Leaching Behavior of Coal Combustion Products and the Environmental Implication in Road Construction. Project Progress Report. Jianmin Wang NUTC R201

Transcription

1 Leaching Behavior of Coal Combustion Products and the Environmental Implication in Road Construction Project Progress Report by Jianmin Wang NUTC R21

2 Disclaimer The contents of this report reflect the views of the author(s), who are responsible for the facts and the accuracy of information presented herein. This document is disseminated under the sponsorship of the Department of Transportation, University Transportation Centers Program and the Center for Transportation Infrastructure and Safety NUTC program at the Missouri University of Science and Technology, in the interest of information exchange. The U.S. Government and Center for Transportation Infrastructure and Safety assumes no liability for the contents or use thereof. NUTC ###

3 Technical Repo rt Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. NUTC R21 4. Title and Subtitle Leaching Behavior of Coal Combustion Products and the Environmental Implication in Road Construction: Project Progress Report 5. Report Date January Performing Organization Code 7. Author/s Jianmin Wang 9. Performing Organization Name and Address Center for Transportation Infrastructure and Safety/NUTC program Missouri University of Science and Technology 22 Engineering Research Lab Rolla, MO Performing Organization Report No Work Unit No. (TRAIS) 11. Contract or Grant No. DTRT6-G Sponsoring Organization Name and Address 13. Type of Report and Period Covered U.S. Department of Transportation Research and Innovative Technology Administration Final 12 New Jersey Avenue, SE Washington, DC Sponsoring Agency Code 15. Supplementary Notes 16. Abstract The use of coal fly ash in road base and sub-base applications can provide better properties and performance, and is superior to it being otherwise disposed and becoming a possible environmental liability. Understanding the metal leaching behavior for various fly ashes can help the construction industry and the energy industry in selecting the environmentally benign fly ash for road construction and for other beneficial use applications, and determining the long term environmental impact of fly ash during road construction. Coal fly ash contains many regulated cationic and oxyanionic elements such as antimony, arsenic, barium, boron, cadmium, chromium, cupper, lead, mercury, molybdenum, nickel, and selenium. Due to the implantation of several new air emission control regulations, future fly ash may contain elevated concentrations of volatile trace elements especially oxyanionic elements. Since oxyanionic elements have greater mobility in the environment, being less studied previously, and are generally more toxic than cationic elements, understanding the leaching behavior of oxyanionic elements from fly ash is significant in determining the potential environmental impact of fly ash during disposal or beneficial use, selecting the appropriate fly ash for road construction, and developing methods to control the leaching of oxyanionic elements. This research becomes more urgent due to the implementation of more stringent arsenic standards in drinking water that will become effective in January 26. This research will focus on the leaching behavior of 6 major oxyanionic elements, antimony, arsenic, boron, chromium, molybdenum, and selenium, for various fly ashes under different management scenarios, using both batch and column experiments. Mathematical models will be developed to quantify the leaching behavior of these elements. Speciation of these oxyanionic elements will be determined using the most advanced Perkin-Elmer HPLC-ICP-MS system available at Missouri S&T. 17. Key Words Soil stabilization, fly ash, leaching, heavy metals 18. Distribution Statement No restrictions. This document is available to the public through the National Technical Information Service, Springfield, Virginia Security Classification (of this report) 2. Security Classification (of this page) 21. No. Of Pages 22. Price unclassified unclassified Form DOT F 17.7 (8-72) 41

4 Project Progress Report Leaching Behavior of Coal Combustion Products and the Environmental Implication in Road Construction By Jianmin Wang January 26, 29

5 Index List of Tables... 3 List of Figures Introduction Background Objectives Work accomplished Sample Collection and Characterization Fly ash samples Moisture content and LOI Total composition of 14 fly ashes XRF results for major and trace elements Trace elements Equilibrium-Based Assessment-Batch Leaching Leaching of seven new ashes at four S/L ratios without adjustment Leaching of seven new ashes at S/L ratio 1:1, Sulfate and Impact on Trona Ash Leaching Methods Results Comparison of leaching results for SO 2 control paired samples Comparison of leaching results for SO 3 control paired samples

