Analysis of Electronic and Magnetic Properties at the Interfaces of Transition Metal Heterostructures

Material science is a field of physics that bridges the gap between the microscopic properties of materials and how these properties manifest as tangible, observable characteristics that can be observed or harnessed for applications. Material scientists grow, analyze, modify, and model complex, exotic materials to understand emergent, novel phenomena and create devices which can readily be employed for electronic, magnetic, and other applications. However, many material properties cannot be measured or observed directly; it is not feasible to measure the orbital energies of an atom directly or quantify angstrom-scale magnetic variations in a thin film sample directly. Since these properties are frequently what create meaningful effects at a macroscopic level, an understanding of them is required that only material science techniques can provide. This thesis concerns two separate studies of complicated material systems that require an understanding of their underlying structure and properties that cannot be directly discerned by experiment alone. These samples belong to a class of materials known as heterostructures, structures formed by layering multiple materials with different chemical/elemental compositions. The junctions where different materials in a heterostructure connect are called interfaces, and serve as the sites of emergent physical and chemical phenomena with a myriad of electronic and magnetic applications. The first material system studied is the interface of bulk LaAlO3 and bulk CaTiO3, often simply abbreviated as LAO/CTO. Systems containing interfaces between transition metal compounds have been intensely studied within the past two decades because certain phenomena such as two-dimensional electron gases (2DEG), magnetism, and other effects tend to appear specifically around the interface. Historically, a combination of bulk LaAlO3 and bulk SrTiO3 (LAO/STO) was studied instead, but the interfacial effects can be changed by swapping out various elements in the compound. This variation is due to the crystal structure near the interface being distorted according to the element introduced, altering the Ti orbital energies near the interface as well. These near-interface orbital energies directly correlate to observed interfacial phenomena, so swapping elements is expected to affect the macroscopic electronic and magnetic properties of the system. The difficulty resides in the fact that orbital energies and 2DEG charge densities cannot be measured directly by any experiment; rather, they need to be extracted from experimental data via sophisticated modelling. The purpose of this study was to probe two samples of LAO/CTO with varying thicknesses, use the extracted experimental data to generate models of the two samples, and finally use this model to discern orbital energies. Special consideration was given to comparing and contrasting the difference between the LAO/STO interfacial electronic structure with that obtained for LAO/CTO. It was found that the orbital energies of LAO/CTO maintain a significantly different configuration from those of LAO/STO, and suggest that LAO/CTO may be more promising for magnetic applications. Furthermore, this difference will foster more investigation into interfaces of this kind, particularly in designing new configurations of different metals to observe what macroscopic effects they produce. The second material system studied is thin films of Fe3GeTe2, often abbreviated FGT. FGT as a bulk material has been studied since the turn of the millennium for potential magnetic applications, and attention has recently moved towards growing the substance in thin film form on the order of angstroms thick. Several sources have found that the electronic and magnetic properties of these thin films vary dramatically vary dynamically as more FGT film layers are grown sequentially in one sample. However, this information is only known at a high level; the magnetic effects are known to differ, but how exactly this manifests on a microscopic level is unknown. Given the angstrom level thickness of the films, it is extremely difficult to probe the magnetic properties in detail. A more sophisticated technique is needed, so here we apply resonant X-ray reflectometry. This study considered two samples: a single FGT layer film (monolayer) and a combination of two FGT layers as a film (bilayer). Experimental results were used to synthesize a model of each film and the magnetized iron distribution was quantified in each case. The two samples were found to have differing magnetized iron distributions, further lending credence to observations that FGT films of various layers will produce different magnetic properties and effects. These two studies represent intriguing but very limited applications of material science. New exotic materials are being actively discovered all the time, each with their own unique need for a method that probes their microscopic properties to understand macroscopic phenomena. Material science techniques are and will continue to be important for these reasons; advancement of technology is now reliant on synthesizing and understanding new materials that improve electronic and magnetic infrastructures, an understanding that material science provides

Morphological, Histological, And Developmental Features Of Perichondral Bone In Skates And Sharks Suggest That Modern Cartilaginous Fishes Make Bone

