Controlling the size and size distribution of colloidal nanoparticles have gained extraordinary attention as their physical and chemical properties are strongly affected by size. Ligands are widely used to control the size and size distribution of nanoparticles; however, their exact roles in controlling the nanoparticle size distribution and the way they affect the nucleation and growth kinetics are poorly understood. Therefore, understanding the nucleation and growth mechanisms and developing theoretical/modeling framework will pave the way towards controlled synthesis of colloidal nanoparticles with desired sizes and polydispersity. This dissertation focuses on identifying the possible roles of ligands and size on the kinetics of nanoparticle formation and growth using in-situ characterization tools such as small-angle X-ray scattering (SAXS) and kinetic modeling. The presented work further focuses on developing kinetic models to capture the main nucleation and growth reactions and examines how ligand-metal interactions could potentially alter the rate of nucleation and growth rates, and consequently the nanoparticle size distribution. Additionally, this work highlights the importance of using multi-observables including the concentration of nanoparticles, size and/or precursor consumption, and polydispersity to differentiate between different nucleation and growth models and extract accurate information on the rates of nanoparticle nucleation and growth. Specifically, during the formation and growth of colloidal nanoparticles, complex reactions are occurring and as such nucleation and growth can take place through various reaction pathways. Therefore, sensitivity analysis was applied to effectively compare different nucleation and growth models and identify the most important reactions and obtain a reduced model (e.g. a minimalistic model) required for efficient data analysis. In the following chapters, a more sophisticated modeling approach is presented (population balance model) capable of capturing the average-properties of nanoparticle size distribution. PBM allows us to predict the growth rate of nanoparticles of different sizes, the ligand surface coverage for each individual size, and the parameters involved in altering the size distribution. Additionally, thermodynamic calculations of nanoparticle growth and ligand-metal binding as a function of size and ligand surface coverage were conducted to further shed light on the kinetics of nanoparticle formation and growth. The combination of kinetic modeling, in-situ SAXS and thermodynamic calculations can significantly advance the understanding of nucleation and growth mechanisms and guide toward controlling size and polydispersity. / Doctor of Philosophy / The synthesis of colloidal metal nanoparticles with superior control over size and size distribution, and has attracted much attention given the wide applications of these nanomaterials in the fields of catalysis, photonics, and electronics. Obtaining nanoparticles with desired sizes and polydispersity is vital for enhancing the consistency and performance for specific applications (e.g., catalytic converters for automotive emission). Ligands are often employed to prevent agglomeration and also control the nanoparticle size and size distribution. Ligands can affect the precursor reactivity and therefore the reduction/nucleation by binding with the metal precursor. Nucleation refers to the assimilation of few atoms to form initial nuclei acting as templates for nanoparticle growth. Additionally, ligands can bind with the nanoparticle surface sites and change the rate of surface growth and therefore the final nanoparticle size. Despite strong effects of ligands in the colloidal nanoparticle synthesis, their exact role in the nucleation and growth kinetics is yet to be identified. Additionally, nucleation and growth models capable of unraveling the underlying mechanisms of nucleation and growth in the presence of ligands are still lacking in the literature. Therefore, obtaining nanoparticles with desired sizes and polydispersity mostly relies on trial-and-error approach making the synthesis costly and inefficient. As such, developing models capable of predicting suitable synthesis conditions is contingent upon understanding the chemistry and mechanism involved during nanoparticles formation. Therefore, in this study, novel kinetic models were developed to capture the nucleation and growth kinetics of colloidal metal nanoparticles under different synthetic conditions (different types of solvents, different concentrations of ligand and metal). In-situ SAXS was further employed to measure the average diameter, concentration of nanoparticles, and polydispersity during the synthesis and extract the nucleation and growth rates (evolution of concentration of nanoparticles and size). First, an average-property model was developed to account for ligand-metal bindings and capture the size and concentration of nanoparticles during the synthesis. Then, a more complex modeling approach; PBM, accompanied by the thermodynamic calculations of surface growth and ligand-nanoparticle binding enthalpies was implemented to capture the size distribution. As it will be shown later, the determination of the underlying mechanisms resulted in a highly predictive kinetic model capable of predicting the synthetic conditions to obtain nanoparticles with desired sizes. The proposed methodology can serve as a powerful tool to synthesize nanoparticles with specific sizes and polydispersity.