6 List of Tables Table 1. Fly ash sample information... 1 Table 2. LOI and moisture content Table 3. Major element content in the 14 fly ash samples (XRF) Table 4. Complete acid digestion procedure... 2 Table 5. Complete acid digestion results Table 6. Total extractable digestion results Table 7. Natural of NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT #121at S/L ratios 1:2, 1:5, 1:1, and 1: Table 8. Leachate of the paired trona samples at S/L 1:2, 1:5, 1:1, and 1: List of Figures Figure 1. Leaching of major elements and anions at S/L ratios 1:2, 1:5, 1:1, and 1:2 without adjustment for NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT # Figure 2. Leaching of trace elements at S/L ratios 1:2, 1:5, 1:1, and 1:2 without adjustment for NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT # Figure 3. Leaching of major and trace cationic elements from NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT #121. S/L=1:1, Figure 4. Leaching of major and trace anionic elements from NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT #121. S/L=1:1, Figure 5. TOC, TIC, and TC in the leachate of NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT #121. S/L=1:1, Figure 6. Comparison of leaching of major and trace cationic elements in the paired sample for SO 2 control. NRT #182 is the control ash, NRT #183 is the trona ash, S/L=1: Figure 7. Comparison of leaching of major and trace oxyanionic elements in the paired sample for SO 2 control. NRT #182 is the control ash, NRT #183 is the trona ash, S/L=1: Figure 8. Comparison of leaching of major and trace cationic elements in the paired sample for SO 3 control. NRT #12 is the control ash, NRT #189 is the trona ash, S/L=1: Figure 9. Comparison of leaching of major and trace oxyanionic elements in the paired sample for SO 3 control. NRT #12 is the control ash, NRT #189 is the trona ash, S/L=1:

7 1. Introduction 1.1. Background This is the third annual report for Project # Project #43352 is designed to establish the leaching characteristics for several different types of ash using a relatively rigorous leaching procedure developed by Kosson et al (22) for a wide range of constituents. That data will ultimately become part of a broader database of leaching characteristics that will be used to identify families of curves for a range of constituents and ash types, for prediction of leaching potential. In addition to the previous work at Missouri S&T (Former UMR) on the leaching of arsenic and selenium from a few selected fly ash samples, more detailed work on arsenic and selenium, including their dominant aqueous species, will be performed in this project. This will include development of data on intrinsic leaching parameters, such as total leachable mass and adsorption constants. The metal leaching behavior information for various coal fly ashes will help the construction industry in determining the types of fly ash that yield the minimum environmental impact for road construction. It will also help the energy industry in determining the potential environmental impact of the fly ash during disposal and other beneficial use applications Objectives This project will (1) evaluate the leaching behavior of several different ash types under possible field management scenarios using the Kosson procedure. (2) Determine control mechanisms for arsenic and selenium release, including evaluation of individual species. (3) Establish a protocol for the determination of total leaching potential of arsenic and selenium in fly ash Work accomplished This part of the project investigates equilibrium leaching behavior of fourteen fly ash samples. NRT #169, NRT #17, NRT #182, NRT #183, NRT #12, NRT #189, NRT #186, NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, NRT #121. Previous reports have presented results for the basic sample characterization, equilibrium based assessment for NRT 4

8 #169, NRT #17, NRT #182, NRT #183, NRT #12, NRT #189, and NRT #186. Mass transfer based assessment on arsenic, and selenium speciation was also studied in our previous report, using paired trona samples. This study will present (1) The recent sample characterization data for all the 14 ashes. (2) The equilibrium based leaching results for the seven ash samples we received on July 21st 28: NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, NRT #121. (3) Impact of and sulfate on the leaching characteristics of trona ash. 2. Sample Collection and Characterization 2.1. Fly ash samples A total of fourteen ash samples were studied in this project. Two samples were generated from sub-bituminous coal: NRT#121, and NRT #186. The rest twelve samples were generated from bituminous coal. The detailed sample information is shown in Table Moisture content and LOI Moisture content was determined for quantifying purpose. Loss-on-ignition (LOI) was determined to indicate the carbon content levels in fly ash. Empty crucibles were dried at 15 o C overnight until stable (We), cooled in a desiccator, and weighed. About 1 grams of ash was weighed into the crucibles (Ws), and dried at 15 o C for at least 2 hours, cooled in a desiccator and weighed (Ww). The samples were then heated to 5 o C for four hours, cooled in a desiccator, and weighed again (Wc). The moisture content is given by ratior of (Ws+We- Ww)/(Ws), the LOI is given by the ratio of (Ww-Wc)/(Ww-We). Three replicates were made for each of the 14 fly ash samples. Table 2 shows the results. The moisture content for each ash was no more than.5 %. The paired sample NRT #182, NRT #183 have much higher LOI value(8.75%, and 1.59% respectively) than other ash samples, LOI values of samples NRT #34,, NRT#169, NRT#17 were close to 5%, LOI values of NRT #94, NRT#13, NRT#14, NRT#12, and NRT #189 ranged from 1.37% to 2.11 %, ash NRT#89, and the two class C ashes NRT #121 and NRT #186 have the lowest LOI values of less than 1%. 5

