Master of Science (MS), Wright State University, 2024, Chemistry

This study examines the complexation behavior of methylthymol blue (MTB) with strontium, particularly focusing on its application in addressing environmental concerns related to radiotoxic 90Sr. Using spectrophotometric techniques, the binding interactions were analyzed at pH = 7.50, 9.60, and 12.20. Results indicate that MTB forms a 1:1 complex with strontium at pH = 7.50, while at pH = 9.60 and 12.20 were assumed to influence complexation due to changes in ligand deprotonation and electrostatic interactions. Equilibrium constants (K1) = 22 (± 2) and molar absorptivities, ε1 = 6.3 x 10^3 (± 0.0008) L·mol⁻¹·cm⁻¹, and ε2 = 9.73 x (± 0.2)10^3 L·mol⁻¹·cm⁻¹ were determined using Beer's law, alpha fraction plots, and 1:1 Single K model fitting was done in Igor Pro 9 software. These findings highlight MTB's potential for environmental remediation of strontium in aqueous solution, with future research suggested to optimize MTB effectiveness as metal ion indicator.

Committee: Steven Higgins Ph.D. (Advisor); Suzanne Lunsford Ph.D. (Committee Member); Eric Fossum Ph.D. (Committee Member) Subjects: Analytical Chemistry; Chemistry

PhD, University of Cincinnati, 2024, Pharmacy: Pharmaceutical Sciences

Among chemical UV filters approved by the US FDA, avobenzone (AVO) is the most efficient and commonly used UVA filter in broad-spectrum sun care products. However, one pitfall of AVO is a lack of photostability leading to a decrease in its UV protection capacity. Its photostability primarily depends on the solvent system (solvents, emollients, and UV filters) and excipients in its vicinity (i.e., other UV filter molecules, and triplet or single quenchers). Moreover, when AVO and octinoxate (OCT), a UVB filter, are used in combination, it appears that the photo-instability of AVO can cause the photolysis of OCT. It has been reported that forming inclusion complexes with ß-cyclodextrins (ß-CD) enhanced the photoactive performance of AVO and OCT by improving their photostability and reducing skin permeation. However, most studies have investigated the complexes in solvents unintended for cosmetic formulations. Most importantly, the mechanism of host-guest complexation and photo-stabilization by ß-CD has not yet been revealed. Therefore, this dissertation aims to investigate the effect of macrocyclic compounds (ß-CD vs Cucurbit[7]uril (CB[7]) on the photostability of AVO and OCT in aqueous environment, which is motivated by three research questions. What are the differences in the complexation of AVO and OCT with ß-CD and CB[7]? How do forming complexes with ß-CD and with CB[7] affect the photostability, skin permeation, and efficacy of AVO and OCT? Finally, what is the impact of ethanol as a cosolvent on the complexation and photostability of AVO and OCT? To examine these questions, we prepared complexes of AVO-ß-CD, AVO-CB[7], OCT-ßCD, and OCT-CB[7] and characterized the complexes both in solution phase and solid state using several analytical techniques. We also conducted photostability studies for all complexes, skin permeation tests for AVO complexes, and evaluated the efficacy for all complexes. The findings from the research show that ß-CD and CB[7] have s (open full item for complete abstract)

Committee: Harshita Kumari Ph.D. (Committee Chair); Frank Heinrich PhD (Committee Member); Kevin Li Ph.D. (Committee Member); Gerald Kasting Ph.D. (Committee Member); Kavssery Ananthapadmanabhan (Committee Member); David Moore Ph.D. (Committee Member) Subjects: Pharmaceuticals

Master of Science (MS), Ohio University, 2023, Civil Engineering (Engineering and Technology)

Tire particles (TP) are the largest source of microplastics in nature. However, the adsorption behavior of TP needs to be better understood. TP used in this study were generated from cryo-milling and aged with 30% nitric acid. Single and competitive adsorption isotherm experiments were conducted to investigate the potential of TP as carriers of heavy metals. Langmuir and Freundlich models were used to analyze adsorption data. Competitive adsorption demonstrated a reduction in the adsorption capacity of TP. The preference for lead to copper by TP was explained by the physical and chemical properties of the metals. The adsorption capacity was maximum at the pH range of 6-12 for lead, and for copper, it was pH 10. pH, zeta potential, FT-IR, and XPS results indicated that electrostatic attraction and surface complexation were involved in the heavy metal adsorption on TP.

Committee: Lei Wu Dr. (Advisor); Natalie Kruse-Daniels Dr. (Committee Member); Daniel Che Dr. (Committee Member); Guy Riefler Dr. (Committee Member) Subjects: Environmental Engineering

Doctor of Philosophy, Case Western Reserve University, 2020, Chemical Engineering

