Publications and Presentations

11. Electrochemical Separation of Alkaline-Earth Elements from Molten Salts Using Liquid Metal Electrodes

Thomas P. Nigl, Timothy Lichtenstein, Yuran Kong, Hojong Kim

ACS Sustain. Chem. Eng. 8(39), 2020, 14818-14824.

Abstract

Closing the nuclear fuel cycle requires recycling used nuclear fuel. Additional waste is generated during recycling due to fission products accumulating in processing salts (LiCl–KCl). Reducing the waste generated during recycling entails recovering alkaline-earth fission products (Ba2+/Sr2+) from molten chlorides with a minimal loss of bulk electrolyte constituents (Li+/K+). Electrochemical codeposition of Ba2+/Li+ and Sr2+/Li+ into liquid metal (Bi, Sb, Sn, and Pb) and alloy (Bi–Sb) electrodes was investigated in LiCl–KCl–(BaCl2, SrCl2) electrolytes at 500 and 650 °C. For the pure Bi (500 °C) and Sb (650 °C) electrodes, the greatest percentage of charge was used to deposit Ba and Sr. Effective recovery of Ba/Sr by liquid Bi and Sb electrodes is supported via experimentally determined activity values of Ba/Sr in Bi and Sb. Alloying Sb with Bi increased Ba recovery but decreased Sr recovery, compared to the recovery using a liquid Bi electrode. The results suggest that alkaline-earth fission products can be recovered from molten chlorides using liquid metal electrodes via electrochemical separation, thereby providing a method to reduce the generation of nuclear waste from nuclear fuel recycling.

10. Recovery of alkaline-earths into liquid Bi in ternary LiCl-KCl-SrCl2-BaCl2 electrolytes at 500 °C

Timothy Lichtenstein, Thomas P. Nigl, Hojong Kim

J. Electrochem. Soc. 167(10), 2020, 102501.

Abstract

Electrochemical reduction of Sr2+ and Ba2+ into liquid Bi was investigated in dilute concentrations of SrCl2/BaCl2 (0‒5 mol%) in LiCl-KCl electrolytes at 500 °C to ascertain the limit of liquid Bi electrodes for alkaline-earth recovery. Analysis of the electrodes after constant current electrolysis to the specific charge of 270 C g−1 showed Sr2+ ions consuming 29% of charge at 5 mol% before dropping to 8%‒10% of the total charge at 0.45‒0.72 mol% SrCl2. Ba2+ ions consumed 54% at 5 mol% BaCl2 before decreasing to 22%‒24% at 0.42‒0.89 mol% BaCl2; substantial co-deposition of Li was observed in all chemistries, consuming up to 53% of charge. Considering only 1% of the total charge was consumed for depositing Ba2+ and Sr2+ ions in ~0.1 mol% SrCl2/BaCl2 electrolyte, the lower recovery limit of Bi for alkaline-earth elements is suggested to be at ~0.4 mol% SrCl2/BaCl2 to achieve appreciable deposition of alkaline-earths (>1.5 mol% Ba/Sr in liquid Bi). The overpotentials of liquid Bi at 5 mol% of SrCl2/BaCl2 were evaluated by electrochemical impedance spectroscopy. The co-deposition of Sr and Li exhibited the largest increase in charge transfer resistances implying sluggish charge transfer kinetics whereas the co-deposition of Ba and Li exhibited a large increase in mass transport resistances due to the slow diffusion of Ba2+ ions in the electrolyte.

9. The Effects of Drilling the Marcellus Shale in Pennsylvania Addressed to: The General Assembly of Pennsylvania

Victoria DeLeo, Brooke Kuei & Thomas Nigl

Journal of Science Policy & Governance. 2019.

Abstract

The extraction of natural gas from the Marcellus Shale Formation in Pennsylvania has significantly improved the state economy, but it is not a sustainable path forward. Extraction from the Marcellus shale is expected to last at most 92 years, not accounting for diminishing returns as gas is continuously extracted. Hydraulic fracturing of the Marcellus shale has also contaminated private water sources and caused localized air pollution. Transparent regulations and government oversight, coupled with the implementation of a state tax, can promote economic development and preserve the health of Pennsylvania citizens and their environment. This memorandum summarizes the current regulations surrounding drilling in the Marcellus Shale Formation in Pennsylvania and policy recommendations to utilize extraction as an excellent transition into the future of the state.