9 Table 1. Fly ash sample information. Sample Plant Sample Sample Unit FA SO3 SO2 Hg Unit Type Source Sulfur SCR/SNCR FGC NRT # ID Type Date* MW Control Control Control Control FA 1/6/4 Bit ESPh Trona LSFO No None FA 12/1/5 4 Bit Ohio High None ESPc None FSI No None FA 1/2/5 Bit ESPc? None None No S FA 4/5/5 Bit SCR on? ESPc None SDA No None FA 4/5/5 Bit None? ESPc None LSFO No None FA 7/6/6 Bit ESPc? None Trona No None? &2 FA 9/6/8 512 Sub Wyoming Low SCR on ESPc None None No None? FA Bit None? ESPc FA/FSI Bit None? ESPc FA Bit None? ESPh FA Bit None? ESPh SDAA Sub None FF 12* 3585 FA Bit SCR ESPc FA Bit SCR ESPc Table 2. LOI and moisture content. Sample ID Moisture content (%) LOI (%) NRT # NRT # NRT # NRT # NRT # NRT # NRT # NRT# NRT# NRT# NRT# NRT# NRT# NRT#

10 2.3. Total composition of 14 fly ashes XRF results for major and trace elements The total composition of major elements and some trace elements of the 14 ashes were analyzed with XRF (NITON Analyzer, XL3T 9, Thermoscientific). The detection limit of XRF was approximately 1 ppm (mg/kg). Elements undetectable with XRF and those lighter than Mg (including Na, Cd, Hg, B, Be and Li) was analyzed with complete acid digestion, and total extractable procedure following EPA method 351A, followed by ICP-OES, ICP-MS or Mercury analyzer. The XRF results of the fourteen ashes were listed in Table 3. As for the typical fly ash samples, the four major elements in all the fourteen fly ashes are Si, Al, Ca, and Fe. Calcium content in ashes NRT #169, and the two class C ashes NRT #121 and NRT #186 are much higher than other ash samples. Sulfur content is high in samples NRT #186 (5.3%), and NRT #169 (3.71%). Iron content is high in ashes NRT #89, NRT #13, NRT #14, NRT #17, NRT #12, and NRT #189. Samples NRT #34, NRT #121, and NRT #186 showed higher strontium content. Mg content was the highest in NRT #121, it is undetectable in other ash samples using the XRF method. Table 3. Major element content in the 14 fly ash samples (XRF). Major Elements Trace Elements Al Si S Ca Fe Mg P Ba Sr Cl Pb Zn Cr Ash ID % % % % % % % % % % ppm ppm ppm NRT# ND NRT# ND NRT# ND NRT# ND NRT# ND ND ND NRT# NRT# ND ND NRT# ND NRT# ND NRT# ND ND NRT# ND NRT# ND NRT# ND ND - Non Detectable.

11 Trace elements The fourteen fly ash samples were initially tried for complete acid digestion, with Multiwave 3 microwave digestor (Anton Paar USA), a procedure with 9 ml HNO 3, 3 ml HCl, and 3 ml HF (Table 4) was recommended by the manufacture for coal fly ash digestion with eight-rotor set up. Table 5 shows the complete acid digestion results. For each batch of digestion, sample duplicate, sample spike, reference material SRM1633b, and reagent blank were included for QA/QC check. Due to the instrumental problems occurred during the digestion procedure, all the 14 fly ashes were digested at least twice, liquid samples generated from the digestion was filtrated with.2 µm filter and analyzed on ICP-MS, ICP-OES, and Tekran Mercury analyzer. The QA/QC for Be, Mo, Se, Ag, Cd, Li, Re were good, but part of the QA/QC for As, Co, Cu, Mn, Ni, Pb, Sb, Sr, Tl, V, and Zn was not satisfactory. In complete digestion procedure, the digestion liquid was clear in the beginning, but after overnight settling, white colloidal particulates formed, and they precipitated at the bottom of the tube in a longer time. After dump the supernatant, adding 1 ml concentrated HF can not dissolve these white particles, and they are not dissolvable even by heating on the hot plate at 15 o C for 2 hours. There are several literatures on the digestion of coal fly ash, most of them concluded that complete digestion is not possible or at least hard to reach, which was proved in our case also. Total extractable digestion is used in most studies, which is sufficient for environmental concern research. Therefore, we tried total extractable digestion for all the 14 fly ashes following EPA method 351A. The digestion procedure is shown in Table 4, and Table 6 shows the total extractable digestion results. Table 4. Complete acid digestion procedure. Method Sample Weight Acid hold time (min) HNO 3 9mL Temperature 24 o C.1 g HCl 3mL Ramp Time 1min HF 3mL Hold Time 3min Complete Digestion EPA 351A.1 g HNO 3 9mL HCl 3mL Temperature 175 o C Ramp Time 5.5 min Hold Time 4.5min 2

