Department of Chemical Engineering and Applied Chemistry

Permanent URI for this collectionhttps://hdl.handle.net/1807/10028

Chemical Engineering and Applied Chemistry at the University of Toronto is one of the oldest and largest departments of its kind in North America. It has a rich history dating back to John Dalton of Dalton's Atomic Theory and a modern reputation based on its state-of-the-art research achievements.

The Department continues to pursue research in pure science, in engineering fundamentals and engineering applications.

News

Browse

Now showing 1 - 20 of 69

Open Access
Microfluidic extensional flow device to study mass transfer dynamics in polymer microparticle formation process
(2024) Sundar, Suryavarshini; Nirmal, Ghata; Borkar, Suraj; Goel, Sachin; Ramachandran, Karthik; Kochhar, Ransom; Hukkanen, Eric J; Chiarella, Renato A.; Ramachandran, Arun
Polymer microparticles are often used to encapsulate drugs for sustained drug-release treatments. One of the ways they are manufactured is by using a solvent extraction process, in which the polymer solution is emulsified into an aqueous bulk phase using a surfactant as a stabilizing agent, followed by the removal of the solvent. The radius of a polymer drop decreases as a function of time until the polymer reaches the gelling point, after which it is separated and dried. Among the various operating parameters, the rate of solvent extraction is a critical step that affects the morphology and porosity, and consequently, the kinetics of drug release. But a fundamental mechanistic understanding of the solvent extraction dynamics as a function of shear is still unexplored. In this study, we have developed an experimental mass transfer model to predict the extraction by using the microfluidic extensional flow device (MEFD) to probe the shear and extraction dynamics at the level of a single drop in a linear extensional flow field. We used a computer-controlled feedback algorithm to manipulate the flow field and hydrodynamically trap a Hele-Shaw drop and observe the extraction process. For the polymer solution, we used a biocompatible polymer, poly-lactic-co-glycolic acid (PLGA) with ethyl acetate (EtOAc) as the solvent. Our experiments were conducted by varying the extensional rate(G) in the channel from ~0.1 s−1 to ~10s−1 , and using an analytical solution of the flow field, we captured the dissolution process and measured the change in drop radius( R) with time( t) . Interestingly, we initially observed a short-time asymptote R~ t, and later the long-time asymptote of R = constant; both trends were physically explained. The transport model developed in this work can be used to predict extraction rates and polymer microparticle composition for any polymer-solvent system. This work is also an important contribution to the literature on mass transfer mechanisms in partially miscible emulsions
Open Access
Low Yield Stress Measurements with a Microfluidic Rheometer
(Royal Society of Chemistry, 2024) Kavishvar, Durgesh; Ramachandran, Arun
Yield stress, 𝜏𝑦, is a key rheological property of complex materials such as gels, suspensions, and emulsions. While there is a range of established techniques to measure 𝜏𝑦 in the order of tens to thousands of pascals, the measurement of low 𝜏𝑦, specifically below 1 Pa, remains underexplored. In this article, we present the measurement of low apparent 𝜏𝑦 using a Hele-Shaw microfluidic extensional flow device (MEFD). In the MEFD, we observe a gradient in shear stress, 𝜏, such that 𝜏 is lower near the center or stagnation point, and higher away from the stagnation point. For a yield stress fluid, we observe that, below a certain flow rate, 𝜏 exceeds 𝜏𝑦 only in an outer region, leading to stagnation or unyielding of the fluid in the inner region. We use scaling analysis based on a Hele-Shaw linear extensional flow to deduce 𝜏𝑦 by measuring the size of the unyielded region, 𝑆. We validate this scaling relationship using carbopol solutions with concentrations ranging between 0.0015 to 0.3%, measuring 𝜏𝑦 as low as ~1 mPa to ~1 Pa, and comparing it with 𝜏𝑦 measured using a standard rheometer. We further report 𝜏𝑦 of human blood samples between 30 mPa to 80 mPa with their hematocrit ranging between 14 to 63%. Additionally, we determine 𝜏𝑦 for a mucus simulant (~0.7 Pa), and lactic drink (~7 mPa) to demonstrate the versatility of the MEFD technique.
