BEGIN:VCALENDAR VERSION:2.0 PRODID:icalendar-ruby CALSCALE:GREGORIAN X-WR-CALNAME:PhD Dissertation Final Defense- Evan D. Richards X-WR-TIMEZONE:Eastern Time (US & Canada) BEGIN:VEVENT DTSTAMP:20260719T211327Z UID:tag:localist.com\,2008:EventInstance_41288375072286 DTSTART:20221018T190000Z DTEND:20221018T210000Z DESCRIPTION:Candidate: Evan D. Richards\n\n Date: Tuesday\, October 18\, 20 22\n\n Time: 3:00 PM – 5:00 PM\n\n In-person: 1145 Benedum Hall\n\n \n\n Title: Development of a Selective Cation Exchanger to Adsorb Ammonium by Coating with a Gas-permeable and Hydrophobic Membrane \n\n \n\nChair: \n\n Dr. Lei Li\, Chemical and Petroleum Engineering Department\, University of Pittsburgh \n\n \n\nCommittee:\n\nDr. Susan Fullerton\, Chemical and Petr oleum Engineering Department\, University of Pittsburgh\n\n Dr. Tagbo Niep a\, Chemical and Petroleum Engineering Department\, University of Pittsbur gh\n\n Dr. William Wagner\, Department of Surgery\, McGowan Institute for Regenerative Medicine\, Department of Bioengineering and Department of Che mical and Petroleum Engineering University of Pittsburgh\n\nDr. Sang-Ho Ye \, Department of Surgery\, University of Pittsburgh\n\nDr. Stephen R. Ash\ , MD – Hemocleanse Technologies\, Pittsburgh\, PA\n\n \n\n Abstract: A s orbent with a high enough capacity for NH4+ could serve as an oral binder to lower urea levels in end-stage kidney disease patients. A hydrogen-load ed cation exchanger such as zirconium phosphate Zr(HPO4)2·H2O (ZrP) is a promising candidate for this application. However\, the NH4+ binding selec tivity versus other ions must be improved. A gas-permeable and hydrophobic surface coating was first developed on an amorphous form of ZrP using tet raethyl orthosilicate and methoxy-terminated polydimethylsiloxane. The hyd rophobic coating served as a barrier to ions in water solution from reachi ng the ion-exchanger’s surface. Meanwhile\, its gas-permeable nature all owed for gaseous ammonia transfer to the cation exchanger. In vitro studie s replicated the small intestine’s expected ion concentrations and expos ure time to the sorbent. The effectiveness of the coating was measured wit h NH4+ and Ca2+ solutions and uncoated ZrP as the negative control. X-ray photoelectron spectroscopy and scanning electron microscopy measurements s howed the coating successfully modified the surface of the cation exchange r. Water contact angle (WCA) studies indicated that coated ZrP was hydroph obic with an angle of (149.8° ± 2.5°). Simulated small intestine soluti on studies showed the coated ZrP removed 94% (± 11%) more NH4+ than uncoa ted ZrP in the presence of Ca2+. Meanwhile\, Ca2+ binding decreased by 64% (± 6%). The nearly four-fold increase in NH4+ selectivity can be attribu ted to the gas-permeable and hydrophobic coating applied on ZrP’s surfac e. But the material’s selectivity decreased by 72% after exposure to sto mach acid conditions.\n\n \n\nAn alternative hydrophobic (WCA = 145.0° ± 3.2°) and gas permeable coating made of a perfluorocarbon backbone was n ext investigated – 1H\,1H\,2H\,2H-perfluorooctyltriethoxysilane. The coa ting was assembled on a polysiloxane-formed membrane on ZrP’s surface. C alculated Langmuir equilibrium and removal rate plots showed that decreasi ng %1H\,1H\,2H\,2H-perfluorooctyltriethoxysilane in coating solution from 10% to 4% improved total NH4+ removal by 27% and removal rate by nearly 67 5%. In vitro studies indicated the perfluorocarbon-based structure attache d to ZrP offers complete selectivity for NH4+ over Ca2+. The studies also showed the material removed as much NH4+ from solution as the polydimethyl siloxane-based coating. But 1H\,1H\,2H\,2H-perfluorooctyltriethoxysilane-c oated ZrP maintained its selectivity and total NH4+ removal capacity after acid exposure. GEO:40.444043;-79.958003 LOCATION:Benedum Hall\, 1145 Benedum Hall SUMMARY:PhD Dissertation Final Defense- Evan D. Richards URL;VALUE=URI:https://calendar.pitt.edu/event/phd_dissertation_final_defens e-_evan_d_richards CATEGORIES:Defenses END:VEVENT END:VCALENDAR