Functional adsorbent and membrane for wastewater treatment

The water pollution problem has been a concerning issue faced by many countries throughout the world. Adsorption and membrane separation are two promising technologies to help remove pollutants from water bodies. From a technical perspective, ceramic membranes have a great potential to play a key role in the pollutant removal process because of their great chemical and mechanical stability. However, the high capital investment costs of ceramic membranes especially nanofiltration ones hinder their applicability in water treatment. Coating graphene oxide (GO) membranes, which have “pore sizes” in the nanofiltration range, on the relatively low-cost microfiltration ceramic membrane could be a way to reduce the overall membrane cost. However, due to their long diffusional path, GO membranes are suffered from low permeability, which needs to be improved to enhance their practical applicability. Metal-organic framework (MOF) is an attractive porous material for the adsorption of pollutants. However, they are usually produced in a fine powder form which requires further modulation into bulk bodies to enable their applicability in practical water treatments. Raschig Ring could be a platform for the anchoring of the MOF particles. However, conventional Raschig Rings are non-porous and have relatively small surface areas per volume, limiting the amount of MOFs that could be loaded on them. This thesis aimed to tackle these problems in three steps. Firstly, an investigation was conducted to find out the optimum synthesis condition for the production of porous Raschig Rings/ microfiltration membranes which were then produced as substrates. Secondly, a mild chemical etching method was utilised to create pores on the surface of GO nanosheets. These pores worked as additional diffusional entrances when GO nanosheets were processed into membranes onto ceramic substrates, which greatly enhanced the performance of the membrane. Lastly, MIL-53 MOF adsorbent was grown on the porous Raschig Rings in a novel way that made use of the alumina Raschig Ring as both metal source and substrate. Their great re-generability and re-synthesisbility demonstrated the promising potential of the MIL-53 Raschig Ring in practical water treatment application.Open Acces

Development of capillary based separation techniques for the separation of proteins equilibrated using hexapeptide ligand libraries

