26 research outputs found
Virus removal in ceramic depth filters: the electrostatic enhanced adsorption approach
Diese Arbeit untersucht den Einsatz von keramischen Materialien in der Trinkwasseraufbereitung mittels Filtration und fokussiert dabei die Entfernung von Viren. Herkömmliche, auf Kieselgur basierende Tiefenfilter (Filterkerzen) mit Porengrößen im unteren Mikrometerbereich, werden hinsichtlich ihres Rückhaltevermögens gegenüber Kolloiden (Viren sowie Polystyrolpartikel) untersucht, um deren Einsatzfähigkeit in der Entfernung von Mikroorganismen im Allgemeinen abschätzen zu können. Ferner wird gezeigt, wie durch ein einfaches Verfahren solche Filter modifiziert werden können, um auch kleinste Viren mit ca. 30 nm Durchmessern aus dem Rohwasser zu entfernen. Die Zugabe von MgO während der Granulierungsstufe im Herstellungsprozess der Filterkerzen bewirkt eine erhebliche Verbesserung des Virenrückhalts bis zu über 99.9999%. Die experimentellen Ergebnisse wurden dabei mit theoretischen Modellen verglichen, um Aussagen über die Mechanismen der Virenentfernung treffen zu können.:Contents
Chapter I Introduction 1
Chapter II Removal or inactivation of microorganisms, in particular viruses, for drinking water purposes with focus on small-scale, decentralised systems: A literature review 7
II. I Physical and chemical treatments 8
II. II Filtration processes 10
II. III Conclusions 15
Chapter III Mechanisms of adsorption in depth filtration 17
III.I Surface charge and the electrical double layer 18
III.II van der Waals interactions 22
III.III DLVO theory 23
III.IV Non-DLVO forces 25
III.V Extended DLVO Theory 27
Chapter IV Virus adsorption studies 29
IV.I A literature review 30
IV.I.I Virus concentration by adsorption-elution 33
IV.I.II Improved virus adsorption in filtration 35
IV.II The electrostatic enhanced adsorption approach 37
Chapter V Viruses 39
V.I Literature review 40
V.I.I Structure and morphology 40
V.I.II The viral life cycle 41
V.I.III Human pathogenic viruses in the aquatic environment 42
V.II Experimental 46
V.II.I The choice of viruses for adsorption studies 46
V.II.II Propagation and enumeration of the bacteriophages 48
V.II.III Characterisation of bacteriophages 51
V.III Results and discussion 54
V.III.I Production of high-titre and high-purity phage stocks 54
V.III.II Characteristics of bacteriophages 59
V.III.III Detection of a viral contaminant - the ‘Siphophage’ 64
Chapter VI The diatomaceous earth-based depth filter 69
VI.I Literature review 70
VI.I.I Diatomaceous earth 70
VI.I.II Retention of microorganisms in the DE-based depth filter 71
VI.II Experimental 73
VI.II.I Manufacturing the depth filter 73
VI.II.II Physical characterisation 74
VI.II.III Performing filter retention tests 75
VI.II.IV Latex retention test 76
VI.II.V Studying adsorption kinetics in a batch experiment 79
VI.II.VI Applying (X-)DLVO theory 80
VI.III Results and discussion 83
VI.III.I Characterisation of the depth filter 83
VI.III.II Latex removal in the depth filter 86
VI.III.III Filter performance on virus removal 94
VI.III.IV Batch-sorption experiments 99
VI.IV Summary and conclusions 102
Chapter VII The magnesium oxide modified depth filter 103
VII.I Experimental 104
VII.I.I Choice of the adsorbent material 104
VII.I.II Manufacturing the MgO-modified filter and characterisation methods 105
VII.II Results and discussion 106
VII.II.I The adsorbent: Magnesium oxide powder 106
VII.II.II Physical characterisation of modified depth filters 108
VII.II.III Virus removal in depth filters containing MgO 113
VII.II.IV Ageing behaviour of MgO modified filters 118
VII.II.V Discussion on the removal mechanisms 130
VII.III Summary and conclusions 134
Chapter VIII Summary, conclusions and outlook 135
VIII.I Summary and conclusions 136
VIII.II Outlook 137
Abbreviations, symbols and physical constants 139
Reference list 14
Adiabatic preparation of fractional Chern insulators from an effective thin-torus limit
We explore the quasi one-dimensional (thin torus, or TT) limit of fractional
Chern insulators (FCIs) as a starting point for their adiabatic preparation in
quantum simulators. Our approach is based on tuning the hopping amplitude in
one direction as an experimentally amenable knob to dynamically change the
effective aspect ratio of the system. Similar to the TT limit of fractional
quantum Hall (FQH) systems in the continuum, we find that the hopping-induced
TT limit adiabatically connects the FCI state to a trivial charge density wave
(CDW) ground state. This adiabatic path may be harnessed for state preparation
schemes relying on the initialization of a CDW state followed by the adiabatic
decrease of a hopping anisotropy. Our findings are based on the calculation of
the excitation gap in a number of FCI models, both on a lattice and consisting
