### EPRI Project Manager: Paul Chu

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- 1338  PO Box 10412, Palo Alto, California 94303
- 0813  USA 800.313.3774  650.855.2121  askepri@epri.com  www.epri.com 

# NICKEL SPECIATION ANALYSES OF RESIDUAL OIL FLY ASHES USING X - RAY TECHNIQUES

Product ID # 070441
Final Report, Decem ber 2010

### DISCLAIMER OF WARRAN TIES AND LIMITATION OF LIABILITIES THIS DOCUMENT WAS PR EPARED BY THE ORGANI ZATION(S) NAMED BELO W AS AN ACCOUNT OF WORK SPON SORED OR COSPONSORED BY THE ELECTRIC POWE R RESEARCH INSTITUTE, INC. (EPR I). NEITHER EPRI, AN Y MEMBER OF EPRI, AN Y COSPONSOR, THE ORGANIZATION(S) BELO W, NOR ANY PERSON AC TING ON BEHALF OF A NY OF THEM: (A) MAKES ANY WARRANTY O R REPRESENTATION WHA TSOEVER, EXPRESS OR IMPLIED, (I) WITH RESPECT TO THE USE OF ANY INFORMATI ON, APPARATUS, METHO D, PROCESS, OR SIMILAR ITEM DISCLOS ED IN THIS DOCUMENT, INCLUDING MERCHANTAB ILITY AND FITNESS FOR A PARTICU LAR PURPOSE, OR (II) THAT SUCH USE DOES N OT INFRINGE ON OR INTERFERE WITH PRIVA TELY OWNED RIGHTS, I NCLUDING ANY PARTY'S INTELLECTUAL PROPERTY, OR (III) T HAT THIS DOCUMENT IS SUITABLE TO ANY PART ICULAR USER'S CIRCUMSTANCE; OR (B) ASSUMES RESPONSIBILI TY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER (INCLUDING ANY CONSE QUENTIAL DAMAGES, EV EN IF EPRI OR ANY EP RI REPRESENTATIVE HAS BEEN ADVISED OF THE POSSIBILITY OF S UCH DAMAGES) RESULTI NG FROM YOUR SELECTION OR USE OF THIS DOCUMENT OR ANY INFORMATION, APPARAT US , METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN TH IS DOCUMENT. THE FOLLOWING ORGANI ZATION(S) , UNDER CONTRACT TO EP RI, PREPARED THIS RE PORT : University of North Dakota Energy & Environmental Research Center



### NOTE For further information about EPRI, call the EPRI Customer Assistance Center at 800.313.3774 or e - mail askepri@epri.com. Electric Power Research Institute, EPRI, and TOGETHER

... SHAPING THE FUTURE OF ELECTRICITY are registered service marks of the Electric Power Research Institute, Inc. Copyr ight © 20 1 0 Electric Power Research Institute, Inc. All rights reserved.

### This publication is a corporate document that should be cited in the literature in the following manner: Nickel Speciation Analyses of Residual Oil Fly Ashes Using X

- Ray Techniques

. EPRI , Palo Alto, CA: 2010

. iii 

# ACKNOWLEDG MENTS

The following organization ( s ) , under contract to the Electric Power Research Institute (EPRI) , prepared this report: University of North Dakota, Energy & Environmenta l Research Center 15 North 23rd Street, Stop 9018 Grand Forks, ND 58202

- 9018 Principal Investigator K. Galbreath Unive rsity of Kentuck y 103 S. J. “Sam” Whalen Bldg 533 S. Limestone Street Lexington, KY 40506

- 0043 Principal Investigator F. Huggins This rep ort describes research sponsored by EPRI

.

### v 

# ABSTRACT

Representative duplicate fly ash samples were obtained from the stacks of two 50

- MW ( U nits 9 and 6 of the Honolulu and Waiau power plants, respectively) and one 80

- MW ( U nit 1 of the Kahe p ower p lant) uti lity boilers using a modified U.S. Environmental Protection Agency Method 17 sampling train assembly as 0.3 to 0.4 wt% sulfur residual (No. 6 fuel) oils were burned during full

- load power plant operations. Residual oil fly ash (ROFA) samples were analyzed for Ni speciation using x

- ray absorption fine structure (XAFS) spectroscopy and x

- ray diffraction (XRD). ROFA deionized H 2 

### O extraction residues were also analyzed for Ni speciation using XAFS and XRD. Total Ni concentrations in the ROFAs ranged from 2.4 to 4.8 wt%. Ni ckel speciation analysis results indicated that 80 % to 95% of the total Ni present in the ROFAs was NiSO 4 

### .6H 2 

### O with subordinate proportions, ≤ 20% of the total Ni, present as a Ni

- containing spinel compound, similar in composition to NiFe 2 

### O 4



### Ke ywords and/or NiO. XAFS and XRD analyses did not detect any sulfidic Ni compounds; the XAFS detection limit was 3% of the total Ni concentration.

N ickel, nickel emissions, nickel speciation, residual (No. 6 fuel) oil, x

- ray absorption fine structure spectroscopy, x

- ray diffraction, residual oil fly ash

### vii 

# CONTENTS

**1** INTRODUCTION
................................ ................................ ................................ .................. 1 - 1
**2** BACKGROUND
................................ ................................ ................................ .................... 2 - 1 XAFS Spectroscopy

................................ ................................ ................................ ............ 2
- 1 Power Plant Sites

................................ ................................ ................................ ................ 2
- 2
**3** EXPERIMENTAL
................................ ................................ ................................ .................. 3 - 1 Residual Oil Analyses

................................ ................................ ................................ .......... 3
- 1 Fly Ash Stack
- Sampling and Analysis Methods

................................ ................................ ... 3
- 1 Soluble Ni Extraction

................................ ................................ ................................ ...... 3
- 1 N i XAFS Spectroscopy

................................ ................................ ................................ ... 3
- 2 XRD

................................ ................................ ................................ ................................ 3
- 4
**4** RESULTS AND DISCUSSI ON
................................ ................................ .............................. 4 - 1 Residual Oil Analyses

................................ ................................ ................................ .......... 4
- 1 ROFA Ni Analyses

................................ ................................ ................................ .............. 4
- 1 EPA Method 29

................................ ................................ ................................ ............... 4
- 1 Ni XAFS Spectroscopy

................................ ................................ ................................ ... 4
- 2 XANES Pre
- Edge Systematics

................................ ................................ ..................... 4
- 11 Least
- Squares Fitting of Ni XANES and EXAFS Spectra

................................ .............. 4
- 14 XR D Analyses

................................ ................................ ................................ .............. 4
- 16
**5** CONCLUSIONS
................................ ................................ ................................ ................... 5 - 1
**6** REFERENCES
................................ ................................ ................................ ..................... 6 - 1
**A** APPENDIX
................................ ................................ ................................ .......................... A - 1
Continued . . .

### viii 

# CONTENTS Continued

PHOTOGRAPHS OF QUARTZ THIMBLE FIL TERS

................................ .......................... A
- 1
**B** APPENDIX
................................ ................................ ................................ .......................... B - 1 X
- RAY DIFFRACTOGRAMS OF BULK ROFA AND NI EXTRACTION RESIDUES

........... B
- 1

### ix 

# LIST OF FIGURES

Figure 2
- 1 XAFS Spectrum o f Elemental Selenium Showing t he Division o f t he Spectrum i nto Separate XANES a nd EXAFS Regions a nd t he Subsequent Generation o f a Radial Structure Function ( RSF ) b y Fourier Transform o f t he EXAFS Region of the Spectrum

................................ ................................ ................................ .......................... 2
- 1 Figure 3
- 1 Photograph of D eposits on Q uartz T himble F ilters from HPP 9

............................... 3
- 3 Figure 4
- 1 Ni XAFS S pectra C ollected at SSRL for T himble F ilter S amples from HPP U nit 9

................................ ................................ ................................ ................................ 4
- 2 Figure 4
- 2 Ni XAFS S pectra C ollected at NSLS for T himble F ilter S amples from KPP and WPP U nits 1 a nd 6, R espectively

................................ ................................ .............. 4
- 3 Figure 4
- 3 Ni XAFS S pectra of D uplicate ROFA S amples a nd a ROFA R esidue S ample from t he S tack of HPP U nit 9; (a) XANES S pectra, (b) D erivative XANES S pectra, (c) EXAFS (k 3 chi) S pectra, and (d) RSF S pectra

