- Toronto, Canada
Huu Doan
Toronto Metropolitan University, Chemical Engineering, Faculty Member
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The objective of the present study was to minimize membrane fouling of a latex solution either through improving the membrane surface charge or using a pretreated feed. Hydrophilic polysulphone (PSU) and Ultrafilic flat membranes, with a... more
The objective of the present study was to minimize membrane fouling of a latex solution either through improving the membrane surface charge or using a pretreated feed. Hydrophilic polysulphone (PSU) and Ultrafilic flat membranes, with a molecular weight cut-off (MWCO) of 60 000 and 100 000 dalton, respectively, were implemented under a constant flow rate and cross-flow mode in ultrafiltration of simulated latex effluent. Hydrophobic polyvinylidene difluoride membrane (PVDF) with a MWCO of 100 000 dalton was also tested. The influence of linear alkyl benzene sulphonate (LAS) on the ionic strength of the simulated latex effluent and the surface charge of latex particles at different LAS concentrations was investigated. LAS was also used, at different concentrations and various treatment times, to ensure the enhancement of the antifouling characteristics of the membrane surface. It was concluded that the LAS-treated membrane surface is much more favourable than the pH-changed feed pre-treatment. As such, the total mass of fouling decreased by 44.00 % and 29.60 % in the cases of treated PVDF membrane surface with LAS at a concentration of 0.0001 g/L, and treated latex feed at pH 11, respectively. Nevertheless, LAS was considered to be an ineffective pre-treatment for limiting the fouling propensity of latex solutions using hydrophilic membranes even at high concentrations and long treatment times.
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Abstract The goal of the present study is to gain an in depth understanding of the influences of air injected concurrently and counter currently on membrane fouling and permeate flux for homogeneous Polycarbonate (PC) and heterogeneous... more
Abstract The goal of the present study is to gain an in depth understanding of the influences of air injected concurrently and counter currently on membrane fouling and permeate flux for homogeneous Polycarbonate (PC) and heterogeneous Polysulfone (PS) membranes in the cross-flow ultrafiltration (UF). The Synchrotron-based X-ray microtomography (SR-µCT) technique, available at the biomedical imaging and therapy (BMIT) beamlines at the Canadian Light Source (CLS), answered the key research questions related to quantitative analysis and the visualization of particle depositions, layer by layer, in heterogeneous membrane matrices that would otherwise be opaque to optical access. In particular, high photon flux to achieve high resolution is infeasible, using lab-based radiography systems. SR-µCT was used to assess the influence of air injection on membrane fouling in each membrane layer of PS membrane matrices. A multiphase cross-flow filtration and the hydrodynamics was simulated, in the rectangular filtration channel, using computational fluid dynamics (CFD) at different air velocities. Furthermore, the scanning electron microscope (SEM) and confocal microscope imaging were used at different positions of the membranes to examine the influences of the velocity profiles on membrane fouling. SR-µCT innovative techniques proved that counter current air flow resulted in the elimination of membrane fouling at the top layers, but severe fouling between intermediate and lower layers of the investigated region inside the PS membrane matrices using counter-current air injection compared to concurrent air injection. These results indicate more particle deposited and trapped inside membrane matrices when air was injected counter-currently, which led to more turbulences and a reduction of the permeate flux. On the other hand, top layer indices depict strongly fouling on the bare PS without air injection. CFD analyses supported the experimental results, where the concurrently injected air was more effective in increasing the shear rate and reducing the concentration polarization while reducing turbulences and vortexes, as compared to the counter currently injected air. This innovative study is the first to report the SR-µCT for investigating membrane fouling in UF process for water and wastewater treatment.
