Toward a Cleaner Future: NOx Binding and Conversion in Individual Cement Phases

SAMUEL LUCAS

IEN SUIN REU 2018

PI: DR. KIMBERLEY KURTIS

MENTOR: QINGXU (BILL) JIN

Southeastern Undergraduate Internship in Nanotechnology, NSF EEC-1757579

1 What’s the big deal about NOx?

https://blog.nus.edu.sg/industrialpollution/2016/08/1 2/about/

http://www.zoombd24.com/oxides-nitrogen-nox/

2 Why cement?

• Nearly 4 million miles of UV source roads in the United States alone • An estimated 3 trillion vehicle NOx miles traveled per year Photocatalytic • Cement can uptake NOx! Reaction • Some innate capacity • Through photocatalytic Road species bind with reactions cementitious material

3 What exactly is cement? •Different types of cements: • Portland cement (OPC, calcium silicate based) • Calcium aluminate cement • Magnesium-based (hydroxyapatite) Cement paste = + + • Gypsum • Calcium sulfoaluminate • Aluminosilicate Mortar = + + +

Concrete = + + + +

4 What are we trying to determine?

- + 1. TiO2 TiO2 + e + h + ℎ𝑣𝑣 + • 2. h + H2O → H + OH - •- 3. e + O2 → O2 •- - 4. NO + O2 → NO3 • - + 5. NO + OH → NO2 + H • • 6. NO + OH → HNO2 + OH → NO2 + H2O • - + 7. NO2 + OH → NO3 + H

1. Why is unmodified cement capable of binding NOx? Why does that matter? 2. How much NOx is converted to nitrate and how much is converted to • Increased NOx binding efficiency  nitrite in individual cement phases? increased real-world practicability 3. How is NOx bound in the cement phases (e.g., physically vs. chemically)

5 How do we test this?

Setup complies with ISO 22197 and JIS R 1701

Pump in (dry air and NOx) 2 g of powder sample was placed in reaction chamber

~1000 ppb NOx analyzer Pump out (system maintained so output reads approx. 1000 ppb NOx

6 With added UV, NOx concentration drops • For unmodified samples, OPC OPC+5%TiO2 NOx remains constant for 1200 the duration • In all photocatalyst + UV 1000 cases, a similar drop occurs 800

600 UV light on UV light off 400 concentration (ppb) concentration x 200 NO

Mix OPC w/c TiO (anatase) 2 0 OPC 1.0 0.4 0 -60 0 60 120 180 240 300 360 Time (mins) OPC+5%TiO2 0.95 0.4 0.05

7 What is in the cement? Capillary 100 porosity C-S-H

75 Calcium hydroxide AFt/AFm 50 Calcium sulfate

C4AF Relative Volume (%) Relative Volume 25 C3A

C2S 0 0 25 50 75 100 C3S Degree of Hydration

8 What is X-Ray Diffraction?

X-Ray Diffraction (XRD) is a characterization tool for determining qualitative information about crystalline substances

9 XRD of AFm-sulfate indicates the presence of nitrogen ion species

10 However, XRD of AFm-carbonate shows no sign of nitrogen ion species

11 And neither does XRD of C-S-H

12 What is UV-visible spectrophotometry?

Results in terms of absorbance (Au) measured at 540 nm

13 What is ion chromatography?

Results in terms of peak area, measured under the portion of the curve representing nitrate

200000 150000 y = 61381x + 10748 R² = 0.9836 100000 Series1 50000 Linear (Series1) 0 0 0.5 1 1.5 2 2.5 3 nitrite (mg/L)

14 These methods quantify NOx conversion!

Nitrite produced nearly Roughly 18% decrease in nitrite Roughly 17% decrease in nitrite 2400 times greater in produced in modified C-S-H, modified than plain AFm- produced in modified AFm- carbonate, still massive increase in nearly 1000 times greater amount sulfate, massive increase in of nitrate produced nitrate production as well nitrate production

15 Conclusions •The presence of relatively high amounts of C-S-H in cements is likely responsible for much of cement’s innate NOx binding ability •The presence of TiO promotes a greatly increased nitrate formation •AFm-sulfate has a minimal2 physical NOx binding capacity, but may still have the ability to chemically bind NOx via substitution •AFm-carbonate has some capacity to bind NOx despite carbonation, which ordinarily hinders NOx binding •UV-visible spectrophotometry and ion chromatography are the only tools we have found to date that are capable of consistent and accurate nitrate and nitrite detection and quantification,

16 Future Work •Complete analysis of -exposed materials •Perform and analyze exposures of pure TiO crystals to determine whether TiO plays a role not just in the reaction but also in the binding of NOx 2 2 •Perform and analyze exposures of both individual phases and OPC with different replacement percentages of TiO to determine why TiO so dramatically increases nitrate formation

•Determine whether2 chemical bonding occurs2 in the AFm phase (i.e. whether the sulfate is substituted for a nitrite or nitrate)

17 Questions?

18 Citations

1. United States, Environmental Protection Agency. (2015). 2011 National Emissions Inventory, Version 2: Technical Support Document. National Emissions Inventory, U.S. Environmental Protection Agency. 2. Yung, M., Holmgreen, E., & Ozkan, U. (2007). Cobalt-based catalysts supported on titania and zirconia for the oxidation of nitric to nitrogen dioxide. Journal of Catalysis,247(2), 356-367. doi:10.1016/j.jcat.2007.02.020. 3. Harrison, B., Diwell, A. F., & Wyatt, M. (1985). Controlling Nitrogen Oxide Emissions from Industrial Sources. Platinum Metals Review,29(2), 50- 56. Retrieved June 20, 2018. 4. United States, Central Intelligence Agency. (2012). Retrieved June 20, 2018 from https://www.cia.gov/library/publications/the-world- factbook/fields/2085.html 5. United States, Environmental Protection Agency. (2015). 2011 National Emissions Inventory, Version 2: Technical Support Document. National Emissions Inventory, U.S. Environmental Protection Agency. 6. J. S. Dalton, P. A. Janes, N. G. Jones, J. A. Nicholson, K. R. Hallam, G. C. Allen, Photocatalytic oxidation of NOx gases using TiO2: a surface spectroscopic approach. Environmental Pollution 120 (2002) 415-422. 7. Q. L. Yu, H. J. H. Brouwers, Indoor air purification using heterogeneous photocatalytic oxidation. Part I: experimental study, Applied Catalysis B: Environmental 92 (2009) 454-461. 8. M. M. Ballari, M. Hunger, G. Hüsken, H. J. H. Brouwers, NOx photocatalytic degradation employing concrete pavement containing . Applied Catalysis B: Environmental 95 (2010) 245-254. 9. Jin, Q. (2018). NOx Sequestration by Photocatalytic Concrete. 9th Advances in Cement Based Materials. Pennsylvania State University, 2018.

19 Additional Information

20 OPC Composition

21 Photocatalyst Characteristics

22