8. Thermodynamic Properties of Ba-Pb Alloys Determined by Emf Measurements Using Binary CaF2-BaF2 Electrolyte

Jarrod Gesualdi, Thomas P. Nigl, Timothy Lichtenstein, Nathan D. Smith, Hojong Kim

J. Electrochem. Soc. 166(8), 2019, D268-D275.

Abstract

The thermodynamic properties of Ba-Pb alloys (activities, phase transitions, and partial molar quantities of Gibbs energy, entropy and enthalpy) were determined based on electromotive force (emf) measurements for thirteen mole fractions (xBa = 0.05–0.76) from 700–1060 K using an electrochemical cell: Ba(s) | CaF2-BaF2 | Ba(in Pb). The activity of Ba in liquid Pb was found to be as low as 2.0 × 10–10 at xBa = 0.05 and 973 K, reflecting a large excess partial molar Gibbs energy of –156 kJ mol–1 due to strong chemical interactions between Ba and Pb. Emf measurements were most reliable in the presence of a liquid phase, but were less reliable for high-melting compositions due to the formation of metastable phases during thermal cycling, confirmed by thermal and structural analyses using differential scanning calorimetry and X-ray diffraction. The experimentally-determined activity values of Ba-Pb alloys provide a new, reliable data set for further refinement in the assessment of thermodynamic properties for the Ba-Pb system.

7. Thermodynamic properties of Sr-Sb alloys via emf measurements using solid CaF2-SrF2 electrolyte

Nathan D. Smith, Nicole Orabona, Timothy Lichtenstein, Jarrod Gesualdi, Thomas P. Nigl, Hojong Kim

Electrochim. Acta 305, 2019, 547-554.

Abstract

The thermodynamic properties of Ba-Pb alloys (activities, phase transitions, and partial molar quantities of Gibbs energy, entropy and enthalpy) were determined based on electromotive force (emf) measurements for thirteen mole fractions (xBa = 0.05–0.76) from 700–1060 K using an electrochemical cell: Ba(s) | CaF2-BaF2 | Ba(in Pb). The activity of Ba in liquid Pb was found to be as low as 2.0 × 10–10 at xBa = 0.05 and 973 K, reflecting a large excess partial molar Gibbs energy of –156 kJ mol–1 due to strong chemical interactions between Ba and Pb. Emf measurements were most reliable in the presence of a liquid phase, but were less reliable for high-melting compositions due to the formation of metastable phases during thermal cycling, confirmed by thermal and structural analyses using differential scanning calorimetry and X-ray diffraction. The experimentally-determined activity values of Ba-Pb alloys provide a new, reliable data set for further refinement in the assessment of thermodynamic properties for the Ba-Pb system.

6. Generation and Use of a Pure Titanium Pillared MCM-36 Structure as a High Efficiency Carbon Dioxide Capture Platform and Amine Loaded Solid Adsorbent

Christopher Cogswell, Thomas P. Nigl, Alyssa Stavola, Andrew Wolek, Yuanci Wang, Jillian Zummo, Yang Lin, Liah Dukaye, Rebeccah Chinn, Sunho Choi Hojong Kim

Microporous Mesoporous Mater. 280, 2019, 151-156.

Abstract

In this work titanium oxide pillared MCM-36 adsorbents have been studied as amine loaded class-1 adsorbents for carbon dioxide capture. This work has shown that pillaring of the MCM support with titanium oxides can yield a material with carbon dioxide capacities higher than silica pillared MCM sorbents (1.62 mmol/g for Ti, 1.02 mmol/g for Si), with similar surface Qarea (∼450 m2/g for Ti versus ∼500 m2/g for Si) observed for the titanium pillared derivative. The titanium oxide pillared adsorbent was also loaded with polyethylenimine and tetraethylenepentamine amine containing molecules. It was observed that the higher initial capacity of the titanium oxide pillared MCM-36 allows for it to retain good CO2 capacities of up to ∼1.79 mmol/g at high amine loadings (∼50 wt% of tetraethylenepentamine). However, it was found that increasing the content of polyethylenimine loaded on the adsorbent led to decreased carbon dioxide capacities.

