon the statistical analysis of the abrasion data, the size of the glass bead does have an impact on the amount of metal leached from the surface with the smallest bead size having the highest mean amounts of measurable arsenic and total metals release into the leaching solution. For the abraded beads in the two smaller size fractions, it is clear from the post analysis of the dataset that additional leaching would be expected after 48 hours (see data in Appendix D). Therefore, the μgmetal/gbeads estimates are lower than they likely would have been if this experiment was carried out over longer durations. This result also indicated that observed leaching is from the surface of the beads as the beads with the higher surface area leached more metal. Figure 3.9. Effect of abrasion on mean arsenic and Σ(heavy metals) leaching from Batch 1 beads. Error bars represent ± one standard deviation. 29

45 Figure Effect of abrasion on mean arsenic and Σ(heavy metals) leaching from Batch 3 beads. Error bars represent ± one standard deviation. 30

46 4. CONCLUSIONS A RECOMMEATIONS Experiments conducted as part of this research evaluated the total content of six metals (As, Cr, Cu, Ni, Cd, and Pb) in recycled glass beads and investigated four experimental variables for their effect on metal release from the beads into solution during the column leaching studies. The four experimental variables examined included solution ph, the duration of exposure to short term high intensity UV light, short term temperature exposures, and abrasion (particle size fraction). Statistical testing revealed that there is an observable effect of solution ph and abrasion on the amount of arsenic and total metals leached into solution. However, the effects of temperature and UV exposure on the amount of arsenic and total metals leached into solution were not statistically similar to non-exposure controls. The overall observable metals leached from the glass beads during the leaching studies was less than a fraction of one percent of the overall metals content observed in the beads. However, concentrations of arsenic in the leaching solutions reached or exceeded 100 µg/l for samples of Batch 1 beads and reached or exceeded 3500 µg/l for samples of Batch 2 and 3 beads in almost all samples collected during the first hour. Following this first hour sample, concentrations of observed metals decrease readily. While the data presented in the body of this report are normalized to the initial mass of beads, the aqueous solution concentrations of arsenic and other metals measured in the column study are given in Appendix D. Tables 4.1 through 4.6 summarize the amount of metal mass determined in the bulk sample compared to the amount of arsenic and other metals measured in Experiment 2: Phase 1 rinse study solution, and the Experiment 2: column study with ph 7 solution. All mass amounts are normalized to the initial mass of glass beads within analyzed bead batches. Figures 4.1 through 4.3 presents the same information graphically for all 31

47 metals to show the magnitude of arsenic content in comparison to the other metals present. Based upon the results of this study, we conclude that metals are present in the bulk bead samples and in the leaching study solutions. The mean total metals content for Batch 1 beads is lower and not statistically similar to the mean total metals content present in Batch 2 and 3 beads. Arsenic is the metal present in the highest amount in all bulk bead and leaching solution samples. Due to the predominance of arsenic s contribution to total metal content in the beads, the mass release of arsenic and total metals into leaching solutions follows a similar trend. The scope of this research did not include risk assessment of the results. Future research should be focused on the presence of arsenic in the beads and resulting leach solutions due to the magnitude of arsenic present in the samples. Table 4.1. Mean ± standard deviation arsenic content in bulk beads, the rinse solution, and the ph 7 leaching solution. KOH Fusion (Total) [μg/g glass bead] Bead Rinse [μg/g glass bead] Column Leaching [μg/g glass bead] Batch ± ± ± Batch ± ± ± Batch ± ± ±

48 Table 4.2. Mean ± standard deviation cadmium content in bulk beads, the rinse solution, and the ph 7 leaching solution. KOH Fusion (Total) [μg/g glass bead] Bead Rinse [μg/g glass bead] Column Leaching [μg/g glass bead] Batch ± Batch ± Batch ± Two of the three replicate analyte concentrations were Not detected Table 4.3. Mean ± standard deviation chromium content in bulk beads, the rinse solution, and the ph 7 leaching solution. KOH Fusion (Total) [μg/g glass bead] Bead Rinse [μg/g glass bead] Column Leaching [μg/g glass bead] Batch ± ± ± Batch ± ± Batch ± ± Two of the three replicate analyte concentrations were Not detected 33

49 Table 4.4. Mean ± standard deviation copper content in bulk beads, the rinse solution, and the ph 7 leaching solution. KOH Fusion (Total) [μg/g glass bead] Bead Rinse [μg/g glass bead] Column Leaching [μg/g glass bead] Batch ± ± Batch ± ± Batch ± ± Two of the three replicate analyte concentrations were Not detected Table 4.5. Mean ± standard deviation lead content in bulk beads, the rinse solution, and the ph 7 leaching solution. KOH Fusion (Total) [μg/g glass bead] Bead Rinse [μg/g glass bead] Column Leaching [μg/g glass bead] Batch Batch ± ± Batch ± 7.98 Two of the three replicate analyte concentrations were Not detected 34