Bone is a mineralized (or calcified) tissue type and a defining feature of the vertebrate skeleton. Ancestral vertebrates made bone and most modern vertebrates including bony fishes and tetrapods retain bone. However, bone has never been characterized in modern chondrichthyans (sharks, skates, rays, and chimaeras), and modern chondrichthyans are hypothesized to have lost the ability to make bone during their evolution. Previous studies show that sharks have mineralized tissues with some morphological and histological features that are consistent with vertebrate perichondral bone. These mineralized tissues in sharks have been described as bone-like and occur in neural arches and a specific histological region (i.e., cap zone) of discretely mineralized tesserae. While these observations in sharks challenge the hypothesis that modern chondrichthyans lack bone, it remains debated whether other modern chondrichthyans like skates and chimaeras have bone-like tissues. Because bone-like tissues have been characterized mostly in adult sharks, it is not known whether important developmental features of perichondral bone such as cartilage maturation is demonstrated by bone-like tissues. Besides bone-like tissues, chondrichthyans also display a unique areolar mineralized tissue in the vertebral body (centrum). These chondrichthyan mineralized tissues display distinct mineralization patterns such as a classic polygonal pattern of tesserae, a compact bone-like pattern of neural arches, and a compact pattern of areolar mineralized tissue. These chondrichthyan mineralization patterns have been described in sharks and skates, but relevant data from chimaeras needed to assess whether all groups of modern chondrichthyans demonstrate these morphological features are lacking. This thesis addresses these and other knowledge gaps in the skeletal biology of modern chondrichthyans by testing the hypothesis that bone-like tissues are shared by modern chondrichthyans and are homologous to perichondral bone in other modern vertebrates. Comparative morphology and embryology were the two main approaches adopted to test this hypothesis. Specifically, mineralized tissues in two skate species (the little skate Leucoraja erinacea and the Eaton’s skate Bathyraja eatonii), a shark (the catshark Scyliorhinus canicular), and a chimaera (the spotted ratfish Hydrolagus colliei) were characterized using desktop and synchrotron micro-CT imaging, histological, histochemical, and immunofluorescence assays. Micro-CT renderings showed a bone-like mineralization pattern in neural arches of the skates and the shark, but this was absent in neural arches of the spotted ratfish. Micro-CT renderings and histological analyses of tesserae showed that the bone-like cap zone was present only in the skates, and the polygonal tesseral mineralization pattern was associated with large and laterally extensive bone-like cap zones. Another mineralization pattern described herein as trabecular tesseral was characterized in several endoskeletal regions of the skates, the catshark, and the spotted ratfish. The trabecular tesseral pattern was morphologically distinct from the polygonal tesseral pattern which is classically associated with the chondrichthyan endoskeleton. Micro-CT renderings and histological data also showed that areolar mineralized tissue, which has been described in only sharks and skates, was also present in the spotted ratfish. Perichondral bone formation in other modern vertebrates is driven by cartilage maturation. Developmental data from the little skate showed that the main histological features of cartilage maturation, such as chondrocyte hypertrophy and initiation of matrix mineralization by hypertrophic chondrocytes, were associated with the development of bone-like tissue in neural arches. In addition to limited reports of bone-like tissues in sharks, data in this thesis showed that other modern chondrichthyans like skates have bone-like tissues. Developmental features of perichondral bone demonstrated by neural arch bone-like tissue suggest that bone-like tissues and perichondral bone are homologous

The Rainbow Bike Experiences of School for Parents Whose Children Have Needs: A Narrative Inquiry into Whose Knowledge Counts