................................ .............................. 4
- 5 Figure 4
- 4 Ni XAFS S pectra of D uplicate ROFA S amples from t he S tacks of KPP a nd WPP U nits 1 and 6, R espectively; (a) XANES S pectra, (b) D erivative XANE S S pectra, (c) EXAFS (k 3 chi) S pectra, a nd (d) RSF S pectra

................................ ................ 4
- 6 Figure 4
- 5 Ni XAFS S pectra of ROFA R esidues C orresponding to KPP a nd WPP U nits 1 a nd 6, R espectively; (a) XANES S pectra, (b) D eriv ative XANES S pectra, (c) EXAFS (k 3 chi) S pectra, a nd (d) RSF S pectra

................................ ................................ ................ 4
- 7 Figure 4
- 6 Ni XAFS S pectra of NiSO 4 , NiSO 4 · H 2 O, a nd NiSO 4 · 6H 2 O; (a) XANES S pectra, (b) D erivative XANES S pectra, (c) EXA FS (k 3 ch i) S pectra, a nd (d) RSF S pectra

................................ ................................ ................................ ............................. 4
- 8 Figure 4
- 7 Ni XAFS S pectra of Ni 3 S 2 , NiS, a nd NiS 2 ; (a) XANES S pectra, (b) D erivative XANES S pectra, (c) EXAFS (k 3 ch i) S pectra, a nd (d) RSF S pectra

................................ ... 4
- 9 Figure 4
- 8 Ni XAFS S pectra of NiO, NiFe 2 O 4 , a nd NiAl 2 O 4 ; (a) XANES S pectra, (b) D erivative XANES S pectra, (c) EXAFS (k 3 ch i) S pectra, a nd (d) RSF S pectra

........... 4
- 10 Figure 4
- 9 Comparison of the N ormalized H eight of t he P re - E dge I nflection F eature at 8333 eV in Ni D erivative XANES S pectra for Ni C ompounds

................................ .......... 4
- 12 Figure 4
- 10 Comparison of t he N ormalized H eight of t he P re - E dge I nflection F eature at 8333 eV in D erivative XANES S pectra of ROFA S ampled from t he T hree Hawaiian U nits

................................ ................................ ................................ ............................... 4
- 12 Figure 4
- 11 Examples of L east
- S quares F its to EXAFS S pectra of ROFA S amples: B ulk ROFA S ample, K1
- Ni
- 2 ( l eft), a nd ROFA H 2 O E xtraction R esidue, K1
- Ni
- 1R ( r ight)

...... 4
- 15 Figure A
- 1 Photograph of a Thimble Filter with ROFA Sampled from KPP Unit 1

................... A
- 1
Continued . . .

### x 

# LIST OF FIGURES C ontinued

Figure A
- 2 Photograph of a Duplicate Thimble Filter with ROFA Sampled from KPP Unit 1

................................ ................................ ................................ ............................... A
- 2 Figure A
- 3 Photograph of a Thimble Filter with ROFA Sampled from WPP Unit 6

.................. A
- 2 Figure A
- 4 Photograph of a Duplicate Thimble Filter w ith ROFA Sampled from WPP Unit 6

................................ ................................ ................................ ............................... A
- 3 Figure B
- 1 X
- ray Diffractogram of ROFA Sample from HPP Unit 9 Indicating Spectral Matches with NiSO 4 · 6H 2 O and CaSO 4 ................................ ................................ ........... B
- 1 Figure B
- 2 X
- ray Diffractogram of Duplicate ROFA Sample from HPP Unit 9 Indicating Spectral Matches with NiSO 4 · 6H 2 O and CaSO 4 ................................ ............................. B
- 2 Figure B
- 3 X
- ray Diffractogram of ROFA Sample from KPP Unit 1 Indicating Spectral Matches with NiSO 4 · 6H 2 O, NiFe 2 O 4 , and CaSO 4 ................................ ........................... B
- 3 Figure B
- 4 X
- ray Diffractogram of Duplic ate ROFA Sample from KPP Unit 1 Indicating Spectral Matches with NiSO 4 · 6H 2 O, NiFe 2 O 4 , and CaSO 4 ................................ ............. B
- 4 Figure B
- 5 X
- ray Diffractogram of ROFA Sample from WPP Unit 6 Indicating Spectral Matches wi th NiSO 4 · 6H 2 O and CaSO 4 ................................ ................................ ........... B
- 5 Figure B
- 6 X
- ray Diffractogram of Duplicate ROFA Sample from WPP Unit 6 Indicating Spectral Matches with NiSO 4 · 6H 2 O and CaSO 4 ................................ ............................. B
- 6

### xi 

# LIST OF TABLES

Table 2
- 1 Power Plant Descriptions and Abbreviations

................................ ............................ 2
- 2 Table 3
- 1 List of S amples C ross - R eferenced to XAFS F ile Names

................................ .......... 3
- 2 Table 3
- 2 List of ROFA H 2 3
- 2 O Extraction Residue Samples Cross
- Referenced to XAFS File Names

................................ ................................ ................................ ....................... Table 4
- 1 Residual Oil Proximate and Ultimate Analysis Results

................................ ............. 4
- 1 Table 4
- 2 Average ROFA Ni Concentrations and Emission Rates

................................ .......... 4
- 2 Table 4
- 3 Ni Contents of the Filter Blank Samples from KPP and WPP Unit s 1 and 6

............. 4
- 4 Table 4
- 4 Estimates of NiS and Ni 3 S 2 in ROFA from T hree HECO Units

............................... 4
- 14 Table 4
- 5 Results of L east
- S quares F itting of C ombin ed B ulk ROFA and C orresponding ROFA H 2 O E xtraction R esidue S pectra to S pectra for NiSO 4 · 6H 2 O and NiO

................ 4
- 15 Table 4
- 6 Results of L east
- S quares F itting of EXAFS S pectra (3

– 10 Å

- 1) for B ulk ROFA a nd ROFA H 2 O E xtraction R esidues to L inear C ombinations of the C orresponding S pectra for NiSO 4 · 6H 2 O, NiFe 2 O 4 , and NiO

................................ ................................ .. 4
- 16 Table 4
- 7 Bulk ROFA Phase Assemblages

................................ ................................ ............ 4
- 17 Table 5
- 1 Ni S pecies E mission Estimates

................................ ................................ ................ 5
- 1

### 1

- 1 

# 1 INTRODUCTION

Nickel is a transition metal that occurs throughout the environment and is discharged into air, wa ter, and soil from various natural and industrial sources. A significant natural source of atmospheric Ni is windborne dust particles derived from the weathering of rocks and soils and from volcanic eruptions [ 1 ]. The average Ni concentration of crustal ro cks is 75 ppm [ 2 ]. Although Ni is a ubiquitous metal, industrialization has increased its flux into the environment [ 3 ]. Anthropogenic stationary sources that release Ni into ambient air include 1) combustion and incineration sources (oil

- and coal

- burning units in utility, industrial, and residential use sectors and medical, municipal, and sewage sludge incinerators), 2) high

- temperature metallurgical operations (steel and Ni alloy manufacturing, secondary metals smelting, and coproduct Ni recovery), 3) pr imary production operations (mining, milling, smelting, and refining), and 4) chemical and catalyst sources (Ni chemical manufacturing , electroplating , Ni

– Cd battery manufacturing , and catalyst production, use, and reclamation) [ 4, 5 ]. The mobile source co ntribution to Ni emission inventories is small and derived primarily from engine wear and impurities in engine oil and fuel additives [ 6 ]. However, commercial marine vessels are significant mobile sources of Ni in areas near harbors [ 7, 8 ]. In the United S tates, the impetus for focusing on individual elements, such as Ni, in air pollution derives from the 1990 Clean Air Act Amendments (CAAA) [ 9 ] and the attainment of National Ambient Air Quality Standards [ 10 ]. Title III of the CAAA identifies 188 chemicals , including Ni and 15 other inorganic trace elements (As, Be, Cd, Cl, Co, Cr, F, Hg, Mn, P, Pb, Sb, Se, Th, and U) as potential hazardous air pollutants (HAPs) or air toxics. The U.S. Environmental Protection Agency ’s ( EPA’s ) Integrated Urban Air Toxics St rategy als o classifies Ni as an urban HAP [ 11 ]. Many stationary sources have had to report Ni emissions as part of the EPA Toxics Release Inventory (TRI) [ 12 ]. Although TRI and similar reporting provide estimates of the amounts of Ni released into the envi ronment, they are not an indicator of toxicity because the acute, chronic, and cancer

