## 5105 XANES Spectroscopic Analysis of Nickel Collected on

Quartz Filters

Contract No. 5105

AirNova, Inc. 5485 Clayton Avenue
Pennsauken, NJ 08109

Date: 2010-10-12

Canadian Light Source Inc.

101 Perimeter Road University of Saskatchewan
Saskatoon, Saskatchewan Canada

“This document has been prepared by Canadian Ligh t Source Inc. (CLSI), and contains experimental synchrotron research and development information. Ne ither CLSI nor any employees, officers, or directors, makes any warranty, expressed or implied, or assume s any legal liability or re sponsibility for accuracy, completeness or usefulness of any information or proce ss disclosed, or represents that its use would not infringe on privately owned rights.”

## Report Review

Signature Date

Author

Jeremy A. Olson 2010-09-27

Reviewer No. 1

Lisa Van Loon October 12, 2010

Reviewer No. 2 October 6, 2010

Jeff WarnerTable of Contents Page i 

## Table of Contents

1.0 Introduc tion .................................................................................. 1

1.1 SAMPLE DESCRIPTION .................................................................................. 1

1.2 MATERIALS AND METHODS ........................................................................... 1

1.2.1 Nickel K-edge XANES ........................................................................ 1

1.2.2 Oxygen K-ed ge XAS .......................................................................... 2

1.2.3 Spectral Analysis ............................................................................... 2



### 2.0 Results .......................................................................................... 2

3.0 Use of Re port ................................................................................ 3

4.0 Refere nces ........................................................................................ 35105 XANES Spectroscopic Analysis of Nickel Collected on Quartz Filters Page 1 

## 1.0 INTRODUCTION

AirNova, Inc. was interested in determining the speciation of nickel in three quartz filter media. In particular, the presence of sulfidic nickel species NiS and Ni 3 S 2 was of interest.



### 1.1 SAMPLE DESCRIPTION

Three used quartz thimble filters (AN1, AN2 and AN3), and one unused filter (ANBlank) were received from AirNova, Inc. A thin strip was cut, using a dedicated blade for each

filter in order to avoi d contamination. The strips were then placed into teflon sample holders for analysis. The nickel compounds used as standards are listed in Table 1.

Table 1. Nickel standard compounds used in the analysis of the nickel collected on the quartz thimble filters.

Nickel Standard Compounds
Nickel sulfide, NiS
Nickel carbonate, NiCO 3 Nickel hydroxide, Ni(OH) 2 Nickel sulfate, NiSO 4 . 6H 2 O
Nickel subsulfide, Ni 3 S 2 Nickel Iron oxide, NiFe 2 O 4 Nickel oxide, NiO Nickel nitrate, Ni(NO 3 ) 2 Nickel chloride, NiCl 2 Nickel(0) powder, Ni 0



### 1.2 MATERIALS AND METHODS

1.2.1 Nickel K-edge XANES

The Nickel K-edge XANES spectra were recorded on the Hard X-ray Micro Analysis (HXMA) beamline (6ID) at the Canadian Light Source (CLS) in August 2010. The HXMA beamline uses a superconducting wiggler operating at 2.0 T as a source magnet. The energy region of interest is selected using a double crystal monochromator equipped with Si (111) crystals. The beam is furt her collimated and fo cused using rhodium

mirrors. The incident beam was detuned to 70% to minimize the harmonic content of the beam at the nickel K-edge. The samples and reference compounds were calibrated at 8333 eV using a Ni foil placed between the second and third ion chambers. The sample spectra were collected in fluoresc ence mode using a 32 element solid state Germanium detector and the standard compound spectra were collected in transmission mode. Sample spectra were recorded fr om 8160 eV to 8640 eV. Two scans were recorded for each filter sample, three scans were recorded for the blank filter and two

scans were recorded for each of the standa rd compounds. The scans were averaged in5105 XANES Spectroscopic Analysis of Nickel Collected on Quartz Filters Page 2 the analysis prior to the linear combination (LC) fitting. One strip from each filter was cut and placed into the sample holder for analysis using XANES spectroscopy.



### 1.2.2 Oxygen K-edge XAS

The oxygen K-edge XAS spectra were collected on the Spherical Grating Monochromator (SGM) beamline (11ID-1) at the Canadian Light Source in September 2010. The energy region of interest was sele cted using a spherical gratin g monochromator using the low grating option. The spectra were collected with a microchannel plate fluorescence yield (FLY) detector. Spectra were recorded from 520 eV to 570 eV. The entrance slits were set at 250 μm and the exit slits were varied between 25 and 50 μm in order to optimize the signal.



### 1.2.3 Spectral Analysis

The sample spectra were analyzed using the XAS data processing software Athena, version 0.8.57. (1) Nickel K-edge XANES sample spectra were calibrated using the in-situ nickel metal foil collected for each scan. The pre-edge range and post-edge range were fit using standard techniques. The normalized spectra were then averaged together to create a single sample spectrum for analysis. Least squares linear combination fitting was used to identify the predominant nickel species present in each sample by fitting each sample spectrum with weighted mixtures of the appropriate reference compounds. The nickel spectra were fit over a 100 eV range.

