EPA/600/R-02/019 

September 2001 

Stabilization and Testing of Mercury 


Containing Wastes: Borden Catalyst


by


Linda A. Rieser, Paul Bishop, Makram T. Suidan, 


Haishan Piao, Renee A. Fauche, and Jian Zhang


Department of Civil and Environmental Engineering


University of Cincinnati


Cincinnati, Ohio 45221-0071


Contract No. 68-C7-0057


Task Order #20


Task Order Manager


Paul Randall


Land Remediation and Pollution Control Division


National Risk Management Research Laboratory


Cincinnati, Ohio 45268


National Risk Management Research Laboratory


Office of Research and Development


U.S. Environmental Protection Agency


Cincinnati, Ohio 45268

Notice 

The U.S. Environmental Protection Agency, through its Office of Research and Development, funded 

and managed the research described here under contract number 68-C7-0057, Task Order #20 to the 

University of Cincinnati. It has been subjected to the U.S. EPA’s peer and administrative review and has 

been approved for publication as an EPA document. Mention of trade names or commercial products does 

not constitute an endorsement or recommendation for use. 

ii 
Foreword 

The U.S. Environmental Protection Agency is charged by Congress with protecting the Nation’s land, air, 

and water resources. Under a mandate of national environmental laws, the Agency strives to formulate 

and implement actions leading to a compatible balance between human activities and the ability of natural 

systems to support and nurture life. To meet this mandate, EPA’s research program is providing data and 

technical support for solving environmental problems today and building a science knowledge base 

necessary to manage our ecological resources wisely, understand how pollutants affect our health, and 

prevent or reduce environmental risks in the future. 

The National Risk Management Research Laboratory is the Agency’s center for investigation of 

technological and management approaches for preventing and reducing risks from pollution that threatens 

human health and the environment. The focus of the Laboratory’s research program is on methods and 

their cost-effectiveness for prevention and control of pollution to air, land, water, and subsurface 

resources; protection of water quality in public water systems; remediation of contaminated sites, 

sediments and ground water; prevention and control of indoor air pollution; and restoration of ecosystems. 

NRMRL collaborates with both public and private sector partners to foster technologies that reduce the 

cost of compliance and to anticipate emerging problems. NRMRL’s research provides solutions to 

environmental problems by: developing and promoting technologies that protect and improve the 

environment; advancing scientific and engineering information to support regulatory and policy decisions; 

and providing the technical support and information transfer to ensure implementation of environmental 

regulations and strategies at the national, state, and community levels. 

This publication has been produced as part of the Laboratory’s strategic long-term research plan. It is 

published and made available by EPA’s Office of Research and Development to assist the user community 

and to link researchers with their clients. 

E. Timothy Oppelt, Director 

National Risk Management Research Laboratory 

iii 
Abstract 

This report was submitted by the University of Cincinnati (UC) in fulfillment of Contract No. 68-C7-

0057 under the sponsorship of the U.S. Environmental Protection Agency (EPA). This report covers a 

period from June 1999 through July 2000; laboratory work was completed as of July 2000. This report 

evaluates the chemical stability of spent mercuric chloride catalyst in an aqueous environment before and 

after treatment with stabilizing agents. The stabilizing agents evalua ted in this study are sulfide and 

phosphate. 

Samples obtained by UC and EPA personnel at the Borden Chemicals and Plastics (BCP) plant on June 

10, 1999 were characterized for total mercury content, pH, and acidity prior to performing the leaching 

tests on untreated waste. Leaching tests and analytical work performed by UC and their contract 

laboratories included the toxicity characteristic leaching procedure (TCLP), solid stability in water, and 

leaching at constant and variable pH values. 

After completing the baseline tests on untreated waste, the spent mercuric chloride catalyst was treated 

with sulfide and phosphate binders to evaluate the effectiveness of these additives on reducing the 

concentration of mercury in the leachate. The mercuric chloride waste was crushed and combined with 

the binders at various molar ratios and pH ranges prior to performing the identical leaching tests noted 

above. 

Measured mercury concentrations in the generated leachates indicate that sulfide treatment lowers the 

aqueous mercury concentration, while phosphate treatment has little effect on decreasing the mercury 

concentration. Analytical results for individual leaching methods carried out over a pH range of 2 to 12 

do not define a consistent trend for mercury concentrations as a function of pH. However, samples treated 

with moderate to large amounts of sulfide (i.e., a S/Hg molar ratio greater than 3) released less mercury. 

iv 
Table of Contents 

Foreword ................. ................. ................. ................. .. iii


Abstract ................. ................. ................. ................. ... iv


1.0 Background ................. ................. ................. ........... 1


1.1 Waste Characterization ................. ................. ............ 1


1.2 Leaching Tests ................. ................. ................. .. 1


1.3 Treatment Reagents ................. ................. ............... 1


2.0 Characterization of BCP Catalyst ................. ................. ......... 2


3.0 Leaching Tests ................. ................. ................. ....... 2


3.1 	 Solid Stability in Water for Untreated Catalyst ................. ........... 2


3.1.1 Introduction ................. ................. ............... 2


3.1.2 Procedure ................. ................. ................ 3


3.1.3 Results ................. ................. ................. . 3


3.1.4 Data Quality Discussion ................. ................. .... 4


3.2	 Acidity of Untreated Catalyst ................. ................. ....... 4


3.2.1 Introduction ................. ................. .............. 4


3.2.2 Procedure ................. ................. ................ 5


3.2.3 Results ................. ................. ................. . 5


3.2.4 Data Quality Discussion ................. ................. .... 6


3.3	 Toxicity Characteristic Leaching Procedure ................. ............. 6


3.3.1 Introduction ................. ................. .............. 6


3.3.2 Procedure ................. ................. ................ 6


3.3.3 Results ................. ................. ................. . 7


3.3.4 Data Quality Discussion ................. ................. .... 7


3.4	 UC Constant pH Leaching Test ................. ................. ...... 8


3.4.1 Introduction ................. ................. .............. 8


3.4.2 Procedure ................. ................. ................ 8


3.4.3 Results ................. ................. ................. . 8


3.5	 RU-SR002.1 (Solubility and Release as a Function of pH) ................. .. 9


3.5.1 Introduction ................. ................. .............. 9


3.5.2 Procedure ................. ................. ................ 9


3.5.3 Results ................. ................. ................. 10


v 
Table of Contents, Continued 

4.0 Stabilization Treatments ................. ................. ................. ......... 11


4.1	 Stabilization of BCP Catalyst by Sulfide ................. ................. ......... 11


4.1.1 Introduction ................. ................. ................. ....... 11


4.1.2 Procedure ................. ................. ................. ......... 11


4.1.3 Results ................. ................. ................. ........... 12


4.1.4 Discussion ................. ................. ................. ......... 18


4.2	 Stabilization of BCP Catalyst by Phosphate ................. ................. ...... 19


4.2.1 Introduction ................. ................. ................. ....... 19


4.2.2 Procedure ................. ................. ................. ......... 20


4.2.3 Results ................. ................. ................. ........... 20


4.2.4 Discussion ................. ................. ................. ........ 23


5.0 Data Quality ................. ................. ................. ................. .... 24


5.1 Background Characterization ................. ................. ................. ..... 24


5.2 Leaching Tests ................. ................. ................. ................ 24


5.3 Acidity ................. ................. ................. ................. ..... 27


5.4 Treatment Reagents ................. ................. ................. ............ 27


6.0 Conclusions ................. ................. ................. ................. .... 33


Appendices 

A Analytical Data - Environmental Enterprises Inc. - Provided upon request, Paul Randall, USEPA, 