Open Access
Regeneration of direct air CO2 capture liquid via alternating electrocatalysis
(Elsevier, 2023-08-02) Xu, Yi; Liu, Shijie; Edwards, Jonathan P.; Xiao, Yurou Celine; Zhao, Yong; Miao, Rui Kai; Fan, Mengyang; Chen, Yuanjun; Huang, Jianan Erick; Sargent, Edward H.; Sinton, David
The direct air capture (DAC) of carbon dioxide (CO2) can potentially contribute to mitigating past and offsetting hard-to-abate future emissions; however, the regeneration of DAC capture liquids requires high temperatures and thermal energy inputs with emissions that diminish their net environmental benefit. Here, we present a low-temperature electrochemical process to regenerate alkaline capture liquids via alternating electrocatalysis (AE). Colocating oxidation and reduction reactions on a single electrode, cycled between electrolyzer and fuel cell modes, mitigates film formation and losses in the regeneration of alkali hydroxide and hydrogen halide. CO2 can be captured and released with an energy input of 6.4 GJ/tCO2 at 100 mA cm−2 and an emission intensity of ∼11 kg CO2e/tCO2.
Open Access
Lab on a chip for a low-carbon future
(2023-02-15) Datta, Sujit S; Battiato, Ilenia; Fernø, Martin A; Juanes, Ruben; Parsa, Shima; Prigiobbe, Valentina; Santanach-Carreras, Enric; Song, Wen; Biswal, Sibani Lisa; Sinton, David
Transitioning our society to a sustainable future, with low or net-zero carbon emissions to the atmosphere, will require a wide-spread transformation of energy and environmental technologies. In this perspective article, we describe how lab-on-a-chip (LoC) systems can help address this challenge by providing insight into the fundamental physical and geochemical processes underlying new technologies critical to this transition, and developing the new processes and materials required. We focus on six areas: (I) subsurface carbon sequestration, (II) subsurface hydrogen storage, (III) geothermal energy extraction, (IV) bioenergy, (V) recovering critical materials, and (VI) water filtration and remediation. We hope to engage the LoC community in the many opportunities within the transition ahead, and highlight the potential of LoC approaches to the broader community of researchers, industry experts, and policy makers working toward a low-carbon future.
Open Access
Conversion of CO2 to multicarbon products in strong acid by controlling the catalyst microenvironment
(Nature Research, 2023-02-09) Zhao, Yong; Hao, Long; Ozden, Adnan; Liu, Shijie; Miao, Rui Kai; Ou, Pengfei; Alkayyali, Tartela; Zhang, Shuzhen; Ning, Jing; Liang, Yongxiang; Xu, Yi; Fan, Mengyang; Chen, Yuanjun; Huang, Jianan Erick; Xie, Ke; Zhang, Jinqiang; O’Brien, Colin P.; Li, Fengwang; Sargent, Edward H.; Sinton, David
Electrosynthesis of multicarbon products from the reduction of CO2 in acidic electrolytes is a promising approach to overcoming CO2 reactant loss in alkaline and neutral electrolytes; however, the proton-rich environment near the catalyst surface favours the hydrogen evolution reaction, leading to low energy efficiency for multicarbon products. Here we report a heterogeneous catalyst adlayer—composed of covalent organic framework nanoparticles and cation-exchange ionomers—that suppresses hydrogen evolution and promotes CO2-to-multicarbon conversion in strong acid. The imine and carbonyl-functionalized covalent organic framework regulates the ionomer structure, creating evenly distributed cation-carrying and hydrophilic–hydrophobic nanochannels that control the catalyst microenvironment. The resulting high local alkalinity and cation-enriched environment enables C–C coupling between 100 and 400 mA cm−2. A multicarbon Faradaic efficiency of 75% is achieved at 200 mA cm−2. The system demonstrates a full-cell multicarbon energy efficiency of 25%, which is a twofold improvement over the literature benchmark acidic system for the reduction of CO2.