- causing effects vary significantly for the different chemical species of Ni. For example, nickel subsulfide (Ni 3 

### S 2 

### ) is considered the most carcinogenic Ni species on the basis of available human epidemiology and animal studies [ 5, 13, 14 ]. In contrast, inhalation exposure to water

- soluble Ni salts alone, such as nickel hexahydrite (NiSO 4 

### · 6H 2 

### O), have not been shown to cause cancer in animal studies [ 15

– 17 ]. Soluble Ni com pounds, however, are more toxic to the respiratory tract than less soluble compounds. Insoluble nickel oxide compounds such as Ni

- containing spinels (e.g., NiFe 2 

### O 4 

### ), although still under investigation, are expected to have relatively low cancer potencies c ompared to Ni 3 

### S 2 

### and may not be bioaccessible [ 5, 13, 14, 18 ]. Therefore, determining the Ni speciation of emission sources is of the utmost importance for assessing the inhalation health risks associated with airborne Ni

containing particles.INTRODUCTION



### 1

- 2 The combusti on of petroleum fuels (distillate fuel oils, residual fuel oil, jet fuel, kerosene, petroleum coke [converted to liquid petroleum], and waste oil) for generating steam and electricity is a significant anthropogenic source of Ni release to the atmosphere. P etroleum

- fired capacity represented 1.1% (46,000,000 MWh) of the total U.S. electric utility capacity in 2008 [ 19 ]. Residual (No. 6 fuel) oil, a by

- product from the petroleum

- refining industry, is the most widely used for generating steam and electricity b ecause of its relatively low cost compared with that of lighter oils. Residual oil production in the United States has declined since the late 198 0s, but remains substantial at ≈ 42,00 0 barrels per month [ 20 ]. In addition to the electric utility industry, residual oil is an important fuel for marine and industrial boilers. The fly ash produced from residual oil combustion (i.e., residual oil fly ash [ROFA]) contributes to ambient particulate matter pollution. Controlling fly ash emissions, however, is difficult because a substantial fraction of residual oil ash particles is generally submicrometer, corresponding to the size range of 0.1

– 1 μ m, where existing industrial gas

- clean ing devices are least effective [ 21

– 23 ]. As part of the EPA Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units

— Final Report to Congress [ 14 ], the inhalation health risks associated with HAP emissions from oil

- fired utility boilers were estimated. EPA estimated that the contribution of Ni to the maximum individual risk exceeded that from all other HAPs by about an order of magnitude primarily because of its relatively high concentration, ge nerally 1

– 4 wt% Ni, in ROFA and kno wn carcinogenic potency when in a Ni 3 

### S 2 

### form. In 2004, EPA proposed Ni emission limits of 210 lb/10 12 

### Btu on an input basis or 0.002 lb/MWh on an output basis for residual oil

- fired electric utility units [ 24 ]. As highlighted in EPA’s study [ 14 ] and propos ed emission limit ruling [ 24 ], the speciation of Ni emissions from oil

- fired utility boilers is uncertain and requires additional investigation. Total Ni emissions were measured at 13 of the 149 power plants that burned oil in 1994, and speciation measurem ents were conducted at seven of them. The limited Ni speciation analyses performed indicate that 3%

– 26% of the total Ni emissions were composed of sulfidic Ni, although it is unknown whether Ni 3 

### S 2 

### was present because of the limitations of the indirect (i.e ., operationally defined) speciation method employed, sequential Ni extraction [ 25

– 28 ]. Sequential Ni extraction methods are based on treating a small but representative sample of fly ash or particulate matter to successive leaching steps to separate analy te Ni species from the sample matrix. Ni species concentrations in the extracted fractions are then determined using sensitive analytical techniques, such as anodic stripping voltammetry, graphite furnace atomic absorption spectroscopy (GFAAS), and inducti vely coupled plasma

– atomic emission spectroscopy (ICP

– AES). Sequential extractions provide an operationally defined (e.g., based on particle size, solubility, bonding, and reactivity differences) determination of Ni forms (soluble, sulfidic, metallic, and oxidic) that is susceptible to errors because of inefficient and nonselective extractions and subse quent Ni redistribution effects [ 29 ]. In contrast, Galbreath et al. [ 30, 31 ] used definitive speciation techniques, x

- ray diffraction (XRD) and x

- ray absorpt ion fine structure (XAFS) spectroscopy, to identify the Ni species occurring in ROFAs sampled from 385

- and 400

- MW utility boiler stacks. Direct speciation measurements indicated that >95% of the total Ni in ROFAs was present as a mixture of NiSO 4 

### · xH 2 

### O a nd nickel oxide spinel compound, similar in composition to NiFe 2 

### O 4 

### . The lack of sulfidic Ni emissions from these particular boilers was contrary to EPA’s risk assessment assumption that the Ni compound mixture emitted from oil

-INTRODUCTION



### 1

- 3 fired utilities is 50% as car cinogenic as Ni 3 

### S 2 

### [ 14 ]. The Ni cancer risk from residual oil

- fired boile rs may be greatly overestimated [ 30, 31 ]. In this investigation, three compl e mentary methods

— XAFS, XRD, and water

- soluble Ni extraction

— were used to identify and quantify the Ni speci es occurring in fly ashes stack

sampled in duplicate from three residual oil

- fired units, owned and operated by Hawaiian Electric Company, Inc. (HECO). The XAFS technique is especially well suited for determining Ni speciation because it can directly and no ndestructively analyze fly ash filt er samples with ppm sensitivity [ 29

– 34 ]. XAFS spectroscopy involves recording the variation of the x

- ray absorption coefficient as a function of energy in the vicinity of a characteristic absorption edge for an element of interest. The x

- ray flux is supplied from a very intense synchrotron x

- ray source such as those used in this investigation at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory, New York, and the Stanford Synchrotron Radiation La boratory (SSRL), Stanford University, California. Analysis of x

- ray absorption coefficient variations in the x

- ray absorption near

- edge structure (XANES) and extended x

- ray absorption fine structure (EXAFS) spectral regions of the XAFS spectrum provides st ructural information concerning the local environment of the analyte element in terms of oxidation state, interatomic distances, and the type and number of coordinating ligands.

### 2

- 1 

# 2 BACKGROUND

XAFS Spectroscopy XAFS spectroscopy is a powerful method for dete rmining the speciation of an element in any material (gas, liquid, crystalline solid, amorphous solid). As its name implies, XAFS spectroscopy measures the fine structure associated with one of the characteristic x - ray absorption edges of an element of int erest. The fine structure is usually of two types ( Figure 2

- 1) : a fine structure associated with the absorption edge itself and a second fine structure consisting of a weak , periodic oscillatory structure that occurs above the absorption edge and normally diminishes in intensity the further it is from the edge. Either or both of these regions of the XAFS spectrum can be used to determine how the element occurs in a material.

Figure 2 - 1 XAFS Spectrum o f Elemental Selenium Showing t he Division o f t he Spectrum i nto Separate XANES a nd EXAFS Regions a nd t he Subsequent Generation o f a Radial Structure Function ( RSF ) b y Fourier Transform o f t he EXAFS Region o f t he Spectrum. The Peak i n t he RSF Spectrum Represents X - Ray Scattering Interactions Between t he Selenium Atom a nd Its Immediate Neighbors a nd Can Be Considered a One - Dimensional Representation o f t he Structure Local t o t he Selenium AtomBACKGROUND



### 2

- 2 The structure associated with the edge it self is known as the XANES region, whereas the periodic structure above the edge is known as the EXAFS region. Analysis of each region is performed independently. Typically, the XAFS spectrum is first normalized to the edge step and then divided into separ ate XANES and EXAFS regions. The latter region can be further manipulated mathematically to obtain a RSF. Where the EXAFS region provides structural information, the XANES region provides bonding and valence state information. 