Cincinnati, OH, 513 569-7673 or email Randall.Paul@epa.gov 

vi 
List of Tables 

2.1 Chemical Characterization of Untreated BCP Catalyst ................. ......... 2


3.1 Solid Stability in Water for Untreated Spent Catalyst ................. .......... 4


3.2 Acidity Results ................. ................. ................. ...... 5


3.3 TCLP Resultsfor Untreated Catalyst ................. ................. ...... 7


3.4 Constant pH Leaching Results for Untreated Catalyst ................. .......... 9


3.5 RU-SR002.1 Leaching Results for Untreated Catalyst ................. ........ 10


4.1 Sample Test Matrix ................. ................. ................. . 12


4.2 Mercury Results for Sulfide Stabilization ................. ................. . 13


4.3 Stabilization Efficiency (%) ................. ................. ............ 15


4.4 TCLP Mercury Results (mg/L) for Sulfide Stabilization ................. ....... 16


4.5 Stabilization Efficiency for TCLP Data ................. ................. ... 17


4.6 Mercury Results for Phosphate Stabilization ................. ................ 21


4.7 TCLP Mercury Results (mg/L) for Phosphate Stabilization ................ . .... 23


5.1	 Laboratory QC Data for EEI Total & TCLP Mercury Results ................. .. 25


Background Data


5.2	 Laboratory QC Data for EEI Total Mercury Results ................. ......... 26


Solid Stability in Water


5.3	 Laboratory QC Data for EEI Total Mercury Results ................. ......... 26


University of Cincinnati pH Test


5.4	 Laboratory QC Data for EEI Total Mercury Results ................. ......... 27


Rutgers University pH Test


5.5	 Laboratory QC Data for EEI Total Mercury Results ................. .......... 29


Sulfide and Phosphate Stabilization


5.6	 Laboratory QC Data for EEI TCLP Mercury Results ................. ......... 31


Sulfide and Phosphate Stabilization


5.7	 Experimental QC Data for Test Duplicates ................. ................. 32


Sulfide and Phosphate Stabilization


vii 
List of Figures 

3.1 Acidity of Untreated Catalyst vs. Sample Solid ................. ............... 6


4.1 Mercury Results for Sulfide Stabilization as a Function of pH ................. .. 14


4.2 Stabilization Efficiency(%) ................. ................. ............ 15


4.3 TCLP Mercury Results for Sulfide Stabilization ................. ............. 16


4.4 Stabilization Efficiency for TCLP Data ................. ................. ... 17


4.5 Distribution of the Various Hg-H-S Species as a Function of pH ................. 19


4.6 Mercury Results for Phosphate Stabilization ................. ................ 21


4.7 TCLP Mercury (mg/L) Results for Phosphate Stabilization ................ . .... 22


viii 
1.0 Background 

The Borden Chemicals and Plastics plant (BCP) in Geismar, Louisiana 

produces, among other chemicals, vinyl chloride. The vinyl chloride synthesis 

employs a mercuric chloride catalyst, which is the subject of this study. 

1.1 Waste Characterization 

Spent mercuric chloride catalyst samples collected at the BCP plant 

werecharacterized for total mercury content, pH and acidity by UC and a contract 

laboratory prior to initiating the leaching tests. A summary of this information is 

provided in Section 2.0. 

1.2 Leaching Tests 

A variety of leaching tests were carried out with the untreated and treated 

mercuric chloride waste to evaluate the physiochemical controls on mercury mobility 

(e.g., dissolution, diffusion and/or solubility). The liquid/solid mass ratio was varied 

from 20 to 200 to investigate diffusion gradients, TCLP tests were used to evaluate 

the suitability of disposing of untreated and treated waste in landfills, and constant and 

variable pH tests were used to examine the leaching behavior of mercury over the pH 

range of 2 to 12. Section 3.0 presents the procedures and results for all test sequences. 

1.3 Treatment Reagents 

Treatment reagents applied to the spent catalyst consisted of sodium sulfide 

and sodium phosphate. The treated waste forms were prepared at various molar ratios 

(e.g., S/Hg = 1, 3, 5 and 7) and then leached at pH values that were initially set at 2, 

4, 6, 8 and 10. Results are provided in Section 4.0. 

1

2.0 Characterization of BCP Catalyst 

On June 10, 1999 UC and EPA personnel collected samples of spent 

mercuric chloride catalyst from 55-gallon drums staged at the Geismar, 

Louisiana BCP plant. Approximately 10 kilograms (kg) of waste was 

collected and homogenized prior to performing the baseline characterization. 

The waste was homogenized by tumbling in a five gallon container for 24 

hours before sampling. Observations of the homogenized waste detected no 

visual heterogeneity. The samples were analyzed for total mercury, pH and 

acidity (Table 2.1) to establish baseline conditions for the waste prior to 

initiating the leaching tests. Laboratory QC data associated with the reported 

mercury results are presented and discussed in Section 5.1. 

Table 2.1 Chemical Characterization of Untreated BCP Catalyst 

Chemical Parameter Concentration M etho d of A naly sis 

Total M ercury 

(2 grab sam ples) 

20,800 m g/kg SW-846-7470A1 

22,300 m g/kg SW-846-7470A1 

pH 2.10 pH electrode2 

Acid ity 0.54 mg CaCO3/g Standard Methods2 

(1) Analysis performed by Environmental Enterprises Incorporated, Cincinnati, Ohio 

(2) Analysis performed by University of Cincinnati, Cincinnati, Ohio 

3.0 Leaching Tests 

3.1 Solid Stability in Water for Untreated Catalyst 

3.1.1 Introduction 

This test varies the liquid/solid mass ratio to study the effect of the 

aqueous contaminant concentration on the diffusion of contaminants from 

the waste form. If the amount of contaminant released from the waste form 

2

decreases as the liquid-solid ratio decreases, then the contaminant 

concentration in the leachate may be great enough to reduce the 

concentration gradient between the leachate and the waste form and impede 

its diffusion from the waste. 

3.1.2 Procedure 

Samples of spent mercuric chloride catalyst were dried at room 

temperature for 24 hours in an exhaust hood.(1) Four tests were run using 

10, 20, 50 and 100 grams of waste. Each solid sample was placed in a 2-

liter Nalgene HDPE bottle and then filled with 2 liters of deionized water. 

The bottles were capped and tumbled for 18 hours and then each leachate 

sample was filtered through a 0.45 �m filter and placed in a sample 

container. Each leachate sample was acidified to a pH of less than 2 with 

HNO3 and stored at 4o

C until analyzed within the 28 day holding-time 

requirement. Mercury concentrations were measured by cold vapor atomic 

absorption spectroscopy (CVAAS). 

3.1.3 Results 

As shown in Table 3.1, the aqueous mercury concentration 

increased and the percent of total mercury leached from the waste 

decreased as the liquid/solid mass ratio decreased (i.e., the mass of solid 

increased). In terms of total mercury leached from the waste, Sample 1 

released over 4 times more mercury than Sample 4. This observation, 

along with the higher aqueous concentration seen in Sample 4, suggests that 

a reduction in the concentration gradient between the leachate and waste 

may impede the diffusion of mercury from the waste form. Alternatively, 

the similarity in aqueous concentration for Samples 3 and 4 may indicate a 

1	 This represents a change from the QAPP oven drying method. Assuming that moisture 

could still be present in the catalyst, values obtained could be conservative as compared to 

the oven dry, dry weight basis. Moisture content analysis, however, showed no moisture 

present in the catalyst. 

3

solubility limit is controlling the amount of mercury released from the 

waste. 

Table 3.1 Solid Stability in Water for Untreated Spent Catalyst1 

Sam ple 

1 

Sam ple 

2 

Sam ple 

3 

Sam ple 

4 

Liquid / So lid M ass Ra tio 200 :1 100 :1 40:1 20:1 

Spent Catalyst (g/L) / Mercury (mg) 5/108 10/216 25/539 50/108 

Mercury in Leachate (mg/L) 2.88 4.34 6.30 6.76 

Total Mercury Leached (%) 2.7 2.0 1.2 0.6 

(1) Mercury Analysis performed by Environmental Enterprises Incorporated, Cincinnati, Ohio 

3.1.4 Data Quality Discussion 

The solid stability-in-water test provides only single point estimates. 

