PRISM :: Browsing by Author "Ponnurangam, Sathish"

Browsing by Author "Ponnurangam, Sathish"

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Open Access
Adsorption of Methyl Orange on Activated Carbon: Influence of Cerium Oxide Loading
(2017) Puthoor, Sreelakshmi; Hill, Josephine; Roberts, Edward; Ponnurangam, Sathish
Adsorption by carbon is a commonly used treatment method for the removal of organic contaminants from waste water. The surface properties of activated carbon can be modified to enhance their adsorption affinity for target contaminants. In this study, the influence of cerium oxide loading onto carbon materials with different pore sizes in improving their adsorption capacity for methyl orange, which is an anionic organic pollutant, was analyzed. The adsorption capacity was increased by seven times after cerium oxide loading in mesoporous carbon materials at a pH of 5, whereas in microporous materials there was no notable increase in adsorption capacity. Also, the increase in adsorption capacity was directly proportional to the weight percentage of cerium oxide loading in the mesoporous activated carbon material. Methyl orange adsorbs on cerium oxide through electrostatic interactions. More specifically, the anionic methyl orange is attracted to the localized positive charges on the cerium oxide supported on the carbon materials. Decreasing pH resulted in an increased adsorption capacity likely because of the abundance of protons in the solution, causing an increase in localized positive charge density on the cerium oxide. Results from this study may be extended to more complex systems, such as the adsorption of naphthenic acids contained in oil sands process water.
Open Access
Advanced Oxidative Processes for Treatment of Emerging Contaminants in Water
(2016) Mehrabani-Zeinabad, Mitra; Achari, Gopal; Langford, Cooper; Bergerson, Joule; Tay, Joo-Hwa Andrew; Ponnurangam, Sathish; Surampalli, Rao
In this research, degradation of emerging contaminants in municipal and industrial wastewater was studied by using a variety of advanced oxidation processes. Bisphenol A (BPA) and bisphenol S (BPS) were selected as candidate emerging contaminants in municipal wastewater and sulfolane as a candidate for industrial wastewater. Degradation kinetics of different oxidation processes in spiked water and contaminated wastewater/groundwater were investigated in batch as well as in a flow-through photo-reactor. Degradation of BPA and BPS in spiked water and post-secondary treated wastewater was studied using UVC, UVC/H2O2, O3 and UVA/O3 in a batch photo-reactor. The effective parameters of each process were identified and their impacts on degradation rates were further investigated. Based on the results obtained, the fate of BPA and BPS in municipal wastewater as they move through the UV disinfection unit of a local wastewater treatment plant in Calgary, Canada, was evaluated. It was found that only 1% of BPA and 6% of BPS were degraded in the disinfection unit. However, should 0.042 M H2O2 be added to the wastewater stream entering the disinfection unit, 56% of BPA and 47% of BPS can be degraded. By implementation of O3 and UVA/O3 processes, degradation levels could exceed 95%. Several oxidative methods were used to degrade sulfolane in spiked water and contaminated groundwater in a batch photo-reactor. These include UVA and UVC irradiation with suitable photoactive oxidants, including O3, H2O2, TiO2-based photocatalysis and their combinations. A synergistic effect was observed in the combination of H2O2 and O3 photolysis. The highest rate of sulfolane loss was attributed to UVC/O3/H2O2, UVC/H2O2 and UVC/O3 processes. Finally, the science established in the batch experiments for degradation of the candidate emerging contaminants in municipal and industrial wastewater was further developed into a technology for treating BPS and sulfolane in a flow-through photo-reactor with recirculation. It was found that the most effective process in terms of overall mineralization of BPS and sulfolane in post-secondary treated wastewater and contaminated groundwater, respectively, is the UVC/O3/H2O2 process. The effective parameters were identified and optimized for each of the emerging contaminants.
Open Access
Analysis of Flow and Heat Transfer in OTSGs and Injection Wells
(2023-04-21) Sivagnanam, Mohan; Gates, Ian Donald; Mehrotra, Anil Kumar; Hejazi, Hossein; Ponnurangam, Sathish; Mwesigye, Aggrey; Sanders, Sean R.
Steam for enhanced oil recovery, generated by using once-through steam generators (OTSGs), is injected into extra heavy oil (bitumen) bearing formations to raise the temperature of the oil within. At elevated temperatures, the oil mobility is raised enabling it to be produced to surface. To improve the performance of steam-based processes, the research documented here focuses on two components of the process. The first component is steam generation in OTSGs and the second is injection of steam into the reservoir. More specifically, in the first component, the impact of foulant is examined and how a deliberate flow perturbation can be used to delay the onset of foulant. In the second component, steam flows through slotted liners and flow control devices are investigated. The results show that the thicker the foulant, the higher the outer tube wall temperature and the lower is the water temperature – the foulant acts as an insulator on the inner wall of the tube. Flow perturbations are demonstrated to yield benefits for lowering the outer tube wall temperature. An examination of thermocouples used to measure the temperature of the tube surface in OTSGs is also presented. Simulation results for a thermocouple welded on an OTSG tube showed a discrepancy between the actual temperature and the thermocouple measurement. The use of a radiation shield is shown to provide a better estimate of the bare tube temperature. The analysis of a slotted liner shows that the slot area plays a crucial role in flow distribution within the well and reservoir. Supersonic flow in flow control devices is strongly dependent on steam quality and some of the systems examined exhibited a condensation shock and shock diamonds with exit velocity greater than the inlet. A longer diffuser is shown to minimize the impact of shock waves on the exit velocity.
