The objective of this work is development of a new adsorbent on the base of an organoclay with a chelating ligand covalently attached to the clay mineral surface. The presence of a chelating ligand in the clay structure significantly improves its ability to immobilize heavy metal ions from contaminated sludge of wastewater. Montmorillonite and kaolinite were chosen as typical examples of expandable and non-expandable clay minerals. A two-step modification procedure comprised of sequential modification with oxides and grafting of a chelating agent to the modified clay minerals was used. Modifications with silica and ferric oxide were conducted by reacting the dispersed raw clay minerals with tetraethoxysilane and ferric nitrate solution. A chelating ligand, N-[3-(trimethoxysilyl)propyl]ethylenediamine triacetic acid trisodium salt, was introduced into interlayer space of raw and modified clay minerals in aqueous solutions. Laboratory tests of the organoclay efficiency for purification of wastewater were conducted with the most promising sample, i.e., organoclay with the highest specific loading of chelating agent. Experiments were conducted with model wastewater containing either individual or mixed heavy metal ions. The modified organoclay displayed high adsorption capacity for heavy metal cations even in acidic media. The method of modification presented in this work can be used for synthesis of efficient adsorbents for applications in contaminated areas.

Shortly after the discovery of the usefulness of chelating compounds by agriculturists, whereby metallic cations are supplied in available form to plants, another use was proposed. This paper is dedicated to this resulting use, namely, that certain chelates appear to have value in keeping phosphate compounds from becoming “fixed” or “tied-up” in the soil.

No description available.

Aldehyde oxidase catalysed oxidation of various quinolinium and related cations has been studied in vitro. Oxidation products were identified by comparison of their spectral and chromatographic characteristics with those of authentic compounds. The N-heterocyclic cations and quinolones used required synthesis. Incubation of N-methylquinolinium, N-methyl-7,8-benzoquinolinium and N-phenylquinolinium yielded the corresponding 2- and 4-quinolones simultaneously. The ratio of 2- to 4-quinolone formation was found to be species dependent; the proportion of 4-quinolone was greater with guinea pig enzyme than with rabbit enzyme. Incubation of N-methyl-4-methylquinolinium, N-methyl-4-phenylquinolinium and N-methylphenanthridinium produced the expected 2-quinolones. Cations substituted adjacent to the ring nitrogen, i. e. N-methyl-2- methylquinolinium, N-methyl-2-phenylquinolinium and N-phenyl-2-phenylquinolinium, were oxidised to the corresponding 4-quinolones. Kinetic constants were determined spectrophotometrically. The Km values obtained with rabbit enzyme ranged from 1.6 x 10-3 M for N-methylquinolinium to <10-5 M for N-phenyl-2-phenylquinolinium. Quaternary compounds were found to be better substrates than their non-quaternary counterparts, except for N-methylisoquinolinium and N-methylphenanthridinium. In general, guinea pig aldehyde oxidase was shown to have a greater affinity for N-heterocyclic cations than rabbit enzyme. The substrate binding site has been discussed in the light of the results outlined below. Oxidation of N-methyl-4-phenylquinolinium (to the 2-quinolone) was competitively inhibited by N-methyl-2-phenylquinolinium (which yields the 4-quinolone), indicating that both these cations interact at the same active site. The ratio of 2- to 4-quinolone production from N-methylquinolinium was constant under various conditions, including purification of the enzyme but changed at high pH or in the presence of N-methylphenanthridinium. Inhibition studies indicated that both quaternary and non-quaternary compounds act at the same site on the enzyme. Km and Vmax values for phthalazine, N-methyl-2-phenylquinolinium and N-methylquinolinium were determined over the pH range 5.4 to 10.2. In each case, results indicated that the enzyme has an ionisable group at the active site with a pK ca. 8. Aldehyde oxidase was shown to catalyse the dehydrogenation of the pseudobases 3,4-dihydro-4-hydroxy-3-methyl-2-quinazolinone and 3,4-dihydro- 4-hydroxy-3-methylquinazoline.