12 Table 5. Complete acid digestion results. Ash ID Ba Sr Mn Cu Cr Zn Ni Li Mo Pb Co Se (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# Ash ID V As Be Sb Tl Cd Ag Re Hg (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppb) NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT#

13 NRT# NRT# NRT# Table 6. Total extractable digestion results. B K Mg Na Ba Sr Mn Cu Cr Zn Ni Li Mo Ash ID (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# NRT# Pb Co Se V As Be Sb Tl Cd Ag Re Hg Ash ID (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppb) NRT# ND NRT# ND NRT# NRT# NRT# ND ND

14 NRT# ND NRT# ND ND NRT# NRT# NRT# ND ND ND 5.8 NRT# NRT# NRT# ND

15 3. Equilibrium-Based Assessment-Batch Leaching The purpose of batch leaching experiments was to determine the leaching equilibrium as a function of and solid/liquid (S/L) ratio using batch leaching methods for the constituents listed in Table 2 of the proposal. Batch leaching experiments for the fourteen fly ash samples was carried out at S/L ratios 1:2, 1:5, 1:1, 1:2 without adjustment, and at S/L ratio 1:1 with adjusted to 2-12 (12 points) or 4-12 (6 points). The results for NRT #169, NRT #17, NRT#182, NRT#183, NRT #12, NRT #189, and NRT #186 have been presented in previous two reports. This report will illustrate the batch leaching result for NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT #121(7 new ashes samples) Leaching of seven new ashes at four S/L ratios without adjustment Table 7 shows the leachate of NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT #121 at four S/L ratios. Leachate of ashes NRT #34 and NRT #153 was strongly acidic, close to 4. Leachate of ashes NRT #13, NRT #14, and NRT #121 was strongly basic, with the greater than 12. Leachate of ashes NRT #89 and NRT #94 was slightly basic. Table 7. Natural of NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT #121at S/L ratios 1:2, 1:5, 1:1, and 1:2. Leachate NRT NRT # NRT # NRT NRT NRT NRT # #13 #14 #153 #121 1: : : : Figure 1 shows the leaching of major elements(in ppm level) under different S/L ratios 1:2, 1:5, 1:1, 1:2 without adjustment, while Figure 2 shows the leaching of trace elements (in ppb level). For all the 7 ashes, Ca, K concentrations were higher among major cationic elements leached out (in ppm level), while SO 2-4 leached out the most 6

16 among the major anions. Mg concentration was also high in the leachate of NRT #34, NRT #89, NRT #94, and NRT #153, B concentration was high in leachate of NRT #94, NRT #13, and NRT #14. Li, Mo, Zn concentration was the highest among all the trace elements, leachate of NRT #89, NRT#94, NRT #13, NRT #14, NRT #121 also contained significant amount of Ba, while leachate of NRT #34, and NRT #153 contained high concentration of Cu. For most elements, the soluble concentration increased with increase of S/L ratio, such as Li, B, K, Na, Sr, Mo, and Se. This may be because these elements tend to be in soluble phase at the natural condition; whereas others showed an opposite trend, such as As, Tl, and Ba in ash NRT #89, NRT #94, NRT #13, and NRT #14, and Al in ash NRT # 121. This may be caused by the precipitation of them with other elements as the S/L ratio increased. Conc (mg/l) NRT# Ca TDS SO42-1:2 1:1 1:5 1:2 1 Al B Si Mg K Na Fe Sr F- Cl- TC TIC TOC Conc (mg/l) NRT# Ca TDS SO42-1:2 1:1 1:5 1:2 1 Al B Si Mg K Na Fe Sr F- Cl- TC TIC TOC 7

17 9 NRT#89 Conc (mg/l) Ca TDS SO42-1:2 1:1 1:5 1:2 18 Al B Si Mg K Na Fe Sr F- Cl- TC TIC TOC 12 Conc (mg/l) Ca TDS SO42-1:2 1:1 1:5 1:2 2 Al B Si Mg K Na Fe Sr F- Cl- TC TIC TOC Conc (mg/l) NRT# Ca TDS SO42-1:2 1:1 1:5 1:2 3 Al B Si Mg K Na Fe Sr F- Cl- TC TIC TOC 8

18 16 NRT#14 Conc (mg/l) Ca TDS SO42-1:2 1:1 1:5 1:2 4 2 Conc (mg/l) Al B Si Mg K Na Fe Sr F- Cl- TC TIC NRT# Ca TDS Na Sr 1:2 1:1 1:5 1:2 Al B Si Mg K Fe F- Cl- SO42- TC TIC TOC Figure 1. Leaching of major elements and anions at S/L ratios 1:2, 1:5, 1:1, and 1:2 without adjustment for NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT #121. 9