### Power Plant Sites The oil

- fir ed power plants that were sampled for Ni speciation are described in Table 2

- 1. AirKinetics, Inc

. , was at the Honolulu, Kahe, and Waiau power plants April 12

– 15; June 7

– 11, 13, and 14; and May 9

– 13, 2010, respectively, to perform EPA Section 114 HAP emissi ons and Ni speciation testing. The average electric generation attained for each unit during metals testing is presented in Table 2

- 1. Table 2 - 1 Power Plant Descriptions and Abbreviations

Facility Unit Abbreviation Unit Gross Ele ctric Generation , MW e Honolulu Power Plant (HPP) 9 H 9 53 Kahe Power Plant (KPP) 1 K 1 85 Waiau Power Plant (WPP) 6 W 6 52

### 3

- 1 

# 3 EXPERIMENTAL

Residual Oil Analyses Proximate, ultimate, and metal analyses were performed on composite residual oil samples colle cted from HPP, KPP, and WPP as described in AirKinetics reports [ 35

– 37 ]. 

### Fly Ash Stack Sampling and Analysis Methods ROFA was sampled isokinetically and in duplicate by AirKinetics personnel for ≤ 5 hr/day from the stacks of the three units ( Table 2

- 1) usi ng a modified EPA Method 17 sampling train assembly , with the nozzle, probe, and quartz thimble filter maintained at >290 ° C, well above the sulfuric acid dew point temperature. The nozzle and filter holder were constructed of quartz and glass, respectively , to prevent contamination of ROFA by metal surfaces. The sampling train and procedures used in obtaining representative fly ash samples are described in detail by EPA [ 38 ]. The sampling approach employed is consistent with previous investigations of the N i speciation of stack emissions from oil

- fired utility boilers and sewage sludge incinerators [ 26

– 28, 30, 31, 39 ]. Plant operating and monitoring data and continuous emission monitoring results indicated that the modified EPA Method 17 stack sampling occur red during steady, representative power plant operations. In addition to modified EPA Method 17, ROFA samples were sampled according to EPA Method 29 and analyzed for Ni as described in Air Kinetics reports [ 35

– 37 ]. All of the quartz thimble samples receiv ed by the Energy & Environmental Research Center ( EERC ) and University of Kentucky for analysis are described in Table s 3

- 1 and 3

- 2 . Several of the field and trip blanks were not analyzed using XAFS , but were prepared using microwave

assisted acid digestio n (EPA Method 3050 and ASTM International Standard Practice D5513) and analyzed using ICP

– AES (EPA Method 6010A and 7000 series).
**Soluble Ni Extraction** The ROFA filters were exposed to deionized H 2 

### O for about 30 minutes. ROFA H 2 

### O extraction residues were d ried in an oven at 50 ° C before analyzing them using XAFS spectroscopy and XRD. The leaching procedure was intended to dissolve readily soluble species such as NiSO 4 

### · 6H 2 

### O from the filters and preconcentrate insoluble Ni species such as Ni oxides and sulfide s. Analyses of ROFA H 2 

### O extraction residues minimize potential x

- ray absorption and diffraction spectral overlaps caused by the presence of multiple Ni species. The extraction residue samples are listed in Table 3

- 2

.EXPERIMENTAL



### 3

- 2 Table 3 - 1 Li st of S amples C ross - R eferenced to XAFS F ile N ames Power Plant and U nit XAFS Analysis Facility Thimble Filter Identification XAFS File HPP 9 SSRL, May 2010 1 H9
- Ni
- 1 NiASH_011.003 2 H9
- Ni
- 2 NiASH_010.003 Field b lank H9
- Ni
- FB NiASH_017.001 Trip b la nk H9
- Ni
- TB NiASH_018.001 W PP 6 NSLS, August 2010 1 W6
- Ni
- 1 NiROFA_025

– 027 2 W6
- Ni
- 2 NiROFA_028

– 030 Field b lank W6
- Ni
- FB NA Trip b lank 1 W6
- Ni
- TB NA K PP 1 NSLS, August 2010 1 K1
- Ni
- 1 NiROFA_031

– 033 2 K1
- Ni
- 2 NiROFA_034

– 036 Field b la nk K1
- Ni
- FB NA Trip b lank K1
- Ni
- TB NA

1 Not analyzed by XAFS

.

Table 3 - 2 List of ROFA H 2 Power P lant and Unit O Extraction Residue Samples Cross - Referenced to XAFS File N ames XAFS Analysis Facility Thimble Filter Identificati on XAFS File HPP 9 SSRL, May 2010 2 H9
- Ni
- 2R NiLEACH_026.016 W PP 6 NSLS, August 2010 1 W6
- Ni
- 1R NiROFAL_045

– 048 2 W6
- Ni
- 2R NiROFAL_049

– 053 K PP 1 NSLS, August 2010 1 K1
- Ni
- 1R NiROFAL_037

– 040 2 K1
- Ni
- 2R NiROFAL_041

– 044 

### Ni XAFS Spectroscopy Nickel XAFS measurements were made in both absorption and fluorescence geometry at B eamline 4

- 1 at SSRL or at B eamline X

- 18B at NSLS using a fluorescence detector to detect the x - rays emitted by Ni in the investigated materials in response to the x - ray ab sorption process. Soller slits and a 6

- μ m cobalt filter were also used at SSRL to enhance the fluorescentEXPERIMENTAL



### 3

- 3 signal/noise ratio. Harmonic r ejection was accomplished by de tuning the intensity of the incident beam by about 30%. The spectra were collected as a function of energy from about 200 eV bel ow t he K absorption edge of Ni at 8 333 eV to as much as 1000 eV (16 k) above by measuring the absorption and fluorescence signals as a function of the angular rotation of the silicon (220) monochromator at SSRL or the Si (111) monochromator at NSLS. The ab sorption spectrum of a Ni 0 

### foil, obtained simultaneously in absorption geometry, was used as the primary energy calibration standard in both sets of experiments. If necessary, the thimble filters were cut in half lengthwise to expose the deposited material , and then a 5

- cm - long section containing the thickest and most coherent deposit was cut from one

- half of the filter ( Figure 3

- 1 ). This section, approximately 3 × 5 cm in size, was taped to the sample holder so as to expose the ROFA to an x - ray beam. Photo graphs of the other filters from KPP and WPP U nits 1 and 6, respectively, are presented in Appendix A. Excellent

- quality fluorescence spectra were obtained at SSRL from the samples prepared in this manner using a standard Lytle fluorescence detector. Data of a lmost as good quality were obtained at NSLS using a passivated, implanted, planar silicon ( PIPS ) detector to measure fluorescence radiation. The XAFS spectra of eight standard Ni compounds, Ni 3 

### S 2 

### , NiS, NiS 2 

### , NiSO 4 

### , NiSO 4 

### · H 2 

### O, NiSO 4 

### · 6H 2 

### O, NiSO 4 

### · 7H 2 

### O, an d NiO, obtained during the course of a similar testing program for an additional utility provider, were also used as reference spectra for this investigation.

Figure 3 - 1 Phot ograph o f Deposits o n Quartz Thimble Filters f rom HPP 9. Thimbles Have Been Cut t o Expose ROFA t o t he X - Ray BeamEXPERIMENTAL



### 3

- 4 **XRD** Representative sections of the ROFA

- containing thimble filters were mounted in the XRD for analys i s. XRD patterns were collected over 5

– 60 ° 2

- theta with a Bruker D8 Advance theta

– theta x - ray diffractometer system operating at 40 kV and 40 mA ( parallel

- b eam g eometry using a n incident beam Goebel m irror to monochromatize and co llimate Cu K

- á radiation, 0.02 ° 2

- theta steps, 7 to 15 sec/step). Dif fraction peaks were identified using the Bruker EVA evaluation software utilizing the International Centre for Diffraction Data ( ICDD ) PDF

- 2 inorganic and organic powder diffraction database.