Yes / The effect of screw configuration on granule size distribution (GSD) using gPROMS FormulatedProduct (gFP) software to perform optimization, estimation of complex processes, and analyses is evaluated. Twin-screw granulation modeling was used to investigate the contribution of screw configuration and liquid-to-solid (L/S) ratio on GSD. Lactose and Avicel were the granulating materials. Twelve different configurations were investigated under three feed rates as consistent with literature and at various L/S ratios. Results indicate that kneading elements promote the recovery of 100–1000 µm granules while reducing the production of oversized granules. Higher feed rates support the production of fines and agglomerates, while a low feed rate produces 100–1000 µm granules. / Ghana Scholarship Secretariat

No / Results of a study on the influence of process parameters such as impeller speed, granulation time and binder viscosity on granule strength and properties are reported. A high shear granulator (Cyclomix manufactured by Hosokawa Micron B.V., The Netherlands) has been used to produce granules. Calcium carbonate (Durcal) was used as feed powder and aqueous polyethylene glycol (PEG) as the binder. The dried granules have been analysed for their strength, density and size distribution. The results show that increasing the granulation time has a great affect on granules strength, until an optimum time has been reached. The underlying cause is an increase in granule density. Granules are consolidated more at higher impeller speeds. Moreover, the granule size distribution seems not to be affected significantly by an increase in impeller speed. Granules produced with high binder viscosity have a considerably lower strength, wide strength distribution due to poor dispersion of binder on the powder bed. Binder addition methods have showed no considerable effect on granule strength or on granule size distribution.

Master of Science / Department of Biological & Agricultural Engineering / Ronaldo G. Maghirang / Large cattle feedlots emit considerable amounts of particulate matter (PM), including TSP (total suspended particulates), PM[subscript]10 (PM with equivalent aerodynamic diameter of 10 μm or less), and PM[subscript]2.5 (PM with equivalent aerodynamic diameter of 2.5 μm or less). Particulate emissions result from pen surface disturbance by cattle hoof action, vehicle traffic on unpaved roads and alleyways, and wind erosion. Research is needed to determine concentrations of various size fractions, size distribution, and emission rates from various sources in feedlots. This research was conducted to measure particle size distribution using laser diffraction method and estimate emissions from unpaved roads and wind erosion. Particle size distribution and concentrations of PM[subscript]10 and PM[subscript]2.5 at a commercial cattle feedlot in Kansas (Feedlot 1) were measured over a 2-yr period. The feedlot had a capacity of 30,000 head and total pen area of 50 ha and was equipped with a sprinkler system for dust control. Collocated low-volume samplers for TSP, PM[subscript]10, and PM[subscript]2.5 were used to measure concentrations of TSP, PM[subscript]10, and PM[subscript]2.5 at the upwind and downwind edges of the feedlot. Dust samples that were collected by TSP samplers were analyzed with a laser diffraction analyzer to determine particle size distribution. Particle size distribution at the downwind edge of the feedlot was also measured with micro-orifice uniform deposit impactor (MOUDI). The laser diffraction method and MOUDI did not differ significantly in mean geometric mean diameter (13.7 vs. 13.0 μm) but differed in mean geometric standard deviation (2.9 vs. 2.3). From laser diffraction and TSP data, PM[subscript]10 and PM[subscript]2.5 concentrations were also calculated and were not significantly different from those measured by low-volume PM[subscript]10 and PM[subscript]2.5 samplers (122 vs. 131 μg/m[superscript]3 for PM[subscript]10; 26 vs. 35 μg/m[superscript]3 for PM[subscript]2.5). Both PM[subscript]10 and PM[subscript]2.5 fractions decreased as pen surface moisture contents increased, while the PM[subscript]2.5/PM[subscript]10 ratio did not change much with pen surface moisture content. Published emission models were used to estimate PM[subscript]10 emissions from unpaved roads and wind erosion at Feedlot 1 and another nearby feedlot (Feedlot 2). Feedlot 2 had a capacity of 30,000 head, total pen surface area of 59 ha, and used water trucks for dust control. Estimated PM[subscript]10 emissions from unpaved roads and wind erosion were less than 20% of total PM[subscript]10 emissions obtained from inverse dispersion modeling. Further research is needed to establish the applicability of published emission estimation models for cattle feedlots.