Open Access
Energy- and carbon-efficient CO2/CO electrolysis to multicarbon products via asymmetric ion migration–adsorption
(2023-01-12) Ozden, Adnan; Li, Jun; Kandambeth, Sharath; Li, Xiao-Yan; Liu, Shijie; Shekhah, Osama; Ou, Pengfei; Zou Finfrock, Y.; Wang, Ya-Kun; Alkayyali, Tartela; Pelayo García de Arquer, F.; Kale, Vinayak S.; Bhatt, Prashant M.; Ip, Alexander H.; Eddaoudi, Mohamed; Sargent, Edward H.; Sinton, David
Carbon dioxide/monoxide (CO2/CO) electrolysis provides a means to convert emissions into multicarbon products. However, impractical energy and carbon efficiencies limit current systems. Here we show that these inefficiencies originate from uncontrolled gas/ion distributions in the local reaction environment. Understanding of the flows of cations and anions motivated us to seek a route to block cation migration to the catalyst surface—a strategy we instantiate using a covalent organic framework (COF) in bulk heterojunction with a catalyst. The π-conjugated hydrophobic COFs constrain cation (potassium) diffusion via cation–π interactions, while promoting anion (hydroxide) and gaseous feedstock adsorption on the catalyst surface. As a result, a COF-mediated catalyst enables electrosynthesis of multicarbon products from CO for 200 h at a single-pass carbon efficiency of 95%, an energy efficiency of 40% and a current density of 240 mA cm−2
Open Access
High-throughput parallelized testing of membrane electrode assemblies for CO2 reduction
(Royal Science of Chemistry, 2022-10-17) Kose, Talha; O'Brien, Colin P.; Wicks, Joshua; Abed, Jehad; Xiao, Yurou Celine; Sutherland, Brandon; Sarkar, Amitava; Jaffer, Shaffiq A.; Sargent, Edward H.; Sinton, David
High-throughput characterization of electrochemical reactions can accelerate discovery and optimization cycles, and provide the data required for further acceleration via machine-learning guided experiment planning. There are a range of high-throughput methods available for catalyst discovery. However, the development and testing of electrochemical systems – integrated electrocatalysts, membranes, and electrodes – currently relies on serial, labor-intensive lab processes. Membrane electrode assembly (MEA) cells have shown particular promise in carbon dioxide (CO2) reduction, providing commercially viable reaction rates. Experimental testing of MEAs is slow, requiring a serial assembly process that can result in electrode compression levels that are non-uniform over the cell area and challenging to reproduce. Here we demonstrate a new MEA testing system that offers an accelerated, parallelized assembly process and enables high-throughput electrochemical system testing. The approach accelerates electrochemical system testing, controls compression and improves repeatability and reliability. We benchmark our system with CO2 reduction to ethylene, running 10 MEA experiments in parallel, demonstrating an acceleration factor up to 12× over conventional approaches, and achieving a cell-to-cell gas selectivity deviation of ±2.5%.
Open Access
Permselective MOF-Based Gas Diffusion Electrode for Direct Conversion of CO2 from Quasi Flue Gas
(American Chemical Society, 2022-11-22) Al-Attas, Tareq; Nabil, Shariful Kibria; Zeraati, Ali Shayesteh; Shiran, Hadi Shaker; Alkayyali, Tartela; Zargartalebi, Mohammad; Tran, Thien; Marei, Nedal N.; Al Bari, Md. Abdullah; Lin, Haiqing; Roy, Soumyabrata; Ajayan, Pulickel M.; Sinton, David; Shimizu, George; Kibria, Md Golam
Industrial activities lead to a substantial share of current anthropogenic CO2 emissions and are some of the most challenging to abate. Direct utilization of industrial flue gases to produce fuels or value-added chemicals is challenging due to the presence of impurities and low concentrations of CO2. Herein, we demonstrate a rational assembly of a permselective gas diffusion electrode (PGDE) for direct CO2 conversion from quasi flue gas (i.e., 10–15% CO2, 4% O2, and N2 balance at 100% relative humidity). The electrode design consists of a metal–organic framework (MOF) based mixed matrix membrane (MMM) that enables the selective permeation of CO2 to a silver electrocatalyst. The MOF is CALF-20, notable for the ability to physisorb CO2 in wet gas streams. Applying this approach, we convert N2-diluted CO2 streams to CO at a faradaic efficiency of 95% compared to 58% for the nonmodified counterpart electrode with MMM. The PGDE retained its electrochemical performance when introducing O2 by preventing ∼84% loss of current toward parasitic oxygen reduction reaction (ORR) and reported 30 mA cm–2 CO partial current density. Further, wetting the gas stream showed a negligible effect on the MOF and the electrochemical performance. Using our PDGE, we report nearly constant CO selectivity over 19 h in a membrane electrode assembly electrolyzer. This approach offers the potential for direct utilization of low-concentration CO2 while avoiding the economic and environmental costs of obtaining purified CO2 feedstocks.