19 Conc (ug/l) NRT#34 Mn Ni Cu Zn Mo Li 1:2 1:1 1:5 1:2 4 2 Ag As Be Cd Co Cr Pb Re Sb Se Tl V Ba Conc (ug/l) Zn Mo Li NRT#94 1:2 1:1 1:5 1:2 4 Ag As Be Cd Co Cr Pb Re Sb Se Tl V Mn Ni Cu Ba Conc (ug/l) NRT#89 Zn Mo Li 1:2 1:1 1:5 1:2 4 Ag As Be Cd Co Cr Pb Re Sb Se Tl V Mn Ni Cu Ba 1

20 :2 1:1 Conc (ug/l) Ni Cu Zn Mo Li 1:5 1:2 5 Ag As Be Cd Co Cr Pb Re Sb Se Tl V Mn Ba 14 NRT#13 Conc (ug/l) Zn Mo Li Ba 1:2 1:1 1:5 1:2 2 Ag As Be Cd Co Cr Pb Re Sb Se Tl V Mn Ni Cu Conc (ug/l) NRT#14 Zn Mo Li Ba 1:2 1:1 1:5 1:2 2 1 Ag As Be Cd Co Cr Pb Re Sb Se Tl V Mn Ni Cu 11

21 Conc (ug/l) Ba NRT# Mo Li 1:2 1:1 1:5 1:2 5 Ag As Be Cd Co Cr Pb Re Sb Se Tl V Mn Ni Cu Zn Figure 2. Leaching of trace elements at S/L ratios 1:2, 1:5, 1:1, and 1:2 without adjustment for NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT # Leaching of seven new ashes at S/L ratio 1:1, 4-12 Figures 3 illustrates the leaching of major and trace cationic elements (Ca, Al, Mg, Fe, K, Na, Sr, Ba, Zn, Ni, Cu, Co, Be, Pb, Tl, Cd and Ag ) at S/L ratio 1:1, and 4-12 (6 s). Figure 4 shows the leaching results of major and trace anionic elements (B, Si, V, Mo, Se, As, Cr, Sb, and Mn) and the major anion SO Subbituminous coal ash NRT #121 generally leached significantly higher amount of major elements (Al, Mg, Sr, B) than other 6 bituminous coal ash samples at 3, this could be cause by the fly ash dissolution at this, since this ash is highly alkaline (natural =12.6 at S/L 1:1), large amount of concentrated HNO 3 (2 ml 7% HNO 3 ) was added during titration to reach this level. During the leaching experiment, once MQ water was added into the bottle with NRT #121 ash, cementation started, and it could not be easily dissolved even large amount of acid was added. This may contribute to the inconsistent leaching curve of NRT #121. Ca in the 7 ash samples displayed the highest leachability among all the elements, and its leaching decreased with increase of. Precipitation of Ca(OH) 2 may be the reason for the sharp decrease of Ca concentration at greater than 12. The Ca leaching curve also 12

22 indicated that at the same, ash NRT #13 and NRT#14 can release significantly more Ca than other bituminous coal ashes. The three major elements Al, Si, Mg and Fe, and nine trace elements Mn, Cu, Pb, Be, Tl, Cd. Zn, Ni, and Co showed a typical leaching behavior as other cationic metals. Their leaching generally was negligible at alkaline conditions, but increased significantly as is decreased to below a certain level, which was 8 here for the four elements. Similar leaching behavior was observed for other elements including Ca, Sr, Ba, and B, and SO 2-4 from NRT #121. However, the release of these elements was decreasing gradually over The remarkable release of these elements at low might be caused by not only surface desorption, but also by acid/base dissolution, because significant amount of acid was used to reduce for ashes NRT #13, NRT #14, and NRT #121, while significant amount of strong base was added to adjust the for ash NRT #34, and NRT #153. The leaching results of K, and Li indicated that they were in soluble phase in entire range. SO 2-4 from NRT #34, NRT #89, NRT #94, NRT #153 showed similar leaching trend, leaching of Re and SO 2-4 from NRT #13, NRT #14 are similar over < 9, but there is a sharp decrease at high, the sharp decrease at higher was probably caused by particle precipitation. Pb, Be, Re, and Ag displayed the least leaching potential (< 1 ug/l), and larger error was expected for their analysis with ICP-MS, because the sample concentration were close to detection limit after dilution (1 to 1 times dilutions were required for most samples, because the high TDS in samples will shorten the life of cones in ICP-MS). F -, Cl - release was not significant either, because there concentrations are below detection limit on IC after 5 times dilution. Therefore, the leaching curve for F -, and Cl - were not presented in this report. For all the seven ashes, B and Si showed the highest leachability among all oxyanions, and their leaching increased with the decrease of, similar trend was observed for Mn in Figure 4. For most of the seven ashes, leaching of As, V, Se, and Cr demonstrated similar trends, which had the least release range, and leaching is increased as was 13