Having chosen narrative inquiry as my research methodology, I sat for hours in my first narrative inquiry class wondering how I was going to tell my story. I observed countless examples of rich narratives. They all spoke to me in different ways, but I still did not know how to begin. Finally, the metaphor of the rainbow bike crashed into my head, just as it crashed so long ago as a little girl. I decided to use the rainbow bike metaphor to conceptualize and tell my story of experience and as an entry into this narrative inquiry. As a child, my rainbow bike was a place of escape from pain and hurt. As a narrative inquirer in the field, I continued to ride my rainbow bike when I needed help to carry the heaviness of the stories my research participants shared and I needed to escape to places of safety and comfort to unpack those stories. As I engaged in analysis and interpretation of my field text, my rainbow bike carried me to places of discovery and joy. Now, as I conclude this narrative inquiry, I park my rainbow bike for some much needed rest. It was through writing my own narrative beginnings that I learned how to portray the lived experiences and stories of my research participants: three pairs of parent partners who have a child with needs, the term I use to step away from the language and labelling of ‘special needs’ that ‘others’ children and their families. Parents with children with needs often find themselves pushed to the margins at their children’s schools, seen to be lesser than other parents, seen to be less knowing. My purpose in inquiring into their lived experiences was to foreground the parent knowledge they hold, individually as parents and together as parent partners, that can be used alongside teachers’ knowledge to inform their children’s schooling experiences. Attentive to the three-dimensional space of this narrative inquiry, I captured participants’ stories as they unfolded over time, moving between earlier moments, present realities, and imagined future possibilities. I was drawn to their innermost thoughts and feelings as we engaged in conversations in the social space of our living rooms. Through the sharing of our stories, we journeyed to childhood homes, communities, and schools. This narrative inquiry has been a long and in-depth rainbow bike ride, backward and forward, inward and outward, visiting many places during the sharing of stories of our lives. As stories were lived and told, I understood more deeply how parent knowledge is held and used, either individually, exercised as a form of roving leadership within their partnership, or co- constructed to create new shared knowledge for both parents. It became clear that if parent knowledge is used alongside teacher knowledge, it is possible to dramatically transform the current hierarchy of schools, creating teaching and learning centres in which parents have a place and voice. It is my hope that the lived experiences of the parents in my inquiry have been educative for themselves and will be for other parents on a similar journey, for educators who will “walk alongside” the parents as their children with needs enter schools and school systems, and for schools and school systems in which some parents and families find themselves in the margins of the school landscape

Catalytic Reaction of Ozone and Ethylene at Ambient Temperature: Ozonative Epoxidation and Deep Ozonation

The abstract of this item is unavailable due to an embargo

NUCLEAR FACTOR ERYTHROID 2 RELATED FACTOR-1 (NRF1) MEDIATES CELASTROL-INDUCED GENE REGULATION, DEPENDING ON ITS HETERODIMERIC INTERACTIONS

Oxidative stress has been recognized as critical in human aging and the progression of many chronic diseases, including cancer. Cells undergo oxidative stress when the overproduction of reactive oxygen species (ROS) within the cell outweighs its antioxidant defenses. As a defense mechanism, a series of cytoprotective genes is initiated and regulated by various transcription factors in order to minimize oxidative damage to the cell. NF-E2-related factor 1 (NRF1) is a Cap'N'Collar (CNC) transcription factor family member that plays a major role in regulating genes involved in defense against cell stress and damage. For example, NRF1 is a vital regulator of antioxidant and proteasome genes to counteract ROS and impaired protein homeostasis. Upon stress caused by impaired protein turnover, NRF1 undergoes endoplasmic reticulum to nuclear translocation and binds antioxidant response elements (ARE) located in close proximity to stress defense genes throughout the genome. The result is altered transcription of the associated gene. While this general concept has been established, the mechanism by which NRF1 is processed, selected for nuclear translocation rather than degradation, and the role of post-translational modifications is not understood. Moreover, previous studies show NRF1 must form a heterodimer with other transcription factors such as small musculoaponeurotic fibrosarcoma oncogene homolog (MAF) proteins to bind AREs and regulate gene transcription. The mechanism underlying NRF1 heterodimer formation and ARE binding and whether distinct heterodimers regulate distinct genes is unclear. I hypothesize NRF1 regulates proteasome and oxidative stress defense via specific heterodimer interactions. In this thesis, I describe our identification of the nutraceutical celastrol as a stimulant for NRF1’s transcriptional activity. For centuries, celastrol has been used to treat inflammatory and chronic diseases and more recently found to influence a multitude of stress pathways and suppress chymotrypsin-like activity of the proteasome. I then proceeded to use celastrol to investigate my hypothesis. Using cultured Hep3B cells, I show celastrol elicits dose-dependent inhibition of the proteasome and this increases the level of a cleaved NRF1 protein product known to regulate transcription. Using clustered regularly interspaced short palindromic repeats (CRISPR)/cas9 based technology to produce NRF1 loss-of-function cells, I show celastrol induces transcription of proteasome and oxidative stress defense genes in an NRF1-dependent manner. Likewise, quantitative polymerase chain reaction measurement of immunoprecipitated chromatin revealed that NRF1 binds to AREs in stress defense genes GCLC, GCLM, HO1, NQO1A in a manner that corresponds with transcription regulatory profiles. Moreover, ablation of NRF1 heterodimers MAFG, MAFK, or MAFF resulted in refractory responses to celastrol that partially and nonredundantly matched NRF1 deficiency. Collectively, results of my research support a model whereby NRF1 heterodimerization with MAFK regulates one gene sub-set or program, whereas heterodimerization with MAFG or MAFF regulates another one. In other words, specific heterodimeric interactions coordinately stimulate or repress the transcription of a group of target genes