of coupled wires. By analytical calculation of the gap in the limit of strongly
anisotropic hopping, we show that its scaling is compatible with the
preparation of large size FCIs for sufficiently large hopping anisotropy. Our
numerical simulations in the framework of exact diagonalization explore the
full anisotropy range to corroborate these results
Avoiding drying-artifacts in transmission electron microscopy: Characterizing the size and colloidal state of nanoparticles
Standard transmission electron microscopy nanoparticle sample preparation generally requires the complete removal of the suspending liquid. Drying often introduces artifacts, which can obscure the state of the dispersion prior to drying and preclude automated image analysis typically used to obtain number-weighted particle size distribution. Here we present a straightforward protocol for prevention of the onset of drying artifacts, thereby allowing the preservation of in-situ colloidal features of nanoparticles during TEM sample preparation. This is achieved by adding a suitable macromolecular agent to the suspension. Both research- and economically-relevant particles with high polydispersity and/or shape anisotropy are easily characterized following our approach (http://bsa.bionanomaterials.ch), which allows for rapid and quantitative classification in terms of dimensionality and size: features that are major targets of European Union recommendations and legislation
A quantitative study of particle size effects in the magnetorelaxometry of magnetic nanoparticles using atomic magnetometry
The discrimination of immobilised superparamagnetic iron oxide nanoparticles (SPIONs) against SPIONs in fluid environments via their magnetic relaxation behaviour is a powerful tool for bio-medical imaging. Here we demonstrate that a gradiometer of laser-pumped atomic magnetometers can be used to record accurate time series of the relaxing magnetic field produced by pre-polarised SPIONs. We have investigated dry in vitro maghemite nanoparticle samples with different size distributions (average radii ranging from 14 to 21 nm) and analysed their relaxation using the Néel–Brown formalism. Fitting our model function to the magnetorelaxation (MRX) data allows us to extract the anisotropy constant K and the saturation magnetisation MS of each sample. While the latter was found not to depend on the particle size, we observe that K is inversely proportional to the (time- and size-) averaged volume of the magnetised particle fraction. We have identified the range of SPION sizes that are best suited for MRX detection considering our specific experimental conditions and sample preparation technique
Bis-TEGylated poly(p-benzamide)s: combining organosolubility with shape persistence
The synthesis of perfectly planar, bis-substituted aromatic polyamides is reported herein. With highly flexible triethylene glycol chains attached and conformational restriction through intramolecular, bifurcated hydrogen bonds these are among the most shape-persistent yet organo-soluble polymers to date. Starting from 4-nitrosalicylic acid, our group developed a route to phenyl-2,5-bis-TEGylated aminobenzoate, which could be polymerized by addition of lithium bis(trimethylsilyl)amide (LiHMDS). Since this technique has not been applied to step-growth polycondensations of polyaramides so far, the influence of two different solvents and an N-protective group was investigated. Therefore, substituted phenyl aminobenzoate derivatives carrying a free amine or an N-protective group have been polymerized. Additionally, the tendency for self-assembly of the readily soluble bis-TEGylated poly(p-benzamide) was observed by transmission electron microscopy (TEM) in the dried state. Dynamic light scattering (DLS) measurements of chloroform solutions did not indicate the formation of aggregates. Thus, intermolecular interactions, which other aromatic polyamides typically exhibit, are prevented. The access to bis-substituted, entirely rigid poly(p-benzamide)s via this new polycondensation method paves the way for exciting new structures in materials science and supramolecular chemistry
UV-protection of wood surfaces by controlled morphology fine-tuning of ZnO nanostructures
One of the most significant limitations for a wider utilisation of the renewable and CO2-storing resource wood is its low ultraviolet (UV) light stability. The protection of the wood surface without altering its aesthetic appeal requires an optically transparent but UV protective coating which should be strongly attached to the rough and inhomogeneous substrate. For this purpose, ZnO nanostructures were deposited onto the wood surface via a chemical bath deposition process. The morphology of crystalline ZnO was controlled by aluminium nitrate or ammonium citrate in the growth step resulting in nanorod arrays or platelet structures, respectively. Detailed structural, chemical and mechanical characterisations as well as accelerated weathering exposure revealed the effective performance of the platelet structure, which formed a dense and thin ZnO coating on spruce. The total colour change (ΔE in the CIE system) was calculated to be 20.5 for unmodified wood, while it was about three for the modified samples after 4 weeks accelerated weathering test. Moreover, the ZnO coating also suppressed crack initiation and propagation indicating a substantial increase in durability