As leachates were measured at a single time point (18 hours), there is no 

information on whether the interval was sufficient to establish mercuric 

equilibrium between the solid and solution phases. Section 5.2 provides the 

data quality analysis for Solid Stability in Water Results. 

3.2 Acidity of Untreated Catalyst 

3.2.1 Introduction 

Acidity is related to the capacity of a material to react with a strong 

base. An acidity titration was run on each leachate produced from the solid 

stability tests to assess the acidic content of the spent catalyst. Each sample 

was titrated with a strong base to an end point pH of 9 to obtain a smooth 

titration curve. Construction of the titration curve identifies the inflection 

points and determines the buffering capacity of the leachate. 

4 
3.2.2 Procedure 

A known volume of leachate (40 mL) from the solid-stability-in-water 

test was placed in a breaker and a 0.1N sodium hydroxide titrant was added 

to the sample in incremental amounts until the end point was obtained. The 

amount of sodium hydroxide required to neutralize the acidity of the sample 

is expressed as equivalent milligrams (mg) of CaCO3 relative to a liter (L) of 

leachate and normalized to a gram (g) of the spent catalyst. An Orion 

electrode was used to measure the pH of the leachate. 

3.2.3 Results 

The resulting acidity for each sample is shown in Table 3.2, and Figure 

3.1 shows measured acidity in the leachate versus mass of spent catalyst. The 

plot is linear, indicating that acidity is dependent on the amount of spent 

catalyst available for leaching. 

Table 3.2 Acidity Results1 

Liquid/Solid Ratio (w/w) 20:1 40:1 100 :1 200 :1 

Spent Catalyst (g/L) 50 25 10 5 

Acidity (as mg CaCO3/L) 51.25 22.50 8.75 7.50 

Normalized acidity(mg CaCO3/g) 1.03 0.90 0.88 1.50 

(1) Analysis performed by University of Cincinnati, Cincinnati, Ohio 

5

3.2.4 Data Quality Discussion 

Data generated in acidity analyses consist of single point estimates. 

Section 4.5.6 provides the data quality analysis for the Acidity data. 

3.3 Toxicity Characteristic Leaching Procedure (TCLP) 

3.3.1 Introduction 

This test is used to determine the potential mobility of contaminants 

in an acetic acid solution that is intended to serve as simulated leachate under 

landfill conditions. 

3.3.2 Procedure 

Prior to performing the TCLP analysis, an initial pH measurement of 

the waste must be made to determine the appropriate pH of the extraction 

fluid (4.93 or 2.88) that must be used in the test. The pH of the untreated BCP 

6

spent catalyst is 2.10. This pH value is well below pH 5, thus the TCLP 

method dictates that the extraction fluid corresponding to a pH of 4.93 must 

be used. 

A total of 100 grams of dried spent catalyst were added to a 2-liter 

container with 2 liters of extraction fluid to yield essentially no head space in 

the container. The containers were sealed and then rotated end-over-end for 

18 hours. Each leachate sample was then filtered through a 0.70 �m filter and 

placed in a sample container. The leachate samples were acidified to a pH of 

less than 2 with HNO3 and stored at 4o

C until analyzed within the 28 day 

holding-time requirement. Mercury concentrations were measured by 

CVAAS. 

3.3.3 Results 

Table 3.3 summarizes the analytical results for the TCLP test and 

indicates that both samples of untreated catalyst had mercury leachate 

concentrations orders of magnitude above the TCLP limit of 0.2 mg/L. 

Table 3.3 TCLP Results for Untreated Catalyst1 

Sam ple Limit 1 2 

TCLP (mg/L) 0.2 123 120 

Total Mercury (mg/kg) 20,800 22,300 

(1) Mercury analysis performed by Environmental Enterprises Incorporated, Cincinnati, Ohio 

3.3.4 Data Quality Discussion 

The relative percent difference for the TCLP duplicate is 2.47%. 

Laboratory QC data associated with the reported mercury results are 

presented and discussed in Section 5.1. 

7

3.4 UC Constant pH Leaching Test 

3.4.1 Introduction 

Constant pH leaching tests are a means to determine the effect pH has 

on mobilizing contaminants found in waste samples. The basic premise of this 

test is to leach samples in a constant pH solution, adjusting the sample pH to 

the set point as necessary. 

3.4.2 Procedure 

The leaching tests were run at pH values of 2, 4, 6, 8, 10 and 12 using 

500 mL of deionized water and 25 grams of dried solid to produce a 

liquid/solid mass ratio of 20:1. A duplicate test was run at a pH value of 8. 

The samples were stirred using stirring bars on stir plates throughout the 

experiment. The pH was maintained at the initial value for a 24 hour period, 

with samples being extracted for analysis at 2, 10 and 24 hours. The samples 

were filtered through a 0.7 �m glassfiber filter, acidified to a pH of less than 

2 with HNO3 and stored at 4o

C until analyzed within the 28 day holding-time 

requirement. All samples were analyzed via CVAAS. 

3.4.3 Results 

Table 3.4 summarizes the reported mercury concentrations for each 

distinct pH test carried out. At a pH of 2, a steady-state condition may have 

been reached between 10 and 24 hours, as the mercury concentrations for 

these time intervals are within 10 percent of each other. For other pH values, 

it is hard to tell if a steady-state condition was reached because mercury 

concentrations continued to increase through the entire time interval. A longer 

testing period is recommended for future research. In any event, the mercury 

concentrations are highest at the low and high pH values, with the minimum 

values observed at a pH of 8. All sample test blanks are below the method 

detection limit of 0.0005 mg/L, indicating cross-contamination of the 

experimental samples is not evident. Laboratory QC data associated with the 

reported mercury results are presented and discussed in Section 5.2. 

8

Table 3.4 Constant pH Leaching Results for Untreated Catalyst1 

Mercury (mg/L) 

pH 2 pH 4 pH 6 pH 8 

(1) 

pH 8 

(2) 

pH 10 PH 12 

2 hr 13.8 5.74 4.28 2.12 1.78 1.14 8.58 

10 hr 19.2 9.82 9.36 7.00 9.72 11.4 13.4 

24 hr 17.6 15.0 12.8 10.3 11.3 14.0 26.6 

Blank <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 

(1) Mercury analysis performed by Environmental Enterprises Incorporated, 

Cincinnati, Ohio 

3.5 RU-SR002.1 (Solubility and Release as a Function of pH) 

3.5.1 Introduction 

The pH leaching tests developed at Rutgers University are an alternate 

means to determine the effect pH has on the stability of a sample. The basic 

premise of this test is to adjust the initial pH to the desired set point and then 

allow the pH of the solid and liquid system to reach its natural endpoint. 

3.5.2 Procedure 

Using the acidity or alkalinity data on the solid samples, an acid or 

base addition schedule is developed to set the initial pH ranges of 3 to 12. 

Based on this schedule, the acid or base is added to 75 mL of deionized water 

and 15 g of dry sample (particle size less than 5 mm) to produce a liquid/solid 

mass ratio of 5:1. The sample containers are sealed and tumbled in an endover-end fashion for 14 days and then centrifuged to separate the solid and 

liquid phases prior to pH measurement. Following pH measurement, the 

samples are filtered through 0.45 �m polypropylene filters, acidified to a pH 

of less than 2 with HNO3 and stored at 4o

C until analyzed within the 28 day 

holding-time requirement. All samples in this study were analyzed via 

CVAAS. 