Towards High Throughput Determination of Biotransformation Rates of Chemical Mixtures Using Isolated Perfused Trout Livers

In the field of environmental risk assessment, aquatic contaminants are typically characterized by their persistence, bioaccumulation potential, and toxicity (PBT). Bioconcentration factor (BCF) is the most common metric for evaluating bioaccumulation potential and is frequently estimated using Quantitative-Structure-Activity-Relationships (QSARs) and other in silico tools. These methods can estimate BCF based upon the physicochemical characteristics of a chemical and the toxicokinetic parameters of a model organism for chemicals which do not undergo biotransformation. For chemicals which are actively biotransformed, whole animal in vivo exposures have classically been required to determine BCF for regulatory acceptance. Recently, in vitro substrate depletion assays have been adopted as an alternative to in vivo testing due to concerns of cost and ethics. The results of these assays have been met with doubt due to uncertainties involved with in vitro-in vivo extrapolation (IVIVE) methods required to bridge the gap between target organs of biotransformation such as the liver, and whole-organism outcomes. The overall objective of this thesis was to validate an IVIVE approach for estimating biotransformation in rainbow trout (Oncorhynchus mykiss) by using the isolated perfused liver method, which represents an intermediate between in vitro and in vivo. The first study (Chapter 2) involved comparing direct measurements of hepatic clearance in the isolated perfused liver with in vitro determinations of clearance which were previously published as part of a collaborative international trial for the regulatory adoption of in vitro substrate depletion assays. This comparison was performed for the model biotransformation substrate chemicals pyrene, phenanthrene, 4-n-nonylphenol, deltamethrin, and methoxychlor. The hepatic clearance rate of these chemicals was determined in isolated perfused livers by measuring the difference between chemical concentration as it entered and exited the liver, giving a measure of chemical elimination due to biotransformation. Experiments were performed over a period of several hours to validate physiological performance, and measurements of glucose efflux and pH were used to confirm aerobic respiration and thus metabolic activity. In addition, the influence of protein binding on hepatic clearance was investigated by varying the concentration of bovine serum albumin (BSA) in perfusates spiked with chemical. Measured clearances were in good agreement with in vitro substrate depletion models coupled with an IVIVE approach which takes protein binding into account. Overall, this study indicated that uncertainty associated with current IVIVE models is likely due to extrahepatic biotransformation, variability in BCF test designs, and inaccuracies in partitioning estimates or other kinetic processes such as uptake across the gills, rather than the reliability of in vitro test methodologies. The second study (Chapter 3) focused on expanding the domain of applicability of the isolated perfused liver method following validation in Chapter 2 as well as concurrent research investigating mixture experiments in ionizable organic compounds (IOCs). One of the primary concerns about bioaccumulation assessment methods regardless of in silico, in vitro, or in vivo approaches is the limited number of chemicals which have been successfully tested. To achieve the throughput needed by modern chemical risk assessment frameworks, a mixture experiment was performed using the isolated perfused liver model. This study used a chemical mixture obtained from the United States Environmental Protection Agency (EPA) as part of the EPA’s non-targeted analysis collaborative trial (ENTACT). This mixture contained over 500 chemicals, and the study utilized advanced high-resolution-mass-spectrometry (HRMS) methods to detect individual compounds in mixture at the very low concentrations required for mixture experiments. Hepatic clearance was determined for 20 substances in this mixture simultaneously, representing diverse classes of chemicals including pharmaceuticals, pesticides, and industrial chemicals. This study demonstrated that the isolated perfused liver method can be a valuable tool for bioaccumulation screening, and validated the performance of this model for diverse groups of chemicals. Chapter 4 discusses the present state of bioaccumulation assessment with regard to biotransformed chemicals, focusing on the role of the isolated perfused liver method and the goals of validation and demonstration set out by this thesis. Many studies have focused on which factors involved in IVIVE drive the discrepancies between BCFs determined by in vivo exposures with those predicted by IVIVE approaches. The difference between chemical freely available for biotransformation in the systemic circulation in vivo versus in vitro has been identified as a source of uncertainty. This ratio has typically been assumed to be identical, as this assumption whilst mechanistically impossible leads to a more reliable prediction of BCF. In Chapter 2, it was demonstrated that the influence of protein binding on hepatic clearance can be incorporated into an IVIVE model to increase reliability, indicating that prior assumptions were inappropriate. Concerns over limited domain of applicability were addressed in Chapter 3 as well as in concurrent work involving IOCs, focusing on the high-throughput nature of these experiments in which six fish were used to screen 20 chemicals. In summary, the isolated perfused liver model advanced in this thesis work has contributed to the field of bioaccumulation assessment by validating presently adopted in vitro assays. Furthermore, this work has expanded the chemical scope of methods developed to achieve high-throughput predictions of biotransformation, serving as the basis for incorporation into reliable IVIVE models