Open Access
Application of low-cost waste material from the petroleum industry in wastewater treatment and polymer composites
(2022-07-28) Eshraghian, Afrooz; Sundararaj, Uttandaraman; Ponnurangam, Sathish; Yarranton, Harvey
In this thesis, diverse applications of solid petroleum waste, including asphaltene and clay, are discussed. As part of this thesis, it is hypothesized that asphaltene and clay interact with polymers and pollutants in wastewater. By interacting with pollutants, they can adsorb pollutants, and by interacting with polymers, they can disperse in polymers, and thus can be used as adsorbents for wastewater treatment and as fillers in polymer composites. To use asphaltene for adsorbing pollutants from wastewater, it is hypothesized that asphaltene functionalization will change the surface properties of asphaltene, leading to enhanced adsorption. Acid-treated asphaltene is used as an adsorbent for the removal of methyl orange from wastewater. Modified asphaltene has a large surface area and oxygen and nitrogen functionalities, leading to 96% removal of MO from 20 mg/L MO solution. Moreover, the Freundlich isotherm model, pseudo-second-order, and intraparticle diffusion models describe the adsorption process very well. In addition, the asphaltene can be easily regenerated using ethanol, and the removal percent is still 64% after five cycles.The second part investigates the compatibility of different asphaltenes, with different polymers including polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), and polycarbonate (PC). By careful choice of the polarity of asphaltene-polymer pairs, mixing technique, and melt viscosity of the polymer, the dispersion of asphaltenes and final properties of composite materials can be tuned. For example, at 2.5 wt.% of asphaltene, more polar asphaltene showed 26% and 177% larger asphaltene agglomerates in PP and PS, respectively, than the less polar asphaltene. In the third part of this thesis, clay functionalization is hypothesized to improve clay-polymer interactions. Thus, the effect of nanoclay, representative of clay waste from petroleum industry, on dielectric properties in the X-band (8.2-12.4 GHz) of synthesized nitrogen-doped carbon nanotube (N-CNT)/nanoclay/ polyvinylidene fluoride (PVDF) nanocomposites is investigated. The incorporation of nanoclay improves the dielectric properties, i.e., the dissipation factor of N-CNT/PVDF nanocomposites. For instance, incorporation of 0.5 wt% nanoclay into N-CNT/PVDF nanocomposite at 1.0 wt% N-CNT loading results in 61% and 57% reduction in the dissipation factor and agglomeration area ratio, indicating improved N-CNT dispersion in PVDF.
Open Access
Asphaltene Mesoscale Aggregation Behavior in Organic Solvents
(2019-01-10) Ahmadi, Mohammad; Abedi, Jalal; Hassanzadeh, Hassan; Chen, Zhangxin; Ponnurangam, Sathish; Sanati-Nezhad, Amir; Torabi, Farshid
Asphaltenes have received significant attention over the past decade, primarily because of their complex self-assembly behavior that results in their aggregation and deposition either in the reservoir formation or the production facilities. The aggregation and deposition of asphaltenes causes severe problems in both upstream and downstream sectors of the petroleum industry. For this reason, significant effort has been expended in shedding light on the basic molecular and colloidal properties of asphaltenes to identify the key parameters controlling their stability in the crude oil mixture. Molecular simulations provided invaluable information on the main molecular mechanisms leading to the asphaltene aggregation and also the principal intermolecular forces governing this process. However, the high computational cost of these simulation approaches did not allow the scientists to fully produce the aggregation behavior of asphaltenes in the past. In this work, we aimed at studying the asphaltene self-assembly behavior at mesoscales wherein the primary colloidal particles portray the asphaltene nanoaggregates. The Brownian dynamics (BD) simulations have been utilized to investigate the aggregation behavior of asphaltenes in different solvent environments at various volume fractions of asphaltene nanoaggregates under no- and simple shear-flow conditions. The BD simulations enabled us to access significantly larger length and time scales compared to the molecular simulations resulting in complete reproduction of asphaltene aggregation hierarchy. The effects of asphaltene volume fraction, solvent quality, and the shear rate on the kinetics of aggregation, the internal structure of the formed aggregates, and the self-diffusion coefficients of asphaltenes were also discussed.
Open Access
Asphaltene Precipitation from Bitumen/Multicomponent Solvent Mixtures
(2021-03-01) Rivero Sanchez, Javier Alberto; Yarranton, Harvey W.; Ponnurangam, Sathish; Mehrotra, Anil Kumar
Bitumen is sometimes diluted with multicomponent solvents in oilfield processes and it is useful to predict if and how much asphaltenes may precipitate from these mixtures. The Modified Regular Solution (MRS) approach was adapted for these applications. For this purpose, the onset and yield of asphaltene precipitation from heavy oil diluted with multicomponent solvents were determined at temperatures from 21 to 180°C and pressures up to 10 MPa. The solvents considered include: 1) mixtures of n-pentane, n-heptane, cyclohexane, and toluene; 2) petroleum solvents such as condensates, diesel, and kerosene. The asphaltene yields at ambient conditions and high pressures were measured gravimetrically in a bench top apparatus and in a blind cell apparatus, respectively. The onset of asphaltene precipitation was extrapolated from asphaltene yield data at ambient conditions and determined optically at higher pressures with titrations performed in a high-pressure microscope. Temperature dependent binary interaction parameters (BIP) were introduced to a previously developed MRS approach to model asphaltene precipitation from heavy oil diluted with blended pure solvents. BIP for the cyclohexane/asphaltene and toluene/asphaltene pseudo-component pairs were sufficient to match all of the data collected with binary solvent blends. All other BIP were set to zero. The model with the BIP obtained from the binary solvent blends predicted the asphaltene onsets and yields from heavy oil with ternary solvent blends, generally to within the error of the measurements. A methodology to characterize petroleum solvents based on their GC assays to predict their molecular weight, density, and solubility parameters was developed. The methodology was tested against their measured densities at standard conditions and the solubility parameters determined by fitting the MRS model to yield data collected for bitumen diluted with these solvents. The asphaltene yields modeled using the proposed correlations as input to the MRS model matched the experimental data for all but one of the petroleum solvents and their blends with n-heptane with an overall average absolute deviation and bias of 1.1 wt% and -0.8 wt%, respectively. The MRS model did not match the asphaltene yield from the naphtha.