### 4

- 1 

# 4 RESULTS AND DISCUSSI ON

Residual Oil Analyses Presented in Tabl e 4

- 1 are proximate and ultimate analysis results for the composite residual oil samples. Sulfur only ranged from 0.3 to 0.4 wt%. The calorific (i.e., heating) value of the residual oil sampled from WPP U nit 6 is significantly greater relative to the two o ther oils. AirKinetics also had the composite oil samples analyzed for Ni and many other elements , but the Ni concentrations were all reported as <5.0 mg/kg [ 35

– 37 ]. Table 4 - 1 Residual Oil Proximate and Ultimate Analysis Results, as - received basis Analysis Parameters HPP Unit 9 KPP Unit 1 WPP Unit 6 Avg. ±95% C.I. n 1 Avg. ±95% C.I. 2 n Avg. ±95% C.I. n Proximate Analysis Water, vol % <0.05 4 <0.05 7 <0.05 5 Ash, wt % <0.01 4 0.02 ±0.01 7 0.05 ±0.02 5 Ultimate Analysis, wt % Hydrogen 10.9 ±0.1 4 11.6 ±0.2 7 11.1 ±0.6 5 Carbon 87.3 ±0.1 4 87.5 ±0.2 7 84.9 ±4.6 5 Nitrogen 0.25 ±0.07 4 0.21 ±0.08 7 0.31 ±0.07 5 Sulfur 0.37 ±0.01 4 0.39 ±0.02 7 0.32 ±0.00 5 Oxygen 1.23 ±0.22 4 0.38 ±0.19 7 0.74 ±0.14 4 Calorific Valu e, Btu/lb 17958 ±22 4 17963 ±183 7 18346 ±583 5 1 Average ± 95% confidence interval. 2 

### ROFA Ni Analyses Number of samples analyzed.



### EPA Method 29 Compared in Table 4

- 2 are the average Ni contents of the ROFAs based on triplicate EPA Method 29 results. ROFA from the KPP contains significantly less Ni relative to the other twoRESU LTS AND DISCUSSION



### 4

- 2 Table 4 - 2 Average ROFA Ni Concentrations and Emission Rates Facility Average Ni ±95% Confidence Inte rval, wt % Average Ni Emission, lb/10 6 HPP , Unit 9 Btu 4.2 6 ±0.97 6.33E
- 04 ±1.6E
- 05 KPP , Unit 1 2.40 ±0.37 1.19E
- 03 ±2.3E
- 04 WPP , Unit 6 4.78 ±0.14 4.28E
- 04 ±1.7E
- 05 

### power plants , but the Ni emissions from KPP were the highest , probably because it was consuming the most oil to produce the most power , as indic ated in Table 2

- 1. Even though ROFA from WPP had the highest Ni concentration, its Ni emission rate was intermediate to HPP and KPP , probably because it was producing a similar amount of power (Table 2

- 1) to HPP but with a residual oil whose calorific valu e was significantly higher. **Ni XAFS Spectroscopy** Spectra collected for the HPP U nit 9 samples are shown in Figure 4

- 1

. Spectra of the duplicate ROFA samples are very similar, both in overall intensity and appearance. Also compared in Figure 4

- 1 are the cor responding spectra of the trip and field filter blanks and th e ROFA H 2 

### O

Figure 4 - 1 Ni XAFS Spectra Collected a t SSRL f or Thimble Filter Samples f rom HPP U nit 9. The Spectra f or t he Field a nd Trip Blanks Do Not Differ Significantly a nd , Thus , Superimpose a s a Single Trace a t t he Plotted Scale. Inset Shows a Vertical Expansion o f t he Scale f or t he H9 - Ni - 2R a nd Blank SamplesRESULTS AND DISCUSSION



### 4

- 3 extraction residue. The spectrum for the residue sampl e is much weaker relative to bulk ROFA samples , indicating that the leaching extracted a large amount of soluble Ni species. No significant feature appears at the Ni absorption edge in the blank sample spectra , indicating that Ni was below the XAFS detecti on limit. Presented in Figure 4

- 2 are the XAFS spectra for the ROFA samples obtained from KPP and WPP U nits 1 and 6, respectively. Spectra for the duplicate ROFA samples are essentially identical for a given power plant. The field and trip blank thimble fi lters for the KPP and WPP U nits 1 and 6, respectively, were not analyzed because ICP

– AES measurements, presented in Table 4

- 3, indicated that Ni was n o t present in high enough concentrations to produce Ni XAFS spectra from them . Comparative data for the RO FA H 2 

### O extraction residue, H9

- Ni

- 2R, are also shown in Figure 4

- 2. The Ni XAFS data obtained from the ROFA samples were divided into separate XANES and EXAFS region s according to the procedures described in Figure 2

- 1. Plots of the XANES and EXAFS data wer e prepared for each set of samples from the three units. These spectra are shown in Figures 4

- 3 and 4

- 4 for the samples measured at SSRL and NSLS, respectively. Spectra obtained from the ROFA H 2 

### O extraction residue sample, H9

- Ni

- 2R, are also included in Fi gure 4

- 3. The Ni XANES and EXAFS spectra of the four ROFA H 2 

### O extraction residues from KPP and WPP are presented in Figure 4

- 5. Except for the W6

- Ni

- 2R sample, there was sufficient Ni

Figure 4 - 2 Ni XAFS Spectra Collected a t NSLS f or Thimble Filter Samples from KPP a nd WPP U nits 1 a nd 6, Respectively
. The Spectrum of a ROFA H 2 O Extraction Residue , W6 - Ni - 2R , i s Shown for ComparisonRESULTS AND DISCUSSION



### 4

- 4 Table 4 - 3 Ni Content s of the Filter Blan k Samples from KPP and WPP Units 1 and 6, respectively Sample Ni, ppm KPP Unit 1 Trip Blank 1.16 KPP Unit 1 Field Blank 0.81 WPP Unit 6 Trip Blank 0.88 WPP Unit 6 Field Blank 1.10



### remaining on the filters after the aqueous leachin g procedure to produce acceptable

- quality spectra at all stages of the spectral data reduction process. For the W6

- Ni

- 2R sample, however, the EXAFS region was too noisy to permit a meaningful RSF spectrum to be generated from the EXAFS (k 3 

### chi) spectrum. Ni ckel XAFS spectra of various reference Ni compounds are presented in Figures 4

- 6

– 4

- 8

. Figure 4

- 6 compares the Ni XAFS data obtained for three different nickel sulfates, NiSO 4 

### (anhydrous), NiSO 4 

### · H 2 

### O, and NiSO 4 

### · 6H 2 

### O. Figure 4

- 7 shows the processed XAFS spect ra for the three Ni sulfides, Ni 3 

### S 2 

### , NiS, and NiS 2 

### . These spectra differ significantly from those shown in Figure 4

- 6 for the Ni sulfates in three major ways: (i) there is no sharp large peak at the absorption edge for the Ni sulfides compared to the Ni su lfates; (ii) the major peak in the RSF occurs at about 2.0 Å for the Ni sulfides and at about 1.5 Å for the Ni sulfates; and (iii) the peak maximum in the derivative XANES spectra occurs at a significantly lower energy for the Ni sulfides than for the Ni s ulfates (compare Figures 4

- 6 [b] and 4

- 7 [b]). These differences make it easy to distinguish Ni sulfides from Ni sulfates. Furthermore, the Ni sulfides all show significant absorption in a small region of the spectrum (8335 to 8340 eV) that is devoid of sig nificant absorption for Ni oxide and sulfate compounds. Figure 4

- 8 shows Ni XAFS data for three Ni oxide species, NiO, NiFe 2 

### O 4 

### , and NiAl 2 

### O 4 

### . These spectra are the best that we have in our database for these compounds; however, it seems possible to improve on the quality of these data. In particular, the spectral data for the nickel ferrite, NiFe 2 

### O 4 

### , are quite weak, as indicated by the noisy nature of the derivative XANES spectrum (Figure 4

- 8 [ b ] ). The EXAFS regions and RSF spectra of all three compounds (Fi gures 4

- 8 [c], [d]) are complex, which is typical of the high

- symmetry structures exhibited by compounds with cubic crystal structures, MO (halite [NaCl]

- type) and AB 2 

### O 4 

### (spinel

- type). For NiO, peaks representing the 4th and 5th and even more distant coord ination shells are discernable in the RSF (Figure 4

- 8 [d]). For both NiO and NiFe 2 

### O 4 

### , the second peak in the RSF spectrum at ≈ 2.5

– 2.6 Å exceeds the height of the NiO peak at ≈ 1.5 Å. This peak derives from the second nearest coordination shell in the oxid e structure and consists of metal (Ni or Fe) atoms. The enhanced back

- scattering power of the higher

- atomic

- number elements, Ni and Fe, compared to oxygen, as well as the larger coordination number for the second coordination shell in these structures, acc ount for the enhanced nature of this peak relative to the first coordination shell peak.RESULTS AND DISCUSSION



### 4

- 5 Figure 4 - 3 Ni XAFS Spectra of Duplicate ROFA Samples a nd a ROFA Residue Sample from t he Stack o f HPP U nit 9; ( a ) XANES Spectra, ( b ) Derivative XANES Spectra, ( c ) EXAFS (K 3 chi) Spectra, a nd ( d ) RSF Spectra. Data Collected a t SSRLRESULTS AND DISCUSSION