23 at two extremes used in the experiment (to a lower range, and higher range), and the minimum release range was between 6 and 9 for these three elements. However, the leaching of As from NRT #89 was decreasing with the increase of over Leaching of Mo generally increased with the increase of over 4-9.5, but decreased over >9.5, similar decrease of As, V, Se, Cr, and Sb was also observed for other ash samples (especially Cr, Sb leaching from NRT #13 and NRT #14) at this higher range, this could because of the Ca precipitation impact. NRT #13 and NRT #14 generally leached more Mg, Ca, Cd, Tl, Fe, B, Si, Mo, and Cr than other ashes over NRT #34 released more Al, Sr, Cu, Li. The leachate of NRT #121 had higher concentrations of Zn, Ni, Ba, and Co, and higher Se concentration at extreme acidic range. NRT #153 released more As, V, Sb, and Se at alkaline range. Al concentration was also high in leachate of NRT #94 over 4-12, and there was also a higher concentration of Se over alkaline range. The leachate of NRT #89 had higher concentration of Al, Mg over 4-12, and higher concentrations of As over <9. 14

24 Al (mg/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 ) Al (mg/l NRT# Mg (mg/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 Mg (mg/l) NRT# NRT#34 NRT#94 NRT#121 Sr (mg/l) NRT#89 NRT#13 NRT#14 Sr (mg/l)

25 Ca (mg/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 Ca (mg/l) NRT# K (mg/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 NRT#121 Fe (mg/l) TDS (mg/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 TDS (mg/l) NRT#

26 Ba (ug/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 NRT#121 Li (ug/l) Co (ug/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 NRT#121 Cu (ug/l) Ni (ug/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 NRT#121 Zn (ug/l)

27 Cd (ug/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 NRT#121 Tl (ug/l) Be (ug/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 NRT#121 Pb (ug/l) NRT#34 NRT#94 4 Re (ug/l) 3 2 NRT#89 NRT#13 NRT#14 Ag (ug/l) NRT# Figure 3. Leaching of major and trace cationic elements from NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT #121. S/L=1:1,

28 B (mg/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 B (mg/l) NRT# Si (mg/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 Si (mg/l) NRT# SO4 2- (mg/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 SO4 2- (mg/l) NRT#

29 As (ug/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 NRT#121 Mn (ug/l) V (ug/l) 9 6 NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 NRT#121 Se (ug/l) Mo (ug/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 NRT#121 Cr (ug/l)

30 Sb (ug/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 NRT# Figure 4. Leaching of major and trace anionic elements from NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT #121. S/L=1:1,

31 Figure 5 shows the total organic carbon (TOC), total inorganic carbon (TIC), and total carbon (TC) concentrations in the seven new ash samples, similar to the case of former fly ash samples, the curves for TOC and TC do not show any consistent trend. Leachate of ashes NRT #34 and NRT #14 contained higher concentrations of TC and TOC than other five ashes. Except for ash NRT #13, the TIC in these fly ash leachates generally increased with the increase of, the TIC of which decreased at around 8.5, which could mean that precipitation occurred or analytical error. TC (mg/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 NRT#12 TOC (mg/l) TIC (mg/l) NRT#34 NRT#94 NRT#89 NRT#13 NRT#14 NRT# Figure 5. TOC, TIC, and TC in the leachate of NRT #34, NRT #89, NRT #94, NRT #13, NRT #14, NRT #153, and NRT #121. S/L=1:1,

32 4. Sulfate and Impact on Trona Ash Leaching Our previous study compared the leaching results of two paired trona ash samples, and found that most trace elements concentrations in the Trona ash were higher than that of the according control ash, especially for the paired sample for SO2 control, the leaching of oxyanionic elements enhanced significantly, which could pose great environmental concerns for the disposal of the trona ash. Based on the XRF and total composition result, the major difference between trona ash and the control ash was the sulfur, sodium content, and the of the leachate. We suspect higher sulfur content will compete with oxyanions such as As, Se, V, Mo, Cr for adsorption onto fly ash surface, and has been found to be an important factor impacting the leaching of these elements. So this study focused on the impact of sulfate and on the leaching of fly ash, using the two paired trona ash, which is NRT #182&NRT #183 for SO 2 control, NRT #12&NRT #189 for SO 3 control Methods Based on the XRF result, this study added sulfate into the control ash to reach the similar sulfur content as the according trona ash, the addition was.79 g K 2 SO 4 / g NRT#182, and.43 g K 2 SO 4 /g NRT#12. One batch leaching experiment for the control ash was carried out with only sulfate addition, and the other batch leaching experiment with not only sulfate addition, the was also adjusted to the level similar to the according trona ash. The leachate of these batch leaching experiments were filtered through.2 µm filters, and analyzed on ICP-MS and ICP-OES Results The leaching results for major elements, trace elements were compared among the four batch experiments: (1) Control ash, (2) Control ash + sulfate addition, (3) Control ash + sulfate addition + adjustment, and (4) Trona ash. Figure 6 and Figure 7 illustrate the comparison for paired sample of SO 2 control. Figure 8 and Figure 9 present the comparison for paired sample of SO 3 control. Figure 6 and Figure 8 illustrate the leaching results for major and trace cationic elements; Figure 7 and Figure 9 illustrate the leaching 23