Open Access
Behaviour and Interaction of Calcium and Potassium during Catalytic Gasification
(2019-04-29) Arnold, Ross Alexander; Hill, Josephine M.; Ponnurangam, Sathish; Nassar, Nashaat N.
Gasification is a technique for the conversion of carbon sources such as biomass into syngas. Catalysts reduce the necessary gasification temperature and increase the reaction rate. Potassium is more active than calcium, but calcium addition has been shown to promote the rate of potassium-catalyzed gasification. The mechanism by which this promotion occurs was not well-understood. This thesis used switchgrass and biosolids as carbon feeds, as well as ash-free carbon black to isolate the effects of potassium and calcium. Calcium was found to promote potassium both indirectly and directly. Indirectly, calcium served as a sacrificial species, reacting with aluminosilicates, limiting the sites on which potassium could deactivate by forming catalytically inactive potassium aluminosilicates. X-ray diffraction demonstrated calcium aluminosilicate formation. Directly, calcium carbonate formed a low-melting eutectic phase with potassium carbonate above 820 °C, demonstrated by differential scanning calorimetry and scanning electron microscopy. The eutectic increased the diffusivity of potassium, facilitating the movement of potassium between active carbon sites, increasing the gasification rate below 40% conversion. Above 50% conversion, the eutectic phase inhibited the gasification rate by hindering CO2 diffusion to the carbon. Activation energy calculations showed that diffusion became the rate-determining step at higher conversions. Two mixing methods, hand-mixing and ball-milling, were compared as to their effect on potassium- and calcium-catalyzed gasification. The diffusivity of potassium was high enough that increased dispersion by ball-milling with carbon black did not increase the reaction rate compared to ball-milling the components separately. Ball-milling calcium and carbon black together greatly increased the gasification rate when compared to ball-milling the components separately. The lower diffusivity of calcium compared to potassium explained its lower activity. As the reaction progressed, calcium sintered and hindered CO2 access to the carbon, which reduced the reaction rate even below uncatalyzed carbon black. Reducing the calcium particle size prior to gasification minimized inhibition in addition to increasing catalytic surface area. The experimental results helped to better understand the individual catalytic behaviours of calcium and potassium during gasification, as well as their interactions. The results will help in the design of gasifiers for carbon feeds containing potassium and calcium.
Open Access
Cell Design and Electrode Material for All Vanadium Redox Flow Battery
(2018-03-09) Li, Jialang; Roberts, Edward P. L.; Ponnurangam, Sathish; Mahinpey, Nader; Roberts, Edward
The all-vanadium redox flow battery (VRFB) is one of the most promising renewable energy storage systems due to its high energy efficiency, reliability, design flexibility and environmental friendly. In order to improve the performance of VRFB, cell design and electrode materials were studied in this project. A novel flow field design using a flow going through the porous electrode for the VRFB has been evaluated. By dividing the flow between flow-by and a portion of the flow going through the electrode, a significant improvement in the performance was obtained. A vanadium electrolyte system was used and charging and discharging cycles were performed and compared with the flow-by design. With a portion of flow going through the electrode, the voltage efficiency was increased from 74% to 80% and the voltage loss was decreased by 23%. The results indicate that the “flow through” condition can enhance the mass transfer rate at the surface of electrode. A templated nano-carbon scaffold (NCS) electrode material was evaluated for using in the VRFB. Scanning electron microscopy (SEM) was used to characterize the morphology of the electrode materials. This material has an organized nanoporous structure and the pore size can be as small as 22 nm. To investigate the performance of NCS as an electrode material, the NCS was attached to the surface of conventional carbon paper electrodes. The charge discharge performance of the VRFB was determined using a flow through mode of operation. The performance of nano carbon scaffold (NCS) with different pore size and thickness was compared with a conventional heat-treated carbon paper. The results show that by using nano carbon scaffold (NCS-85-HT), the voltage efficiency increased from 74% to 91% at 10 mA cm-2. The energy efficiency also increased from 56% to 70% at 10 mAcm-2 due to the increased voltage efficiency. The results indicate that the large surface area of the NCS, associated with its nano structure, lead to a reduction in overpotential of around 65%, and thus higher battery efficiencies. Cell performance under different current density was also explored and the improved efficiencies for NCS were maintained at all the current densities studied.