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Abstract End stage renal disease (ESRD, or kidney failure) affects ∼10% of the world’s population. Kidney transplantation, which best duplicates native kidney function, can extend the lifespan, but the number of available kidneys does not... more
Abstract End stage renal disease (ESRD, or kidney failure) affects ∼10% of the world’s population. Kidney transplantation, which best duplicates native kidney function, can extend the lifespan, but the number of available kidneys does not meet current demand; furthermore, the potential for organ rejection is ever-present, requiring life-long immunosuppression to address the associated risk of life-threatening infections. Hemodialysis (HD) is a life-sustaining extracorporeal blood purifying treatment for ESRD patients. However, this membrane-based therapy is associated with acute side effects, life-threatening chronic conditions, and unacceptably high morbidity and mortality. Current HD membranes are limited in terms of two key aspects: bio-incompatibility and poor clearance of middle-molecule (MM) uremic toxins. Renal Replacement Therapies (RRT) have several modalities, one of which involves the careful purification of patients’ blood volumes in dialyzers. These blood samples come in contact with non-physiologic dialyzer membrane materials with varying molecular structures, surface chemistries and symmetries. With cellulose HD membranes, health concerns of the complexities by their contact with blood have almost led to their complete discontinuity. For cellulose dialysis membranes, hydroxyl groups within their polymer chains initiates complement, leukocyte and even coagulation activations upon contact with blood, leading to several cardiovascular diseases. The principal factor behind some of these drawbacks has been addressed in this review, in an attempt to improve hemobiocompatibility and reduce health complications. Solutions are proffered within the bounds of material science, biomedicine and surface chemistry from outlined published experimental results in scientific investigations. This review focuses on biocompatibility as a factor that determines the consequences of surface/blood interactions during HD therapy, with special attention to the historical developments of cellulosic hemodialyzer membranes. The reintroduction of acetylated cellulose as well as the advantages of new generation cellulose triacetate (CTA) membranes have also been addressed. Recent progresses on the development of cellulose HD membranes has been vividly discussed while recent challenges and future perspectives have also been highlighted in line with selective removal of uremic toxins using cellulosic HD membranes. In the quest to improve quality of life for critically RRT patients undergoing HD, the use of membranes with sustainable biocompatibility are encouraged. This review centers beyond the different avenues of minimizing the health complications associated with biological pathways activation from cellulosic membrane materials. New approaches toward improvement of hemocompatibility have been reviewed to include the effect of complete acetylation of cellulose (CTA) membrane on inflammation. For instance, carbazate modified cellulosic membranes have supported the complete elimination of carbonylated proteins, and their effects on pH stability have been widely explained. In line with designing hybrid adsorption systems with hemodialysis membranes, this review has also highlighted beyond sustainable techniques for removing all uremic toxins in serum samples of chronic kidney disease (CKD) patients. New insights and perspectives have also been highlighted to focus on selective removal of uremic toxins using cellulose membranes.
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Proteins in dairy streams result in organic fouling and function loss for ceramic membrane's porous structure. Synchrotron‐based X‐ray microtomography (SR‐µCT) is a new method with a high signal to noise ratio and accordingly... more
Proteins in dairy streams result in organic fouling and function loss for ceramic membrane's porous structure. Synchrotron‐based X‐ray microtomography (SR‐µCT) is a new method with a high signal to noise ratio and accordingly significant level of accuracy. The goal of this study was to perform an in situ assessment of ceramic membrane fouling in the dairy stream filtration process, using SR‐µCT. This study attempted to assess porosity variation and membrane fouling through different layers from the top, middle, and bottom layers of the ceramic microfiltration membrane before and after skimming milk filtration. Molecular dynamics simulation (MDS) was used for depth understanding of milk protein interactions with the ceramic membrane. Fouling was found to be more intense on the top of the ceramic membrane even though the top layer was slightly more porous, which indicates that top layers were more prone to fouling. A regression model was derived to correlate the porosity loss due ...