### 4

- 6 Figure 4 - 4 Ni XAFS Spectra o f Duplicate ROFA Samples from t he Stacks of KPP a nd WPP U nits 1 a nd 6, Respectively; ( a ) XANES Spectra, ( b ) Derivative XANES Spectra, ( c ) EXAFS (K 3 chi) Spectra, a nd ( d ) RSF Spectra. Data Collected at NSLSRESULTS AND DISCUSSION



### 4

- 7 Figure 4 - 5 Ni XAFS Spectra o f ROFA Residues Corresponding t o KPP a nd WPP U nits 1 a nd 6, Respectively; ( a ) XANES Spectra, ( b ) Derivative XANES Spectra, ( c ) EXAFS (K3chi) Spectra, a nd ( d ) RSF Spectra. Data Collected a t NSLSRESULTS AND DISCUSSION



### 4

- 8 Figure 4 - 6 Ni XAFS Spectra o f Ni SO 4 , Ni SO 4 · H 2 O , a nd Ni SO 4 · 6H 2 O ; ( a ) XANES Spectra, ( b ) Derivative XANES Spectra, ( c ) EXAFS (K 3 chi) Spectra, a nd ( d ) RSF SpectraRESULTS AND DISCUSSION



### 4

- 9 Figure 4 - 7 Ni XAFS Spectra o f Ni 3 S 2 , N i S , a nd N i S 2 ; ( a ) XANES Spectra, ( b ) Derivative XANES Spectra, ( c ) EXAFS (K 3 chi) Spectra, a nd ( d ) RSF SpectraRESULTS AND DISCUSSION



### 4

- 10 Figure 4 - 8 Ni XAFS Spectra of N i O , N i F e 2 O 4 , a nd N i A l 2 O 4 ; ( a ) XANES Spectra, ( b ) Derivative XANES Spectra, ( c ) EXAFS (K 3 chi) Spectra, a nd ( d ) RSF SpectraRESULTS AND DISCUSSION



### 4

- 11 All of the RSFs for the ROFA samples (Figures 4

- 3 [d] and 4

- 4 [d]) have a small but significant peak at 2.5 Å, which is always more prominent for the corresponding ROFA H 2 

### O extraction residue samples (Figure 4

- 5 [d]). Of the sulfates, only NiSO 4 

### shows a significant second coordination shell peak (Figure 4

- 6 [d]); h o wever, the peak is located at ≈ 2.8 Å, rather than 2.5 Å. Conversely, NiSO 4 

### · 6H 2 

### O, which is most likely the Ni sulfate contributing to the spectra of the residual oil samples, lacks a significant second coordination shell peak. Also, none of the Ni sulfide species exhibit a peak at 2.5 Å in their RSFs (Figure 4

- 7 [d]). These observations suggest that the source of the 2.5

- Å peak in the ROFA sample spectra is a minor amount of NiFe 2 

### O 4 

### or NiO rather than a Ni sulfate or sulfide compound. For the ROFA H 2 

### O extra ction residues, the enhanced nature of the 2.5

- Å peak, especially for the H9

- Ni

- 2R sample (Figure 4

- 3 [d]) and K1

- Ni

- 1R and

- 2R samples (Figure 4

- 5 [d]), indicates the prevalence of NiFe 2 

### O 4



### XANES Pre **- Edge Systematics**  or NiO.

Based on the spectral fe atures for the Ni sulfate and sulfide standards (Figures 4

- 6 and 4

- 7 ), there are several systematic differences that enable a distinction between Ni sulfate and sulfide species. Oxidic Ni species, such as NiO and various Ni spinels (NiFe 2 

### O 4 

### , NiAl 2 

### O 4 

### , NiV 2 

### O 4 

### , etc.), are similar to Ni sulfates because the Ni 2+ 

### ion is bonded to oxygen anions, thus their XAFS spectra have more in common with those of Ni sulfates than Ni sulfides. Indeed, the spectra for NiFe 2 

### O 4 

### and NiAl 2 

### O 4



### Detailed examina tions of the pre

- edge region (8330

– 8 340 eV) of the XANES and derivative XANES spectra for all Ni show much the same pre

- edge characteristics as t he Ni sulfate standards. These systematic differences were used to evaluate whether a sulfidic Ni species was present in ROFA.

2+ 

### compounds reve aled that there is a ubiquitous peak or inflection feature at about 8 332

– 8 333 eV that occurs because of the electron transition from Ni 1s orbitals to 3d orbitals induced by the x - ray absorption process. Furthermore, the intensity of this feature can be us ed to discriminate Ni 2+



### As indicated in Figure 4

- 9, the relative height of the inflection featu re is always more than 0.05 for metallic Ni and Ni sulfides and less than 0.025 for Ni sulfate and oxide phases, except for NiO , which exhibits an intermediate value of about 0.032. Figure 4

- 10 presents the normalized pre - edge inflection feature heights de termined from the derivative XANES spectra of the bulk ROFA samples and their corresponding ROFA H ions coordinated with sulfur anions versus oxygen anions. Plotted in Figure 4

- 9 are the relative intensities of the inflection feature for various Ni compounds.

2 

### O extraction residues. The relative heights for the bulk ROFAs and corresponding residues range similarly between 0.009 and 0.017, whereas in comparison , the range for a suite of ROFA samples from Florida power plants was much smaller at 0.015 to 0.018. Clearly, data for the ROFA samples measured at NSLS (KPP and WPP U nits 1 and 6, respectively) have values consistently lower than those measured at SSRL for RO FA samples from HPP U nit 9. This difference is attributable to resolution differences between the two synchrotrons, principally as a result of different monochromator crystal orientations. The use of the Si (111) crystals at NSLS results in a somewhat broa dened and less intense pre

- edge peak at NSLS compared to that measured at SSRL.RESULTS AND DISCUSSION



### 4

- 12 Figure 4 - 9 Comparison of t he Normalized Height of t he Pre - Edge Inflection Feature a t 8333 eV i n Ni Derivative XANES Spectra for Ni Compounds

Figure 4 - 10 Comparison o f t he Normalized Height o f t he P re - Edge Inflection Feature a t 8 333 eV i n Derivative Xanes Spectra o f Ro fa Sampled f rom t he Three Hawaiian Units. Light Bars Represent Data f or t he R OFA H 2 O Extraction Residue SamplesRESULTS AND DISCUSSION



### 4

- 13 Since the inflection feature height values for the ROFA samples from Hawaii are less than or comparable to those for the Ni sulfates and oxides , such small values indicate that there may be a minimal contribution from Ni sulfides. However, the difference between the two synchrotrons in the intensity of this feature implies that we cannot develop the height of the pre

- edge peak as a general quanti tative measure for estimating sulfide contents; such correlations would have to be restricted to a given mo nochromator orientation or beam line. In a companion study of ROFA emissions from Florida power plants, various correlations were established between composition and absorption intensity at the positions of the major peaks in the Ni derivative XANES spectra for mixtures of Ni 3 

### S 2 

### and NiSO 4 

### · 6H 2 

### O, Ni 3 

### S 2 

### and NiFe 2 

### O 4 

### , and NiS and NiSO 4 

### · 6H 2 

### O. From these correlations, the following equations were derived for e stimating the proportions of Ni 3 

### S 2 

### F or Ni or NiS in ROFA:

3 

### S 2 

### – NiSO 4 

### · 6H 2 

### O mixtures: Ni 3 

### S 2 

### F or Ni , % = 813 h(8336)

– 4.3 [Eq. 1 ]

3 

### S 2 

### – NiFe 2 

### O 4 

### mixtures: Ni 3 

### S 2 

### For NiS

– NiSO , % = 892 h(8336)

– 13.8 [Eq. 2 ]

4 

### · 6H 2 

### Equa tions 1 and 3 are applicable to the bulk ROFA samples in which NiSO O mixtures: NiS, % = 952 h(8337)

– 8.0 [Eq. 3 ]

4 

### · 6H 2



### Using E quations 1

– 3, Ni O is the major phase, while E quation 2 is more appropriate for the Ni extraction residues after Ni sulfates have been removed.