Open Access
Characterization and Kinetic Study of Ilmenite Ores for Methane Chemical-Looping Combustion
(2018-01-12) Khakpoor, Nima; De la Hoz Siegler, Hector; Mahinpey, Nader; Ponnurangam, Sathish; Nassar, Nashaat
Emitted carbon dioxide from fossil fuels combustion is one of the most influential greenhouse gases leading to global warming. Chemical-looping combustion (CLC) is one of the most efficient methods for carbon capture, resulting in no energy penalty compared to alternative carbon capture methods. CLC is a nonconventional unmixed combustion process where the fuel and air reactions occur in separate reactors. CLC is, however, still a conceptual process due to a series of technical challenges, mainly related to the oxygen carrier. In particular, there is a need for a low-cost, highly stable oxygen carrier capable of withstanding multiple cycles without loss of its oxygen transport capacity and reactivity. Reactivity and oxygen-transport capacity of Canadian and commercial ilmenite ores in the chemical-looping combustion of methane were investigated in a thermogravimetric analyzer (TGA). Oxygen carrier performance was evaluated in multiple cycles during which Canadian ilmenite oxygen transport capacity increased from 2.7% to 14.2% and the commercial sample maintained an approximately constant oxygen transport capacity at 4.5%. XRD and SEM results indicate that new phases were formed, and surface morphology was transformed significantly during cyclic operation. The latter experimental finding explains the increased oxygen transport capacity of the Canadian ilmenite. Studies on carbon deposition on the ilmenite surface indicate that lower methane partial pressure and reduction temperatures are favorable to effectively prevent this phenomenon. The kinetic grain model (GM) was found satisfactorily to fit reduction rate data obtained at atmospheric pressure. Intrinsic reaction rates and kinetic parameters were assessed, accordingly. The activation energy values of 106.7 ± 10.6 kJ/mol and 95.0 ± 8.5 kJ/mol were estimated for the Canadian and commercial samples, respectively.
Open Access
Characterization and Removal of High Concentration Silica in Steam-Assisted Gravity Drainage (SAGD) Evaporator Blowdown Wastewater
(2024-05-21) Rao, Saheli; Mehrotra, Anil Kumar; Achari, Gopal; Ponnurangam, Sathish; Lu, Qingye
Evaporator blowdown (EBD) wastewater is a highly alkaline stream generated from the evaporation-based treatment of produced water arising from steam-assisted gravity drainage operations. It contains elevated concentrations of dissolved solids, of which silica poses a major challenge in both the waste stream treatment and its disposal. Silica has a propensity for scaling and fouling the process equipment. Additionally, pH-neutralization of highly concentrated silica brines results in silica gelation. This makes it difficult to filter and dewater before its disposal via down-hole injection. Moreover, the interaction of silica and other chemicals present in the EBD with those in underground formation waters can result in the plugging of the injection wells due to mineral precipitation. In this research, the removal of silica from these concentrated waste streams (largely comprised of brine solution) is investigated, while also understanding the speciation of silica to mitigate challenges during deep well injections. A systematic experimental program was conducted to investigate the effects of SiO2 concentration, NaCl:SiO2 ratio, and pH on the residual silica concentration, percent silica removal, filtration rate, and filtration effectiveness. The objective was to prevent silica gelation. The results indicated that when the NaCl:SiO2 ratios were higher than 4.5, silica precipitation during pH reduction did not lead to the formation of gel or sol. Additionally, the optimal ranges of factors for achieving the maximum silica removal, the highest filtration rate, the best filtration effectiveness, and the minimum residual silica concentration were determined using 3D response surfaces. Further, an investigation into the characterization and treatment of evaporator blowdown was conducted. The impact of acid treatment to remove silica and organics by filtration was studied. Both HCl and H2SO4 gave similar silica and organic removal efficiencies. The HCl-treatment was investigated further with both the EBD and lab-prepared silica solutions for silica removal efficiency and filtration performance. The experiments conducted at ~20°C demonstrated higher silica removal efficiencies at pH of 10 and 8, whereas higher organic removal efficiencies were obtained at pH of 4 and 2. The experiments conducted at an elevated temperature (~80°C) showed enhanced silica removal at a pH of 8 and higher organic removal at a pH of 2. The precipitated solids were characterized using XRD and ATR-FTIR spectroscopy to identify the minerals and functional groups. The XRD patterns demonstrated that the solids generated were amorphous. This research was undertaken to investigate the speciation and saturation indexes of minerals under various process conditions using equilibrium geochemical modelling in EBD wastewater and mixed waters resulting from combining EBD and formation waters. Parameters such as pH, acid type, and temperature were assessed for their impact on the speciation of silica and other species, as well as mineral saturation indices in EBD. Results highlighted the significant influence of pH on the speciation of silica and other species. The addition of either HCl or H2SO4 had no significant effect on the saturation indexes of silicate minerals, or the concentrations of silica and carbonate species. Additionally, simulations were performed for the mixture of untreated EBD and treated EBD at alkaline, neutral, and acidic pH levels with two formation waters. The major species in these mixed waters were silicates, sulphates, and carbonates. Simulations conducted on these mixed waters suggested that disposing of neutral to slightly acidic evaporator blowdown, as opposed to the alkaline EBD, in deep wells is conducive to preventing plugging and clogging issues that may result from mineral precipitation.