33 results for oxyanionic elements. Four S/L ratios 1:2, 1:5, 1:1, and 1:2 were used in the batch leaching study, the of the leachate is shown in Table 8. Table 8. Leachate of the paired trona samples at S/L 1:2, 1:5, 1:1, and 1:2. S/L NRT#182 Sulfate Sulfate+ NRT#183 1: : : : S/L NRT#12 Sulfate Sulfate+ NRT#189 1: : : : Comparison of leaching results for SO 2 control paired samples Figure 6 and Figure 7 demonstrated that, for the paired sample NRT #182 & NRT #183 (SO 2 control), both sulfate addition and adjustment reduced the leaching of Li, Zn, Sb, Ca, and Be, but the leaching of these elements in the trona ash NRT#183 was actually increased over the control ash NRT#182, indicating the different leaching characteristics observed between trona ash (NRT #183) and control ash (NRT #182) is not caused by the competitive adsorption from sulfate or the increase, further studies are needed to find out the mechanism. Results in Figure 6 and Figure 7 also indicate that the higher sulfur content and alkalinic of the trona ash are responsible for the increased leaching of Cu, As, Cr, Mo, Al, Pb, because both sulfate addition and adjustment enhanced the leaching of these elements from the control ash. Sulfate addition increased the leaching of Se, B, and Cd from the control ash, but further increase the will reduce the leaching of these elements from the control ash. Contrary results were observed for V, Si, Re, and Ag, where sulfate reduced the leaching of these elements, but further increase the will enhance their leaching, all these elements released more in the trona ash than the control. Ba, Fe, Sr, Mn, Ni, Co, Tl, Mg was released less in the trona ash than the control, as the comparison in these two figures demonstrate, precipitation by sulfate could possibly explain the reduced leaching of Ba and Fe, while increase is more responsible for the reduced leaching of Sr, Mn, Ni, Co, Tl, and Mg. 24

34 Comparison of leaching results for SO 3 control paired samples For the paired sample NRT #12 & NRT #189 (SO 3 control) in Figure 8 and Figure 9, both sulfate addition and adjustment (decrease the from 9.7 to 7.1) reduced the leaching of Ba, but Ba leaching was much higher in the trona ash than the control, contrary results were observed for Sr, and Tl, indicating the increased leaching of Ba and decreased leaching of Sr, and Tl in the trona ash NRT #189 was caused by mechanism other than the competitive adsorption from sulfate or the change. The higher sulfur content and lower of the trona ash were responsible for the increased leaching of Sb, Mn, Pb, and Be, because both sulfate addition and adjustment enhanced the leaching of these elements from the control ash, as demonstrated by the leaching results in Figure 8 and Figure 9. Sulfate addition increased the leaching of As, Se, Cr, and V from the control ash, but further decrease the will reduce the leaching of these elements from the control, contrary results were observed for Si, Ni, Co, Mg, B, Cd, and Re, where sulfate reduced the leaching of these elements, but further decrease will enhance their leaching, all these elements released more in the trona ash than the control. Ca, Fe, Al was released less in the trona ash than the control; precipitation by sulfate could possibly explain the reduced leaching of Ca and Fe, while decrease is more responsible for the reduced leaching of Al. It should be noted that sulfate addition + adjustment for the control ash NRT #182 almost reached the similar leaching levels of Mo, B, and Pb with that of the trona ash NRT #183. Similarly, sulfate addition + adjustment for the control ash NRT #12 almost reached the similar leaching levels of Pb with that of the trona ash NRT #189. For the other elements, neither sulfate addition or sulfate addition + adjustment of the control ash got equivalent leaching results with that of the trona ash, indicating there are some other mechanisms responsible for the different leaching characteristics of these elements in the control ash and the trona ash, further studies are needed to find out the reason. 25

35 L) Ca (mg/ NRT#182 NRT#182+Sulfate NRT#182+Sulfate+ adjustment NRT#183 Fe (mg/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1: Al (mg/l) NRT#182 NRT#182+Sulfate NRT#182+Sulfate+ adjustment NRT#183 Mg (mg/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 6 8 Sr (mg/l) 4 2 NRT#182 NRT#182+Sulfate NRT#182+Sulfate+ adjustment NRT#183 Cu (ug/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 26