9 
3.5.3 Results 

Table 3.5 summarizesthe reported mercury concentrations for each pH 

test. Leaching of the spent catalyst lowered the pH of all leachate samples, 

except for the test carried out at a pH of 12. The pH 12 test also produced a 

significantly higher mercury concentration relative to the other tests. 

Observation of the mercury concentrations and corresponding pH values 

indicates that there is no positive or negative trend between the two 

parameters. These results are somewhat different than those reported in 

Section 3.4, where a minimum mercury concentration is observed to occur at 

a pH of 8. Other notable observations on the data in Table 3.5 are the poor 

replication of results for the pH 10 test and the high mercury concentration 

measured in the blank. Poor replication of the pH 10 test may indicate 

heterogeneity in the distribution of mercury in the spent catalyst, which may 

also account for the scatter of measured concentrations across the tested pH 

range. The elevated mercury concentration in the experimental blank indicates 

that some cross-contamination may be present in the reported results, although 

this is not a significant bias given the high mercury concentrations reported for 

the leachate samples. Laboratory QC data associated with the reported 

mercury results are presented and discussed in Section 5.2. 

Table 3.5 RU-SR002.1 Leaching Results for Untreated Catalyst1 

Initial pH 12 11 10 9 8 7 

Final pH 12.9 8.28 7.87 6.41 4.69 3.95 

M ercury (mg/L) 190 15.1 17.6 29.7 23.3 22.8 

27.7 (2) 

Initial pH 6 5 4 3 Natural (3) Blank 

Final pH 3.29 3.41 2.17 0.89 2.10 5.47 

M ercury (mg/L) 19.4 16.3 14.8 59.1 10.4 0.38 

59.0 (2) 

(1) Mercury analysis performed by Environmental Enterprises Incorporated, Cincinnati, Ohio 

(2) Indicates test duplicate 

(3)As received. 

10

4.0 Stabilization Treatments 

4.1 Stabilization of BCP Spent Catalyst by Sulfide 

4.1.1 Introduction 

Sulfide is one of the most widely used reactants for stabilizing mercury 

waste streams because of the low solubility of mercuric sulfide. The mechanism 

of sulfide-induced treatment is expected to be precipitation. However, due to the 

complexity of mercury-sulfide chemistry and the compositional variability in 

mercury waste streams, the process of sulfide-induced stabilization of mercury 

wastes has not been sufficiently developed. Therefore, further research is needed 

to optimize process-controlling parameters. In this study, pH and sulfide dosage 

were varied to test their effects on the stabilization of spent BCP mercuric 

chloride catalyst. 

4.1.2 Procedure 

The procedure and test matrix for sulfide stabilization of spent BCP 

mercuric chloride catalyst is briefly described below: 

1.	 Weigh 20 g of catalyst (approximately 431 mg of mercury) and an amount of 

Na2S�9H2O sufficient to meet the indicated S/Hg molar ratio (Table 4.1). 

Place the solids into HDPE bottles. 

2.	 Add 200 mL of deionized Ultra-filtered (D.I.U.F) water into the bottles (a 

liquid/solid mass ratio of approximately 10 is maintained due to the 

complete dissolution of the sodium sulfide). 

3. Adjust the pH of the above mixtures to the initial pH values (2, 4, 6, 8 and 

10) using 1N NaOH and/or 2N HNO3. 

4. Tumble the mixtures for 24 hours and then take a final pH measurement. 

5.	 Filter the mixtures through a 0.45 mm glass fiber filter and collect a 100 mL 

filtrate sample. 

6.	 Acidify the sample to a pH of less than 2 with HNO3 and store at 4o

C (up to 

28 days) until analyzed for total mercury by CVAAS. 

11

7.	 Dry the filter cakes (i.e., the stabilized spent catalyst) in an oven at 40 °C 

until the mass is stable to within +/- 0.01 g (overnight is generally sufficient 

to obtain the required control). 

8.	 Weigh 10 g of the stabilized and dried spent catalyst and submit the samples 

for TCLP testing and analysis by CVAAS. 

Table 4.1 Sample Test Matrix 

S/H g Ratio pH 2 pH 4 pH 6 pH 8 pH 10 

0 (Blank) X X X X X 

1 X X X X X 

3 X X X X X 

5 X X X X X 

7 X X X X X 

4.1.3 Results 

Table 4.2 and Figure 4.1 summarize the results for sulfide-stabilized BCP 

spent catalyst. Experimental duplicates were runfor S/Hg = 3/pH = 6 and S/Hg 

= 5/pH = 4 (Table 4.2). Results are expressed as measured mercury concentration 

in the leachate and as the percent of total mercury leached from the untreated and 

treated spent catalyst [e.g., ((92.8 mg/L * 0.2 L) / 431 mg) * 100 = 4.31 %]. 

Mercury concentrations in the filtered leachate obtained from treated spent 

catalyst are well below those obtained from the untreated waste, with the 

exception of the pH 8 and 10 results for a S/Hg molar ratio of 3. The anomalous 

mercury value of 207 mg/L for these two samples exceeds the highest mercury 

value reported for leachate obtained from the untreated waste, indicating 

problems may have occurred with filtration of the samples. Therefore, these data 

points are rejected. Laboratory QC data and experimental duplicates associated 

with the reported mercury results are presented and discussed in Section 5.2. 

Below a pH of 5, there is no improvement in the stabilization of mercury 

in the spent catalyst when using an S/Hg molar ratio above 3. Above a pH of 5, 

analytical results appear to be quite scattered for S/Hg molar ratios of 3, 5 and 7. 

12

There are no clear trends toward increasing or decreasing mercuryconcentrations 

over the pH interval of 6 to 10 for the individual S/Hg molar ratios of 3, 5 and 7. 

However, there is an overall trend toward decreasing mercury concentrations at 

pH 8 and 10 as sulfide increases, suggesting the mercuric sulfide solubility 

product is controlling mercury concentrations. 

The above observations are also reflected in the calculated values for 

percent total mercury released to the leachate. In a 24-hour period, 4.0 to 6.5 

percent of the mercury is released to leachate that contacts the untreated waste. 

The addition of sulfide to the spent catalyst suppresses the release of mercury to 

the leachate for all treated samples, except the two anomalous sample results at 

S/Hg = 3. Again, this is consistent with the precipitation of mercuric sulfide from 

the leachate as it contacts the treated waste forms. 

Table 4.2 Mercury Results for Sulfide Stabilization 

Target 

pH S/Hg = 0 S/Hg = 1 S/Hg = 3 S/Hg = 5 S/Hg = 7 

Molar Ratio 

pH(1) Hg Hg pH(1) Hg Hg pH(1) Hg Hg pH(1) Hg Hg pH(1) Hg Hg 

mg/L(2) %(3) mg/L(2) %(3) mg/L(2) %(3) mg/L(2) %(3) mg/L(2) %(3) 

2 2.01 92.8 4.31 1.96 12.3 0.571 2.02 0.0310 0.001 2.14 0.120 0.006 2.22 0.0314 0.001 

4 4.31 140 6.50 3.93 4.40 0.204 3.38 0.0129 0.001 3.58 

0.0428(4) 

0.0402 0.002 4.51 0.0970 0.005 

6 7.12 101 4.69 5.87 3.87 0.180 3.99 

13.6 (4) 

13.9 0.635 5.44 0.0260 0.001 5.40 0.266 0.012 

8 7.96 86.8 4.03 7.59 3.71 0.173 7.83 207 9.61 8.68 37.3 1.73 8.99 1.58 0.073 

10 9.83 88.1 4.09 8.86 5.93 0.276 9.36 207 9.61 9.55 8.03 0.373 9.54 0.0561 0.003 

(1) The pH values were taken after a 24 hour treatment period.


(2) Concentration in the leachate after filtering.


(3) Percentage of total mercury released from untreated (S/Hg = 0) and treated spent catalyst.