Open Access
Chemical modification of petroleum coke and applications of derived materials
(2021-05-07) Huang, Qing; Hill, Josephine M.; Lu, Qingye; Ponnurangam, Sathish
Petroleum coke (petcoke) is a by-product from the oil industry and is a solid product mainly composed of carbon (> 80 wt%) with some impurities. These impurities, in particular sulfur, limit petcoke as feedstock for the application-like fuel. The aim of this thesis was to explore the possible application of petcoke without activation procedure, which took advantage of the highly aromatic structure and high sulfur content (6.5 wt%) of petcoke. Petcoke was used as a precursor for preparing solid acid catalysts through direct functionalization (i.e., without an activation step) with nitric acid to access the inherent sulfur. For comparison, catalysts were also prepared using sulfuric acid and a mixture of nitric and sulfuric acid (1:3 vol ratio). Although compared to the sulfonated petcoke, nitric acid-treated petcoke showed higher strong acidity, the ester yield was lower than that of sulfonated petcoke. The effect of acid treatment conditions and ball milling pretreatment on the nitric acid-treated solid acid catalysts were investigated. Higher treatment temperature resulted in higher total acidity but did not increase the amount of sulfonic acid groups. The acidity increased with the increase of the treatment time and remained stable after 6 hours. However, the yield of the product is not only related to the number of sulfonic groups but shows a negative correlation with total acidity/oxygen-containing functional groups implying the adsorption effect of oxygen-containing functional groups might hinder the esterification reaction. With ball milling pretreatment, the defects and aromatic hydrogen of petcoke increased, which promoted the subsequent acid treatment to obtain more sulfonic acid groups. DFT calculations were used to analyze the pathways of sulfonic acid group formation, and the reaction pathway with NO2• was the most thermodynamically and kinetically preferable. The side product from the nitric acid treatment of petcoke was collected and it showed fluorescence characteristics and therefore was used to synthesis carbon dots-TiO2 photocatalysts, which improved the hydrogen production in the photocatalytic hydrogen generation reaction. The results in this thesis helped to explore the possible modifications and applications for using petcoke and taking advantage of its highly aromatic structure and high sulfur content.
Open Access
Co-Fermentation Strategy for Augmented Carbon Source Availability in Biological Nutrient Removal Systems: Optimization and Performance Evaluation
(2024-09-18) Hosseini Yazdi, Seyed Mohammad Sadegh; Chu, Angus; Achari, Gopal; Black, Kerry; Ponnurangam, Sathish; Hamza, Rania
This research delves into an innovative approach within the field of wastewater treatment, focusing on the co-fermentation of Primary Sludge (PS) with Fermented Sludge (FS), Soft Drink Wastewater (SDWW), and Yeast Wastewater (YWW) to produce volatile fatty acids (VFA). The utilization of waste materials in wastewater treatment, particularly for the synthesis of VFA, represents a significant stride towards sustainable and eco-friendly practices. VFA is crucial intermediates in the biological nutrient removal (BNR) process and play a key role in the anaerobic digestion and biosynthesis of bioplastics and biofuels. The study employs batch fermentation experiments using PS obtained from wastewater treatment facilities, a critical step in the advanced treatment of wastewater. The aim was to investigate the impact of co-substrate addition and different feeding mode on VFA production and composition. Key VFA identified include acetic acid, propionic acid, iso-butyric acid, butyric acid, isovaleric acid, and valeric acid, with acetic acid and iso-butyric acid predominantly yielding the highest. Further, the research explores the optimization of Food-to-Microorganism ratios, temperatures, and mixing conditions. This is in line with the latest advancements in wastewater treatment which emphasize process optimization for enhanced efficiency and sustainability. The findings reveal substantial enhancements in VFA/SCOD ratios under specific operational conditions, indicating a promising avenue for improved biogas production. Microbial community analysis in the study provides deeper insights into the biological aspects of wastewater treatment. Dominant phyla like Bacteroidota, Campilobacterota, Firmicutes, Fusobacteriota, and Proteobacteria were identified, which are instrumental in the biodegradation and nutrient cycling processes in wastewater systems. The study's outcomes hold significant implications for the advancement of wastewater treatment technologies. The addition of biodegradable SDWW and YWW not only improves the fermentation profile but also substantially enhances VFA yields, showcasing the potential of co-fermentation in wastewater treatment. These findings underline the importance of integrating innovative biological processes for effective wastewater management, ultimately contributing to the development of more sustainable, efficient, and eco-friendly treatment strategies.
Embargo
Computational Improvements for PT Flash Calculations: A New Look at the Initiation and Underemphasized Aspects of Calculation Method Modifications
(2024-09-20) Shirazi Manesh, Amir Ahmad; Clarke, Matthew; Maini, Brij; Ponnurangam, Sathish; Yarranton, Harvey; Mehta, Sudarshan; Zendehboudi, Sohrab
Phase equilibrium calculations at constant pressure and constant temperature, PT flash calculations, are at the heart of thermodynamic modeling and simulations. Reliability and efficiency of simulations are heavily dependent on these calculations. Accordingly, there has been many attempts to improve these calculations using the available mathematical tools and the knowledge amassed in this regard is considerable. However, in relation to the characteristics of the problem, it seems that there are still capacities in the mathematical methods and these capacities should be used to attain better results. This study is an attempt to employ the connection between the special structure of the flash problem and the author’s understanding of mathematical methods to improve efficiency of the calculations while preserving reliability of the results. It was found a consideration should be made in design of the unidirectional search algorithms or in application of the line search methods to the problem and effect of making this consideration on flash results was discussed. It was shown that line search methods with a specific search direction can be applied to improve the efficiency of stability test calculations in hard cases. The efficiency of the line search methods with different types of factorization was evaluated and similarity of their abilities was found. With respect to initial guesses required to conduct stability analysis in PT flash calculations, as a global optimization problem, it was shown that considerably smaller sets of guesses, compared to the sets suggested in the literature, can provide the same level of results reliability. Application of these sets to the calculations can lead to a significant computational burden reduction. Two approaches which are customarily used in the stability analysis were evaluated and it was shown that searching for the lowest negative minimum of modified tangent plane distance function can cause considerably extra computational cost for the optimization-based calculations. Using the results, an approach to initialization of the calculations with a previously recommended stability test and prioritization of the guesses in the reduced size sets was suggested. A case of failure of successive substitution method in phase split calculations was reported and a combined line search-trust region method to remedy was suggested. Patterns of stability test and phase split iterations convergence behaviour with respect to the location of successive substitution method basin of attraction in stability test calculations were reported. A modification for line search methods to improve the efficiency of stability test calculations in difficult to converge specifications was introduced.