The Regulation of Social Media in Nigeria and its Effect on Free Speech: Perspectives from Constitutional Law and International Norms

This thesis explores the multifaceted and evolving topic of social media regulation, with a focus on Nigeria. As social media platforms have become central to communication, information dissemination, and public discourse, concerns have arisen about their impact on individuals, society, and democracy. The research question addressed in this thesis is whether the Nigerian bills on restriction of social media can legally restrict false speech and hate speech without overreaching on the right to freedom of expression, and if not, what measures can be taken to improve these bills. The thesis begins by analyzing three key theories for the justification of freedom of expression, which show that freedom of expression is essential to the discovery of truth, self-autonomy, and promotion of an open and vibrant democratic discourse. However, these theories are not an absolute justification and may be restricted. The thesis also examines the conditions for justification of limits on freedom of expression in Nigeria, which is that the law must be shown to be within reasonable limits permissible in a democratic society. Section 45 of the Nigerian Constitution states specific grounds for the restriction of freedom of expression, but the section is vague as it gives no further direction as to how Nigerian courts should balance competing interests, such as freedom of expression on the one hand and public interest on the other. The thesis argues that the importation of proportionality analysis and international standards is necessary to restrict hate speech and false speech in Nigeria while protecting the right to freedom of expression. The delicate balance between preserving freedom of expression and addressing harmful content, such as hate speech and false information, is a critical consideration in social media regulation. The thesis suggests that drawing from Canadian law and international standards could enhance Nigeria’s regulation of free speech on social media. The thesis concludes that the protection of freedom of expression is crucial, especially in a diverse cultural, political, and socio-economic landscape such as Nigeria

Morphological, Histological, And Developmental Features Of Perichondral Bone In Skates And Sharks Suggest That Modern Cartilaginous Fishes Make Bone