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Gaining an in-depth understanding of the characteristics and dynamics of ultrasound (US)-generated bubbles is crucial to effectively remediate membrane fouling. The goal of present study is to conduct in-situ visualization of US-generated... more
Gaining an in-depth understanding of the characteristics and dynamics of ultrasound (US)-generated bubbles is crucial to effectively remediate membrane fouling. The goal of present study is to conduct in-situ visualization of US-generated microbubbles in water to examine the influence of US frequency on the dynamics of microbubbles. This study utilized synchrotron in-line phase contrast imaging (In-line PCI) available at the biomedical imaging and therapy (BMIT) beamlines at the Canadian Light Source (CLS) to enhance the contrast of liquid/air interfaces at different US frequencies of 20, 28 and 40 KHz at 60 Watts. A high-speed camera was used to capture 2,000 frames per second of the bubble cavitation generated in water under the ultrasound influence. Key parameters at the polychromatic beamlines were optimized to maximize the phase contrast of gas/liquid of the microbubbles with a minimum size of 5.5 mu m. ImageJ software was used to analyze the bubble characteristics and their behavior under the US exposure including the microbubble number, size, and fraction of the total area occupied by the bubbles at each US frequency. Furthermore, the bubble characteristics over the US exposure time and at different distances from the transducer were studied. The qualitative and quantitative data analyses showed that the microbubble number or size did not change over time; however, it was observed that most bubbles were created at the middle of the frames and close to the US field. The number of bubbles created under the US exposure increased with the frequency from 20 kHz to 40 kHz (about 4.6 times). However, larger bubbles were generated at 20 kHz such that the average bubble radius at 20 kHz was about 6.8 times of that at 40 kHz. Microbubble movement/traveling through water was monitored, and it was observed that the bubble velocity increased as the frequency was increased from 20 kHz to 40 kHz. The small bubbles moved faster, and the majority of them traveled upward towards the US transducer location. The growth pattern (a correlation between the mean growth ratio and the exposure time) of bubbles at 20 kHz and 60 W was obtained by tracking the oscillation of 22 representative microbubbles over the 700 ms of imaging. The mean growth ratio model was also obtained.
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The capability of wheat straw to adsorb Ni2+ and Zn2+ was investigated using a batch system. The equilibrium removal of metal ions was obtained between 2.5 and 5h for Ni2+ and about 3h for Zn2+ over the initial concentration range from 5... more
The capability of wheat straw to adsorb Ni2+ and Zn2+ was investigated using a batch system. The equilibrium removal of metal ions was obtained between 2.5 and 5h for Ni2+ and about 3h for Zn2+ over the initial concentration range from 5 to 150ppm. Of the total amount of metal uptake by wheat straw, about 50% was adsorbed in the first 30min. At a low initial concentration of 5ppm, wheat straw was capable to reduce the metal concentration down to less than 1ppm. For single-metal solutions, among the three models tested, namely the Langmuir, the Freundlich and the Temkin isotherms, the Freundlich model was suitable to describe the adsorption equilibrium for Ni2+ and Zn2+. For bimetal solutions, the IAST-Freundlich multicomponent isotherm best fitted the experimental data, among the four isotherm models investigated, the modified Langmuir multicomponent model, the Langmuir partially competitive model, the Freundlich multicomponent model and the IAST-Freundlich multicomponent model. The negative Gibbs free energy changes obtained at lower concentrations indicates that the adsorption was spontaneous. However, the spontaneity of the biosorption decreased with increases in the metal concentration from 5 to 50ppm. For metal concentrations higher than 50ppm, the adsorption became non-spontaneous. Scanning electron microscopic (SEM) images of wheat straw were also taken to exam the surface structure of the wheat straw along with the energy dispersive spectrum (EDS) analysis. The results obtained confirmed the adsorption of Ni2+ and Zn2+ on wheat straw, and showed that the inner surface of the wheat straw appeared to provide more adsorption sites for metal binding.
Research Interests: Engineering, Environmental Engineering, Chemistry, Renewable Energy, Modeling, and 15 moreBiosorption, Corrosion Engineering, Adsorption, Desalination, Gibbs Free Energy, Metal, Nickel, Ni, CHEMICAL SCIENCES, Scanning Electron Microscope, Metal ion, Langmuir, Experimental Data, Competition Model, and Model test
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Biosorption of Cd2+ and Cu2+ by wheat straw (Triticum sativum) using a batch system and a continuous up-flow fixed-bed column was studied. For the batch system, the effect of pH over a range from 3.0 to 7.0 and the temperature from 20 to... more
Biosorption of Cd2+ and Cu2+ by wheat straw (Triticum sativum) using a batch system and a continuous up-flow fixed-bed column was studied. For the batch system, the effect of pH over a range from 3.0 to 7.0 and the temperature from 20 to 40°C on the metal removal was investigated. Various initial metal concentrations from 20 to 150mgL−1 were used.