Open Access
Direct Carbonate Electrolysis into Pure Syngas
(Royal Science of Chemistry, 2022) Celine Xia, Y; Gabardo, C. M.; Liu, S.; Lee, G; O’Brien, C; Miao, R. K; Xu, Y.; Edwards, J; Fan, M; Huang, J. E; Sargent, E. H; Li, J; Papangelakis, P; Alkayyali, T; Sedighian, Rasouli; Zhang, J; Sinton, David
Syngas, a mixture of carbon monoxide (CO) and hydrogen (H2), is a feedstock for a wide variety of chemical processes and is currently produced from fossil fuels. The need to reduce carbon dioxide (CO2) emissions motivates the production of syngas from atmospheric CO2, powered by renewable electricity. Current CO2 electrolyzers require costly separation processes to purify the CO2 reactant stream and to remove unreacted CO2 from the product stream. We demonstrate direct carbonate electrolysis (DCE) in a reactive capture system that avoids the initial CO2 purification process and produces pure syngas with sufficient CO content for direct industrial use (H2/CO ratios of 1 – 2). The DCE system incorporates a composite CO2 diffusion layer (CDL) that attains high CO selectivity by achieving high alkalinity and available CO2 concentration at the cathode. Applying this strategy, we produce pure syngas in the cathode outlet gas stream with a H2/CO ratio of 1.16 at 200 mA cm-2, corresponding to a CO Faradaic efficiency (FE) of 46% and an energy intensity of 52 GJ tsyngas-1. By eliminating intensive upstream and downstream processes, DCE achieves syngas production with 13% less energy than CO2 electrolysis combined with water electrolysis, 39% less energy than past carbonate reduction work, and 75% fewer emissions than the conventional fossil fuel based route.
Open Access
Toxicity of nanoplastics to zooplankton is influenced by temperature, salinity, and natural particulate matter
(Royal Science of Chemistry, 2022-06-23) Lins, Tiago F.; O'Brien, Anna M.; Kose, Talha; Rochman, Chelsea M.; Sinton, David
Plastic pollution is ubiquitous and understanding its environmental effects is a matter of urgency. Nanoplastics (NPs) are the smallest class of plastic pollution, and may elicit more detrimental biological effects than larger plastic particles. However, nanoplastic toxicity may depend on variable environmental parameters, such as temperature, salinity and the presence of other particulate matter—a parameter set too large for conventional toxicity measurement approaches. We applied a high-throughput approach to examine toxic effects of NPs on A. franciscana across 112 combinations of temperature (three levels, 15–29 °C), salinity (four levels, 35–261 g L−1 salts), and particulate matter (humic acids or natural colloids at 5 g L−1, or none) and NP particles (4 levels, 0–100 mg L−1). The influence of experimental conditions on toxicity to A. franciscana strongly depended on NP surface charge. We did not observe any effects from negatively charged NPs over 48 hours. There was not any mortality caused by positively charged NPs below 100 mg L−1 at room temperature (22 °C), but there was decreased survival and motility by more than 50% at higher salinities and warmer temperature. The extent to which natural particulates mitigated nanoplastic toxicity to A. franciscana (up to 20%), and the retention of NPs inside A. franciscana were also temperature- and salinity-dependent. In sum, we found nanoplastic toxicity to A. franciscana varies greatly across ecologically relevant ranges of temperature and salinity, highlighting the importance of environmental conditions to nanoplastic effects on this species. Our findings hinged on the combinatorial experimental treatments that our automated system enabled, demonstrating the power of high-throughput platforms for ecotoxicology.