5. Thermodynamic Properties of Strontium-Lead Alloys Determined by Electromotive Force Measurements

Thomas P. Nigl, Timothy Lichtenstein, Nathan D. Smith, Jarrod Gesualdi, Yuran Kong, Hojong Kim

J. Electrochem. Soc. 165(14), 2018, H991-H998.

Abstract

The thermodynamic properties of Sr-Pb alloys were determined by electromotive force (emf) measurements. A Sr(s)|CaF2-SrF2|Sr(in Pb) electrochemical cell was used to measure emf values at 773–1073 K for Sr-Pb alloys at mole fractions xSr = 0.07–0.59. These emf measurements were used to determine thermodynamic properties of Sr-Pb alloys, including activity, partial molar entropy, and partial molar enthalpy. At 873 K, activity values of Sr in Pb were as low as aSr = 1.72 × 10–9 at mole fraction xSr = 0.07, implying strong atomic interactions between Sr and Pb. Phase transition temperatures of Sr-Pb alloys, observed during emf measurements, were corroborated by thermal analysis (0.07 ≤ xSr ≤ 0.34) by differential scanning calorimetry (DSC), and the phase constituents of Sr-Pb alloys (0.07 ≤ xSr ≤ 0.75) were characterized using X-ray diffraction (XRD). Experimentally-determined thermodynamic properties were compared to the assessed thermodynamic properties of the Sr-Pb system, confirming the phase transition temperatures and highlighting discrepancies in solution properties (activity and excess Gibbs energy).

4. Electrochemical deposition of alkaline-earth elements (Sr and Ba) from LiCl-KCl-SrCl2-BaClsolution using a liquid bismuth electrode

Timothy Lichtenstein, Thomas P. Nigl, Nathan D. Smith, Hojong Kim

Electrochim. Acta. 281, 2018, 810-815.

Abstract

Electrochemical deposition of Sr and Ba into liquid Bi metal was investigated in LiCl-KCl-SrCl2-BaCl2 electrolytes at 500 °C as a means to separate stable alkaline-earth ions from the molten salts (eutectic LiCl-KCl) utilized for recycling used nuclear fuel, by leveraging the strong chemical interactions between alkaline-earth metals and liquid Bi. The liquid Bi electrodes were subjected to cathodic discharge up to 270 C g–1 at a constant current density of 50 mA cm−2 in eutectic LiCl-KCl with the addition of 5 mol% total of SrCl2 and/or BaCl2. The use of Bi resulted in complex electrode reactions, leading to co-deposition of Sr (2.0–6.5 mol%), Ba (4.1–12.8 mol%), and Li (5.9–16.2 mol%), and coulombic efficiencies of 63–67% were achieved. The observed co-deposition was also supported via thermodynamic analyses of electrode potentials by incorporating the experimentally determined activity values of each alkali/alkaline-earth metal in Bi. The results of this work suggest that alkaline-earth fission products accumulated in molten salts (Sr2+ and Ba2+) can be recovered into liquid Bi by electrochemical separation, which could be employed as a critical step for recycling the process salt (LiCl-KCl) in order to minimize the generation of additional nuclear wastes.

3. Interphotoreceptor Matrix Based Biomaterial: Impact on Human Retinal Progenitor Cell Attachment and Differentiation

Joydip Kundu, Andrew Michaelson, Petr Baranov, Marco Chiumiento, Tom Nigl, Michael J. Young, Rebecca L. Carrier

J. Biomed. Mater. Res. Part B: Appl. Biomater. 106B, 2018, 891-899.

Abstract

While cell transplantation therapies show great promise as treatments for retinal degeneration, the challenge of low cell survival upon transplantation motivates exploration of materials that may serve as cell delivery vehicles and promote survival and differentiation. In this study, we explored the native matrix that surrounds the outer segments of photoreceptors and promotes their homeostasis, interphotoreceptor matrix (IPM), as a substrate for human retinal progenitor cells (hRPCs). Bovine IPM was characterized to determine its structure and biochemical composition, and processed to develop substrates for cells. Cell viability, morphology, proliferation and expression of photoreceptors marker genes were studied on IPM‐based substrates in vitro. We explored different preparations of IPM as a scaffold. Lectin staining revealed that a distinct honeycomb structure of native IPM is lost during centrifugation to prepare a more concentrated suspension of matrix. Biochemical analysis of bovine IPM indicated presence of glycosaminoglycans and proteins. IPM mediated hRPC attachment and spreading with no signs of cytotoxicity. Cells proliferated more on native IPM substrates compared to IPM that was centrifuged to create a concentrated suspension. Cells cultured on IPM substrates expressed markers of photoreceptors: rhodopsin, NRL and ROM1. Together this data supports further exploration of IPM as a tool for retinal tissue engineering.