Open Access
Cytotoxicity, cellular localization and photophysical properties of Re(I) tricarbonyl complexes bound to cysteine and its derivatives
(Springer Nature, 2020-06-24) Capper, Miles S.; Enriquez Garcia, Alejandra; Macia, Nicolas; Lai, Barry; Lin, Jian-Bin; Nomura, Masaharu; Alihosseinzadeh, Amir; Ponnurangam, Sathish; Heyne, Belinda; Shemanko, Carrie S.; Jalilehvand, Farideh
The potential chemotherapeutic properties coupled to photochemical transitions make the family of fac-[Re(CO)3(N,N)X]0/+ (N,N = a bidentate diimine such as 2,2'-bipyridine (bpy); X = halide, H2O, pyridine derivatives, PR3, etc.) complexes of special interest. We have investigated reactions of the aqua complex fac-[Re(CO)3(bpy)(H2O)](CF3SO3) (1) with potential anticancer activity with the amino acid l-cysteine (H2Cys), and its derivative N-acetyl-l-cysteine (H2NAC), as well as the tripeptide glutathione (H3A), under physiological conditions (pH 7.4, 37 °C), to model the interaction of 1 with thiol-containing proteins and enzymes, and the impact of such coordination on its photophysical properties and cytotoxicity. We report the syntheses and characterization of fac-[Re(CO)3(bpy)(HCys)]·0.5H2O (2), Na(fac-[Re(CO)3(bpy)(NAC)]) (3), and Na(fac-[Re(CO)3(bpy)(HA)])·H2O (4) using extended X-ray absorption spectroscopy, IR and NMR spectroscopy, electrospray ionization spectrometry, as well as the crystal structure of {fac-[Re(CO)3(bpy)(HCys)]}4·9H2O (2 + 1.75 H2O). The emission spectrum of 1 displays a variance in Stokes shift upon coordination of l-cysteine and N-acetyl-l-cysteine. Laser excitation at λ = 355 nm of methanol solutions of 1–3 was followed by measuring their ability to produce singlet oxygen (1O2) using direct detection methods. The cytotoxicity of 1 and its cysteine-bound complex 2 was assessed using the MDA-MB-231 breast cancer cell line, showing that the replacement of the aqua ligand on 1 with l-cysteine significantly reduced the cytotoxicity of the Re(I) tricarbonyl complex. Probing the cellular localization of 1 and 2 using X-ray fluorescence microscopy revealed an accumulation of 1 in the nuclear and/or perinuclear region, whereas the accumulation of 2 was considerably reduced, potentially explaining its reduced cytotoxicity.
Embargo
Design of Electrochemically Exfoliated Graphene for Supercapacitors
(2023-09-22) Raei, Mohammad Javad; Natale, Giovanniantonio; Roberts, Edward; Ponnurangam, Sathish; Kibria, Golam
Graphene, a 2D carbon-based material with exceptional characteristics, has proven its potential in various applications, branching into fields such as electronics, energy storage, sensors, and more. Various techniques have been developed to synthesize single and multi-layer graphene sheets. However, each method for utilizing graphene still presents a range of challenges, such as low yield, the use of toxic reagents, methods that are not scalable, time-consuming processes, and multi-step procedures. Among all these methods, electrochemical exfoliation is considered as a facile and environmentally friendly method which can prepare the doped and functionalized graphene with different elements, metals, metal oxides and polymers. In this work, we have modified the electrochemical exfoliation method and developed a novel procedure which can simultaneously produce doped and functionalized graphene with nitrogen, sulphur, phosphor, MnO2 and tannic acid. It was shown that the chemical structure of the graphene can easily be tuned for a specific application by utilizing different electrolytes. Additionally, the yield of this process has been increased by 78% by its combination with the liquid-phase exfoliation method, all without requiring any additional steps. Subsequently, as-synthesized composites have been investigated for energy storage in liquid and solid-state supercapacitors. We prepared the freestanding and flexible working electrodes by vacuum filtration of the graphene composites without the addition of any conductive additive and binder. It was shown that the pseudocapacitance behaviour of MnO2 can increase the capacitance of the graphene by 192% while showing 98.4% capacitance retention after 10,000 cycles. The obtained results suggest the great potential of the electrochemical exfoliation method for synthesizing graphene-based composites for application in energy storage devices.