Bone is a mineralized (or calcified) tissue type and a defining feature of the vertebrate skeleton. Ancestral vertebrates made bone and most modern vertebrates including bony fishes and tetrapods retain bone. However, bone has never been characterized in modern chondrichthyans (sharks, skates, rays, and chimaeras), and modern chondrichthyans are hypothesized to have lost the ability to make bone during their evolution. Previous studies show that sharks have mineralized tissues with some morphological and histological features that are consistent with vertebrate perichondral bone. These mineralized tissues in sharks have been described as bone-like and occur in neural arches and a specific histological region (i.e., cap zone) of discretely mineralized tesserae. While these observations in sharks challenge the hypothesis that modern chondrichthyans lack bone, it remains debated whether other modern chondrichthyans like skates and chimaeras have bone-like tissues. Because bone-like tissues have been characterized mostly in adult sharks, it is not known whether important developmental features of perichondral bone such as cartilage maturation is demonstrated by bone-like tissues. Besides bone-like tissues, chondrichthyans also display a unique areolar mineralized tissue in the vertebral body (centrum). These chondrichthyan mineralized tissues display distinct mineralization patterns such as a classic polygonal pattern of tesserae, a compact bone-like pattern of neural arches, and a compact pattern of areolar mineralized tissue. These chondrichthyan mineralization patterns have been described in sharks and skates, but relevant data from chimaeras needed to assess whether all groups of modern chondrichthyans demonstrate these morphological features are lacking. This thesis addresses these and other knowledge gaps in the skeletal biology of modern chondrichthyans by testing the hypothesis that bone-like tissues are shared by modern chondrichthyans and are homologous to perichondral bone in other modern vertebrates. Comparative morphology and embryology were the two main approaches adopted to test this hypothesis. Specifically, mineralized tissues in two skate species (the little skate Leucoraja erinacea and the Eaton’s skate Bathyraja eatonii), a shark (the catshark Scyliorhinus canicular), and a chimaera (the spotted ratfish Hydrolagus colliei) were characterized using desktop and synchrotron micro-CT imaging, histological, histochemical, and immunofluorescence assays. Micro-CT renderings showed a bone-like mineralization pattern in neural arches of the skates and the shark, but this was absent in neural arches of the spotted ratfish. Micro-CT renderings and histological analyses of tesserae showed that the bone-like cap zone was present only in the skates, and the polygonal tesseral mineralization pattern was associated with large and laterally extensive bone-like cap zones. Another mineralization pattern described herein as trabecular tesseral was characterized in several endoskeletal regions of the skates, the catshark, and the spotted ratfish. The trabecular tesseral pattern was morphologically distinct from the polygonal tesseral pattern which is classically associated with the chondrichthyan endoskeleton. Micro-CT renderings and histological data also showed that areolar mineralized tissue, which has been described in only sharks and skates, was also present in the spotted ratfish. Perichondral bone formation in other modern vertebrates is driven by cartilage maturation. Developmental data from the little skate showed that the main histological features of cartilage maturation, such as chondrocyte hypertrophy and initiation of matrix mineralization by hypertrophic chondrocytes, were associated with the development of bone-like tissue in neural arches. In addition to limited reports of bone-like tissues in sharks, data in this thesis showed that other modern chondrichthyans like skates have bone-like tissues. Developmental features of perichondral bone demonstrated by neural arch bone-like tissue suggest that bone-like tissues and perichondral bone are homologous

INFLUENCE OF MICROBIAL SULFATE REDUCTION ON PORE-WATER CHEMISTRY IN OIL SANDS FROTH TREATMENT TAILINGS

Oxidative weathering of froth treatment tailings (FTT) at oil sands mines in Northern Alberta has the potential to generate acidic and metalliferous porewater. Residual bitumen and light hydrocarbons in FTT support growth of a diverse range of microbes, including those capable of dissimilatory sulfate reduction (DSR). This biogeochemical process can be effective in removing sulfide-mineral oxidation products such as Fe, SO4, and trace elements including As, Co, Cu, Ni, Se, and Zn through sulfate reduction and sulfide mineral precipitation under anoxic conditions. While previous experiments that have stimulated sulfidogenesis through organic carbon amendments effectively decreased the mass flux of sulfide-mineral oxidation products in mining environments, the extent of this process and its ability to attenuate sulfide-mineral oxidation products in FTT supported by residual hydrocarbons is unknown. The objective of this thesis is to assess the impact of microbial sulfate reduction on FTT pore-water geochemistry and to determine the potential extent to which this process may be supported by residual hydrocarbons within the tailings deposit. Laboratory experiments were designed to examine the influence of sulfidogenesis on pore-water chemistry and to constrain rates of sulfate reduction, while assessing the capacity for metal(loid) removal due to this process. Through batch and column experiments sulfate reduction was found to contribute to metal(loid) and sulfate removal, as well as pH buffering and H2S generation. Removal of As, Co, Ni, and Se exceeded 90% in simulated porewater over a pH range of 5 – 8. Removal of Fe was minimal below pH 7, but exceeded 95% in solutions above pH 7 with long residence times. Zn removal was influenced by ∑S(-II)(aq) concentrations, with increased Zn removal seen at lower ∑S(-II)(aq) concentrations. Sulfur isotope samples taken during the batch experiment show an increase in 34S-SO4 with decreasing SO4(aq) concentrations over time, showing ongoing microbial sulfate reduction during the experiment. A mass-based approach to determine sulfate removal found sulfur removal rates remained constant around 1.5 μmol d-1 g-1 when solutions were not saturated with respect to gypsum. Residence time and pH were major influences on the effectiveness of sulfate reduction, with enhanced metal(loid) removal occurring with longer residence times at circumneutral pH. These results show the pool of organic carbon in FTT deposits is capable of supporting dissimilatory sulfate reduction and this process can decrease mass fluxes of sulfide-mineral oxidation products in FTT porewater