<p> In a study of the structures of some polyatomic cations of Group VI and VII, the compound Se4(HS2O7)2 has been prepared and its structure determined by single crystal X-ray diffraction. The bonding in the square planar cation has been discussed in terms of molecular orbital and valence bond theory. The anion geometry has been discussed and simple rules proposed to predict the changes which occur in bond length and bond angle when one or more oxygen in an SO4 tetrahedron is bonded to another atom or group.</p> <p> A θ/θ vertical diffractometer has been constructed, and computer programmes written, so that cation structures could be determined in solution. The structures of the Se4 2+ and Te4 2+ cations have been determined in fluorosulphuric acid, and are shown to be square planar.</p> <p> Liquid diffraction studies of 3:1, I2/S2O6F2 solutions have shown the presence of a cation containing a linear chain of three iodine atoms.</p> / Thesis / Doctor of Philosophy (PhD)

<p> Investigations on the stability and reactions of various isomers of the benzohomotropylium/bridged [11]-annulene system are presented in this thesis. As 1,6-methano-[11]-annulenium cations are isomeric with benzohomotropylium cations in principle it is possible for these systems to be interconverted by a circumambulatory migration of the 'bridging' methano group. If this reaction were to proceed to equilibrium it would allow the examination of the thermodynamic stability of the various isomers.</p> <p> Homotropylium cations with two methyl groups at C8 are known to undergo facile circumambulatory rearrangements. Thus in this work the 1-hydroxy 8,8-dimethyl-2,3-benzohomotropylium and 1-hydroxy 8,8-dimethyl-4,5-benzohomotropylium cations have been prepared by protonation of the corresponding 2,3- and 4,5- benzohomotropones in FSO3H. On the basis of their 1H NMR spectra it is concluded that they can properly be regarded as homoaromatic cations. The thermal isomerizations of these cations have been studied in detail. The thermal isomerization of these cations led to the formation of a series of products but does not yield the corresponding [11]-annulenium isomer. In addition the barriers to ring inversion in these cations were found to be much lower than those of other homotropylium cations. This suggests that the former cations have a very open structure. Besides this experimental approach, the relative stability of these isomers has been explored using MNDO calculations. The calculated heats of formation (ΔHf) showed that the 1-benzohomotropylium cation is more stable than the corresponding [11]-annulenium ion by 21 kcal/mol.</p> / Thesis / Master of Science (MSc)

<p> Treatment of chromium hexacarbonyl with a series of benzyl alcohols yields the corresponding (R-C6H4CH2OH)Cr(CO)3 complexes, where R = 3-methoxy, 3-methyl, 4-methoxy or 4-methyl. These complexes were characterized by NMR spectroscopy.</p> <p> Protonation of the tricarbonylchromium alcohols with CF3SO3H at low temperature yields a benzyl cation complex which can be isolated and examined by variable-temperature 13C NMR spectroscopy. The spectra show a splitting of the carbonyl carbons at low temperature, providing evidence of electronically restricted rotation of the tripodal ligand. Evaluation of the simulated spectra provides the rotational barrier for this dynamic process. These results are rationalized by means of EHMO calculations.</p> <p> Evidence suggests tripodal rotation was also electronically hindered in the analogous fulvene complexes. Variable-temperature 13C NMR spectra of (6,6-Diphenylfulvene)Cr(CO)3 and (6-Methyl-6-phenylfulvene)Cr(CO)3 show respective 2:1 and 1:1:1 splitting of the carbonyl carbons a low temperature. Barriers of 8.3 kcal/mol and 8.8 kcal/mol were obtained by spectral simulation and were explained by using EHMO calculations.</p> <p> The calculated rotational barrier for the [α-(C5H5CH2)Cr(CO)2NO]+ cation suggests that NMR spectral evidence for hindered rotation may be difficult to obtain.</p> / Thesis / Master of Science (MSc)

No description available.