Literature review on the performance of diffusive samplers for the measurement of ammonia in ambient air and emissions to air
The information in this document has formed the basis from which a new standard on measurements employing ammonia diffusive samplers by CEN TC264 WG11 'Ambient air - Diffusive samplers' is being developed and provides an open reference document for the ammonia passive sampling techniques
Virus removal in ceramic depth filters: the electrostatic enhanced adsorption approach
Diese Arbeit untersucht den Einsatz von keramischen Materialien in der Trinkwasseraufbereitung mittels Filtration und fokussiert dabei die Entfernung von Viren. Herkömmliche, auf Kieselgur basierende Tiefenfilter (Filterkerzen) mit Porengrößen im unteren Mikrometerbereich, werden hinsichtlich ihres Rückhaltevermögens gegenüber Kolloiden (Viren sowie Polystyrolpartikel) untersucht, um deren Einsatzfähigkeit in der Entfernung von Mikroorganismen im Allgemeinen abschätzen zu können. Ferner wird gezeigt, wie durch ein einfaches Verfahren solche Filter modifiziert werden können, um auch kleinste Viren mit ca. 30 nm Durchmessern aus dem Rohwasser zu entfernen. Die Zugabe von MgO während der Granulierungsstufe im Herstellungsprozess der Filterkerzen bewirkt eine erhebliche Verbesserung des Virenrückhalts bis zu über 99.9999%. Die experimentellen Ergebnisse wurden dabei mit theoretischen Modellen verglichen, um Aussagen über die Mechanismen der Virenentfernung treffen zu können.:Contents
Chapter I Introduction 1
Chapter II Removal or inactivation of microorganisms, in particular viruses, for drinking water purposes with focus on small-scale, decentralised systems: A literature review 7
II. I Physical and chemical treatments 8
II. II Filtration processes 10
II. III Conclusions 15
Chapter III Mechanisms of adsorption in depth filtration 17
III.I Surface charge and the electrical double layer 18
III.II van der Waals interactions 22
III.III DLVO theory 23
III.IV Non-DLVO forces 25
III.V Extended DLVO Theory 27
Chapter IV Virus adsorption studies 29
IV.I A literature review 30
IV.I.I Virus concentration by adsorption-elution 33
IV.I.II Improved virus adsorption in filtration 35
IV.II The electrostatic enhanced adsorption approach 37
Chapter V Viruses 39
V.I Literature review 40
V.I.I Structure and morphology 40
V.I.II The viral life cycle 41
V.I.III Human pathogenic viruses in the aquatic environment 42
V.II Experimental 46
V.II.I The choice of viruses for adsorption studies 46
V.II.II Propagation and enumeration of the bacteriophages 48
V.II.III Characterisation of bacteriophages 51
V.III Results and discussion 54
V.III.I Production of high-titre and high-purity phage stocks 54
V.III.II Characteristics of bacteriophages 59
V.III.III Detection of a viral contaminant - the ‘Siphophage’ 64
Chapter VI The diatomaceous earth-based depth filter 69
VI.I Literature review 70
VI.I.I Diatomaceous earth 70
VI.I.II Retention of microorganisms in the DE-based depth filter 71
VI.II Experimental 73
VI.II.I Manufacturing the depth filter 73
VI.II.II Physical characterisation 74
VI.II.III Performing filter retention tests 75
VI.II.IV Latex retention test 76
VI.II.V Studying adsorption kinetics in a batch experiment 79
VI.II.VI Applying (X-)DLVO theory 80
VI.III Results and discussion 83
VI.III.I Characterisation of the depth filter 83
VI.III.II Latex removal in the depth filter 86
VI.III.III Filter performance on virus removal 94
VI.III.IV Batch-sorption experiments 99
VI.IV Summary and conclusions 102
Chapter VII The magnesium oxide modified depth filter 103
VII.I Experimental 104
VII.I.I Choice of the adsorbent material 104
VII.I.II Manufacturing the MgO-modified filter and characterisation methods 105
VII.II Results and discussion 106
VII.II.I The adsorbent: Magnesium oxide powder 106
VII.II.II Physical characterisation of modified depth filters 108
VII.II.III Virus removal in depth filters containing MgO 113
VII.II.IV Ageing behaviour of MgO modified filters 118
VII.II.V Discussion on the removal mechanisms 130
VII.III Summary and conclusions 134
Chapter VIII Summary, conclusions and outlook 135
VIII.I Summary and conclusions 136
VIII.II Outlook 137
Abbreviations, symbols and physical constants 139
Reference list 14