Open Access
Determination of Solubility Parameter of Carbon Dioxide in Heavy Oil
(2020-05-06) Ferreira Cala, Jorge Nicolay; Yarranton, Harvey W.; Mehrotra, Anil K.; Ponnurangam, Sathish
Asphaltene precipitation and the subsequent deposition of asphaltenes can damage the reservoir and foul surface equipment and pipelines. Hence, there is a need to predict at what composition, temperature and pressure asphaltenes will precipitate from crude oils. The Modified Regular Solution (MRS) approach has been used to model asphaltene precipitation in heavy oils diluted with solvents. This model has not yet been rigorously applied to asphaltene precipitation from depressurized live oils (oils with dissolved gases) partly because the solubility parameters of the dissolved gases are required, but not known. The objective of this study is to determine the solubility parameter of dissolved carbon dioxide (CO2). Live oils were prepared from Western Canadian bitumen and CO2 and the bitumen and live oil phase behavior was measured from 20 to 130°C and pressures from 0.1 to 60 MPa. The densities were measured in a vibrating tube density meter. The onsets of asphaltene precipitation from the oils diluted with n-pentane were measured visually using a high pressure microscope (HPM). Asphaltene yields of the oils mixed with n-pentane were measured in a blind cell apparatus. The solubility parameter of dissolved CO2 was determined by fitting the MRS model to the asphaltene onsets and yields from the live oils. The model was fitted by adjusting the dissolved gas solubility parameters; all of the other model inputs were known. As the CO2 content in the live oil increased, the amount of n-pentane required to initiate precipitation decreased and the yield increased; that is, the asphaltenes became less soluble confirming that CO2 is a poor solvent for asphaltenes. When CO2 was present, precipitation occurred in two stages: low yields up to 12 wt% n-pentane above the initial onset followed by a dramatic increase in yield at higher dilutions. The model could not represent both stages and a correlation for the carbon dioxide solubility parameter was developed based only on the second stage yields. Discrepancies in the model are attributed to the use of a one-dimensional solubility parameter that accounts for dispersion force interactions not for polar or hydrogen bonding interactions which can be significant for CO2.
Open Access
Determination of Solubility Parameter of Methane in Heavy Oil
(2021-06-24) Paniagua Fernández, Daniela; Yarranton, Harvey; Ponnurangam, Sathish; Gates, Ian
Asphaltenes are the least soluble fraction of crude oil and can phase separate from the oil due changes in pressure, temperature, or oil composition. Some examples where asphaltene precipitation occur in oilfield operations are: dilution of a heavy oil with an incompatible solvent (e.g. an n-alkane), depressurization of a light conventional oil during production, and gas injection into a light conventional oil reservoir. Methane is often a major component of the dissolved gases in a crude oil and has a significant negative impact in the oil’s ability to solubilize asphaltenes. The Modified Regular Solution (MRS) model has been previously used to model asphaltene precipitation from heavy oils and bitumen diluted with n-alkanes at different temperatures and pressures. The input parameters of the MRS model are the mole fractions, molar volumes, and solubility parameters of the bitumen (characterized into SARA fractions), and the n-alkane solvent. However, the MRS model is not yet able to predict asphaltene solubility in the presence of dissolved gases, such as methane, because the solubility parameter of the dissolved methane is unknown. To determine these parameters, asphaltene onsets and yields from mixtures of bitumen, n-pentane, and methane were measured at temperatures of 21 and 130°C and pressures of 10 and 60 MPa. The onsets (solvent content at which precipitation first occurred) were measured by titrating the bitumen with a mixture of methane and n-pentane in a High-Pressure Microscope. Asphaltene yields (mass of asphaltenes divided by mass of bitumen in feed) were measured in a blind cell apparatus for mixtures with the same methane content as the onset measurements. The methane solubility parameter was determined by fitting the MRS model to the measured asphaltene precipitation data. The fitted values ranged from 6.1 to 9.5 MPa0.5 depending on the temperature. A correlation for the methane solubility parameter was developed for use in the MRS model. The MRS model using the correlation matched the onsets and yields with average deviations of 1.1 wt% solvent and 8.1 wt%, respectively. The updated model now applies to in situ heavy oils that contain dissolved methane.
Open Access
Development and Mechanistic Analysis of Novel CO2 Reduction Electrocatalysts
(2023-01-13) Dubrawski, Zachary Sachiel; Piers, Warren; Roesler, Roland; Birss, Viola; Herbert, David; Ponnurangam, Sathish
The ever-growing anthropogenic concentrations of CO2 in our atmosphere has led to an entire industry centered around Carbon Capture and Utilization (CCU). One central pillar of the CCU ideology is the conversion of captured CO2 to “value-added” products such as carbon monoxide, formic acid, or commercial products such as plastics or vodka. However, the technologies that this industry rely on are not robust with suspect surface characterization and transient catalytically active sites. Solution phase molecular electrocatalysts are inherently impractical for industrial-scale CO2 conversion due to several complicating factors. However, the insights and knowledge developed from these homogeneous systems can often be directly utilized within industrial-scale heterogeneous electrolyzers with dramatic improvements to catalytic efficacy. Therefore, through the study of homogeneous systems, significant progress can be potentially made towards the effective valorization of CO2. With this in mind, the research outlined in this thesis details the development, exploration and mechanistic analysis of a range of novel CO2RR electrocatalysts with a special focus on earth abundant systems. Using ligand design principles developed through the literature, novel ligands were explored and CO2 reduction capabilities investigated. Once a promising target was identified, an intense mechanistic analysis was undertaken using spectroelectrochemistry and chemical reduction studies to identify and characterize key intermediates in the catalytic cycle. Through this analysis we have confirmed ideas on the importance of redox non-innocent ligands and developed new design principles centered around structural torsional strain. These insights provide value to developing next generation CO2RR electrocatalysts.