Challenges in research areas such as chemistry, medicine, environmental toxicology and biology require the analysis of complex samples. Fast analysis of these samples using separation techniques with spectrometric or spectroscopic detection is common. Most often, chromatographic separation techniques such as gas and liquid chromatography coupled to mass spectrometry are chosen. These techniques, however, often reach their limits when highly charged analytes are investigated. Here, electromigrative separation techniques with their orthogonal separation mechanism are an attractive alternative. A very promising electrophoretic separation technique, which is primarily used during this work, is capillary electrophoresis (CE). One of the greatest challenges using this technique lies in the separation of biological samples, since analytes such as polyamines, peptides and proteins interact with and adsorb on the surface of “bare fused silica”-capillaries which impairs reproducibility. Without efficient suppression of these interactions, separation efficiency and run-to-run reproducibility suffer. A good way to suppress these detrimental interactions of analytes with the capillary surface is to modify the surface using of dynamic, statically adsorbed or covalently bound capillary coatings. In this work, I present approaches for the reproducible separation of polyamines, peptides and proteins: 1) In Chapter 2, the use of poly ethylene oxide as dynamic coating in SDS-CE enables the size-based separation of proteins up to a weight of 100 kDa. Advantages of this technique over classic gelbased SDS-PAGE are separation times of about 20 min and direct quantification via on-line UVdetection without the need of preliminary labeling or subsequent dyeing. Separation times were reduced to 5 min by short-end-injection and modification of the aperture for UV-detection. The presented separation system offers outstanding matrix tolerance: even complex samples such as serum were successfully separated without additional processing. Increased separation performance and efficiency were aspired by the addition of alkanols to the BGE, variation of temperature and the use of enrichment plugs in the capillary. Therein, especially the use of 2- propanol in the BGE proves fruitful regarding separation efficiency in the mass range up to 40 kDa. In Chapter 3 I will interpret my results with an extensive literature search to show, that the observed increase in separation efficiency is linked to a change of the separation mechanism from Reptation- to Ogston-sieving. 2) In Chapter 4, I proudly present, that I achieved CE-separation with MS-hyphenation not only for small polyamines and peptides, but also of large, non-digested proteins. This was possible using a single capillary coating only based on N-acryloylamido ethoxyethanol (AAEE). This highly polar and covalently bound capillary coating offers enjoyably high reproducibly and stability, the latter enabling operating times of 100 h, even when complex samples such as human serum and polyamines in fish eggs were analyzed. In Chapter 5 a novel and parallelized approach for the synthesis of this capillary coating is presented. SEM-measurements of the capillary surface between reaction steps forced me to postulate a novel reaction-mechanism for the formation of the coated surface. Additionally, I present, that pre-conditioning of capillaries with hypercritical water can result in higher reproducibility of capillary-to-capillary performance and reduced synthesis time. In Chapter 6 I will show that the presented separation techniques are excellent for the separation and detection of proteins equilibrated using hexapeptide ligand libraries (HLL). A novel approach for the consecutive equilibration of small sample volumes, which enables a deep insight into the proteome, is critically discussed. Challenges intrinsic to the solid phase extraction of proteins using HLLs are traced back to irreversible binding sites on HLLs. To tackle this issue, different elution and pre-equilibration protocols are designed and investigated. To re-establish binding conditions in consecutive equilibration, which is consecutive equilibration, different protocols for the processing of eluates from HLLs using 10 kDa cut-off filters are presented. Aspects that critically impair yields and recovery rates come to the fore and improved protocols are presented. A further project focused on CE-MS-based pI-value determination of a hardly soluble, cyclic and antibiotic peptide (Chapter 7). Detection of this peptide was not possible using AAEE-coated capillaries. This problem was overcome by using non-coated capillaries and BGEs containing small amounts of citric acid, which functions not only as buffer but also as a dynamic capillary coating. To confirm the determined pI-vaues, a novel and time-saving approach for the sequential injection of amino acid reference substances was developed.Fragestellungen in der Chemie aber auch in vielen anderen Disziplinen wie der Medizin, Umwelttoxikologie und Biologie, erfordern die Untersuchung von