(4) Test duplicates.


13

Figure 4.1 Mercury Results for Sulfide Stabilization as a function of stabilization pH 

Table 4.3 and Figure 4.2 show the efficiency of the sulfide-stabilization process based 

on the percentage of total mercury released from the untreated and treated waste. The 

stabilization efficiency is defined as: 

(% Hguntreated waste - %Hgtreated waste) / (%Hguntreated waste) * 100% 

The efficiency calculations indicate that treatment of the spent catalyst with sodium 

sulfide is very effective in lowering mercury concentrations in the leachate. In general, over 90 

percent of the mercury released from the untreated waste was retained in the treated waste, with 

three exceptions noted in Table 4.3. Approximately half of the treated samples retained over 

99 percent of the mercury released from the untreated waste. 

14

Table 4.3 Stabilization Efficiency (%) 

Target Molar Ratio 

pH S/Hg = 1 S/Hg = 3 S/Hg = 5 S/Hg = 7 

pH(1) Efficiency 

4 3.93 96.86 3.38 99.99 

6 5.87 96.17 3.99 86.44 

8 7.59 95.73 7.83 (2) 

10 8.86 93.27 9.36 (2) 

Efficiency 

99.97 

99.93 

99.74 

98.18 

99.94 

pH(1) Efficiency pH(1) Efficiency pH(1) 

2 1.96 86.75 2.02 99.97 2.14 99.87 2.22 

3.58 99.97 4.51 

5.44 99.97 5.40 

8.68 57.03 8.99 

9.55 90.89 9.54 

(1) The pH values are taken after a 24 hour treatment period. 

(2) Efficiency cannot be calculated due to rejected data points. 

Figure 4.2 Stabilization efficiency(%) 

TCLP results for mercury are shown in Table 4.4 and on Figure 4.3. Experimental 

duplicates were run for S/Hg = 0/pH = 6 and S/Hg = 3/pH = 6 (Table 4.4). At S/Hg molar ratios 

of 1, 3 and 7, mercury concentrations generally decreased as pH increased, whereas this trend 

is not evident for results associated with S/Hg = 5. Although the sulfide treatment substantially 

lowers the mercury concentrations relative to untreated samples, only 5 samples (bold boxes in 

Table 4.4) passed the TCLP limit of 0.2 mg/L. Results might be improved if the treated solids 

were dried at 100oC, rather than 40oC, prior to undergoing TCLP testing. A higher drying 

temperature might promote a higher degree of crystallinity in the mercuric chloride precipitate, 

with an expected decrease in the amount of mercury leached from the solid. Laboratory QC data 

15

and experimental duplicates associated with the reported mercury results are presented and 

discussed in Section 5.2. 

Table 4.4 TCLP Mercury Results (mg/L) for Sulfide Stabilization 

Target Molar Ratio 

pH S/Hg = 0 S/Hg = 1 S/Hg = 3 S/Hg = 5 S/Hg = 7 

pH(1) TCLP Hg pH(1) TCLP pH(1) TCLP Hg pH(1) TCLP pH(1) TCLP Hg 

Hg Hg 

2 2.01 129 1.96 57.5 2.02 13.4 2.14 2.27 2.22 0.476


4 4.31 160 3.93 52.9 3.38 8.34 3.58 0.191 4.51 0.161


6 7.12


130 (2) 

150 5.87 39.0 3.99 

4.22 (2) 

4.09 5.44 0.343 5.40 0.191 

8 7.96 139 7.59 39.7 7.83 7.55 8.68 1.51 8.99 0.0336 

10 9.83 128 8.86 37.5 9.36 3.01 9.55 0.531 9.54 0.0185 

(1) The pH values are taken after a 24 hour treatment period and represent the pH of the treatment mixture


prior to drying the solid and conducting the TCLP test. 


(2) Test duplicates.


Figure 4.3 TCLP Mercury Results for Sulfide Stabilization 

16

Stabilization efficiencies for the TCLP results are shown in Table 4.5 and in Figure 4.4. 

The efficiency was calculated as noted above. Except for the stabilization scenarios with S/Hg 

= 1, the stabilization efficiencies were higher than 90% for all other S/Hg molar ratios. 

However, the most successful treatment is noted at neutral to high pH for S/Hg = 7, as all these 

samples passed the TCLP test (Table 4.4). 

Table 4.5 Stabilization Efficiency for TCLP Data 

Target Molar Ratio 

pH S/Hg = 1 S/Hg = 3 S/Hg = 5 S/Hg = 7 

pH(1) Efficiency pH(1) Efficiency pH(1) Efficiency pH(1) Efficiency 

2 1.96 55.43 2.02 89.61 2.14 98.25 2.22 99.64 

4 3.93 66.52 3.38 94.55 3.58 99.88 4.51 99.90 

6 5.87 74.34 3.99 97.37 5.44 99.78 5.4 99.88 

8 7.59 71.44 7.83 94.57 8.68 98.89 8.99 99.97 

10 8.86 72.01 9.36 97.72 9.55 99.59 9.54 99.99 

(1)	 The pH values are taken after a 24 hour treatment period and represent the pH of the treatment 

mixture prior to drying the solid and conducting the TCLP test. 

Figure 4.4 Stabilization Efficiency for TCLP Data 

17

4.1.4 Discussion 

Mercuric sulfide (HgS) is very insoluble in water, with a solubility 

product (Ksp) of 10-52 (Bard, 1966)1

. However, the solubility of HgS in water can 

be increased by association with various hydrogen sulfide species to form a 

number of mercuric-hydrogen-sulfide ions that enhance the solubility of HgS in 

water (Clever et al., 1985)2. These associations can lead to the formation of 

HgS�2H2So

, Hg(HS)3

-

, HgS�2HS-, and HgS2

2- (Figure 4.5). HgS�2H2So

 is the 

- dominant aqueous specie at pH values less than 6.2, while Hg(HS)3 is the 

dominant form between the pH values of 6.2 and 7. HgS�2HS- is the most 

abundant mercury complex between the pH of 7 and 8.3, and HgS2

2- dominates 

above a pH of 8.3. In fact, the concentration of HgS2

2- increases linearly with 

the hydroxyl ion concentration for pH values over 8.3 (Figure 4.5). 

According to Figure 4.5, mercury and sulfide reach their highest 

concentrations above neutral pH by forming complexes with HS- and S2-. 

However, the results in Figure 4.5 cannot be reconciled with the experimental 

results because some of the lowest mercuryconcentrations were measured at pH 

8 and 10 when the S/Hg molar ratio was 7 (1.58 and 0.056 mg/L, Table 4.2). 

This observation may indicate that the sulfide-stabilization did not reach 

equilibrium within the 24 hour period. Based on our preliminary research on 

the formation kinetics of sulfide and mercury surrogates(data not report here), 

sulfide-stabilization of mercury waste cannot reach equilibrium within 24 hours 

when high pH and high sulfide dosage are applied. Therefore, a much longer 

reaction time is recommended for future research. 

1

Bard, A.J., Chemical Equilibrium, Harper and Row, Publishers, New York, 1966.
 2

Clever, H.L., S.A. Johnson, and M.E. Derrick, “The Solubility of Mercury and Some Sparingly


Soluble Mercury Salts in Water and Aqueous Electrolyte Solutions,” J. Phys. Chem. Ref. Data, Vol.


14, No. 3, 1985.


18 
Figure 4.5 Distribution of the various Hg-H-S species as a function of pH 

4.2 Stabilization of BCP Spent Catalyst by Phosphate 

4.2.1 Introduction 

Phosphates have been shown to be effective in stabilizing heavy metals (CotterHowells et.al., 19961

; Eighmy et.al., 19972

; Ma et.al., 19953

; O’Hara et.al., 19884

). 

