Supplementary Information

Combinations of NIR, Raman spectroscopy and physicochemical

measurements for improved monitoring of solvent extraction processes using

hierarchical multivariate analysis models

K. Neea, S. Bryanb, T. Levitskaiab, J. Wei-Ju Kuoa, M. Nilssona,c*

a: Department of Chemical Engineering and Materials Science, University of California Irvine, 916 Engineering

Tower, Irvine, CA 92697-2575, USA.b: Pacific Northwest National Laboratory, Richland, WA, 99354, USAc: Department of Chemistry, University of California Irvine, 1102 Natural Sciences 2, Irvine, CA 92697-2025, USA.

Experimental Details

Table S1 below show the composition of each of the 95 solutions used in this study.

Table S1

Sample ID

[H+] (as HNO3) (M)

[Na+] (as NaNO3) (M)

[Nd3+] (as Nd(NO3)3) (M)

Actual Total [NO3

-] (M)

Actual Total Ionic Strength

(mol/kg)1 0.000 0.000 0.002 0.007 0.0142 0.000 0.000 0.010 0.030 0.0613 0.000 0.000 0.020 0.061 0.1234 0.000 0.000 0.041 0.123 0.2465 0.000 0.622 0.002 0.628 0.6166 0.000 0.500 0.010 0.530 0.5477 0.000 0.621 0.019 0.677 0.7138 0.000 0.571 0.038 0.684 0.7769 0.000 2.354 0.002 2.358 2.113

10 0.000 2.245 0.008 2.268 2.06011 0.000 2.423 0.016 2.471 2.24512 0.000 2.283 0.030 2.374 2.21113 0.000 3.212 0.002 3.218 2.77414 0.000 3.394 0.008 3.418 2.93815 0.000 2.883 0.016 2.931 2.60116 0.000 3.164 0.030 3.254 2.88417 0.489 0.000 0.002 0.495 0.49418 0.506 0.000 0.010 0.537 0.56119 0.503 0.000 0.018 0.556 0.60120 0.500 0.000 0.034 0.602 0.69521 0.499 0.661 0.002 1.166 1.12022 0.497 0.656 0.008 1.178 1.14923 0.497 0.614 0.017 1.161 1.16024 0.497 0.588 0.033 1.184 1.23125 0.501 1.964 0.002 2.471 2.22526 0.496 2.147 0.008 2.668 2.39827 0.500 2.120 0.034 2.722 2.51828 0.500 2.054 0.032 2.651 2.45829 0.494 2.979 0.002 3.478 2.98830 0.490 3.197 0.008 3.710 3.17331 0.486 2.927 0.015 3.458 3.01232 0.498 3.242 0.030 3.829 3.32433 0.992 0.000 0.002 0.999 0.97934 0.995 0.000 0.009 1.021 1.01935 1.010 0.000 0.018 1.064 1.08736 1.020 0.000 0.036 1.127 1.19937 1.000 0.562 0.002 1.568 1.48938 1.010 0.546 0.009 1.582 1.521

Sample ID

[H+] (as HNO3) (M)

[Na+] (as NaNO3) (M)

[Nd3+] (as Nd(NO3)3) (M)

Actual Total [NO3

-] (M)

Actual Total Ionic Strength

(mol/kg)39 1.010 0.599 0.017 1.659 1.61440 1.010 0.610 0.034 1.723 1.72241 0.988 1.992 0.001 2.984 2.64342 1.010 2.128 0.008 3.162 2.79943 0.945 2.334 0.015 3.324 2.93944 1.030 2.110 0.031 3.234 2.92445 1.020 2.950 0.002 3.976 3.37246 1.180 3.246 0.008 4.451 3.72847 1.000 3.055 0.016 4.104 3.50348 1.040 3.230 0.031 4.364 3.72949 4.070 0.000 0.002 4.075 3.62950 4.050 0.000 0.008 4.075 3.64951 4.040 0.000 0.017 4.090 3.68452 3.980 0.000 0.033 4.079 3.72453 4.080 0.572 0.002 4.657 4.03954 4.040 0.540 0.008 4.604 4.02155 3.980 0.467 0.016 4.494 3.96456 3.980 0.570 0.031 4.644 4.11757 4.030 1.882 0.002 5.918 4.85558 4.080 1.997 0.008 6.102 4.99159 4.020 1.972 0.016 6.041 4.97560 4.000 1.996 0.033 6.094 5.05661 3.990 2.567 0.002 6.562 5.23762 4.020 3.004 0.008 7.047 5.53663 4.030 2.435 0.015 6.511 5.25364 4.060 2.902 0.030 7.053 5.61165 4.940 0.000 0.002 4.946 4.29966 5.040 0.000 0.008 5.064 4.40767 5.020 0.000 0.016 5.067 4.43268 5.000 0.000 0.031 5.094 4.49769 5.960 0.478 0.002 6.444 5.33870 6.050 0.453 0.008 6.528 5.41771 6.060 0.473 0.017 6.584 5.47872 6.040 0.587 0.033 6.725 5.61173 6.060 2.208 0.002 8.274 6.36874 6.050 2.058 0.008 8.133 6.31375 6.100 2.018 0.016 8.167 6.36076 6.010 1.996 0.031 8.100 6.36277 0.000 0.636 0.000 0.636 0.61878 0.000 2.394 0.000 2.394 2.13779 0.000 3.353 0.000 3.353 2.86880 0.483 0.000 0.000 0.483 0.47781 0.511 0.615 0.000 1.126 1.078

