published_or_final_version / Botany / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 1998. / Includes bibliographical references (leaf 108-117).

Les travaux concernent la mise au point et l'étude de microcapsules de composés naturels réticulés pour des applications en cosmétologie. / The study deals with the development of microcapsules from reticulated natural products, for cosmetological applications.

The goal of this thesis was to develop a process of producing small monodisperse alginate gel beads. The phenomenon of controlled jet break-up of alginate solution jet with assisted vibration was used to form uniform sodium alginate droplets which were subsequently crosslinked with divalent calcium ion to form gel beads. Producing uniform alginate beads below 500 microns has been a problem which previous researchers have faced. Also, there is no commercially viable system available which can produce microbeads of uniform size. This study was an attempt to solve some of these problems. Vibration was applied to the alginate solution jet in both axial and transverse direction to cause jet break-up. Also, different modes of transmitting the vibration to the jet, like vibrating the full assembly or vibrating a diaphragm, were investigated. This resulted in construction of different types of bead generator apparatus. The droplet formation involves the formation of a jet through an orifice and superposition of vibration in order to control the break-up the jet. Both of these fluid flow phenomena depend on the properties of the liquid used to form the droplets. Specifically, the viscoelastic properties of the liquid play a major role in determining the break-up dynamics of the jet. The rheology of the Keltone LV (alginate) solutions (1-2% w/v) was studied using a rotational Bohlin CS-50 Rheometer and a Clark High Shear Capillary Viscometer. The best results were obtained by using the axial vibrating diaphragm droplet generator. Good monodispersed beads (160-1000 microns) were produced by using two different size orifices 100 micron and 200 microns. The vibration frequency range used was 200-6000 Hz and the flowrate range was 2-7 ml/min. The alginate droplets were crosslinked in 0.1 M calcium chloride and the shrinkage of the alginate droplets due to gelation was studied over a period of 7 days. Based on our study a design for producing sub-100 micron size beads has been proposed which uses a piezoceramic crystal for producing high frequency vibrations. / Graduation date: 1997

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 152-176).

Thesis (Ph.D.)--Drexel University, 2008. / Includes abstract and vita. Includes bibliographical references (leaves 216-237).

Thesis (Ph. D.)--Virginia Commonwealth University, 2010. / Prepared for: Dept. of Microbiology & Immunology. Title from resource description page. Includes bibliographical references. Unavailable until 5/12/2020.

Nanoscale zero-valent iron (NZVI) particles and iron cross-linked alginate (FCA) beads were successfully used for the first time for phosphate removal and recovery. NZVI was successfully used for phosphate removal and recovery. Batch studies indicated a removal of ~96 to 100% phosphate in 30 min (1, 5, and 10 mg PO43--P/L with 400 mg NZVI/L). Phosphate removal efficiency by NZVI was 13.9 times higher compared to Microscale ZVI (MZVI) particles. The successful rapid removal of phosphate by NZVI from aqueous solution is expected to have great ramification for cleaning up nutrient rich waters. The presence of sulfate, nitrate, and humic substances and the change in ionic strength in the water marginally affected phosphate removal by NZVI. A maximum phosphate recovery of ~78% was achieved in 30 min at pH 12. Novel iron cross-linked alginate (FCA) beads were synthesized, characterized and used for phosphate removal. The beads removed up to 37-100% phosphate from aqueous solution in 24 h. Freundlich isotherm was found to most closely fit with experimental data and the maximum adsorption capacity was found to be 14.77 mg/g of dry beads. The presence of chloride, bicarbonate, sulfate, nitrate, and natural organic matters in aqueous solution did not interfere in phosphate removal by FCA beads. The phosphate removal efficacy FCA beads was not affected due to change in pH (4-9). Nanosacle zero-valent iron (NZVI) and iron cross-linked alginate beads were also tested for phosphate removal using actual wastewater treatment plant effluent and animal feedlot runoff. The FCA beads could remove ~63% and ~77% phosphate from wastewater and feedlot runoff in 15 min, respectively. Bioavailability of phosphate was examined using algae and higher plants. Phosphate and iron bioavailability of the NZVI sorbed phosphate was examined by supplying spent particles (NZVI with sorbed phosphate) to Tyee Spinach (Spinacia oleracea) and algae (Selenastrum capricornutum). Results revealed that the phosphate was bioavailable for both the algae and spinach. Also, presence of the nanoparticles enhanced the algae growth and plant growth and increases in biomass and plant length were observed. Iron (from spent NZVI) was found to be bioavailable for spinach.

Calcium alginate gels are widely used in the biotechnology, food, and pharmaceutical industries for cell immobilization, food additives, and controlling the release of therapeutic agents. Different gelation conditions can lead to different gel structures which affects the diffusion of solutes in gels, thus mathematical models were developed to describe diffusion and calcium alginate gel formation. This thesis on calcium alginate gel formation is divided into two parts, each with a mathematical model and corresponding experimental study. The objectives of this thesis were to: 1) Determine the significance of mass transfer resistance and estimate diffusion and mass transfer coefficients for calcium ions, glucose, and acetaminophen diffusing into calcium alginate gel. 2) Develop a moving boundary model of calcium alginate gel formation which predicts the rate of gelation. To study the significance of mass transfer resistance and to estimate coefficients, a mathematical model and limiting procedure were developed. This model and experimental study indicated that mass transfer resistance is significant for calcium ions and glucose, but not acetaminophen, diffusing into calcium alginate gel. The limiting algorithm developed to simultaneously estimate the diffusion and mass transfer coefficients is very sensitive to experimental error, but shows promise in situations with small numbers of accurate data points taken from non-interacting homogeneous gel systems. The model of calcium alginate gel formation was based upon a moving boundary problem, solved numerically using the implicit method of finite differences, and programmed in FORTRAN. This study of the rate of calcium alginate gel formation indicated that increasing the concentration of calcium ions and/or decreasing the concentration of alginate increases the rate of gelation. The predicted gelation rates from this mathematical model were in good agreement with the measured gelation rates based upon stoichiometric binding coefficients, experimental initial concentrations of calcium ions and alginate, and diffusion coefficients of Ca������ and alginate. / Graduation date: 1997