Mercury phosphates also have very low solubility (Qvarfort-Dahlman, 19755; Clever 

et.al., 19856). However, there has been little work done on phosphate-stabilization of 

mercury waste forms. This experiment was designed to investigate the effect of 

phosphate on mercury stabilization. In this experiment, variables such as pH and 

phosphate dosage were tested for their effects on phosphate-induced BCP catalyst 

stabilization. 

19

4.2.2 Procedure 

The procedure and test matrix for phosphate stabilization of spent BCP mercuric 

chloride catalyst is briefly described below: 

1.	 Weigh 20 g of catalyst (approximately 431 mg of mercury) and an amount 

of Na2HPO4 sufficient to meet the indicated P/Hg molar ratio (Table 4.6). 

Place the solids into HDPE bottles. 

2.	 Add 200 mL of D.I.U.F water into the bottles (a liquid/solid mass ratio of 

approximately 10 is maintained due to the complete dissolution of the 

sodium phosphate). 

3.	 Adjust the pH of above mixtures to the initial pH values (3, 6, 8,10 and 12) 

using 1N NaOH and/or 2N HNO3. 

4. Tumble the mixtures for 24 hours and then take a final pH measurement. 

5.	 Filter the mixtures through a 0.45 mm glass fiber filter and collect a 100 

mL filtrate sample. 

6.	 Acidify the sample to a pH of less than 2 with HNO3 and store at 4oC (up 

to 28 days) until analyzed for total mercury by CVAAS. 

7.	 Dry the filter cakes (i.e., the stabilized spent catalyst) in an oven at 40 °C 

until the mass is stable to within +/- 0.01 g (overnight is generally 

sufficient to obtain the required control). 

8.	 Weigh 10 g of the stabilized and dried spent catalyst and submit the 

samples for TCLP testing and analysis by CVAAS. 

4.2.3 Results 

Table 4.6 and Figure 4.6 summarize results for the phosphate treatment of spent 

mercuric chloride catalyst. Experimental duplicates were run for P/Hg = 0.5/pH = 8 and P/Hg 

= 1/pH = 10 (Table 4.6). The measured mercury concentrations indicate that the addition of 

phosphate has virtually no effect on stabilizing mercury in the waste form. Over the pH range 

tested, mercury concentrations in the leachate derived from treated samples were close to those 

of untreated (P/Hg = 0) samples. Laboratory QC data and experimental duplicates associated 

with the reported mercury results are presented and discussed in Section 5.3. 

20

Figure 4.6 Mercury Results (mg/L) for Phosphate Stabilization 

Table 4.6 Mercury Results for Phosphate Stabilization 

Molar R atio 

Target P/Hg=0 

pH pH(1) Hg 

mg/L(2) 

2 2.01 

4/3 4.31 

6 7.12 

8 7.96 

10 9.83 

12 12.00 

92.8 

140 

101 

86.8 

88.1 

222 

P/H g=0 .1 P/H g=0 .3 P/H g=0 .5 P/Hg=1 

pH(1) Hg pH(1) Hg pH(1) Hg pH(1) Hg 

mg/L(2) mg/L(2) mg/L(2) mg/L(2) 

3.12 107 3.19 95.4 3.22 115 3.06 104 

5.95 127 6.33 100 5.9 100 5.56 110 

96.2 (3 

7.89 107 7.93 89.1 7.87 84.5 7.71 92.8 

123 (3) 

9.68 88.9 9.83 99 9.67 79.5 9.32 117 

12.01 290 12.00 244 11.93 230 12.11 252 

(1) The pH values are taken after a 24 hour treatment period.


(2) Concentration in the leachate after filtering.


(3) Test duplicates.


21 
Table 4.7 and Figure 4.7 show TCLP results for phosphate-stabilized catalyst. 

Experimental duplicates were run for P/Hg = 0.5/pH = 8 and P/Hg = 1/pH = 10 (Table 4.7). 

Obviously, all samples failed the TCLP test. Phosphate-stabilized samples have 

approximately the same TCLP results as the untreated catalyst. Laboratory QC data and 

experimental duplicates associated with the reported mercury results are presented and 

discussed in Section 5.3. 

Figure 4.7 TCLP Mercury (mg/L) Results for Phosphate Stabilization 

22

Table 4.7 TCLP Mercury (mg/L) Results for Phosphate Stabilization 

pH Molar Ratio 

P/Hg=0 P/Hg=0.1 

3 

6 

8 

10 

12 

145 159 

140 172 

139 172 

128 173 

101 105 

(1) Test duplicates 

4.2.4 Discussion 

P/Hg=0.3 

123 

148 

104 

115 

69.7 

P/Hg=0.5 P/Hg=1 

176 169 

213 163 

137 (1) 

123 173 

133 

118 (1) 

135 

99 53.7 

The spent mercuric chloride catalyst will release chloride ions during the 

leaching tests. It has been reported that the presence of chloride ion decreases the 

formation of mercury phosphate precipitates (Feick et.al., 19727; Wang et.al., 19918), 

due to the formation of strong aqueous mercury chloride species. This is hypothesized 

to be the reason why the phosphate treatment was ineffective in this study. Although 

the same mercury chloride species form in the presence of the sulfide-treated waste, the 

very low solubility of HgS appears to overcome the association constants of the 

aqueous mercury chloride 

species. 

23

5.0 Data Quality 

5.1 Background Characterization 

Table 5.1 summarizes the laboratory QC data for the total mercury and 

TCLP results reported in Tables 2.1 and 3.3. The calibration curve was established 

using mercury standards of 0.50, 2.00, 5.00, 10.00 and 40.00 mg/L, with a 

corresponding correlation coefficient of 0.9998. Initial and continuing calibration 

standards and the LCS (Laboratory Control Sample) were within the laboratory 

control limit of 85 to 115 percent. The initial and continuing blank samples were all 

below the reporting detection limit of 0.0005 mg/L. Results for the laboratory 

duplicate and spike are within the stated QAPP control limits of ±25 percent 

(duplicate) and 75 to 125 percent (spike recovery). 

5.2 Leaching Tests 

Table 5.2 summarizes the laboratory QC data for the total mercury results 

reported in Table 3.1. The calibration curve was established using mercury standards 

of 0.50, 2.00, 5.00, 10.00 and 40.00 mg/L, with a corresponding correlation 

coefficient of 0.9996. Initial and continuing calibration standards and the LCS were 

within the laboratory control limit of 85 to 115 percent. The initial and continuing 

blank samples were all below the reporting detection limit of 0.0005 mg/L. Results 

for the laboratory duplicate and spike are within the stated QAPP control limits of 

±25 percent (duplicate) and 75 to 125 percent (spike recovery). 

Table 5.3 summarizes the laboratory QC data for the total mercury results 

reported in Table 3.4. The calibration curve was established using mercury standards 

of 0.50, 2.00, 5.00, 10.00 and 40.00 mg/L, with a corresponding correlation 

coefficient of 0.9999. Initial and continuing calibration standards and the LCS were 

within the laboratory control limit of 85 to 115 percent. The initial and continuing 

blank samples were all below the reporting detection limit of 0.0005 mg/L. Results 

24

for the laboratory duplicate are within the stated QAPP control limit of ±25 percent. 

A post-digestion spike was not reported for this batch of samples. 