teilweise sehr komplexen Stoffgemischen. Eine schnelle Untersuchung von komplexen Proben ist mittels Trenntechniken, gefolgt von spektroskopischer oder spektrometrischer Detektion möglich. Zu den am weitesten verbreiteten Techniken gehören hierbei chromatographische Methoden wie die Gas- und Flüssigchromatographie, häufig gekoppelt mit Massenspektrometrie. Geraten diese chromatographischen Techniken an ihre Grenzen, beispielsweise bei hoch geladenen Stoffen, so bietet sich der Einsatz von elektromigrativen Trenntechniken an, da diese einen orthogonalen Trennmechanismus besitzen. Die Kapillarelektrophorese (engl.: capillary electrophoresis, CE), mit welcher sich diese Arbeit befasst, zählt zu den elektromigrativen Trenntechniken. Eine große Herausforderung dieser Technik besteht u.a. in der geringen Reproduzierbarkeit bei der Analytik von Biomolekülen, welche sich auf die Verwendung von „bare fused silica“-Kapillaren und deren Wechselwirkung mit den Analyten zurückführen lässt. Wird diese Wechselwirkung nicht effizient unterdrückt, so sinkt die Trenneffizienz innerhalb und die Wiederholbarkeit zwischen Trennungen. Durch die Verwendung von dynamischen, statisch adsorbierten oder kovalent gebundenen Kapillarbeschichtungen kann diese Wechselwirkung effizient unterdrückt werden. In dieser Arbeit werden mehrere Möglichkeiten zur reproduzierbaren Trennung von Polyaminen, Peptiden und Proteinen vorgestellt: 1) In Kapitel 2 wird durch die Verwendung von Polyethylenoxid als dynamische Beschichtung und Siebmatrix in der SDS-CE die größenbasierte Trennung von Proteinen bis zu einer Masse von 100 kDa erreicht. Ein Vorteil gegenüber klassischen gelbasierten Verfahren wie SDS-PAGE ist hierbei, dass Proben innerhalb von 20 min getrennt und durch on-column UV-Detektion quantifiziert werden können, ohne vor- oder nachträgliches Anfärben oder Derivatisieren. Durch eine selbst entworfene Modifikation der Trennapparatur und Injektion vom kurzen Ende der Kapillare konnte diese Trennzeit für ein schnelles Screening auf 5 Minuten reduziert werden. Das vorgestellte Trennsystem zeichnet sich durch eine hohe Matrixtoleranz aus; selbst Proben wie menschliches Serum können ohne Aufarbeitung injiziert werden. Eine Verbesserung der Auflösung und Trenneffizienz wurde durch die Verwendung von verschiedenen Alkoholen im Hintergrundelektrolyten, die Variation der Trenntemperatur und die Etablierung von Anreicherungszonen in der Kapillare angestrebt. Hierbei zeigte vor allem die Verwendung von 2- Propanol im Hintergrundelektrolyten eine erhöhte Trenneffizienz im Massenbereich bis ca. 40 kDa. In Kapitel 3 wird anhand der eigenen Ergebnisse und durch ausführliche Literaturarbeit gezeigt, dass diese Verbesserung der Auflösung durch eine Verschiebung des Trennmechanismus von Reptation- zu Ogstonsieben ermöglicht wird. 2) Durch die Verwendung einer sehr polaren kovalenten Kapillarbeschichtung, dem NAcryloylamido- ethoxyethanol (AAEE), lässt sich die kapillarelektrophoretische Trennung von kleinen Polyaminen und Peptiden, aber auch großen und unverdauten Proteinen, bei gleichzeitiger massenspektrometrischer Detektion erreichen. Dies wird in Kapitel 4 vorgestellt. Erfreulich hohe Einsatzzeiten von ca. 100 h und gute Wiederholbarkeiten werden sogar bei der Untersuchung von menschlichem Serum oder Polyaminen in Fischeiern beobachtet. In Kapitel 5 werden ein neuer und ABSTRACT (DEUTSCH) 4 parallelisierter Ansatz zur Kapillarsynthese sowie ein koexistenter und durch SEM-Aufnahmen postulierter Reaktionsmechanismus vorgestellt. Zusätzlich wird ein Ansatz zur Vorbehandlung der Kapillaren durch die Verwendung von überkritischem Wasser vorgeschlagen, welcher ersten Versuchen nach zu einer höheren Reproduzierbarkeit der Beschichtung und einer beschleunigten Synthese führen kann. In Kapitel 6 werden die vorgestellten Analysetechniken werden für die Bestimmung von Proteinen in mittels Hexapeptidligandenbibliotheken angereicherten Proben verwendet. Ein Ansatz zur mehrfachen Anreicherung, der einen tiefen Blick ins Proteom erlauben soll, wird kritisch bewertet. Herausforderungen in der Festphasenanreicherung werden auf irreversible Bindungsstellen zurückgeführt. In diesem Zusammenhang werden verschiedene Elutions- und PreÄquilibrierungsprotokolle untersucht. Für die erfolgreiche Wiederbeladung, welche einen tieferen Blick ins Proteom erlaubt, werden verschiedene Protokolle zur Aufarbeitung des Eluats mittels 10 kDa-Cut-off-Filtern vorgestellt. Kritische Aspekte, welche die Ausbeuten beeinträchtigen, werden beleuchtet und Lösungswege aufgezeigt. In Kapitel 7 wird die MS-basierte pI-Wertbestimmung eines schwerlöslichen zyklischen Peptidantibiotikums vorgestellt. Dieses konnte mit AAEE-beschichteten Kapillaren nicht erfasst werden. Diese Herausforderung konnte durch die Verwendung unbeschichteter Kapillaren und geringen Mengen Zitronensäure im Hintergrundelektrolyt, welche als dynamische Beschichtung fungiert, umgangen werden. Zur Absicherung der bestimmten pI-Werte mit Aminosäurestandards wurde ein neuer und zeitsparender Ansatz der sequentiellen Injektion entwickelt