36 12 15 Zn (ug/l) 9 6 NRT#182 NRT#182+Sulfate NRT#182+Sulfate+ adjustment NRT# 183 Li (ug/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1: NRT#182 NRT#182+Sulfate 12 Ba (ug/l) NRT#182+Sulfate+ adjustment NRT# 183 Ni (ug/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1: Tl (ug/l) NRT#182 NRT#182+Sulfate NRT#182+Sulfate+ adjustment NRT# 183 Co (ug/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 27

37 12 15 Cd (ug/l) NRT#182 NRT#182+Sulfate NRT#182+Sulfate+ adjustment NRT# 183 Pb (ug/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 4 2 Ag (ug/l) 3 2 NRT#182 NRT#182+Sulfate NRT#182+Sulfate+ adjustment NRT# 183 Be (ug/l) 1 1:2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 Figure 6. Comparison of leaching of major and trace cationic elements in the paired sample for SO 2 control. NRT #182 is the control ash, NRT #183 is the trona ash, S/L=1:1. 28

38 25 8 Si (mg/l) NRT#182 NRT#182+Sulfate NRT#182+Sulfate+ adjustment NRT#183 B (mg/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 Se (ug/l) NRT#182 NRT#182+Sulfate NRT#182+Sulfate+ adjustment NRT# 183 As (ug/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1: NRT#182 NRT#182+Sulfate NRT#182+Sulfate+ adjustment NRT# Mo (ug/l) 15 1 V (ug/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 29

39 4 3 L) Sb (ug/ NRT#182 NRT#182+Sulfate NRT#182+Sulfate+ adjustment NRT# 183 Mn (ug/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 15 Cr (ug/l) NRT#182 NRT#182+Sulfate NRT#182+Sulfate+ adjustment NRT# :2 1:1 1:5 1:2 Figure 7. Comparison of leaching of major and trace oxyanionic elements in the paired sample for SO 2 control. NRT #182 is the control ash, NRT #183 is the trona ash, S/L=1:1. 3

40 Ca (mg/l) NRT#12 NRT#12+Sulfate NRT#12+Sulfate+ adjustment NRT#189 Fe (mg/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 Al (mg/l) NRT#12 NRT#12+Sulfate NRT#12+Sulfate+ adjustment NRT#189 Mg (mg/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 6 2 Sr (mg/l) 4 2 NRT#12 15 NRT#12+Sulfate NRT#12+Sulfate+ adjustment NRT#189 Cu (ug/l) 1 5 1:2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 31

41 64 NRT#12 NRT#12+Sulfate Ba (ug/l) NRT#12+Sulfate+ adjustment NRT#189 Li (ug/l) :2 1:1 1:5 1:2 6 1:2 1:1 1:5 1:2 Tl (ug/l) NRT#12 NRT#12+Sulfate NRT#12+Sulfate+ adjustment NRT#189 Ni (ug/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1: Zn (ug/l) NRT#12 NRT#12+Sulfate NRT#12+Sulfate+ adjustment NRT#189 Cd (ug/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 32

42 16 9 NRT#12 12 NRT#12+Sulfate NRT#12+Sulfate+ adjustment NRT#189 6 Co (ug/l) 8 4 Pb (ug/l) 3 1:2 1:1 1:5 1:2 1:2 1:1 1:5 1: Ag (ug/l) NRT#12 NRT#12+Sulfate NRT#12+Sulfate+ adjustment NRT#189 Be (ug/l) 4 2 1:2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 Figure 8. Comparison of leaching of major and trace cationic elements in the paired sample for SO 3 control. NRT #12 is the control ash, NRT #189 is the trona ash, S/L=1:1. 33

43 9 1 Si (mg/l) 6 3 NRT#12 NRT#12+Sulfate NRT#12+Sulfate+ adjustment NRT#189 B (mg/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 4 1 Se (ug/l) NRT#12 NRT#12+Sulfate NRT#12+Sulfate+ adjustment NRT#189 As (ug/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1: NRT#12 NRT#12+Sulfate NRT#12+Sulfate+ adjustment NRT# Mo (ug/l) V (ug/l) 8 4 1:2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 34

44 Cr (ug/l) NRT#12 NRT#12+Sulfate NRT#12+Sulfate+ adjustment NRT#189 Mn (ug/l) :2 1:1 1:5 1:2 1:2 1:1 1:5 1:2 3 Sb (ug/l) NRT#12 NRT#12+Sulfate NRT#12+Sulfate+ adjustment NRT# :2 1:1 1:5 1:2 Figure 9. Comparison of leaching of major and trace oxyanionic elements in the paired sample for SO 3 control. NRT #12 is the control ash, NRT #189 is the trona ash, S/L=1:1. 35