Table 5.1 Laboratory QC Data for EEI Total & TCLP Mercury Results 

Background Data 

Sample ID True 

mg/L 

Found 

mg/L 

Percent 

Recovery 

RPD 

% 

Dilution 

Factor 

Reported Result 

mg /kg (mg /L) 

Work Order 80-04-319: Total Mercury Results 

ICV 5.00 5.18 104 na na na 

CCV1 5.00 4.89 97.8 na na na 

CCV2 5.00 4.82 96.4 na na na 

CCV3 5.00 4.84 96.8 na na na 

CCV4 5.00 4.87 97.4 na na na 

LCS 10.00 10.34 103 na na na 

ICB <0.50 <0.50 na na na na 

CCB1 <0.50 <0.50 na na na na 

CCB2 <0.50 <0.50 na na na na 

CCB3 <0.50 <0.50 na na na na 

CCB4 <0.50 <0.50 na na na na 

01A na 6.68 na 28.2 100,000 668,000 

01A-duplicate na 5.03 na 100,000 503,000 

05A-spike 5.00 5.36 107 na na na 

Work Order 80-04-319: TCLP Mercury Results 

ICV 5.00 5.13 103 na na na 

CCV1 5.00 5.02 100 na na na 

CCV2 5.00 5.10 102 na na na 

CCV3 5.00 5.50 110 na na na 

CCV4 5.00 4.97 99.4 na na na 

LCS 10.00 10.80 108 na na na 

ICB <0.50 <0.50 na na na na 

CCB1 <0.50 <0.50 na na na na 

CCB2 <0.50 <0.50 na na na na 

CCB3 <0.50 <0.50 na na na na 

CCB4 <0.50 <0.50 na na na na 

22A na 12.08 na 1.84 10,000 (121,000) 

22A-duplicate na 11.86 na 10,000 (119,000) 

22A-spike 5.00 6.03 121 na na na 

na = not applicable


Lab reports that a spike was run on diluted sample, post digestion


25

Table 5.2 Laboratory QC Data for EEI Total Mercury Result 

Solid Stability in Water 

Sample ID True 

mg/L 

Found 

mg/L 

Percent 

Recove 

ry 

RPD 

% 

Dilution 

Factor 

Reported Result 

mg /L 

Work Order 99-10-276: Total Mercury Results 

ICV 5.00 4.94 98.8 na na na 

CCV1 5.00 4.62 92.4 na na na 

CCV2 5.00 4.62 92.4 na na na 

LCS 10.00 9.91 99.1 na na na 

ICB <0.50 0.53 na na na na 

CCB1 <0.50 <0.50 na na na na 

CCB2 <0.50 <0.50 na na na na 

05A na 3.14 na 0.32 2 6.28 

05A-duplicate na 3.15 na 2 6.30 

05A-spike 10.00 9.01 90.1na na na 

na = not applicable 

Table 5.3 Laboratory QC Data for EEI Total Mercury Result 

University of Cincinnati pH Test 

Sample ID True 

mg/L 

Found 

mg/L 

Percent 

Recovery 

RPD 

% 

Dilution 

Factor 

Reported Result 

mg /L 

Work Order 99-10-211: Total Mercury Results 

ICV 5.00 4.82 96.8 na na na 

CCV1 5.00 4.81 96.2 na na na 

CCV2 5.00 4.52 90.4 na na na 

CCV3 5.00 4.58 91.6 na na na 

CCV4 5.00 4.45 89.0 na na na 

CCV5 5.00 4.63 92.6 na na na 

LCS 10.00 9.72 97.2 na na na 

ICB <0.50 <0.50 na na na na 

CCB1 <0.50 <0.50 na na na na 

CCB2 <0.50 <0.50 na na na na 

CCB3 <0.50 <0.50 na na na na 

CCB4 <0.50 <0.50 na na na na 

CCB5 <0.50 <0.50 na na na na 

27A na 0.88 na 2.25 2,000 1,760 

27A-duplicate na 0.90 na 2,000 1,800 

na = not applicable


Lab reports that a spike was not run due to reported result exceeding 1,000 mg /L


Table 5.4 summarizes the laboratory QC data for the total mercury results 

reported in Table 3.5. The calibration curve was established using mercury 

standards of 0.50, 2.00, 5.00, 10.00 and 40.00 mg/L, with a corresponding 

26

correlation coefficient of 0.9998. Initial and continuing calibration standards and 

the LCS were within the laboratory control limit of 85 to 115 percent. The initial 

and continuing blank samples were all below the reporting detection limit of 0.0005 

mg/L. Results for the laboratory duplicate and spike are within the stated QAPP 

control limits of ±25 percent (duplicate) and 75 to 125 percent (spike recovery). 

Table 5.4 Laboratory QC Data for EEI Total Mercury Result 

Rutgers University pH Test 

Sample ID True 

mg/L 

Found 

mg/L 

Percent 

Recovery 

RPD 

% 

Dilution 

Factor 

Reported Result 

mg /L 

Work Order 99-12-045: Total Mercury Results 

ICV 5.00 4.81 96.2 na na na 

CCV1 5.00 4.66 93.2 na na na 

CCV2 5.00 4.75 95.0 na na na 

CCV3 5.00 4.63 93.0 na na na 

LCS 10.00 10.40 104 na na na 

ICB <0.50 <0.50 na na na na 

CCB1 <0.50 <0.50 na na na na 

CCB2 <0.50 <0.50 na na na na 

CCB3 <0.50 <0.50 na na na na 

01A na 8.95 na 11.1 20,000 179,000 

01A-duplicate na 10.00 na 20,000 200,000 

01A-spike 5.00 4.65 93.0 na na na 

na = not applicable


Lab reports that a spike was run on diluted sample, post digestion


5.3 Acidity 

Prior to the titration, the pH meter was calibrated using a two-point 

calibration with certified calibration standards, pH 4 and pH 10. The calibration 

efficiency is defined as the measured value divided by the known value, and the 

value of 1.02 is in the range of 1.05 to 0.95, per the QAPP. 

5.4 Treatment Reagents 

Table 5.5 summarizes the laboratory QC data for the total mercury results 

reported in Tables 4.2 and 4.6. The calibration curves were established using 

mercury standards of 0.50, 2.00, 5.00, 10.00 and 40.00 mg/L, with corresponding 

27

correlation coefficients of 0.999665 and 999693. Initial and continuing calibration 

standards and the LCS were within the laboratory control limit of 85 to 115 percent. 

The initial and continuing blank samples were all below the reporting detection limit 

of 0.0005 mg/L. Results for the laboratory duplicate and spike are within the stated 

QAPP control limits of ±25 percent (duplicate) and 75 to 125 percent (spike 

recovery). 

28

29

Table 5.5 Laboratory QC Data for EEI Total Mercury Result

Sulfide and Phosphate Stabilization

Sample ID True

mg/L

Found

mg/L

Percent

Recovery

RPD

%

Dilution

Factor 

Reported

Result

mg /L

Work Order 80-05-219: 

