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Marinas, Benito J Marinas, Benito J Bellon, Pascal Espinosa-Marzal, Rosa Cusick, Roland Mosiman, Daniel S 2022-01-12T21:45:38Z 2022-01-12T21:45:38Z 2021-07-12 2021-08 Fluoride (F-) is one of the most significant inorganic contaminants endemic to groundwaters worldwide. An estimated 200 million people, mostly in rural low-income regions, have or risk incurring fluorosis because they consume water with F- levels above the World Health Organization’s (WHO) recommended level of 1.5 mg/L. Calcium hydroxyapatite (HAP, Ca5(PO4)3X, where X=OH) nanoparticles (NPs) formed into pellets and used in fixed-bed column reactors are among a handful of technologies recommended by the WHO for low income contexts. In the environmental engineering discipline, HAP has historically been considered a F- adsorbent, understood as surface-limited uptake by replacement of OH- at surface-terminated X lattice sites. However, this work demonstrates that HAP NPs not only adsorb but also internalize F- into the bulk of its structure under environmentally relevant conditions (i.e. pH=5-9 and [F-]=1.5-30 mg/L) by the migration of F- to subsurface X and defect lattice sites, yielding fluoro-hydroxyapatite solid solutions (FHAP, Ca5(PO4)3X, where X=OH/F). The practical implication is that there is a potential four to ten-fold increase in F- removal capacity with the utilization of bulk sites. To accomplish this (Chapter 2), an array of experimental techniques were employed to develop a robust particle model to quantify the adsorption and total (i.e. adsorption and bulk) F- capacity specific to the B-type carbonated HAP sample under investigation. Comparison with batch test F- removal revealed uptake far exceeding the adsorption capacity, thereby indirectly validating the occurrence of F- internalization. Rietveld refinement of X-ray diffraction patterns yielded apatite unit cell parameter values a and c. Consistent with the fact that the a parameter of fluorapatite (FAP, Ca5(PO4)3X, where X=F) is significantly smaller than that of HAP, the a parameter of fluoridated HAP samples decreased with increased F- uptake, providing strong physical evidence of F- internalization. Time-resolved quantitative 19F and 1H solid-state Nuclear Magnetic Resonance spectroscopy (NMR) showed the speciation and quantities of removed F- as well as the corresponding losses of HAP OH-, suggesting that a significant portion of F- inserted into conventional and alternative lattice sites occurs without direct replacement of OH-. One dimensional and two dimensional 1H and 1H-19F NMR techniques demonstrated that the removed F- was heterogeneously distributed within the HAP NPs, indicating strong F- concentration gradients are formed at the NP surface with an inwardly migrating boundary. An attempt was made to directly observe the F- distribution in single fluoridated HAP NPs by utilizing a nascent and powerful microscopy technique, atom probe tomography (APT), at the Australian Centre for Microscopy and Analysis (Chapter 3). The particle model framework was used to investigate F- uptake for a number of HAP variants, revealing that F- does not internalize equally or sometimes at all in different types of HAP (Chapter 4). An investigation of their physicochemical properties helped to isolate factors that significantly affect both F- adsorption and internalization. This led to better insights about the potential mechanism of F- internalization as well as ways in which HAP NPs can be synthesized for enhanced performance. Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2022-01-12 without embargo terms The student, Daniel Mosiman, accepted the attached license on 2021-07-12 at 10:57. The student, Daniel Mosiman, submitted this Dissertation for approval on 2021-07-12 at 11:17. This Dissertation was approved for publication on 2021-07-12 at 17:10. DSpace SAF Submission Ingestion Package generated from Vireo submission #16860 on 2022-01-12 at 12:44:56 Made available in DSpace on 2022-01-12T21:45:38Z (GMT). No. of bitstreams: 3 MOSIMAN-DISSERTATION-2021.pdf: 9736507 bytes, checksum: b0fb011cf57dcbd102668db1c5c0b31d (MD5) LICENSE.txt: 4211 bytes, checksum: 972a44191b766ffcab25a5e45dd9b4b2 (MD5) PROQUEST_LICENSE.txt: 4557 bytes, checksum: c2d252f260d89e4d95ac975f691a9459 (MD5) Previous issue date: 2021-07-12 application/pdf http://hdl.handle.net/2142/113019 en Copyright 2021 Daniel Mosiman hydroxyapatite fluoride water treatment Probing structure-property relationships of calcium hydroxyapatite defluoridation to enhance performance text Thesis Civil & Environmental Eng Environ Engr in Civil Engr University of Illinois at Urbana-Champaign Dissertation Ph.D.