André Y. Tremblay

The influence of casting solution structure on the microporosity of polyetherimide gas separation membranes prepared by the coagulation post-leaching method

The microporosity and performance of polyetherimide (PEI) membranes produced by the coagulation post-leaching technique were investigated. Computational chemistry and chemical structure principles indicate that a lithium cation solvated in NMP (N-methyl-2-pyrrolidinone) forms a complex with two NMP molecules. This complex was determined to be stable in NMP and isopropanol but not in methanol or water. Increasing the additive (LiNO3) concentration in the casting solution lead to a greater number of micropores in the 0.7–1.2 nm range, while the peak in the micropore distribution remained unchanged at 1.0 nm. Molecular mechanics calculations indicate that the PEI polymer chain can form coils having an inner section of 0.7nm×1.0 nm. Micropore measurements and computational chemistry results suggest that the inherent size of the PEI polymer coils remains unchanged on the addition of LiNO3 but the number of polymer coils increases. A linear relation was found to exist between the permeance of the membranes to air and micropore volume. Larger micropores were present at higher LiNO3 concentrations and caused a decline in the actual separation factor for these membranes.

Novel applications of membrane processes in soil cleanup operations

A combination of membrane processes, microfiltration and nanofiltration, was employed to enhance the removal of heavy metals from contaminated soil using acid leaching. Microfiltration was used to separate soil particles from the metal-containing leachate. The leachate was then processed using nanofiltration to reduce the leachates volume and recover spent acid from the slurry. Results of the bench-scale study demonstrated the advantages of incorporating membrane processes into soil treatment operations: faster and more complete removal of metals; reduced volume of waste products; and the possibility for acid reuse.

Design and performance of an inorganic MF/polymeric UF hybrid system for the treatment of a difficult waste stream containing both colloidal and micron sized particles☆

Wastewater streams containing colloids, used oils and suspended solids are difficult to treat using membrane technologies. Bilge water accumulating onboard a ship is a typical example of such a wastewater. This paper will discuss the merits of using a back-flushed, small tube, inorganic microfiltration membrane followed by a hollow fiber polymeric ultrafiltration membrane in treating this particular wastewater.

Membranes as fractals: Implication and consequences

Abstract The fractal nature of synthetic membranes suggests a new approach to implement pore size distributions in membrane characterization. The fractal definition of membrane morphology implies that the pore size distribution of a synthetic membrane can be described by a set of three parameters such as the minimum and maximum pore radius and the fractal dimension D . The effect of such a pore size distribution on solute sieving curves has been determined parametrically for the permeation of dilute aqueous solutions of polyethylene glycols through ultrafiltration membranes. These results have been compared to sieving curves obtained from the normal and log-normal pore size distributions which represent the conventional approach in defining the porosity of synthetic membranes.

Correlation of the Transport Properties for the Ethanol-Water System Using Neural Networks

Process design and simulation rely heavily on the accuracy and availability of transport property correlations. General models that combine the properties of pure components often lack the necessary accuracy. In this investigation, neural networks were used to model some important transport properties for the ethanol-water binary system. Specifically, a three-layer feed-forward neural network with six neurons in the hidden layer was used to model viscosity, thermal conductivity, surface tension and the Fick diffusion coefficient based on an array of experimental data. These neural network models were then compared to some conventional models that are commonly used to predict the aforementioned transport properties. The results showed that the neural network models were able to represent the experimental data very well for the system studied. One advantage in using neural network models to represent these properties is their ability to predict complex and interrelated behaviors without a priori information about the underlying model structure. Further, since all the models retain the same simple matrix structure, their integration into computer codes becomes straightforward and non-repetitive.

n-Hexadecane Fuel for a Phosphoric Acid Direct Hydrocarbon Fuel Cell

The objective of this work was to examine fuel cells as a possible alternative to the diesel fuel engines currently used in railway locomotives, thereby decreasing air emissions from the railway transportation sector. We have investigated the performance of a phosphoric acid fuel cell (PAFC) reactor, with n-hexadecane, C16H34 (a model compound for diesel fuel, cetane number = 100). This is the first extensive study reported in the literature in which n-hexadecane is used directly as the fuel. Measurements were made to obtain both polarization curves and time-on-stream results. Because deactivation was observed hydrogen polarization curves were measured before and after n-hexadecane experiments, to determine the extent of deactivation of the membrane electrode assembly (MEA). By feeding water-only (no fuel) to the fuel cell anode the deactivated MEAs could be regenerated. One set of fuel cell operating conditions that produced a steady-state was identified. Identification of steady-state conditions is significant because it demonstrates that stable fuel cell operation is technically feasible when operating a PAFC with n-hexadecane fuel.

Petroleum Diesel and Biodiesel Fuels Used in a Direct Hydrocarbon Phosphoric Acid Fuel Cell

The performance of a direct hydrocarbon phosphoric acid fuel cell, PAFC, was investigated using petroleum diesel, biodiesel, and n-hexadecane as the fuels. We believe this is the first study of a fuel cell being operated with petroleum diesel as the fuel at the anode. Degradation in fuel cell performance was observed prior to reaching steady state. The degradation was attributed to a carbonaceous material forming on the surface of the anode. Regardless of the initial degradation, a steady-state operation was achieved with each of the diesel fuels. After treating the anode with water the fuel cell performance recovered. However, the fuel cell performance degraded again prior to obtaining another steady-state operation. There were several observations that were consistent with the suggestion that the carbonaceous material formed from the diesel fuels might be a reaction intermediate necessary for steady-state operation. Finally, the experiments indicated that water in the phosphoric acid electrolyte could be used as the water required for the anodic reaction. The water formed at the cathode could provide the replacement water for the electrolyte, thereby eliminating the need to provide a water feed system for the fuel cell.