Doctor of Philosophy / Department of Biological & Agricultural Engineering / Ronaldo G. Maghirang / Emissions of particulate matter (PM) are an increasing concern for large open beef cattle feedlots. Research is needed to develop science-based information on PM emissions and abatement measures for mitigating those emissions. This research was conducted to (1) measure PM concentrations emitted from large cattle feedlots, (2) compare different samplers for measuring concentrations of PM with equivalent aerodynamic diameter of 10 µm or less (PM10), (3) evaluate the relative effectiveness of pen surface treatments in reducing PM10 emissions, and (4) predict PM control efficiency of vegetative barriers. Concentrations of PM with equivalent aerodynamic diameter of 2.5 µm or less (PM2.5), PM10, and total suspended particulates (TSP) upwind and downwind of two large cattle feedlots (KS1, KS2) in Kansas were measured with gravimetric samplers. The downwind and net concentrations generally decreased with increasing water content (WC) of the pen surface; for effective control of PM emissions from feedlots, it appears that pen surface WC should be at least 20% (wet basis). Three types of samplers for measuring PM10 concentrations in feedlots KS1 and KS2 were compared: Tapered Element Oscillating Microbalance™ (TEOM), high-volume (HV), and low-volume (LV) PM10 samplers. Measured PM10 concentration was generally largest with the TEOM PM10 sampler and smallest with the LV PM10 sampler. A laboratory apparatus was developed for measuring the PM10 emission potential of pen surfaces as affected by surface treatments. The apparatus was equipped with a simulated pen surface, mock cattle hooves that moved horizontally across the pen surface, and PM10 samplers that collected emitted PM10. Of the surface treatments evaluated, application of water (6.4 mm) and hay (723 g/m2) exhibited the greatest percentage reduction in PM10 emission potential (69% and 77%, respectively) compared with the untreated manure layer. Computational fluid dynamics (CFD) was applied to predict airflow and particle collection by a row of trees (2.2 m high × 1.6 m wide). Predicted particle collection efficiencies generally agreed with published data and ranged from less than 1% for 0.875-µm particles to approximately 32% for 15-µm particles.

No description available.

A new continuous one-dimensional sedimentation model incorporating a new continuous flocculation model that considers aggregation and fragmentation processes was derived and tested. Additionally, a new procedure to model sediment particle size distribution (PSD) was derived. Basic to this development were three different parametric models: Jaky, Fredlund and the Gamma probability distribution (GPD) were chosen to fit three different glass micro-spheres PSDs having average particle sizes of 7, 25 and 35 microns. The GPD provided the best fit with the least parameters. The bimodal GPD was used to fit ten sediment samples with excellent results (< 5% average error). A continuous flocculation model was derived using the method of moments for solving the continuous Smoluchowski coagulation equation with fragmentation. The initial sediment PSD was modeled using a bimodal GPD. This new flocculation model resulted in a new general moments’ equation that considers aggregation and fragmentation processes, which is represented by a system of ordinary differential equations. The model was calibrated using a genetic algorithm with initial and flocculated PSDs of four sediment samples and four anionic polyacrylamides flocculants. The results show excellent correlation between predicted and observed values (R2 > 0.9878). A new continuous one-dimensional sedimentation model that resulted in a scalar hyperbolic conservation law was derived from the well-known Kynch kinematic sedimentation model. The model was calibrated using column tests results with glass micro-spheres particles. Two different glass microspheres particle size distributions (PSDs) were used with average diameters of 7 and 37 microns. Excellent values of coefficient of determination (R2 > 0.89, except for one test replicate) were obtained for both the small and large glass micro-spheres PSDs. These results suggest that the proposed sedimentation model can be expanded to model the sedimentation process inside a sediment pond.