Sample ID

[H+] (as HNO3) (M)

[Na+] (as NaNO3) (M)

[Nd3+] (as Nd(NO3)3) (M)

Actual Total [NO3

-] (M)

Actual Total Ionic Strength

(mol/kg)82 0.500 2.150 0.000 2.650 2.35983 0.498 2.667 0.000 3.164 2.75284 0.999 0.000 0.000 0.999 0.97285 0.985 0.572 0.000 1.557 1.47386 0.997 1.966 0.000 2.963 2.62487 1.069 3.179 0.000 4.248 3.55888 4.029 0.000 0.000 4.029 3.58889 4.087 0.560 0.000 4.647 4.02890 4.010 1.895 0.000 5.905 4.84191 4.280 2.966 0.000 7.246 5.64692 6.141 0.000 0.000 6.141 5.16493 6.197 0.673 0.000 6.870 5.60694 6.202 2.086 0.000 8.289 6.38495 6.264 2.014 0.000 8.278 6.385

The segmentation of the spectral data is shown in Figure S1.

Figure S1. Segmentation of spectra for PCA analysis used in sub-model building (A) NIR spectra; (B) Raman spectra.

Raman spectra for various solutions at varying temperatures are shown in figures S2-S5 below.

Figure S2. Symmetric O-H stretching bands on Raman spectra at 25 °C and 65 °C. (A) 4 M HNO3. (B) 2 M NaNO3. (C) 0.0188 M Nd(NO3)3.

Figure S3. Symmetric O-H stretching bands on Raman spectra at 25 °C. (A) Varied HNO3. (B) Varied NaNO3. (C) Varied Nd(NO3)3.

Figure S4. Symmetric Raman stretching for NO3- at 25 °C. (A) Varied HNO3. (B) Varied NaNO3. (C) Varied

Nd(NO3)3.

Table S2 Partial least square parameters for the model obtained from conductivity and temperature measurements.

Component LV RMSEC RMSECV RMSEP %RMSEP R2, %

H+ 2 1.630 M 1.639 M 1.500 M 69.8 44.61

NO3- 2 2.513 M 2.510 M 2.101 M 59.2 14.59

Nd3+ 2 0.0115 M 0.0115 M 0.0112 M 112 10.30

Na+ 2 0.951 M 0.953 M 0.879 M 64.2 34.67

Ionic Strength 2 2.156 mol/Kg 2.159 mol/Kg 2.105 mol/Kg 69.5 14.24

Figure S5 – S9 below show the predicted vs experimental comparison for all combinations of data tested and Tables S3 – S7 are the corresponding model fits for each experimental condition.

Figure S5. Predicted versus measured NO3- concentrations by (A) Raman. (B) Raman + Conductivity +

Temperature. (C) Raman (843.73 cm-1 to 1286.50 cm-1). (D) Raman (843.73 cm-1 to 1286.50 cm-1) + Conductivity + Temperature. (E) NIR (884 nm to 1262.5nm). (F) NIR (884 nm to 1262.5nm) + Conductivity + Temperature. (G) NIR (884 nm to 1262.5 nm) + Raman + conductivity + temperature. (H) NIR (884 nm to 1262.5 nm) + Raman. The line indicates 1:1 Line where predicted = measured (Y=X).

Table S3. Results from the PLS model for total nitrate. For Raman ‘All’ mean 345.07 – 4285.46 cm -1. Concentration of nitrate ranged from 0 M to 8.29 M and average concentration was 3.51 M.