3 

### S 2 

### and NiS contents were estimate d from the derivative Ni XANES spectra; estimates are presented in Table 4

- 4 . The proportions in Table 4

- 4 are ≤ 3 % of the total Ni present in the bulk ROFA, but the analytical uncertainty is ±2% so the values are essentially equal to zero. These proportions are maximum estimates for Ni 3 

### S 2 

### and NiS in the bulk ROFA samples because NiSO 4 

### · 6H 2 

### O has the lowest h ( 8336) value of all the standards. Substitution of any other Ni sulfate or a Ni oxide species for NiSO 4 

### · 6H 2 

### O in the calibration procedure results in smaller estimates of the Ni sulfide proportions, as would the presence of a third component such as NiFe 2 

### O 4 

### or NiO in the calibration procedure. Applying similar calculations to the ROFA H 2 

### O extraction residue samples, produces slightly higher estimates for Ni 3 

### S 2 

### and NiS; however, for the ROFA H 2 

### O extraction residues, it is likely that NiFe 2 

### O 4 

### or NiO are present and should be used in the calibration procedures rather than a Ni sulfate. Using NiFe 2 

### O 4 

### in the calibration procedure actually results in negative Ni 3 

### S 2 

### estimates for most of the ROFA H 2 

### O extraction residues, based on the use of h (8336) values in Table 4

- 4 and E quation 3. Such negative values probably indicate that some Ni sulfate remained on the ROFA H 2 

### In conclusion, a detailed examination of Ni pre

- edge XANES systematics indicates that the Ni O extraction residues.

3 

### S 2 

### or NiS contents of ROFA from the th ree HECO units are negligible and comp rise ≤ 3% of the total Ni , if any. This simple two

- component calibration procedure is sufficient because both Ni sulfides are negligible in all the ROFA samples. A more sophisticated three

- component approach would be a pplicable if significant amounts of either or both of the sulfides were present.RESULTS AND DISCUSSION



### 4

- 14 Table 4 - 4 Estimates of NiS and Ni 3 S 2 in ROFA from T hree HECO U nits

Sample Bulk ROFA ROFA H 2 h(8336) O Extraction Residues Ni 3 S 2 h(8337) , % NiS , % h(8336) Ni 3 S 2 h(8337) , % NiS , %
H9
- Ni
- 1 0.0043
- 1 0.0067
- 2 NA NA 1 NA NA H9
- Ni
- 2 0.0042
- 1 0.0065
- 2 0.0079 2 (
- 7) 0.0145 2 6 W6
- Ni
- 1 0.0054 0 0.0103 2 0.0114 5 (
- 4) 0.0175 9 W6
- Ni
- 2 0.0058 0 0.0091 1 0.0172 10 (2) 0.0072
- 1 K1
- Ni
- 1 0.0072 2 0.0113 3 0.0126 6 (
- 3) 0.0171 8 K1
- Ni
- 2 0.0079 2 0.0108 2 0.0139 7 (
- 1) 0.0154 7



### Least **- Squares Fitting of Ni XANES and EXAFS Spectra**  In addition to the Ni derivative XANES spectral correlations ( E quations 1

– 3), a least

- squares fitting of Ni XANES and EXAFS spec tra was performed to evaluate the Ni species contents of the ROFAs. The most reliable simulation approach consisted of combining the spectra for the bulk ROFA (consisting predominantly of NiSO 4 

### · 6H 2 

### O) and corresponding ROFA H 2 

### O extraction residue (consistin g mainly of NiFe 2 

### O 4 

### and/or NiO) with that of NiSO 4 

### · 6H 2 

### O and NiO. These simulations were performed for the EXAFS (k 3 

### chi) spectra of all six samples. As indicated in Table 4

- 5 , these simulations confirm that NiSO 4 

### · 6H 2 

### O is the predominant sulfate phase. Some of the fits were marginally improved with the addition of NiO in the least

- squares fitting, especially for the W6

- Ni

- 1 and

- 2 samples. However, we suspect that NiO is a major component of the Ni remaining in the ROFA H 2 

### O extraction residues and that the di fference in least

- squares fitting between fits with and without NiO is largely an experimental artifice. This is most likely the case for the K1

- Ni

- 1 and

- 2 samples, where the Ni proportion as NiO is relatively minor and clearly compl e ments the Ni % for th e ROFA H 2


### Least

- squares fitting of bulk ROFA and corresponding ROFA H O extraction residue sample in the fitting.

2 

### O extraction residue Ni EXAFS spectra to linear combinations of spectra for two or more standard compounds (NiSO 4 

### ·6H 2 

### O, NiFe 2 

### O 4



### The least

- squares fitting results indicate that the Ni in H9

- Ni

- 1 and

- 2 samples are predominantly (>95%) present as NiSO , and/or NiO) wa s performed as shown in Figure 4

- 11 and reported in Table 4

- 6. The fits did not require the presence of Ni sulfide(s). For the H9

- Ni

- 1 and

- 2 samples, several different fits were statistically similar, and these results are also included in Table 4

- 6, in a ddition to the best linear combination fit.

4 

### ·6H 2 

### O, with only very minor amounts of NiFe 2 

### O 4 

### and/or NiO. In a corresponding ROFA H 2 

### O ext raction residue, H9

- Ni

- 2R, NiSO 4 

### ·6H 2 

### O remains dominant despite the large reduction in soluble Ni as indicated by the reduction in the overall absorption intensityRESULTS AND DISC USSION



### 4

- 15 Table 4 - 5 Results of L east - S quares F itting of C ombined B ulk ROFA a nd C orresponding ROFA H 2 O E xtraction R esidue S pectra to S pectra for NiSO 4 · 6H 2 Sample O and NiO EXAFS Region (3
– 10 Å - 1 Residue, % ) Fitting NiSO 4 NiO , % , % Red χ H9
- Ni
- 1 2 11 89

– 0.124 H9
- Ni
- 2 5 95

– 0.159 W6
- Ni
- 1 9 77 14 0.407 W6
- Ni
- 2 3 84 14 0.452
K1
- Ni
- 1 28 72

– 0.320 18 76 6 0.269
K1
- Ni
- 2 26 74

– 0.372 15 78 7 0.302

Figure 4 - 11 Examples o f Least - Squares Fits t o EXAFS Spectra o f ROFA Samples: Bulk ROFA Sample, K1 - Ni - 2 ( l eft), a nd ROFA H 2 O Extraction Residue, K1 - Ni - 1R ( r ight). The Spectra Are Fitted t o a Linear Combination o f EXAFS Spectra f or Ni SO 4 · 6H 2 O , N i F e 2 O 4 

### (Figure 3

- 1). Each of t he two Ni oxides comp ri se about 20% of the total Ni in H9

- Ni

- 2R. The proportions of oxidic Ni in the bulk ROFA samples from the other two units were significantly larger than those in the H9

- Ni

- 1 and

- 2 samples. Least

- squares fitting indicated that between 10 % and 20% of the Ni in these unleached samples was present as NiFe , a nd N i O

2 

### O 4 

### and/or NiO. In the K1

- Ni

- R1 and

- R2 samples, NiSO 4 

### · 6H 2 

### O is reduced to about 30%, while NiFe 2 

### O 4 

### and NiO account for the remaining Ni. Spectra of the ROFA H 2 

### O extraction residue W6

- Ni

- 1R and

- 2R samples were too weak to perform similar analyses.RESULTS AND DISCUSSION



### 4

- 16 Table 4 - 6 Results of L east - S qua res F itting of EXAFS S pectra (3
– 10 Å

- 1) for B ulk ROFA and ROFA H 2 O E xtraction R esidues to L inear C ombinat ions of the C orresponding S pectra for NiSO 4 · 6H 2 O, NiFe 2 O 4 Sample , and NiO Total Ni, % Red. χ NiSO 2 4 · 6H 2 NiFe O , % 2 O 4 NiO , % , %

H9
- Ni
- 1 96 4

– 0.177 97

– 3 0.169 96 2 2 0.165

H9
- Ni
- 2 100

– – 0.180 98 2

– 0.168 98

– 1 0.173 98 2 0 0.169 H9
- Ni
- 2R 63 16 21 0.600 W6
- Ni
- 1 85

– 15 0.471 W6
- Ni
- 2 91

– 9 0.485 K1
- Ni
- 1 83 10 7 0.438 K1
- Ni
- 2 81 9 9 0.314 K1
- Ni
- 1R 34 45 21 0.821 K1
- Ni
- 2R 34 39 27 1.720



### Analyses of XAFS spectra obtained for ROFA samples from Hawaiian oil

- burning power plants indic ate that NiSO 4 

### ·6H 2 

### O is the most abundant Ni

- bearing phase in them. Minor amounts of oxide phases such as NiFe 2 

### O 4


### XRD Analyses and NiO are also present, but in subordinate amounts. No evidence exists for the presence of Ni sulfide(s) or other Ni sulfates.