Deep eutectic solvents (DES) are attracting attention for their potential use in energy storage applications such as redox flow battery. In such application, knowledge of the transport and electrochemical kinetics properties of DES is critically important. To date, attempts to measure the kinetics parameters of the Cu2++e <-> Cu1+ reaction in ethaline DES have yielded unreliable kinetic results. In this work, detailed recommendations are developed and verified for avoiding pitfalls in kinetics analysis of highly resistive DES electrolytes. Incorporating these recommendations, a comprehensive study of the kinetics and transport properties of the aforementioned redox reaction was carried out. Using steady–state and transient polarization measurements on RDE and microelectrodes combined with diffusion–reaction modeling, we demonstrate that the Cu2+/Cu1+ transition exhibits a charge transfer coefficient in the range of 0.49 – 0.54 and a reaction rate constant in the range (1.78 – 1.95) × 10-4 cm/s. The result indicates that the Cu2+/Cu1+ redox reaction in chloride–containing DES media suffers from sluggish charge transfer kinetics. The effects of DES composition and temperature on kinetics provided insights into the origins of the sluggish kinetics. Specifically, species complexation with Cl– which is present in excess in the chosen DES systems is shown to be the reason for slow charge transfer. For potential application in rare-earth metal recovery from spent waste, the electrodeposition of neodymium (Nd) metal from NdCl3–containing molten LiCl–KCl eutectic melts was investigated using voltammetry and diffusion–reaction modeling. Voltammetry studies confirmed that Nd electrodeposition is a two–step reduction process involving first a reversible one–electron transfer reduction of Nd3+ to Nd2+, followed by quasi–reversible reduction of Nd2+ to Nd metal. In the electrode potential range where Nd3+ is reduced to Nd2+, the peak current density measured in a voltammetry (open full item for complete abstract)

Committee: Rohan Akolkar Ph.D. (Committee Chair); Robert Savinell Ph.D. (Committee Member); Uziel Laudau Ph.D. (Committee Member); Mark De Guire Ph.D. (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, The Ohio State University, 2015, 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 (open full item for complete abstract)

Committee: John Lenhart PhD. (Advisor); Heather Allen PhD. (Committee Member); Yu-Ping Chin PhD. (Committee Member); Linda Weavers PhD. (Committee Member) Subjects: Environmental Engineering

Doctor of Philosophy, The Ohio State University, 2010, Chemical and Biomolecular Engineering

Cephalexin is an important and widely used semi-synthetic cephalosporin. Cephalosporins along with penicillins are β-lactam antibiotics and they account for the majority of the antibiotic world market. Cephalexin is traditionally produced by a 10-step chemical synthesis. An enzymatic synthesis for Cephalexin has been developed, and offers several advantages over the classical route. The enzymatic synthesis reduces energy and solvent waste, but its use for industrial production has been limited due to the difficult separation. Liquid membranes, in particular supported liquid membranes (SLMs), are a promising solution to the separation. SLMs are not used commercially, as they are still plagued with instability. SLM with the additional modification of strip dispersion has been a recent development to solve this issue. This study describes work in which Cephalexin is separated from complex reaction mixtures encountered in the enzymatic synthesis using SLMs with strip dispersion. SLMs with strip dispersion and carrier, Aliquat 336, were used for the recovery of Cephalexin from aqueous solutions. The separation of Cephalexin from single component solutions was first investigated. Key experimental parameters were indentified and Cephalexin recovery of over 99% has been achieved for most cases. In addition, the mass transfer resistances from the process were analyzed and the resistance from the extraction reaction between Cephalexin and Aliquat 336 was found to be dominant. Recovery of Cephalexin from non-ideal solutions was also investigated, which involved co-extraction from buffer anions and other components present in the enzymatic reaction mixture during Cephalexin synthesis. In situ extraction was also demonstrated in which Cephalexin was removed from enzymatic reaction mixtures as it was synthesized with the enzyme penicillin acylase, and resulted with an increase in Cephalexin yield compared to synthesis without in situ removal. Along with these promising results, t (open full item for complete abstract)

Committee: W. S. Winston Ho (Advisor); L. James Lee (Committee Member); Andre Palmer (Committee Member); Roberto C. Myers (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, The Ohio State University, 2008, Civil Engineering

Numerous naturally-occurring organic acids (low- or high-molecular weight organic acids) are commonly found in the natural environment, often at significant concentrations. These acids adsorb strongly to mineral surfaces and affect the fate and transport of contaminants and nutrients as well as other basic biogeochemical processes (e.g., mineral dissolution). An accurate assessment of the impact the adsorbed organic acid has on these processes hinges on developing, at the molecular-level, an understanding of the interactions occurring at the mineral-water interface. The objectives of this investigation were 1) to evaluate how differences in the molecular structure of organic acids can affect adsorption behavior at the mineral-water interface as a function of environmental conditions; 2) to develop a surface complexation modeling strategy to successfully integrate the molecular-level information with observations made at the macroscopic results; 3) to elucidate how competitive interactions between multiple organic acids and the mineral-water interface alters adsorption behavior in advective systems. To meet these objectives, a systematic investigation of the adsorption of four low- molecular weight (LMW) dicarboxylic acids (phthalic acid, maleic acid, succinic acid, and fumaric acid) on the hematite surface was performed. These acids were chosen to determine the influence of simple structural differences, in particular the orientation of the carboxylic groups, on adsorption. Results are presented for a variety of systems studied using traditional equilibrium batch adsorption experiments, in-situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), theoretical molecular orbital calculations, potentiometric titration experiments, surface complexation models (SCMs), and column experiments. From the batch adsorption experiment, it was found that the orientation of the carboxylic groups in each dicarboxylic acid and their pKa values signific (open full item for complete abstract)

Committee: John Lenhart PhD (Advisor); Harold Walker PhD (Committee Member); Linda Weavers PhD (Committee Member); Nicholas Basta PhD (Committee Member) Subjects: Environmental Engineering; Environmental Science; Geochemistry