Ion selective gates : active device component for 3D microfluidic architecture

This thesis describes the development of porous ion-transport oxide interconnects that allow molecular communication between microchannels in complex microfluidic architectures. New methods to control the permeability of interconnects to certain species by externally tuneable parameters was investigated. DC electric fields were used to impose a driving force for the transport of selected cationic and anionic species. Electric fields are preferred over pressure gradients in nanochannels, because very large pressure drops are required to drive flow in small channels, while typical operating voltages are below the potential difference required for decomposition of water. Applying an external electric field across the interconnects, a potential difference is created across the membrane, which makes it is possible to selectively drive charged species from one liquid into the other through interconnects, by means of ion migration, Fick diffusion and/or electroosmotic flow

Tailor-Made Nanostructured Ion Selective MCM-48 Membranes

Mesoporous templated MCM-48 silica was prepared using a C16 surfactant as template. The MCM-48 powders and thin films were characterized by different techniques. Two types of porous supports were used, namely macroporous ¿-alumina and silicon microsieves. The supported MCM-48 layers were applied as liquid permeable membranes in pressure-driven nanofiltration and electric field-mediated ion transport experiments

Techno-economic evaluation of an ultrasound-assisted Enzymatic Reactive Distillation process

Enzymatic Reactive Distillation (ERD) is a bioreactive process, in which enzymes are immobilized on column internal surface, and helps to overcome chemical reaction and phase equilibrium limitations. The activation of enzymes by ultrasound (US) leads to ultrasound-assisted ERD (US-ERD) which might display more eco-efficiency than standard processing of valuable chemicals. Reaction rate improvements of more than 50% could be achieved by the assistance of US. An US-ERD process for the synthesis of butyl butyrate (10 kilotons per year, 99 wt% purity) was designed. A techno-economic evaluation via process optimization was carried out to minimize the annual costs, by using an evolutionary algorithm. The techno-economic evaluation shows that the US-ERD process and the ERD share nearly equal costs. Installation costs of the US equipment are high but they are compensated by a 12% lower reactive section height and a 7% lower total height of the US-ERD column in comparison to ERD

The Synthesis and Composition of Dual-Phase 3Y-TZP/RuO2 Electrode Powders

This research was performed to learn more about the electron conducting yttria doped zirconia/ruthenia dual-phase system. The study indicated that for all starting powder precipitates (by either co-precipitation or sequential precipitation) strong separation between the Ru and Zr-species upon heating occurred already at the unexpected low temperature of 100–200°C. The solubility of RuO2 in 3Y-TZP (zirconia stabilised into a tetragonal phase by a 3 mol% Y2O3 addition) after calcination at 600°C was estimated at 3 mol%, independently of the used synthesis technique

Fast initial oxidation of formic acid by the fenton reaction under industrial conditions

The present study investigates the oxidation of formic acid by the Fenton and Fenton-like reaction. An experimental study was performed at industrially relevant conditions, which means that the concentrations of reagents were generally higher than concentrations previously reported. The most interesting result is the fast oxidation rate of formic acid in the first two minutes of the Fe(II)/H2O2 reaction. In an industrial setting this fast initial oxidation can be used to remove a significant part of the formic acid without the need for large reactors with long residence times and large excesses of H2O2 and Fe(II). In contrast, the Fe(III)/H2O2 reaction shows a slower, constant decrease of formic acid over time strongly depending on temperature and H2O2 concentration. The initial decrease in formic acid concentration in the Fe(II)/H2O2 reaction could not be explained by previously proposed kinetic models for formic acid oxidation by the Fenton's reagent. The specific conditions used require a more elaborate kinetic model to describe the results obtained. In the Fe(II)/H2O2 reaction, the formic acid reacts with the [rad]OH radical and forms an [rad]OOH radical that regenerates the Fe(II). The reaction of Fe(III) and the [rad]OOH radical to regenerate Fe(II) and thereby restart the Fe(II)/H2O2 reaction can most likely explain the fast initial decrease observed. Furthermore, the addition of reactions describing the formation and decomposition of inorganic and ferric-formate complexes to the kinetic model improved the fit to all experimental data, in particular for the initial part of the reaction of Fe(II)/H2O2 with formic acid

Pore size and surface chemistry effects on the transport of hydrophobic and hydrophilic solvents through mesoporous y-alumina and silica MCM-48

The structural and solvent transport properties of supported mesoporous γ-alumina and MCM-type silica membranes are reported. Templated mesoporous silica layers and powders were characterized by XRD, permporometry, XPS and BET measurements. The results indicate that the γ-alumina membrane is 1 μm thick, while the silica membrane is 30 nm thick, has a pore size of 2.8–3.4 nm and possesses the MCM-48 structure. Pressure-driven solvent flow experiments on -alumina supported γ-alumina and MCM-48 membranes indicate that the permeabilities of the mesoporous layers depend on the chemical nature of the solvents. The permeability of hexane and toluene through γ-alumina with 4.5–7.5 nm pores is lower than that of hydrophilic alcohols and water. The permeability of water and alcohols through MCM-48 appears to be affected by solvent–pore interactions on molecular scale. The MCM-48 layer has a higher permeability than γ-alumina, which can be attributed to its much smaller thickness

Controlling the transport of cations through permselective mesoporous alumina layers by manipulation of electric field and ionic strength

The electric field-driven transport of ions through supported mesoporous γ-alumina membranes was investigated. The influence of ion concentration, ion valency, pH, ionic strength, and electrolyte composition on transport behavior was determined. The permselectivity of the membrane was found to be highly dependent on the ionic strength. When the ionic strength was sufficiently low for electrical double-layer overlap to occur inside the pores, the membrane was found to be cation-permselective and the transport rate of cations could be tuned by variation of the potential difference over the membrane. The cation permselectivity is thought to be due to the adsorption of anions onto the pore walls, causing a net negative immobile surface charge density, and consequently, a positively charged mobile double layer. The transport mechanism of cations was interpreted in terms of a combination of Fick diffusion and ion migration. By variation of the potential difference over the membrane the transport of double-charged cations, Cu2 +, could be controlled accurately, effectively resulting in on/off tunable transport. In the absence of double-layer overlap at high ionic strength, the membrane was found to be nonselective