Open Access
Development of a Highly Efficient Amidoxime Functionalized Cellulose Adsorbent for Enhanced Separation of Vanadium using Acetate as a Complexing Agent
(2020-12-16) Bakuska, Derrick C. R.; Ponnurangam, Sathish; Roberts, Edward; Hill, Josephine; Hu, Jinguang
Vanadium is a strategic alloying metal that is used in high strength steel for varying applications, from high performance tools to earthquake resistant rebar. However, most vanadium is produced as a by-product of iron ore mining and this cannot meet increasing demand. Several new vanadium deposits, such as stone coal or carbonaceous shales, are suitable for low-cost hydrometallurgical extraction, which involves dissolving metal ions into solution for recovery. Currently, purifying vanadium ions from other dissolved metals is done with solvent extraction, which utilizes organic solvents and toxic extractants. In this work, a cellulose-based adsorbent material was developed that demonstrates high selectivity towards vanadium. Cellulose powder was functionalized with amidoxime functional groups via a simple two step heterogenous reaction, first adding nitrile groups to the surface followed by conversion to amidoxime. We developed a new hybrid approach for amidoxime functionalization on cellulose which uses fewer reagents under benign conditions, resulting in an adsorbent with high adsorption capacity for vanadium (70 mg g-1). Furthermore, by dissolving acetic acid as a complexing agent, the vanadium adsorption capacity of the adsorbent was found to increase by over a factor of 4, from 70 mg g-1 to 330 mg g-1. Additionally, the inclusion of acetate enhanced the selectivity towards vanadium over chromium, increasing from 2.0 ± 0.5 to 7.0 ± 0.2 at an acetate concentration of 0.5 M. When in competition with simple divalent metal ions such as copper or nickel, the adsorbent had a selectivity towards vanadium of more than 150, the lower bound of detectability. Following adsorption, vanadium was found to be easily recovered through elution with dilute sulfuric acid (0.5 M) which makes the adsorbent promising for future applications. The applicability of amidoxime functionalized cellulose was further demonstrated through the synthesis and utilization of functionalized cellulose beads. Using the insights gained from functionalizing cellulose fibers, cellulose beads were functionalized to yield a similar adsorption capacity per gram of cellulose while at the same time providing mechanical structure for use in an adsorption column. From adsorption column experiments, the kinetic performance was analyzed, and future optimizations were proposed.
Open Access
Development of Aerobic Granular Sludge Membrane Bioreactor (AGMBR) to Mitigate Fouling
(2019-09-04) Iorhemen, Oliver Terna; Achari, Gopal; Hettiaratchi, Joseph Patrick A.; Vijayan, Mathilakath M.; Ponnurangam, Sathish; Dhar, Bipro Ranjan
In this research, the integration of aerobic granular sludge and membrane filtration to develop aerobic granular sludge membrane bioreactor (AGMBR) was explored. The main focus was on the in-depth study of extracellular polymeric substances (EPS) in AGMBR. Firstly, the long-term stability of aerobic granules (AG) was investigated in a sequencing batch reactor (SBR). This was followed by an in-depth analysis of EPS in a continuous-flow submerged AGMBR. And, the capability of AGMBR to remove organic matter, nitrogen, and phosphorus was determined. The combined strategy of long anaerobic slow feeding, fixed 1:3 ratio of feast-famine period within each SBR cycle, and continuous wasting of mature granules controlled EPS content at a suitable level to allow for long-term AG stability. High proteins/polysaccharides (PN/PS) ratios for loosely-bound EPS (LB-EPS) and tightly-bound EPS (TB-EPS) allowed for stable reactor operation for over 240 d without AG disintegration. EPS producers - Thauera, Flavobacterium and Meganema - and slow growing bacteria - Acinetobacter and Simplicispira - contributed to AG stability. The AGMBR exhibited high PN in the TB-EPS, resulting in high PN/PS ratios of 2–16. AG trapped most of the EPS in their matrix. Low soluble EPS resulted in acceptable rise in transmembrane pressure at membrane flux of 12.5 L/m2.h. An increase in soluble EPS PN correlated with increase in membrane fouling (r = 0.581). Compared to conventional membrane bioreactor, the AGMBR achieved seven times reduction in permeability maintenance cleaning frequency of the membrane. The COD showed a significant main effect on both PN and PS components of TB-EPS at α < 0.05. Water jet easily sloughed off the developed membrane cake layer, eliminating the need for chemical cleaning. The AGMBR system achieved 98.7±1%, 99.7±0.5%, 50±30%, and 35±18% removal for organic matter, ammonia-nitrogen, total nitrogen, and phosphorus, respectively. Meganema and Thauera, responsible for organic matter degradation, were present throughout the experimental duration. Nitrosomonas and Nitrospira allowed for complete nitrification. The presence of Azoarcus and Thauera points to anoxic conditions in AG, indicating some denitrification activity. Negligible phosphorus-accumulating organisms were detected; hence, the low phosphorus removal is attributed mainly to consumption for growth, struvite and biologically induced precipitation pathways.