Baigiamajame magistro darbe „Vamzdyno nuogulų tyrimas ir apibūdinimas“, apžvelgus mokslinės literatūros šaltinius, apibūdintos ant vamzdžių vidinių sienelių susidarančios nuogulos, kurių sudėtyje vyrauja geležies junginiai. Nagrinėjama, kokią įtaką vandens kokybei turi ant skirtingų medžiagų vamzdžių vidinių sienelių susidariusios nuogulos. Aptariama, kokios dėl nuogulų susidarymo iškyla problemos vandentiekio sistemoje. Vilniaus Gedimino technikos universiteto Vandentvarkos katedros laboratorijoje buvo atliktas eksperimentas, sumontavus du eksperimentinius stendus. Juos sudarė skirtingų medžiagų (PE, cinkuoto plieno ir seno plieno) vamzdynų sistemos, kuriomis cirkuliavo skirtingos kokybės vanduo. Buvo nustatyta kiekybinė ir kokybinė nuogulų sudėtis. Kiekybinė sudėtis apibūdinta ChDS pokyčiu, esant skirtingai vandens išbuvimo trukmei vamzdyne. Kokybinę sudėtį apibūdina geležies, mangano junginių, amonio jonų, nitritų ir nitratų koncentracijos vandenyje. Tai pat nustatyta vamzdyno nuogulų granuliometrinė sudėtis. Atlikus tyrimus paaiškėjo, kad bendrosios geležies koncentracija mažiausia buvo PE, o didžiausia – seno plieno vamzdyno mėginiuose. PE vamzdyne mangano koncentracija didėjo ilgėjant vandens užsistovėjimo trukmei. Amonio jonų, nitritų ir nitratų kiekiai mėginiuose neviršijo higienos normų. PE vamzdynų nuogulų ChDS rodikliai buvo mažiausi abiejuose stenduose. Palyginus eksperimentinių stendų nuogulų mėginių rezultatus, paaiškėjo, kad ChDS reikšmės priklauso nuo vandens... [toliau žr. visą tekstą] / In the Master‘s Thesis "The research and characterization of pipeline scales" the literature review of scientific sources was described pipeline scales which contains predominantly iron compounds. The impact of water quality on the pipeline scales was investigated. Negative impact of the formation of pipeline scales on water distribution system was analysed. Experimental investigation was carried out in the laboratory scaled equipment at Water Management Department of VGTU. Experimental pipelines consist of different materials (galvanized steel, old steel and polyethylene (PE)) pipe system with circulated different water quality. The quantitative and qualitative composition of the scales was measured. The quantitative composition was described of the change of COD under different water age in to the different pipelines. The qualitative composition was described by iron, manganese compounds, ammonium, nitrite and nitrate concentrations in water. It was also set the particle size content of pipeline scales. Results showed that the lowest iron concentration was in PE pipe samples and the highest in an old steel pipe samples. The concentration of manganese increased with increasing duration of water age in PE pipe. Ammonium ions, nitrite and nitrate levels didn't exceed the requirements of hygiene norm. The lowest COD rates were in PE pipe scales in both laboratory scaled equipments. It was found that COD values depend on the quality of water that circulated in pipeline. It was... [to full text]

While realistic in vitro testing of dry powder inhalers (DPIs) can be used to establish in vitro–in vivo correlations (IVIVCs) and predict in vivo lung doses, the aerodynamic particle size distributions (APSDs) of those doses and their regional lung deposition remains unclear. Four studies were designed to improve testing centered on the behavior of Novolizer®. Different oropharyngeal geometries were assessed by testing different mouth-throat (MT) models across a realistic range of inhalation profiles (IPs) with Salbulin® Novolizer®. Small and large Virginia Commonwealth University (VCU) and Oropharyngeal Consortium (OPC) models produced similar ranges for total lung dose in vitro (TLDin vitro), while results for medium models differed significantly. While either group may be selected to represent variations in oropharyngeal geometry, OPC models were more difficult to use, indicating that VCU models were preferable. To facilitate simulation of human IPs through DPIs, inhalation profile data from a VCU clinical trial were analyzed. Equations were developed to represent the range of flow rate vs. time curves for use with DPIs of known airflow resistance. A new method was developed to couple testing using VCU MT models and simulated IPs with cascade impaction to assess the APSDs of TLDin vitro for Budelin® Novolizer®. This method produced IVIVCs for Budelin’s total lung dose, TLD, and was sufficiently precise to distinguish between values of TLDin vitro and their APSDs, resulting from tests using appropriately selected MT models and IPs. For example, for slow inhalation, TLD values were comparable in vivo and in vitro; TLDin vitro ranged from 12.2±2.9 to 66.8±1.7 mcg aerosolized budesonide while APSDs in vitro had mass median aerodynamic diameters of 3.26±0.27 and 2.17±0.03 µm, respectively. To explore the clinical importance of these variations, a published computational fluid dynamic (CFD) model was modified and coupled to accept the output of realistic in vitro tests as initial conditions at the tracheal inlet. While simplified aerosol size metrics and flow conditions used to shorten CFD simulations produced small differences in theoretical predictions of regional lung deposition, the results broadly agreed with the literature and were generally consistent with the median values reported clinically for Budelin.