Ensuring the in vitro degradation reproducibility of powder metallurgy processed Mg 0.6Ca system

Magnesium degradation is a complex phenomenon that is too difficult to be described by a single influential parameter. Magnesium degradation is often influenced by either overtaking or overlapping factors like the cell culture medium composition, physiological conditions, impurities, and material’s internal microstructure, etc. This poses a challenge in obtaining the reproducible degradation results. Hence, in the present work, microstructural features like porosity and grain size distributions in powder metallurgy (PM) Mg-0.6Ca system were discretely evaluated for their roles in altering the specimen in vitro degradation rates. Importance was also given to the specimen impurity and mechanical properties. Based on the results, the limitations in PM processing conditions towards obtaining robust degradation results or, in other words, the material parameter thresholds to be realized for obtaining reproducible degradation profiles in PM Mg-0.6Ca specimens were put forth. Additionally, using literature evidence, the mechanisms governing pore closure and grain growth during liquid phase sintering of Mg-0.6Ca specimens from the PM processing perspective were determined. PM Mg-0.6Ca specimens were fabricated via powder blending of pure magnesium and master alloy Mg-10Ca powders. Specimens of seven different porosities, from 3% to 21%, were produced by varying sintering temperatures. Specimens with heterogeneous grain size distributions were obtained by surface modification of pure magnesium powders by means of a mechanical sieving treatment. Degradation profiles were analyzed in vitro using a semi static immersion test for 16 days under physiological conditions of 37 °C, 20% O2, 5% CO2, 95% relative humidity. Dulbecco’s modified Eagle’s medium was used as cell culture medium with Glutamax and 10% fetal bovine serum as supplements. Mechanical properties were determined using micro tensile specimens. The results indicate that low mean degradation rates (MDR 95% to ≤ 45% when falling below this value. Similarly, the pore interconnectivity sharply drops from > 95% to < 10% at this porosity, thereby enhancing the degradation reproducibility. From PM processing perspective, the sintering temperature of 570 °C is proven as beneficial to promote liquid fractions high enough to enhance specimen sinter density. The present work also showed that heterogeneous grain growth is prompted by the reduced oxide pinning effect at the grain boundaries during sintering of PM Mg-0.6Ca specimens. The heterogeneous grain growth additionally induced the formation of eutectic lamellar structure α-Mg + Mg2Ca at certain grain boundaries throughout the microstructure, which is otherwise not evident in specimens with a homogeneous grain size. Based on the literature and results of the present work, it is postulated that this eutectic structure is the major reason for a non-reproducible degradation in PM Mg-0.6Ca specimens possessing a heterogeneous grain structure. Though mechanical properties are not majorly affected, it is recommended that heterogeneous grain growth is to be avoided in PM Mg-0.6Ca specimens. The presented results also implicitly conveyed the flexibility of PM as a viable technique to design Mg-Ca materials with tailor made degradation and mechanical strengths

Fabricating microfluidic devices in polymers for bioanalytica applications

The research presented in this document focuses on the fabrication, characterization and application of microfluidic systems fabricated in poly(methyl methacrylate) (PMMA) with the emphasis focused on the fabrication processing steps. Microfluidic devices were produced in PMMA using X-ray lithography. The fabrication methods investigated were sacrificial mask, polyimide membrane mask and embossing techniques. PMMA microfluidic devices fabricated using X-ray lithography were characterized using scanning electron microscopy (SEM) and optical microscopy, while analytical techniques such as electroosmotic flow determination, separations, and fluorescent microscopy were used to characterize fluid transport in these devices. A novel method for the heat annealing of PMMA to PMMA to create a closed system is described. Characterization of this technique was carried out by optical microscopy and scanning electron microscopy. The manufacturing techniques utilized in producing mold inserts for hot embossing and injection molding is discussed as well. Both the mold insert and devices produced from the inserts were characterized using scanning electron microscopy. Devices produced can be used to perform a number of analytical techniques including single molecule detection and fluorescence lifetime monitoring. The primary goal of this research was to develop molding tools consisting of high-aspect-ratio microstructures using robust and reproducible processing steps

