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Surface Complexes Of Lead And Organic Acids At The Hematite / Water Interface

Noerpel, Matthew Robet
http://rave.ohiolink.edu/etdc/view?acc_num=osu1439904226

Abstract Details

2015, Doctor of Philosophy, Ohio State University, Civil Engineering.
Lead is a common and very toxic contaminant in the environment. Consumption of lead by children can cause irreversible harm to the brain and central nervous system. It is crucial to understand the behavior of lead in the environment in order to protect the population from coming to harm. Colloidal iron oxide particles and organic acids are ubiquitous in the natural environment. In combination and independently, they play an important role in the fate of lead and other heavy metal contaminants. Lead can adsorb onto the surface of the particles and remain mobile as the small particles do not settle out of suspension. Organic acids can adsorb on the surface of the mineral particles changing their surface charge, stability and reactivity as well as interacting with lead in solution. It is therefore important to understand the interactions of organic acids and colloidal particles with and without lead in order to fully understand the fate of lead in the environment. Throughout this project, the iron oxide hematite was used as the adsorbent mineral phase. In the first chapter, we investigated the adsorption mechanisms that bond the common organic acid, citric acid, to the hematite surface using batch adsorption, Fourier transform infrared spectroscopy (FTIR), and molecular modeling and surface complexation modeling (SCM). All of the methods used indicated that the dominant adsorption mode is as an outer-sphere complex that changes protonation state with pH, going from singly protonated at low pH to deprotonated at higher pH conditions. There was also evidence of an inner-sphere bidentate complex at low pH. In Chapter 3, the adsorption of lead on bare hematite particles and single crystal surfaces was examined using two synchrotron based X-ray techniques, extended X-ray adsorption fine structure (EXAFS), on particles, and X-ray reflectivity (XR) on single crystal surface with a known surface exposed. The results of the two techniques confirm that lead adsorbs as an inner-sphere bidentate complex in an edge-sharing and corner-sharing arrangement. In addition, the XR method found an additional outer-sphere complex on formed on the single crystal surfaces that is not visible using EXAFS. The reactivity of the three surfaces tested varied greatly. The surface that is considered the most common face, the (001), was the least reactive face and the adsorption did not change with pH. In Chapter 4, the same X-ray techniques were used to determine the influence that organic acids have on the surface. Four acids were tested, citrate, phthalate, humic and fulvic acids. The results showed that at pH 4, the acids enhanced the adsorption of lead onto the particle surfaces, however at pH 6, citrate hindered the adsorption of lead as it likely chelated the lead and held it in solution. The single crystal studies showed that in the presence of organic acids, the lead still adsorbs strongly as an inner-sphere complex. Overall, the specific surface played a larger role in determining the manner in which the lead adsorbed than did the acid added.
John Lenhart, PhD. (Advisor)
Heather Allen, PhD. (Committee Member)
Yu-Ping Chin, PhD. (Committee Member)
Linda Weavers, PhD. (Committee Member)
254 p.
Environmental Engineering
Hematite, Lead, Citrate, Phthalate, Surface Complexation Modeling, EXAFS, X-ray reflectivity, Infrared Spectroscopy

Recommended Citations

Citations

  • Noerpel, M. R. (2015). Surface Complexes Of Lead And Organic Acids At The Hematite / Water Interface [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1439904226

    APA Style (7th edition)

  • Noerpel, Matthew. Surface Complexes Of Lead And Organic Acids At The Hematite / Water Interface. 2015. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1439904226.

    MLA Style (8th edition)

  • Noerpel, Matthew. "Surface Complexes Of Lead And Organic Acids At The Hematite / Water Interface." Doctoral dissertation, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1439904226

    Chicago Manual of Style (17th edition)

osu1439904226
460
© 2015, some rights reserved.Creative Commons License Surface Complexes Of Lead And Organic Acids At The Hematite / Water Interface by Matthew Robet Noerpel is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by The Ohio State University and OhioLINK.