PhD thesis - Faculty of Science / The main aim of this thesis has been to study the way in which Fe(III) and Co(II) incorporation into Si-MCM-41 synthesis gels affects the properties of the unmodified material. Another aim was to investigate the influence of these hetero-atoms on the dispersion and particle size distribution as well as the catalytic activity of supported Au nanoparticles in the CO oxidation reaction. Si-MCM-41 has been successfully synthesized in this work using mixtures containing CTAB as a structure-directing agent (SDA) and water-glass as a SiO2 source. Replacement of water-glass with pre-calcined Si-MCM-41 for SiO2 source in the secondary synthesis step has produced Si-MCM-41 with improved structural properties (XRD, HRTEM and Raman spectroscopy), including restructured and more crystalline pore walls (Raman spectroscopy). The conventional shortcomings of Si-MCM-41 as a support for catalyticallyactive (transition) metal components such as low hydrothermal stability, low PZC, lack of cation exchange capacity and no reducibility have been partially addressed by modification with Fe(III) and Co(II). The premodification was achieved both during framework synthesis and after synthesis by the incipient wetness impregnation (IWI) method. As opposed to the one-pot synthesis of metal-containing derivatives, the IWI method gave materials with high metal loadings and maximal retention of the properties of pristine Si-MCM-41. On the other hand, metal incorporation during synthesis to a loading of ~8.8 wt% using aqueous solutions of metal precursors showed some collapse of the mesostructure. Consequently methods were sought to incorporate this amount of metal (and up to double, i.e., 16 wt%) with maximal retention of the MCM-41 characteristics. These methods included (i) using Si-MCM-41 as a SiO2 source, (ii) dissolving the metal precursors in an acid solution before inclusion into the synthesis gel, and (iii) using freshly precipitated alkali slurries of the metal precursors. The first method produced a highly ordered 16wt% Fe-MCM-41 material with excellent reducibility (TPR showed three well-resolved peaks) and pore-wall structure (Raman spectroscopy). Like the aqueous route, the acid-mediated metal incorporation route did not produce ordered materials at metal contents of ~16 wt%. The base precipitate route produced highly ordered composite materials up to 16 wt% metal content, with characteristics similar to those of Si-MCM-41 (XRD, BET and HRTEM), although some metal phases were observed as a separate phase on the SiO2 surface. Thus, metal-containing MCM-41 materials could be obtained with conservation of MCM-41 mesoporosity. Raman spectroscopic studies have shown that the effect of transition metal incorporation in MCM-41-type materials is to strengthen the pore walls (shift of Si-O-Si peaks to higher frequencies), while TPR studies revealed that the essentially neutral framework of Si-MCM-41 could be rendered reducible by transition metal incorporation. Gold-containing mesoporous nanocomposites were prepared by both direct synthesis and post-synthetically. Catalysts prepared by direct hydrothermal synthesis were always accompanied by formation of large Au particles because of the need to calcine the materials at 500 oC in order to remove the occluded surfactant template. The presence of transition metal components in Me-MCM-41 (Me = Fe and Co) has been found to play a significant role in the particle size distribution and also the dispersion of Au nanoparticles when these materials were used as supports. In general, a base metal-containing support was found to produce smaller Au nanoparticles than the corresponding siliceous support. It has been proposed that the transition metal components serve as anchoring or nucleation sites for the Au nanoparticles, which are likely to sinter during calcination. The anchoring sites thus retard the surface mobility of Au at calcination temperatures above their TTammann. The use of the Au/Me-MCM-41 materials as catalysts in the CO oxidation reaction has led to the following observations: (i) catalyst on metal-containing supports showed better activity than those on Si-MCM-41, probably due to the induced reducibility in metal-MCM-41, (ii) catalysts prepared by direct synthesis showed inferior activity owing to large Au particles, (iii) increasing Au content improves the catalytic performance, (iv) increasing the Fe content of the support at constant Au improves the catalytic performance, and (v) changing the base metal component of the support from Fe to Co led to a significant improvement in catalytic activity. The similarity of the apparent activation energies (Ea) for the 5 wt% Au-containing 5 wt% Fe- and 5 wt% Co-MCM-41 suggested that the difference in catalytic activity is associated with the number of active sites possessed by each catalyst system. The observed order of catalytic activity of these 5 wt% Au-containing systems in terms of the support type is: Co-MCM-41 > Fe-MCM-41 > Si-MCM-41. This was further supported by the average Au particle size, which, in terms of the support, followed the order Co-MCM-41 < Fe-MCM-41 < Si-MCM-41. Thus, metal-support interactions between Au and MCM-41 have been enhanced by introducing Fe(III) and Co(II), which also induced framework charge, ion exchange capacity (IEC) and reducibility in the neutral siliceous support.