NIR(nm)

Raman(cm-1)

Conductivity(ms/cm)

Temperature(oC) LV RMSEC

(M)RMSECV

(M)RMSEP

(M)RMSEP

% R2

All 4 0.231 0.237 0.186 5.24 0.99All All All 4 0.252 0.259 0.207 5.83 0.98

843.73 – 1286.50

cm-14 0.441 0.443 0.276 7.77 0.97

843.73– 1286.50

cm-1All All 4 0.338 0.354 0.2633 7.42 0.98

884 – 1262.5

nm4 0.589 0.594 0.707 19.9 0.93

884 – 1262.5

nmAll All 4 0.441 0.445 0.547 15.4 0.96

884 – 1262.5

nmAll 5 0.239 0.246 0.214 6.03 0.99

884 – 1262.5

nmAll All All 4 0.216 0.224 0.187 5.27 0.99

Figure S6. Predicted versus measured H+ concentrations by (A) Raman. (B) Raman + Conductivity + Temperature. (C) Raman (1203.86 cm-1 to 1286.50 cm-1). (D) Raman (843.73 cm-1 to 1286.50 cm-1) + Conductivity + Temperature. (E) NIR (884 nm to 1262.5nm). (F) NIR (884 nm to 1262.5nm) + Conductivity + Temperature. (G) NIR (884 nm to 1262.5 nm) + Raman + conductivity + temperature. (H) NIR (884 nm to 1262.5 nm) + Raman. The line indicates 1:1 Line where predicted = measured (Y=X).

Table S4. Nitric acid (H+) model results. For Raman ‘All’ mean 345.07 – 4285.46 cm-1. Concentration of nitric acid ranged from 0 M to 6.26 M and average concentration was 2.15 M.

NIR(nm)

Raman(cm-1)

Conductivity(ms/cm)

Temperature(oC) LV RMSEC

(M)RMSECV

(M)RMSEP

(M)RMSEP

% R2

All 4 0.167 0.170 0.121 5.63 0.99All All All 4 0.185 0.189 0.146 6.79 0.99

1203.86 – 4285.46 cm-1 4 0.224 0.228 0.179 8.33 0.99

1203.86 – 4285.46 cm-1 All All 4 0.219 0.224 0.164 7.63 0.99

884 – 1262.5 nm 4 0.260 0.262 0.251 11.7 0.99

884 – 1262.5 nm All All 4 0.254 0.256 0.232 10.8 0.99

884 – 1262.5 nm All 3 0.140 0.143 0.118 5.49 0.99

884 – 1262.5 nm All All All 3 0.159 0.165 0.138 6.42 0.99

Figure S7. Predicted versus measured Nd3+ concentrations by (A) Raman. (B) Raman + Conductivity + Temperature. (C) Raman (1203.86 cm-1 to 4285.46 cm-1). (D) Raman (1203.86 cm-1 to 4285.46 cm-1) + Conductivity + Temperature. (E) NIR. (F) NIR + Conductivity + Temperature. (G) NIR (850 nm to 884 nm). (H) NIR (850 nm to 884 nm) conductivity + temperature. (I) NIR + Raman + conductivity + temperature. (J) NIR + Raman. The line indicates 1:1 Line where predicted = measured (Y=X).

Table S5. Neodymium (III) model results. For Raman and NIR ‘All’ mean 345.07 – 4285.46 cm -1 and 850 – 1262.5 nm, respectively. Concentration of Nd3+ ranged from 0 M to 0.041 M and average concentration was 0.013 M.

NIR(nm)

Raman(cm-1)

Conductivity(ms/cm)

Temperature(oC) LV RMSEC

(M)RMSECV

(M)RMSEP

(M)RMSEP

% R2

All 4 0.0038 0.0039 0.0038 38 0.90All All All 4 0.0038 0.0040 0.0038 38 0.90

1203.86 – 4285.46

cm-14 0.0038 0.0040 0.0036 36 0.90

1203.86 – 4285.46

cm-1All All 4 0.0039 0.0040 0.0040 40 0.90

All 4 0.0020 0.0020 0.0019 19 0.97All All All 4 0.0020 0.0020 0.0018 18 0.97

850 – 884 nm 1 0.0025 0.0025 0.0020 20 0.96

850 – 884 nm All All 2 0.0020 0.0020 0.0018 18 0.97

All All 4 0.0020 0.0020 0.0020 20 0.97All All All All 5 0.0020 0.0021 0.0020 20 0.97

Figure S8. Predicted versus measured NaNO3 (Na+) concentrations by (A) Raman. (B) Raman + Conductivity + Temperature. (C) NIR (884 nm to 1262.5 nm). (D) NIR (884 nm to 1262.5 nm) + Conductivity + Temperature. (E) NIR (884 nm to 1262.5 nm) + Raman + Conductivity + Temperature. (F) NIR (884 nm to 1262.5 nm) + Raman. The line indicates 1:1 Line where predicted = measured (Y=X).

Table S6. Sodium model results. For Raman ‘All’ mean 345.07 – 4285.46 cm -1. Concentration of sodium ranged from 0 M to 3.39 M and average concentration was 1.31 M.