Treatment of Black Liquor Produced From Wheat Straw Pulping Process

With the increasing number of pulp and paper industries, the production of black liquor, which is one of the main by-products of the pulping process, is also being increased simultaneously. The produced black liquor is toxic to human, aquatic life and the environment as a whole because of its high pH and alkalinity, hence, various ways for its treatment and management are being carried out, yet it has been mostly used as energy for fuels only. Furthermore, the black liquor produced, especially, in the wheat straw pulp and paper industry is found to contain high concentrations of lignin, silica, etc., and its poor biodegradability on the other hand hinders the performance of conventional biological degradation methods of wastewater treatment. Hence, this research incorporated the use of an electrocoagulation process as a pretreatment step, where the flocculating agent was generated by electro-oxidation of sacrificial anodes that removed pollutants in black liquor by electrostatic attraction. The study investigated its efficacy for the biological degradation of black liquor under anaerobic conditions with varying concentrations of black liquor. This study included the optimization of the electrocoagulation process of pretreatment of black liquor with the help of the Response Surface Method in which pH (7-11), voltage (10-30 V), and electrolysis time (10-60 min) were used as the operational parameters and Chemical Oxygen Demand (COD), phenol, Total Solid (TS), Total Dissolved Solid (TDS), color, pH, and Specific Energy Consumption (SEC) were used as the analytical parameters. Proximate analysis, Klason lignin analysis, Thermogravimetric Analysis (TGA), Fourier-Transform Infrared Spectroscopy (FTIR), and X-ray Fluorescence were also carried out to understand the characteristics of black liquor samples. Finally, anaerobic digestion was carried out with both untreated and pretreated black liquor for 36 days with varying concentrations from (10% to 30%) to find out the effectiveness of electrocoagulation for biological degradation. The degradation of the black liquor was evaluated by the reduction of COD, pH, TS, and volatile matter (VM). Along with that, biomethane potential was also assessed during the process of anaerobic digestion of black liquor. The overall optimum condition for electrocoagulation treatment of black liquor was initial pH 9, 20 V, and 35 min electrolysis time, which led to a successful removal of 49.40% COD, 43.61% phenol, 53.89% TS, 46.50% TDS, and 29.33% color and a reduction in alkalinity of the black liquor by 0.52 pH. The optimized condition of electrocoagulation resulted in a black liquor with 21,000 mg/L COD, 198 mg/L phenol, 19,690 mg/L TS, 7,000 mg/L TDS, 50.49 whiteness index and 8.48 pH . The operation was conducted with an average current output of 0.87 A and a current density of 33.02 mA/cm2. The specific energy consumption was found to be 1.98 kWh/kg of COD removal. Additionally, it helped reduce lignin by 71.85%, and volatile matter by 12.50% (dry basis) and 58.00% (wet basis). Overall, electrocoagulation treatment of black liquor followed by anaerobic digestion reduced the inhibition time and the retention time for gas production. The biogas yield obtained from 30% EC treated BL in 10 days optimal time was 185.14 mL/g of COD loading, which was double in value than that produced from the raw black liquor. When pretreated, gas yield increased by 40.00% and 99.50% for 10% and 30% black liquor concentration, respectively. 25.14% of COD, 13.43% of TS, and 35.34% of VM was reduced when 30% of pretreated black liquor was digested under anaerobic condition. Hence, this study incorporated the ability to treat black liquor produced in wheat straw pulp and paper industry by an integrated approach of electrocoagulation and biological degradation under anaerobic conditions