ICV 5.00 4.86 97.2 na na na

CCV1 5.00 5.15 103 na na na

CCV2 5.00 4.92 98.4 na na na

CCV3 5.00 4.63 97.8 na na na

CCV4 5.00 4.90 98.0 na na na

CCV5 5.00 4.75 95.0 na na na

CCV6 5.00 4.65 93.0 na na na

LCS 10.00 10.60 106 na na na

ICB <0.50 <0.50 na na na na

CCB1 <0.50 <0.50 na na na na

CCB2 <0.50 <0.50 na na na na

CCB3 <0.50 <0.50 na na na na

CCB4 <0.50 <0.50 na na na na

CCB5 <0.50 <0.50 na na na na

CCB6 <0.50 <0.50 na na na na

07A na 22.24 na 0.495 10,000 222,000

07A-duplicate na 22.13 na 10,000 221,000

07A-spike 50.0 57.7 115 na na na

ICV 5.00 5.15 103 na na na

CCV1 5.00 4.62 92.4 na na na

CCV2 5.00 5.15 103 na na na

CCV3 5.00 4.99 99.8 na na na

CCV4 5.00 4.79 95.8 na na na

CCV5 5.00 5.19 104 na na na

CCV6 5.00 4.97 99.4 na na na

CCV7 5.00 4.89 97.8 na na na

CCV8 5.00 4.96 99.2 na na na

CCV9 5.00 5.07 101 na na na

LCS 10.00 9.62 96.2 na na na

LCS 10.00 10.06 101 na na na

ICB <0.50 <0.50 na na na na

CCB1 <0.50 <0.50 na na na na

CCB2 <0.50 <0.50 na na na na

CCB3 <0.50 <0.50 na na na na

CCB4 <0.50 <0.50 na na na na

CCB5 <0.50 <0.50 na na na na

CCB6 <0.50 <0.50 na na na na

CCB7 <0.50 <0.50 na na na na

CCB8 <0.50 <0.50 na na na na

CCB9 <0.50 <0.50 na na na na

24A na 7.56 na 11.8 1,000 7,560

24A-duplicate na 8.51 na 1,000 8,510

24A-spike 5.00 5.37 107 na na na

Total Mercury Results
45A na 11.77 na 0.853 10,000 118,000 

45A-duplicate na 11.67 na 10,000 117,000 

45A-spike 5.00 5.78 116 na na na 

na = not applicable


Lab reports that a spike was run on diluted sample, post digestion


Table 5.6 summarizes the laboratory QC data for the TCLP mercury results 

reported in Tables 4.4 and 4.7. The calibration curves were established using 

mercury standards of 0.50, 2.00, 5.00, 10.00 and 40.00 mg/L, with corresponding 

correlation coefficients of 999693 (Work Order 80-050219), 999691 and 999836. 

Initial and continuing calibration standards and the LCS were within the laboratory 

control limit of 85 to 115 percent. The initial and continuing blank samples were 

all below the reporting detection limit of 0.0005 mg/L. Results for the laboratory 

duplicate and spike are within the stated QAPP control limits of ±25 percent 

(duplicate) and 75 to 125 percent (spike recovery). 

Table 5.7 summarizes the experimental precision associated with the results 

for test duplicates (Tables 4.2, 4.4, 4.6 & 4.7). The precision between test 

duplicates is better than ±15 percent, which exceeds the precision required for 

duplicate analytical measurements. Therefore, the experimental reproducibility is 

considered acceptable. 

30

31

Table 5.6 Laboratory QC Data for EEI TCLP Mercury Result

Sulfide and Phosphate Stabilization

Sample ID True

mg/L

Found

mg/L

Percent

Recovery

RPD

%

Dilution

Factor 

Reported Result

mg /L

Work Order 80-05-219: Results

ICV 5.00 4.86 97.2 na na na

CCV1 5.00 5.15 103 na na na

CCV2 5.00 4.92 98.4 na na na

CCV3 5.00 4.63 97.8 na na na

CCV4 5.00 4.90 98.0 na na na

CCV5 5.00 4.75 95.0 na na na

CCV6 5.00 4.65 93.0 na na na

LCS 10.00 9.83 106 na na na

ICB <0.50 <0.50 na na na na

CCB1 <0.50 <0.50 na na na na

CCB2 <0.50 <0.50 na na na na

CCB3 <0.50 <0.50 na na na na

CCB4 <0.50 <0.50 na na na na

CCB5 <0.50 <0.50 na na na na

CCB6 <0.50 <0.50 na na na na

42A na 1.65 na 3.07 100,000 165,000

42A-duplicate na 1.60 na 100,000 160,000

42A-spike 500 450 90.0 na na na

Work Order 80-05-218: Results

ICV 5.00 5.18 104 na na na

CCV1 5.00 5.23 105 na na na

CCV2 5.00 5.04 101 na na na

CCV3 5.00 4.97 99.4 na na na

CCV4 5.00 4.98 99.6 na na na

LCS 10.00 9.87 98.7 na na na

LCS 10.00 9.92 99.2 na na na

ICB <0.50 <0.50 na na na na

CCB1 <0.50 <0.50 na na na na

CCB2 <0.50 <0.50 na na na na

CCB3 <0.50 <0.50 na na na na

CCB4 <0.50 <0.50 na na na na

01A na 1.37 na 12.4 100,000 137,000

01A-duplicate na 1.21 na 100,000 121,000

01A-spike 5.00 5.38 108 na na na

16A na 4.25 na 1.66 1,000 4,250

16A-duplicate na 4.18 na 1,000 4,180

16A-spike 5.00 5.13 103 na na na

ICV 5.00 5.11 102 na na na

CCV1 5.00 5.14 103 na na na

CCV2 5.00 5.19 104 na na na

CCV3 5.00 5.21 104 na na na

CCV4 5.00 5.04 101 na na na

CCV5 5.00 5.00 100 na na na

CCV6 5.00 4.93 98.6 na na na

LCS 10.00 10.06 106 na na na

LCS 10.00 10.08 108 na na na

ICB <0.50 <0.50 na na na na

CCB1 <0.50 <0.50 na na na na

CCB2 <0.50 <0.50 na na na na

CCB3 <0.50 <0.50 na na na na

CCB4 <0.50 <0.50 na na na na

CCB5 <0.50 <0.50 na na na na

CCB6 <0.50 <0.50 na na na na

TCLP Mercury

TCLP Mercury
31A na 1.66 na 5.26 100,000 166,000 

31A-duplicate na 1.75 na 100,000 175,000 

31A-spike 5.00 5.13 103 na na na 

41A na 1.67 na 1.78 100,000 167,000 

41A-duplicate na 1.70 na 100,000 170,000 

41A-spike 5.00 4.94 98.8 na na na 

na = not applicable


Lab reports that a spike was run on diluted sample, post digestion


Table 5.7 Experimental QC Data for Test Duplicates 

Sulfide and Phosphate Stabilization 

Sample ID 

mg/L 

True Found 

mg/L 

Percent 

Recovery 

RPD 

% 

Dilution 

Factor 

Reported Result 

mg /L 

Work Order 80-05-219: Total Mercury Results for Sulfide Stabilization (Table 4.2) 

15 na 13.57 na 2.33 1,000 13,600 

16 na 13.89 na 1,000 13,900 

20 na 42.84 na 6.79 1 42.8 

21 na 4.02 na 10 40.2 

Work Order 80-05-218: TCLP Mercury Results for Sulfide Stabilization (Table 4.4) 

3 na 1.30 na 14.3 100,000 130,000 

4 na 1.50 na 100,000 150,000 

15 na 4.09 na 3.13 1,000 4,090 

16 na 4.22 na 1,000 4,220 

Work Order 80-05-219: Total Mercury Results for Phosphate Stabilization (Table 4.6) 

37 na 9.62 na 13.0 10,000 96,200 

38 na 8.45 na 10,000 84,500 

44 na 12.34 na 5.15 10,000 123,000 

45 na 11.72 na 10,000 117,000 

Work Order 80-05-218: TCLP Mercury Results for Phosphate Stabilization (Table 4.7) 

44 na 1.18 na 13.4 100,000 118,000 

45 na 1.35 na 100,000 135,000 

37 na 1.37 na 10.8 100,000 137,000 

38 na 1.23 na 100,000 123,000 

na = not applicable 

32

6.0 Conclusions 

It is concluded from the sulfide-stabilization results that the addition of 

sodium sulfide to spent BCP mercuric chloride catalyst substantially reduces the 

amount of mercury released from the waste when it is leached. Mercurystabilization 

efficiencies exceeded 99 percent and passed the TCLP test at pH values of 4, 6, 8 

and 10 at a S/Hg molar ratio of 7. The treatment performance might be increased 

by allowing more reaction time between the sulfide/waste mixture and by increasing 

the drying temperature of the treated solid prior to running the TCLP test. 

Phosphate failed to effectively stabilize mercury in the BCP spent catalyst. 

It is hypothesized that the high concentration of chloride ion in the leachate 

decreases the formation of mercury phosphate precipitates, due to the formation of 

a strong aqueous mercury chloride complex. 

_________________________________________ 

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34