The fits are limited by the presence of unique spectral features in the spectra and in the reference compounds. The comple xity of sample matrices can make identification of the species present in a sample difficult. This can often limit the technique to an accuracy of ± 5-10% depending on the number and identity of species present.



## 2.0 RESULTS

The nickel K-edge XANES spectra of the standard nickel compounds are shown in Figure 1. The XANES spectra for the nickel species on the sample filters are show in Figure 2 (AN1), Figure 3 (AN2) and Figure 4 (AN3) and include the linear combination fit and the fitted component spectra.

Linear combination (LC) fitting requires a lib rary of standard compounds for comparison. In this study, ten different nickel compounds were selected, representing nickel sulfides,

salts and oxides. The best fit is determined using combinations of different standard spectra.

The results indicate that for each of AN1, AN2 and AN3, th e major species is

NiSO 4 . 6H 2 O, Table 2. Differences between the collected spectra and the fits may be

attributed to the fact that NiSO 4 . 6H 2 O was used as the standard and the actual sulfate species in the samples may be the non-hydrated form or may be a more complex nickel sulfate compound. The spectra observed for AN1-AN3, and the fit associated with the spectra are consistent with resu lts previously reported in the literature for oil fly ash. (2) Because the fit is not perfect, it may also be possible that other nickel species that are not included in the library of standards used in this fitting attempt are present at low5105 XANES Spectroscopic Analysis of Nickel Collected on Quartz Filters Page 3 concentrations. Oxygen K-edge spectra were collected in orde r to eliminate NiCO 3 as a contributing species. Figure 5 shows that the peak positions of the sample correspond to peak positions of the NiSO 4 . 6H 2 O. Furthermore, the lack of a broad feature around

540-550 eV also eliminates NiCO 3

. During the fitting, the presence of oxide species was ruled out due to the lack of a prominent peak around 8365 eV. A better fit was obtained in the absence of NiS, and nickel sulfide was therefore ruled out as a major contributing species. The presence of nickel subsulfide should produce a slight shift in the peak edge, or at the very least a prominent shoulder, the lack of these features suggests that nickel subsulfide is not present at detectable concentrations for LCF. Because Ni 3 S 2 was of particular interest, the LC fitting was tested to determine the detection limits for Ni 3 S 2 when NiSO 4 . 6H 2 O is the main component. Fitting standards were created based on the filter results and a

Ni 3 S 2 component was added. In the fitting, nickel subsulfide could not be detected below

5%.

ANBlank, although it looked clean upon vi sual inspection, show ed relatively small amounts of nickel in the XANES spectrum which is likely due to contamination. The

levels of nickel on the blank filter were to o low to carry out any meaningful LC fitting.

Table 1. Results of the linear combinatio n fitting analysis for the four filters.

Sample

AN1 ~ 100% NiSO 4 . 6H 2 O

AN2 ~ 100% NiSO 4 . 6H 2 O

AN3 ~ 100% NiSO 4 . 6H 2 O

ANBlank Ni is present.



## 3.0 USE OF REPORT

This report does not provide a legal opinio n regarding compliance with applicable laws. The findings and conclusions of this report are valid only for thos e samples analyzed at the time this report was prepared.



## 4.0 REFERENCES

(1) Ravel, B.; Newville, M. J. Synchrotron Rad. 2005, 12, 537.

(2) Pattanaik, S.; Huggins, F.E.; Huffman, G.P.; Linak, W.P.; Miller, A.C. Environ. Sci.

Technol. 2007, 41, 1104.5105 XANES Spectroscopic Analysis of Nickel Collected on Quartz Filters Page 4 Figure 1. Nickel K-edge XANES spectra of the Ni standard compounds5105 XANES Spectroscopic Analysis of Nickel Collected on Quartz Filters Page 55105 XANES Spectroscopic Analysis of Nickel Collected on Quartz Filters Page 6 Figure 2. Nickel K-edge XANES spectrum for sample AN1. The orange bars indicate the fitting

range.5105 XANES Spectroscopic Analysis of Nickel Collected on Quartz Filters Page 7 Figure 3. Nickel K-edge XANES spectrum for sample AN2. The orange bars indicate the fitting

range.5105 XANES Spectroscopic Analysis of Nickel Collected on Quartz Filters Page 8 Figure 4. Nickel K-edge XANES spectrum for sample AN3. The orange bars indicate the fitting

range.5105 XANES Spectroscopic Analysis of Nickel Collected on Quartz Filters Page 9 Figure 5. Oxygen K-edge XAS spectrum for sample AN3, NiCO 3 , and NiSO 4 .6H 2 O. The vertical lines show peak positions of AN3 corresponding to NiSO 4 .6H 2 O.