NIR(nm)

Raman(cm-1)

Conductivity(ms/cm)

Temperature(oC) LV RMSEC

(M)RMSECV

(M)RMSEP

(M)RMSEP

% R2

All 4 0.211 0.216 0.182 13.3 0.97All All All 4 0.194 0.202 0.166 12.1 0.98

884 – 1262.5 nm 4 0.705 0.711 0.881 64.3 0.61

884 – 1262.5 nm All All 4 0.506 0.512 0.525 38.3 0.82

884 – 1262.5 nm All 6 0.182 0.189 0.164 12.0 0.98

884 – 1262.5 nm All All All 6 0.176 0.183 0.152 11.1 0.98

Figure S9. Predicted versus measured ionic strength (I.S.) by (A) Raman. (B) Raman + Conductivity + Temperature. (C) NIR. (D) NIR + Conductivity + Temperature. (E) Raman + NIR + conductivity + temperature measurements. (F) Raman + NIR. The line indicates 1:1 Line where predicted = measured (Y=X).

Table S7. Ionic strength (I.S.) model results. For Raman and NIR ‘All’ mean 345.07 – 4285.46 cm-1 and 850 – 1350 nm, respectively. The ionic strength ranged from 0 to 6.55 mol/kg and average ionic strength was 3.06 mol/kg.

NIR(nm)

Raman(cm-1)

Conductivity(ms/cm)

Temperature(oC) LV RMSEC

(mol/kg)RMSECV(mol/kg)

RMSEP(mol/kg)

RMSEP% R2

All 4 0.219 0.225 0.189 6.24 0.99All All All 4 0.238 0.243 0.212 7.00 0.99

All 4 0.577 0.583 0.690 22.8 0.93All All All 4 0.522 0.528 0.553 18.3 0.95All All 4 0.202 0.209 0.193 6.37 0.99All All All All 6 0.196 0.204 0.191 6.30 0.99

Figure S10 – S15 below show the residual vs measured comparison for all combinations of data tested.

Fig. S10. Residual versus measured values by the partial least square model using conductivity and temperature measurement for: (A) H+. (B) NO3

-. (C) Nd3+. (D) Na+. (E) Ionic strength (mol kg-1).

Figure S11. Residual versus measured NO3- concentrations by (A) Raman. (B) Raman + Conductivity +

Temperature. (C) Raman (843.73 cm-1 to 1286.50 cm-1). (D) Raman (843.73 cm-1 to 1286.50 cm-1) + Conductivity + Temperature. (E) NIR (884 nm to 1262.5nm). (F) NIR (884 nm to 1262.5nm) + Conductivity + Temperature. (G) NIR (884 nm to 1262.5 nm) + Raman + conductivity + temperature. (H) NIR (884 nm to 1262.5 nm) + Raman.

Figure S12. Residual versus measured H+ concentrations by (A) Raman. (B) Raman + Conductivity + Temperature. (C) Raman (1203.86 cm-1 to 1286.50 cm-1). (D) Raman (843.73 cm-1 to 1286.50 cm-1) + Conductivity + Temperature. (E) NIR (884 nm to 1262.5nm). (F) NIR (884 nm to 1262.5nm) + Conductivity + Temperature. (G) NIR (884 nm to 1262.5 nm) + Raman + conductivity + temperature. (H) NIR (884 nm to 1262.5 nm) + Raman.

Figure S13. Residual versus measured Nd3+ concentrations by (A) Raman. (B) Raman + Conductivity + Temperature. (C) Raman (1203.86 cm-1 to 4285.46 cm-1). (D) Raman (1203.86 cm-1 to 4285.46 cm-1) + Conductivity + Temperature. (E) NIR. (F) NIR + Conductivity + Temperature. (G) NIR (850 nm to 884 nm). (H) NIR (850 nm to 884 nm) conductivity + temperature. (I) NIR + Raman + conductivity + temperature. (J) NIR + Raman.

Figure S14. Residual versus measured NaNO3 (Na+) concentrations by (A) Raman. (B) Raman + Conductivity + Temperature. (C) NIR (884 nm to 1262.5 nm). (D) NIR (884 nm to 1262.5 nm) + Conductivity + Temperature. (E) NIR (884 nm to 1262.5 nm) + Raman + Conductivity + Temperature. (F) NIR (884 nm to 1262.5 nm) + Raman.

Figure S15. Residual versus measured ionic strength (I.S.) by (A) Raman. (B) Raman + Conductivity + Temperature. (C) NIR. (D) NIR + Conductivity + Temperature. (E) Raman + NIR + conductivity + temperature measurements. (F) Raman + NIR.