Open Access
Genetic engineering of extremely acidophilic Acidithiobacillus species for biomining: Progress and perspectives
(Elsevier, 2022-06-26) Chen, Jinjin; Liu, Yilan; Diep, Patrick; Mahadevan, Radhakrishnan
With global demands for mineral resources increasing and ore grades decreasing, microorganisms have been increasingly deployed in biomining applications to recover valuable metals particularly from normally considered waste, such as low-grade ores and used consumer electronics. Acidithiobacillus are a genus of chemolithoautotrophic extreme acidophiles that are commonly found in mining process waters and acid mine drainage, which have been reported in several studies to aid in metal recovery from bioremediation of metal-contaminated sites. Compared to conventional mineral processing technologies, biomining is often cited as a more sustainable and environmentally friendly process, but long leaching cycles and low extraction efficiency are main disadvantages that have hampered its industrial applications. Genetic engineering is a powerful technology that can be used to enhance the performance of microorganisms, such as Acidithiobacillus species. In this review, we compile existing data on Acidithiobacillus species' physiological traits and genomic characteristics, progresses in developing genetic tools to engineer them: plasmids, shutter vectors, transformation methods, selection markers, promoters and reporter systems developed, and genome editing techniques. We further propose genetic engineering strategies for enhancing biomining efficiency of Acidithiobacillus species and provide our perspectives on their future applications.
Open Access
A macrotransport equation for the Hele-Shaw flow of a concentrated suspension
(Cambridge University Press, 2021-10-10) Chakraborty, Sourojeet; Ramachandran, Arun
A depth-averaged, convection-dispersion equation is derived for the particle volume fraction distribution in the pressure-driven flow of a concentrated suspension of neutrally-buoyant, non-colloidal particles between two parallel plates, by implementing a two time-scale perturbation expansion of the suspension balance model (Nott and Brady, J. Fluid Mech., 1994) coupled with the constitutive equations of Zarraga et al. (J. Rheol., 2000). The Taylor-dispersion coefficient in the macrotransport equation scales as U 3 2cB /a , where Uc is the characteristic depth-averaged velocity, B is the half depth of the channel and a is the particle radius. Taylor dispersion relaxes gradients in the depth-averaged volume fraction along the local velocity vector. Perpendicular to the flow, however, only shear-induced migration can cause particle redistribution, leading to fluxes down gradients in volume fraction, shear rate and streamline curvature that scale as Uca 2/B . The ratio of the Taylor dispersion flux relative to the shear-induced migration flux is proportional to B 4/a 4, and can be large even for an aspect ratio of B /a = 10. For lateral length scales in the Hele-Shaw geometry that exceed the induction length for shear-induced migration, one only needs to solve two coupled partial differential equations in the pressure and depth-averaged volume fraction, which can be implemented on standard numerical solvers. The macrotransport equation thus greatly reduces the complexity of the determination of velocity and particle distributions in Hele-Shaw suspension flows. Analogous to the macrotransport equation for suspension flow through a circular tube [Ramachandran, J. Fluid Mech. (2013)], the evolution of the particle volume fraction distribution is dependent only on the total strain experienced by the suspension, and is independent of the suspension velocity scale. However, unlike the tube problem, a positive concentration gradient along the flow direction does not reach a steady state; rather, it is susceptible to viscous miscible fingering. A linear stability analysis performed for a step increase in the volume fraction in the direction of flow with a velocity U reveals that the growth rate and wavenumber corresponding to fastest growing mode scale as U a 2/B 3 and a 2/3/B 5/3, respectively, in accordance with the predictions of the theory of Tan and Homsy (Phys. Fluids , 1986).