X RD analyses were performed on the bulk ROFA samples primarily to identify crystalline phases. X

- ray diffractograms for the six ROFA sam p les are presented in Appendix B. The XRD results in Table 4

- 7 for the bulk ROFA samples indicate that amorphous componen ts, glass and unburned carbon, are ubiquitous in the ROFAs. NiSO 4 

### · 6H 2 

### O and CaSO 4 

### are also present in all the ROFAs. The KPP U nit 1 ROFA is distinguished by the presence of FeNi 2 

### O 4 

### which is very similar to the NiFe 2 

### O 4 

### compound identified by XAFS. XRD analysis results of the ROFA H 2 

### O extraction residues indicated that the H 2 

### O extraction removed most of the ROFA , and no crystalline phases were detected. The sensitivity (i.e., limit of detection) of XRD is much poorer relative to XAFS spectroscopy.RESULTS AND DISCUSSION



### 4

- 17 Table 4 - 7 Bulk ROFA Phase Assemblages ROFA Sample NiSO 4 · 6H 2 FeNi O 2 O CaSO 4 Glass and Unburned Carbon 4 H9
- Ni
- 1 X X X H9
- Ni
- 2 X X X K1
- Ni
- 1 X X X X K1
- Ni
- 2 X X X X W6
- Ni
- 1 X X X W6
- Ni
- 2 X X X
1 An “X” denotes that the corresponding amorphous or crystalline phase was identified using XRD.

### 5

- 1 

# 5 CONCLUSIONS

T he Ni speciation of ROFA samples collected in duplicate on quartz thimble filters from three oil

- burning utility boilers was evaluated using two x

- ray techniques, XAFS spectroscopy and XRD. ROFA deionized H 2 

### O extraction residues were also analyzed for Ni s peciation using XAFS and XRD. Ni pre

- edge XANES systematics and the least

- squares fitting of XANES and EXAFS spectra of the six ROFA samples with those from standard Ni compounds indicated that t he major Ni phase, comp ri sing 80%

– 95% of the total Ni, was Ni SO 4 

### · 6H 2 

### O with subordinate proportions, ≤ 20% of the total Ni, present as a spinel compound, similar in composition to NiFe 2 

### O 4 

### and/or NiO. XRD confirmed the presence of NiSO 4 

### · 6H 2 

### O and NiFe 2 

### O 4 

### but not NiO. Spectral evidence for the presence of Ni sulfide com pounds (Ni 3 

### S 2 

### , NiS, or NiS 2

Table 5 - 1 Ni S pecies E mission E stimates 

### ) was absent and , at most , does not exceed 3% of the Ni in any sample. Based on these species proportions and the total Ni emission rates in Table 4

- 2 , the emission rates for the Ni species were calculated as indicated in Table 5

- 1.

Facility NiSO 4 · 6H 2 O, lb/10 6 NiFe Btu 2 O 4 ± NiO, lb/10 6 Ni Btu x S y , lb/10 6 HPP, Unit 9 Btu 5.06E
- 4
─ 6.01E
- 4 ≤ 1.27E
- 4 ≤ 1.90E
- 5 KPP, Unit 1 9.52E
- 4
─ 1.13E
- 3 ≤ 2.38E
- 4 ≤ 3.57E
- 5 WPP, Unit 6 3.42E
- 4
─ 4.07E
- 4 ≤ 8.56E
- 5 ≤ 1.28E
- 5

### 6

- 1 

# 6 REFERENCES

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– 549, 1990. 10. U.S. Environmental Protection Agency. National Ambient Air Quality Standards (NAAQS); Washington, DC, Nov 2002. www.epa.gov/airs/criteria.html (accessed May 2003). 11. U.S. Environmental Protection Agency. National Air Toxics Program: The Integrated Urban Strategy; Washington, DC, July 1999. www.epa.gov/ttn/atw/urban/ urbanpg.html (accessed May 2003). 12. U.S. Environmental Protection Agency. 1996 Toxics Release Inventory, Public Data Release

– Ten Years of Right

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### 6

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– 857. 23. Shendrikar, A.D.; Ensor, D.S.; Cowen, S.J.; Woffinden, G.J.; McElroy, M.W. Size

Dependent Penetration of Trace Elements Through a Utility Baghouse. Atmos. Environ

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– 1421. 24. U.S. Environmental Protection Agency. Proposed National Emission Standards for Hazardous Air Pollutant s; and, in the Alternative, Proposed Standards of Performance for New and Existing Stationary Sources: Electric Utility Steam Generating Units ; Proposed Rule, Federal Register, Vol. 69, No. 20, Jan 31, 2004; pp 4652

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- Fired Utility Boilers. Presented at the 87th Air & Waste Management Association Annual Meeting, Cincinnati, OH, June 1994.REFERENCES



### 6

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– 17, 1995. 27. Bell, A.C.; Wong, J.; Chu, P. Speciation of Nickel Emissions from Oil

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– 28, 1996; Paper 96

– TP56.04. 28. Wong, J.L.; Qian, J.; Chen, C.H. Nickel Speciation of Fly Ash by Phase Extraction. Anal. Chim. Acta 1997 , 349 , 121

– 129. 29. Galbreath, K.C.; Crocker, C.R.; Nyberg, C.M.; Huggins, F.E.; Huffman, G.P.; Larson, K.P. Nickel Speciation Measurements of Urban Particulate Matter: Method Evaluation and Relevance to Risk Assessment. J. Environ. Monitoring 2003 , 5 , 56N

– 61N. 30. Galbreath, K.C .; Toman, D.L.; Zygarlicke, C.J.; Huggins, F.E.; Huffman, G.P.; Wong, J. Nickel Speciation of Residual Oil Fly Ash and Ambient Particulate Matter Using X

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– 1886. 31. Galbreath, K.C.; Sc hulz, R.L.; Toman, D.L.; Nyberg, C.M.; Huggins, F.E.; Huffman, G.P.; Zillioux, E.J. Nickel and Sulfur Speciation of Residual Oil Fly Ashes from Two Electric Utility Steam

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— Am. Chem. Soc., Div. Environ. Chem. 1998 , 38 (2), 143

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- 92/003a; U.S. Environmental Protection Agency, March 19 92.

### A

- 1 

# A APPENDIX

PHOTOGRAPHS OF QUARTZ THIMBLE FILTERS

Figure A - 1 Photograph of a T himble F ilter with ROFA S ampled from KPP U nit 1Appendix



### A

- 2 Figure A - 2 Photograph of a D uplicate T himble F ilter with ROFA S ampled from KPP U nit 1

Figure A - 3 Photograph of a T himble F ilter with ROFA S ampled from WPP U nit 6Appendix



### A

- 3 Figure A - 4 Photograph of a D uplicate T himble F ilter with ROFA S ampled from WPP U nit 6

### B

- 1 

# B APPENDIX

X - RAY DIFFRACTOGRAMS OF BULK ROFA AND N i EXTR ACTION RESIDUES

Figure B - 1 X - ray D iffractogram of ROFA S ample from HPP U nit 9 I ndicating S pectral M atches w ith NiSO 4 · 6H 2 O and CaSO 4Appendix



### B

- 2 Figure B - 2 X - ray D iffractogram of D uplicate ROFA S ample from HPP U nit 9 I ndicating S pectral M atches with NiSO 4 · 6H 2 O and CaSO 4Appendix



### B

- 3 Figure B - 3 X - ray D iffractogram of ROFA S ample from KPP U nit 1 I ndicating S pectral M atches with NiSO 4 · 6H 2 O, NiFe 2 O 4 , and CaSO 4Appendix



### B

- 4 Figure B - 4 X - ray D iffractogram of D uplicate ROFA S am ple from KPP U nit 1 I ndicating S pectral M atches with NiSO 4 · 6H 2 O, NiFe 2 O 4 , and CaSO 4Appendix



### B

- 5 Figure B - 5 X - ray D iffractogram of ROFA S ample from WPP U nit 6 I ndicating S pectral M atch es with NiSO 4 · 6H 2 O and CaSO 4Appendix



### B

- 6 Figure B - 6 X - ray D iffractogram of D uplicate ROFA S ample from WPP U nit 6 Indicating S pectral M atches with NiSO 4 · 6H 2 O and CaSO 4