2. Determination of Thermodynamic Properties of Alkaline Earth-Liquid Metal Alloys Using the Electromotive Force Technique.

Thomas P. Nigl, Nathan D. Smith, Timothy Lichtenstein, Jarrod Gesualdi, Kuldeep Kumar, Hojong Kim

J. Vis. Exp. 129, e56718, doi:10.3791/56718 (2017).

1. Thermodynamic Properties of Barium-Antimony Alloys Determined by Emf Measurements

Timothy Lichtenstein, Jarrod Gesualdi, Thomas P. Nigl, Chen-Ta Yu, Hojong Kim

Electrochim. Acta. 251, 2017, 203-211.

Abstract

The thermodynamic properties of Ba-Sb alloys, including the activity, partial molar entropy, and partial molar enthalpy, were determined using the electromotive force (emf) technique for thirteen compositions spanning the composition range of xBa = 0.03–0.77. Emf measurements were performed at ambient pressure under an inert argon atmosphere using a Ba-Bi(xBa = 0.05)|CaF2-BaF2|Ba(in Sb) electrochemical cell at 723–1073 K. At 923 K, activity values of Ba in Sb were as low as 2.0 × 10−15 at mole fraction xBa = 0.05 and approached unity for mole fractions xBa ≥ 0.77. Phase characterization using X-ray diffraction (XRD) was performed on compositions of xBa = 0.03–0.77 and thermal characterization was performed on compositions up to xBa = 0.40 using differential scanning calorimetry (DSC). Integrating the results from emf, XRD, and DSC measurements, an experimentally determined Ba-Sb phase diagram was constructed.

Conference Presentations

Nigl, T. P.; Lichtenstein, T.; Kong, Y.; Kim, H. Molten Salt Electrolysis of Alkaline-earth Elements Using Liquid Metal and Alloy Electrodes. TMS 2020 Conference, San Diego, CA. Feb 24 2020. Poster Presentation.

Nigl, T. P.; Kong, Y.; Lichtenstein, T.; Kim, H. Electrochemical Deposition of Alkaline-Earth Metals (Ba and Sr) from Molten Salts Using Liquid Metal Electrodes. Waste Management Symposia 2019, Phoenix, AZ. Mar 3 2019. Poster Presentation. 

Nigl, T. P. Thermodynamic Properties of Strontium-Lead Alloys Determined by Electromotive Force Measurements. AIChE 2018 Conference, Pittsburgh, PA. Oct 25 2018. Oral Presentation.

Nigl, T. P.; Lichtenstein, T.; Smith, N.D.; Gesualdi, J.; Kong, Y.; Kim, H. Thermodynamic Properties of Strontium-Lead Alloys Determined by Electromotive Force Measurements. 3M Fellowship Poster Session, St. Paul, MN. Oct 17 2018. Poster Presentation.

Nigl, T. P. Thermodynamic Properties of Strontium-Lead Alloys Determined by Electromotive Force Measurements. 2017 Electrochemical Society Conference, National Harbor, MD. Oct 2 2017. Oral Presentation.

Nigl, T. P. Renuclear: Use of a Molten Salt Breeder Reactor for Nuclear Reactor Decommissioning and Spent Fuel Disposal. AIChE 2016 Conference, San Francisco, CA. Nov 15 2016. Oral Presentation.

Nigl, T. P.; Stavola, A.; Ramberger, J.; Accetta, D.; Gilmore, E.; Cogswell, C. F.; Choi, S. Generation and Use of Titanium Pillared MCM-36 Structure for Carbon Dioxide Capture. AIChE 2015 Conference, Salt Lake City, UT. Nov 09 2015. Poster Presentation.

Marks, E.; Tan, L.; Nigl, T. P.Merlock, A.; Gastfriend, B.; Ramos, A.; Dunagan, M.; Yue, J. How to Host a Successful Regional Conference. AIChE 2015 Conference, Salt Lake City, UT. Nov 07 2015. Oral Presentation.