Security Analysis of Pairing-based Cryptography

Recent progress in number field sieve (NFS) has shaken the security of Pairing-based Cryptography. For the discrete logarithm problem (DLP) in finite field, we present the first systematic review of the NFS algorithms from three perspectives: the degree $\alpha$, constant $c$, and hidden constant $o(1)$ in the asymptotic complexity $L_Q\left(\alpha,c\right)$ and indicate that further research is required to optimize the hidden constant. Using the special extended tower NFS algorithm, we conduct a thorough security evaluation for all the existing standardized PF curves as well as several commonly utilized curves, which reveals that the BN256 curves recommended by the SM9 and the previous ISO/IEC standard exhibit only 99.92 bits of security, significantly lower than the intended 128-bit level. In addition, we comprehensively analyze the security and efficiency of BN, BLS, and KSS curves for different security levels. Our analysis suggests that the BN curve exhibits superior efficiency for security strength below approximately 105 bit. For a 128-bit security level, BLS12 and BLS24 curves are the optimal choices, while the BLS24 curve offers the best efficiency for security levels of 160bit, 192bit, and 256bit.Comment: 8 figures, 8 tables, 5121 word

Separation of H2 and CO2 Containing Mixtures with Mixed Matrix Membranes Based on Layered Materials

Some membrane separation processes are gradually taking over conventional processes such as distillation, evaporation or crystallization as the technology progresses from bench-scale tests to large-scale prototypes. However, membranes for H2 and CO2 separation constitute a daring technology still under development. This overview focuses on mixed matrix membranes (MMMs), a special type of membranes in which a filler is dispersed in a polymer matrix, as a successful strategy to improve their permeability-selectivity performance while keeping the polymer processability. In particular, among all the possible fillers for MMMs, layered materials (porous zeolites and titanosilicates and graphite derivatives) are discussed in detail due to the several advantages they offer regarding selective microporosity, crystallinity and, what is most important, high specific surface area and aspect ratio. In fact, a selective and as thin as possible, i.e. with high aspect ratio, filler would help to develop high performance MMMs

Capillary and microchip gel electrophoresis using multiplexed fluorescence detection with both time-resolved and spectral-discrimination capabilities: applications in DNA sequencing using near-infrared fluorescence

Increasing the information content obtainable from a single assay and system miniaturization has continued to be important research areas in analytical chemistry. The research presented in this dissertation involves the development of a two-color, time-resolved fluorescence microscope for the acquisition of both steady-state and time-resolved data during capillary and microchip electrophoresis. The utility of this hybrid fluorescence detector has been demonstrated by applying it to DNA sequencing applications. Coupling color discrimination with time-resolved fluorescence offers increased multiplexing capabilities because the lifetime data adds another layer of information. An optical fiber-based fluorescence microscope was constructed, which utilized fluorescence in near-IR region, greatly simplifying the hardware and allowing superior system sensitivity. Time-resolved data was processed using electronics configured in a time-correlated single photon counting format. Cross-talk between color channels was successfully eliminated by utilizing the intrinsic time-resolved capability associated with the detector. The two-color, time-resolved microscope was first coupled to a single capillary and carried out two-color, two-lifetime sequencing of an M13 template, achieving a read length of 650 bps at a calling accuracy of 95.1%. The feasibility of using this microscope with microchips (glass-based chips) for sequencing was then demonstrated. Results from capillaries and microchips were compared, with the microchips providing faster analysis and adequate electrophoretic performance. Lifetimes of a set of fluorescent dyes were determined with favorable precision, in spite of the low loading levels associated with the microchips. The sequencing products were required to be purified and concentrated prior to electrophoretic sorting to improve data quality. PMMA-based microchips for DNA sequencing application were evaluated. The microchips were produced from thermo plastics, which allowed rapid and inexpensive production of microstructures with high aspect ratios. It was concluded that surface coating was needed on the polymer chips in order to achieve single-base resolution required for DNA sequencing. The capability of the two-color time-resolved microscope operated in a scanning mode was further explored. The successful construction of the scanner allows scanning of multi-channel microchips for high throughput processing