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Abstract A continuous weighing technique was developed for measuring urea transfer (carbamide, a fertilizer) from a single opening on a coated sphere in a stagnant liquid. Urea release was determined from the changes of the particle... more
Abstract A continuous weighing technique was developed for measuring urea transfer (carbamide, a fertilizer) from a single opening on a coated sphere in a stagnant liquid. Urea release was determined from the changes of the particle weight with time. Mass transfer ...
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ABSTRACT Vapor extraction (VAPEX) is a solvent-based process for the recovery of oil sands. The objective of this work was to investigate on the enhancement of oil recovery in the VAPEX process by varying the solvent injection pressure... more
ABSTRACT Vapor extraction (VAPEX) is a solvent-based process for the recovery of oil sands. The objective of this work was to investigate on the enhancement of oil recovery in the VAPEX process by varying the solvent injection pressure with time. To that end, lab-scale experiments were designed and carried out to investigate this concept. Three different simulated mediums with permeabilities of 204, 102 and 51 Darcy; two heavy oils with viscosities of 14,500 mPa s and 20,000 mPa s; and two physical reservoir model heights of 25 and 45 cm were considered. Butane at four different injection pressures close to the dew point was injected for 6-7 h. It was found that the temporal variation of solvent injection pressure enhanced the extraction process significantly; resulting in an increase in live oil production by 20-30%. Pulse changes in pressure were found to be more effective in increasing the production in comparison with other pressure versus time policies. These results demonstrate that the solvent pressure variations potentially enhance the oil recovery process in VAPEX.
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... 16) Aggarwal, JK; Talbot, L. Electrochemical Measurements of Mass Transfer in Semi-Cylindrical Hollows. Int. J. Heat Mass Transfer1979, 22, 61. ... J. Measurement of Local Mass Transfer Coefficients in A Packed Bed of Pall Rings using... more
... 16) Aggarwal, JK; Talbot, L. Electrochemical Measurements of Mass Transfer in Semi-Cylindrical Hollows. Int. J. Heat Mass Transfer1979, 22, 61. ... J. Measurement of Local Mass Transfer Coefficients in A Packed Bed of Pall Rings using The Electrochemical Technique. MA Sc. ...
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The carbon footprint of buildings is mainly attributed to the embodied carbon of building materials and their hygrothermal performance. In recent years, the search for materials with low gray energy and better hygrothermal performance has... more
The carbon footprint of buildings is mainly attributed to the embodied carbon of building materials and their hygrothermal performance. In recent years, the search for materials with low gray energy and better hygrothermal performance has increased. Foamed geopolymers are among the materials that are attracting a lot of attention. Their high hygrothermal performance and the fact that they can be synthesized from abundant earth elements at ambient hygrothermal conditions are the main reasons for their growing popularity. Foamed geopolymers can also be produced from commonly available industrial wastes providing new opportunities for a circular economy. Many studies have been done to engineer these materials for specific applications in water purification, catalysis, thermal insulation, hazardous waste encapsulation, and acoustic isolation. Several recent papers have been discussing the mechanical features of geopolymers. Recent reviews also focus on the processing, applications, and properties of foamed geopolymers. However, a review about the impact of manufacturing parameters on porosity, pore nucleation, and pore parameters is still missing. These parameters determine the intrinsic and extrinsic thermal isolation properties of foamed geopolymers. This article aims to address this research gap. The effects of pore-forming agents, molar ratios of oxides, water, curing temperature, and pH on the microstructure of foamed geopolymers are discussed in this paper. The influences of these factors on intrinsic and extrinsic pore parameters are presented.