Open Access
The Effect of Burning NCG on Lime Kiln Flame Patterns
(PAPTAC, 2005) Aloqaily, Arafat; Kuhn, David C.S.; Sullivan, Pierre; Tran, Honghi
The stability of the burner flame is critically important in lime kiln operation. It can be affected greatly if noncondensible gases (NCG) are burned in the kiln. A Flow Simulation Apparatus was used to study the mixing and interaction between a simulated main burner jet and a simulated NCG burner jet in a confined cylindrical duct. The results show that the angle of the NCG jet with respect to the duct axis is the dominant factor in determining the mixing and interaction between the two jets. The lateral expansion rate of both jets decreases with an increase in Reynolds number (Re) and in Craya-Curtet number (Ct) of the jets. The expansion of the jet is important, because it determines the shape of the flame (long or bushy), the temperature and heat transfer in the kiln, and whether the flame may impinge on the kiln walls. The results also show that the recirculation zones in the confined duct are longer with two jets than they are with a single jet. This implies that burning NCG tends to lower the temperature of the main burner.
Open Access
Numerical Prediction of Flame Length in Lime Kilns
(PAPTAC, 2007) Aloqaily, Arafat; Kuhn, David C.S.; Sullivan, Pierre; Tran, Honghi
The variation of flame length in lime kilns was numerically investigated using the standard κ−ε model. The results are consistent with experimental measurements, showing that the Craya-Curtet number (Ct) and excess air are the dominant parameters affecting the flame length. The results also show that increasing Ct increases the flame length, while increasing excess air decreases it. The flame length can be controlled using Ct and excess air, which in turn, can be adjusted by primary air and ID fan speed.
Open Access
An Optimized Bistable Metabolic Switch To Decouple Phenotypic States during Anaerobic Fermentation
(American Chemical Society, 2018-10-30) Venayak, Naveen; Raj, Kaushik; Jaydeep, Rohil; Mahadevan, Radhakrishnan
Metabolic engineers aim to genetically modify microorganisms to improve their ability to produce valuable compounds. Despite the prevalence of growth-coupled production processes, these strategies can significantly limit production rates. Instead, rates can be improved by decoupling and optimizing growth and production independently, and operating with a growth stage followed by a production stage. Here, we implement a bistable transcriptional controller to decouple and switch between these two states. We optimize the controller in anaerobic conditions, typical of industrial fermentations, to ensure stability and tight expression control, while improving switching dynamics. The stability of this controller can be maintained through a simulated seed train scale-up from 5 mL to 500 000 L, indicating industrial feasibility. Finally, we demonstrate a two-stage production process using our optimal construct to improve the instantaneous rate of lactate production by over 50%, motivating the use of these systems in broad metabolic engineering applications.
Open Access
Debittering Moringa oleifera (Lam.) Leaves in Fortified South Indian Instant Soup
(Springer Nature, 2020-05-27) Chan, Y. K. Kiki; Gurumeenakshi, G.; Varadharaju, N.; Cheng, Yu-Ling; Diosady, Levente L.
Introduction: Moringa oleifera (Lam.) is a nutritious plant species that has the potential to alleviate food insecurity in low- and middle-income regions. However, the bitter taste associated with M. oleifera leaves is a key barrier to its acceptance as food. It was hypothesized that reducing the bitterness in M. oleifera-fortified instant soups would increase their acceptance. Methods: Acid soaking and the addition of a sweetener (aspartame) were examined for their effectiveness in the removal of bitter taste in M. oleifera leaves. 50 assessors rated the acceptance and perceived bitterness in a randomized complete block sensory evaluation. South Indian instant soup samples with 0%, 50% and 100% replacement of vegetable powder with M. oleifera leaf powder were evaluated. Results: Acceptance for M. oleifera-fortified instant soups was higher for samples with lower perceived bitterness. Addition of sweetener was found to be effective in increasing the acceptability and reducing the perceived bitterness at the 50% replacement level, but not at the 100% replacement level. Perceived bitterness did not decrease in formulations with acid-soaked M. oleifera leaves. Conclusions: Undesirable organoleptic properties need to be masked or removed for the acceptance of M. oleifera leaves as a regular food. We recommend that foods fortified with M. oleifera to include a sweet excipient to reduce the bitter tastes. Implications: Fortified instant soup samples with reduced perceived bitterness had increased acceptability. Debittered M. oleifera-fortified foods would appeal to consumers, which would increase their consumption and could lead to reduced prevalence of micronutrient deficiencies.