While the process of electrifying transportation is already underway, competing with fossil fuels in applications such as long-range vehicles and aircrafts will require energy densities that are beyond what is achievable using conventional Li-ion battery chemistries. Li metal batteries are promising candidates for such applications, yet meeting cycle life, power density, and safety demands while utilizing the unmatched specific capacity of Li metal anodes is a formidable challenge. It is well known that the interfacial layer of electrolyte decomposition products which forms on the Li surface during electrochemical cycling (i.e. the solid electrolyte interphase (SEI)) is critical in dictating Li deposit morphology and subsequent performance. However, both the composition and arrangement of the SEI are difficult to study because the SEI is just nanometers-thin, air-sensitive, and evolves as a function of electrochemical cycling protocol. Thus, it is important to develop in situ and operando techniques which are capable of characterizing the SEI in its native environment. Here, we study interphase formation in carbonate, ether, solid ceramic, and highly concentrated electrolytes to develop a framework for the general design of electrolytes and SEIs for Li metal batteries. In the first chapter, we broadly motivate electrochemical energy storage devices and define the metrics which make them attractive compared to alternative forms of energy storage. We then describe Li-based batteries, outline the differences between Li-ion and Li metal batteries, and present some of the key advantages and challenges that Li metal chemistries face. After, we provide a classical description of electrodeposition frameworks, focusing on the effects of charge-transfer kinetics and ion transport on deposition morphology. Then, we present the SEI as a factor which convolutes this process in Li metal anodes and describe how the SEI is formed and arranged on the electrode surface. Finally, we describe common tools used to characterize the SEI and how these may be used to design future electrolytes. The second chapter focuses on the effect of potassium additives on conventional carbonate electrolytes. Recent work has shown that alkali metal additives can lead to smooth Li deposits, yet the underlying mechanisms are not well understood. In this work, we demonstrate that alkali metal additives (here, K+) alter SEI composition, thickness, and solubility. Through post-mortem elemental analyses, we find that K+ ions do not deposit, but instead modify the reactivity of the electrode-electrolyte interface. Using quantitative nuclear magnetic resonance (NMR) and density functional theory (DFT), we show that K+ mitigates solvent decomposition at the Li metal surface. These findings suggest that alkali metal additives can be leveraged to suppress the formation of undesired SEI components (e.g., Li2CO3, soluble organic species), serving as an alternative approach for SEI modification compared to sacrificial additives. We believe that our work will spur further interest in the underexplored area of cation engineering. In the third chapter, we examine both chemical structure and ion dynamics in the SEI, correlating these properties to electrochemical performance to guide the design of new electrolytes. We use a combination of NMR spectroscopy and X-ray photoelectron spectroscopy (XPS) to show that fast Li transport, well-ordered SEI architectures, and low solubility at the electrode/SEI interface in 0.5 M LiNO3 + 0.5 M LiTFSI electrolyte bi-salt in 1,3-dioxolane:dimethoxyethane (DOL:DME, 1:1, v/v) are responsible for the formation of low-surface-area Li deposits and high Coulombic efficiency (CE). This improved performance in the presence of LiNO3 is observed despite the fact that there are higher quantities and more types of compounds in the SEI than in LiTFSI alone, suggesting that the identity of the electrolyte decomposition products, rather than the amount, alters plating. SEI design strategies that increase SEI stability and Li interfacial exchange rate are thus expected to lead to more even current distribution, ultimately providing a new framework to generate smooth Li morphologies during plating/stripping. The fourth chapter describes the dynamic behavior of the interface between a lithium metal electrode and a solid-state electrolyte, lithium lanthanum zirconium oxide (Li7La3Zr2O12 or LLZO). The evolution of this interface throughout cycling involves multiscale mechanical and chemical heterogeneity at the micro- and nano-scale and plays a critical role in all-solid-state battery performance. These features are dependent on operating conditions such as current density and stack pressure. Here we report the coupling of operando acoustic transmission measurements with NMR and magnetic resonance imaging (MRI) to correlate changes in interfacial mechanics (such as contact loss and crack formation) with the growth of lithium microstructures during cell cycling. Together, the techniques reveal the chemo-mechanical behavior that governs lithium metal and LLZO interfacial dynamics at various stack pressure regimes and with voltage polarization. In the fifth chapter, we redefine the premise of a class of Li metal battery electrolytes known as localized high concentration electrolytes (LHCE). LHCEs operate on the assumption that high concentration electrolytes (HCEs) may be augmented using a “diluent,” which interacts scarcely with both the ionic species and the Li metal surface, forming pockets of localized high concentration Li+ which have advantageous bulk and interfacial properties. We report on the use of operando NMR spectroscopy to observe electrolyte decomposition during Li stripping/plating and identify the influence of individual components in LHCEs on Li metal battery performance. Data from operando 19F solution NMR indicates that both bis(fluorosulfonyl)imide (FSI–) salt and bis(2,2,2-trifluoroethyl)ether (BTFE) diluent molecules play a key role in SEI formation, in contrast to prior reports that suggest diluents are inert. Using solution 17O NMR, we assess differences in solvation between LHCEs and low concentration electrolytes (LCEs). We find that BTFE diluents are reduced during Li metal battery operation, which can be detected with operando NMR, but not conventional electrochemical methods. Solid-state NMR (SSNMR) and XPS measurements confirm that LHCEs decompose to form an SEI on Li metal that contains organic BTFE reduction products (CF2, CF3), trapped BTFE, and high quantities of lithium fluoride, likely due to both BTFE and FSI– reduction. These chemical characterizations are correlated with changes in interfacial impedance measured separately at the anode and cathode using three-electrode electrochemical impedance spectroscopy (EIS). Insight into the mechanisms of SEI and CEI formation in LHCEs suggests that fluorinated ethers exhibit tunable reactivity that can be leveraged to control Li deposition behavior. To conclude, we reflect on some of the broad guidelines for electrolyte and SEI engineering that we gleaned from the previous chapters. Finally, we highlight recent notable works which we think will enable major advances in interfacial characterization of Li metal batteries (focusing on in situ and operando techniques which can be applied to study both structure and dynamics in commercial setups).