50 Table 4.6. Mean ± standard deviation nickel content in bulk beads, the rinse solution, and the ph 7 leaching solution. KOH Fusion (Total) [μg/g glass bead] Bead Rinse [μg/g glass bead] Column Leaching [μg/g glass bead] Batch ± ± Batch ± ± Batch ± Not detected Figure 4.1. Mean heavy metal content in sponsor supplied recycled glass bead. Error bars represent ± one standard deviation. 35

51 Figure 4.2. Mean heavy metal content leached into rinsing solution. Error bars represent ± one standard deviation. Figure 4.3. Mean heavy metal content released into ph 7 solution during the 48 hour column leaching studies. Error bars represent ± one standard deviation. 36

52 REFERENCES Brinkely, A. L. (1994) Characterization of Rocky Flats and Oak Ridge glass containing mixed wastes. MS Thesis, MIT. Clark, D. E., C. G. Pantano, and L. L. Hench (1979) Corrosion of Glass Books for Industry, New York, N.Y. Cerefice, G. S. (1996) Proliferation resistance of borosilicate glass as a host for weapons- grade plutonium. MS Thesis, MIT. EPA Method 6020A (1998). Inductively coupled plasma-mass spectrometry. The Environmental Protection Agency Scheir, R. and F. Fencl. (1996). Using UVC Technology to Enhance IAQ, HPAC Heating/Piping/Air Conditioning v.68 (February 1996) p CFR Appendix B: Part 136. Definition and Procedure for the Determination of the Method Detection Limit 37

53 APPEIX A: QA/QC REVIEWED DATA USED TO DETERMINE METHOD DETECTION LIMITS 38

54 Table A.1. Determination of background instrument response for eight blanks. Arsenic Chromium Copper Mercury Zinc Blank Blank Blank Blank Blank Blank Blank Blank Average Std. Dev times the average

55 Table A.2. Data used to determine Method Detection Limit (MDL). Arsenic Chromium Copper Mercury Zinc Blank Blank Blank Blank Blank Blank Blank Blank Blank Blank Average Std. Dev Method Detection Limit (MDL) mercury and zinc analysis exhibited significant interferences. 40

56 APPEIX B: SURFACE VISUALIZATION A BULK COMPOSITION USING SEM-EDS 41

57 Figure B.2. Figure B.3. Figure B.1. SEM image of slide with glass beads (Batch 1) Figure B.2. SEM image of three black-colored imputrities (Batch 1) 42

58 Figure B.4. Figure B.3. SEM image identifying location of impurities on surface of glass bead (Batch 1). 43

59 Figure B.4. SEM image and EDS spectrum of surface impurity on glass bead (Batch 1). 44

60 Figure B.5. SEM image and EDS spectrum of black-colored impurity (1):Figure B.2. 45

61 Figure B.6. SEM image and EDS spectrum of black-colored impurity (2):Figure B.2. 46

62 Figure B.7. SEM image and EDS spectrum of black-colored impurity (3: Figure B.2. 47

63 Figure B.11. Figure B.10. Figure B.9. Figure B.8. SEM image of slide with glass beads (Batch 2). 48

64 Figure B.9. SEM image of impurity attached to glass bead (Batch 2). Figure B.10. SEM image of fused glass bead (Batch 2). 49

65 Figure B.12. Figure B.13. Figure B.11. SEM imageof surface impurities on a glass bead (Batch 2). 50

66 1 2 Figure B.12. SEM image and EDS spectrum of surface impurity (1) on Batch 2 bead 51

67 1 2 Figure B.13. SEM image and EDS spectrum of surface impurity (2) of glass bead (Batch 2) 52

68 Figure B.14. SEM image and EDS spectrum surface impurity on glass bead (Batch 2) 53

69 Figure B.15. SEM image and EDS spectrum of area around surface impurity (Batch 2) 55

70 Figure B.16. SEM image and EDS spectrumof surface impurity on glass bead (Batch 2) 56

71 Figure B.18. Figure B.21. Figure B.17. SEM image of slide with glass beads (Batch 3). 57

72 Figure B.18. SEM image of impurity attached to glass bead (Batch 3). 58

73 Figure B.19. SEM image of fused glass beads (Batch 3). 59

74 Figure B.20. SEM image of crystalline needle-shaped glass (Batch 3). 60

75 Figure B.21. SEM image of fused glass beads (Batch 3). 61