Open Access
Platinum Stability at the Cathode of an Anion Exchange Membrane Fuel Cell
(Springer Nature, 2020-02-05) Xie, Lin; Kirk, Donald W.
The determination of catalyst stability is as important as the determination of catalyst activity but receives much less attention because of the time required for measurement. Accelerated potential cycling tests do not always reflect the conditions experienced by catalysts operating in a fuel cell environment. Pt cathode electrodes operating at high steady-state potentials (0.8–1 V) in proton exchange membrane fuel cells (PEMFCs) have been reported to degrade due to Pt migration. Whether this phenomenon also occurs in anion exchange membrane fuel cells (AEMFCs) is not clear. In this study, an AEMFC with a Pt on Vulcan® carbon (Pt/C) cathode electrode was operated at 0.9 V steady-state potential for 1500 h. The electrode activity measured using an in situ reference electrode was found to decrease with time. Two significant changes in the Pt catalyst were found; the first was that the finely dispersed Pt catalyst agglomerated on the carbon substrate to form large clusters. The second change was that Pt was found in the polymer membrane structure. The results show that AEMFCs have similar stability concerns as PEMFCs regarding Pt catalyst material at cathodes electrodes.
Open Access
National Near Road Monitoring Workshop - Summary and Recommendations
(2020-03) Evans, Greg
The National Near Road Monitoring Workshop held on November 4, 2019, and attracted 80 in-person and on-line participants from federal, provincial, regional and municipal government agencies, non-governmental organizations, and academia. Presentations by stakeholders in the morning summarized findings and provided context. More in-depth descriptions of research projects were provided through a poster session after lunch. Breakout discussions in the afternoon, both in person and on-line, identified many ways to further mobilize and follow-up on the findings from this study. These are compiled in this report in terms of 1) ways stakeholders can work together to reduce exposure, and 2) recommended follow-up actions.
Open Access
The interfacial tension of the water-diluted bitumen interface at high bitumen concentrations measured using a microfluidic technique
(ACS Publications, 2019-10-20) Goel, Sachin; Joshi, Niyati; Uddin, Muhammad Siraj; Ng, Samson; Acosta, Edgar Joel; Ramachandran, Arun
The interfacial tension (IFT) is a critical parameter to inform our understanding of the phenomena of drop breakup and droplet-droplet coalescence in sheared water-in-diluted bitumen (dilbit) emulsions. A microfluidic extensional flow device (MEFD) was used to determine the IFT of the dilbit - water emulsion system for bitumen concentrations of 33%, 50% and 67% by weight (solvent to bitumen ratio (S/B) = 2, 1 and 0.5, respectively) and two different pH values of water: 8.3 and 9.9. The IFT was observed to increase with the bitumen concentration, and decrease significantly upon lowering the water pH. The time scale for achieving the steady state IFT increased with bitumen concentration, and was less sensitive to the water pH. But the most important feature of our measurements is that the IFTs recorded here were several times smaller than the values reported in the literature. We recognized two important differences between our studies and prior investigations: measurement of the IFT of water drops in dilbit as opposed to dilbit drops in water in earlier studies, and time scales of measurement of IFT that ranged from hundreds of milliseconds to a few seconds, as compared to a minute or longer in past investigations. These differences were examined carefully, but neither was found to explain the low IFTs measured in our studies. Our work leads to the following hypothesis: the mechanical properties of a sheared water-bitumen interface are significantly different from a stagnant one.
Open Access
Near-Road Air Pollution Pilot Study Final Report Appendices
(2019-10) Evans, Greg
These appendices provide detailed descriptions of the study sites, instruments and database, along with additional results.

Browse

Recent Submissions