<p>The chemistry of Xe(II) has been significantly extended to include the first examples of a neutral Xe(II) oxide fluoride species, O(XeF)₂, as well as the first nitrate derivative of Xe(II), FXeONO₂. Until recently, neutral oxide fluorides were known for all formal oxidation states of xenon except Xe(II). The synthesis of the missing oxide fluoride of Xe(II), O(XeF)₂, has been accomplished by reaction of the [FXeOXeFXeF][AsF₆] salt with NOF and characterized by NMR spectroscopy in CH₃CN solution at -78 °C and by Raman spectroscopy. Reaction of NO₂F with [FXeOXeFXeF][AsF₆] has provided the first structurally characterized noble-gas nitrate, FXeONO₂, which slowly decomposes (-78 °C) to XeF₂·N₂O₄. X-ray crystal structures have been determined for FXeONO₂, XeF2·N₂O₄, and XeF2·HNO₃. The preparation of the XeONO₂⁺ cation was attempted by the reaction of FXeONO₂ with AsF₅ at -78 °C, but was not directly observed. It is presumed that the cation initially forms, but rapidly decomposes to give Xe, O₂, and [NO₂][AsF₆].</p> <p>The salt, [XeOTeF₅][Sb(OTeF₅)₆], is a strong, low-temperature oxidant capable of oxidizing halomethanes in SO₂ClF solvent at -78 °C. The CCl₃⁺ and CBr3⁺ cations have been synthesized by oxidation of CCl₄ and CBr₄, respectively. The CBr₃⁺ cation reacts with BrOTeF₅, produced in the initial redox reaction, to give CBr(OTeF₅)₂⁺, C(OTeF₅)₃⁺ , and Br₂. The XeOTeF₅⁺ cation also reacts with BrOTeF₅ to give the Br(OTeF₅)₂⁺ cation. The X-ray crystal structures of [CCl₃][Sb(OTeF₅)₆], [CBr₃][Sb(OTeF₅)₆]•SO₂ClF, and [C(OTeF5)3][Sb(OTeF5)6]·3SO₂ClF have been determined and show that the carbocations are trigonal planar about the central atom.</p> <p>Reactions of chlorofluoro-and bromofluoromethanes with [XeOTeF₅][Sb(OTeF₅)₆] have also been investigated in SO₂ClF solvent by ¹³C and ¹⁹F NMR spectroscopy at -80 °C. The CFCl₂⁺ and CFCl(OTeF₅)⁺ cations are among the carbocations that have been obtained by reactions of CFCl₃ and CF₂Cl₂ with XeOTeF₅⁺. The CF₂Br⁺ cation is an intermediate in the reaction of XeOTeF₅⁺ with CF₂Br₂, undergoing rapid halogen exchange with CF₂Br₂ to form CFBr₂⁺ and CF₃Br. The CFBr₂⁺ cation undergoes further halogen exchange over several hours to form the CBr₃⁺ cation and CF₃Br. Although the highly electrophilic CF₃⁺ cation has not been isolated by the reaction of CF₃Br with XeOTeF₅⁺,¹³C and ¹⁹F NMR spectroscopy indicates the CF₃⁺ cation reacts with BrOTeF₅ to form F₃CBrOTeF₅⁺ and/or abstracts an OTeF₅ group from the Sb(OTeF₅)₆^-anion to yield CF₃OTeF₅ and, ultimately, [SbBr₄][Sb(OTeF₅)₆].</p> <p>The synthesis of C(OTeF₅)₄ has been accomplished by reaction of CBr4 with Br0TeF5 in SO₂ClF solution, and has been fully characterized by NMR spectroscopy, Raman spectroscopy, and single-crystal X-ray diffraction, and its geometric parameters have been compared with those of the isoelectronic B(OTeF₅)₄^-anion in order to assess the symmetry of the E(OTe)₄^-/0 (E = B, C) subgroup.</p> / Doctor of Philosophy (PhD)