Fundamentals of Mercury Oxidation in Flue Gas

The objective of this project is to understand the importance of and the contribution of gas-phase and solid-phase coal constituents in the mercury oxidation reactions. The project involves both experimental and modeling efforts. The team is comprised of the University of Utah, Reaction Engineering International, and the University of Connecticut. The objective is to determine the experimental parameters of importance in the homogeneous and heterogeneous oxidation reactions; validate models; and, improve existing models. Parameters to be studied include HCl, NO{sub x}, and SO{sub 2} concentrations, ash constituents, and temperature. This report summarizes Year 3 results for the experimental and modeling tasks. Experiments have been completed on the effects of chlorine. However, the experiments with sulfur dioxide and NO, in the presence of water, suggest that the wet-chemistry analysis system, namely the impingers, is possibly giving erroneous results. Future work will investigate this further and determine the role of reactions in the impingers on the oxidation results. The solid-phase experiments have not been completed and it is anticipated that only preliminary work will be accomplished during this study

Sugarcane Bagasse-Derived Activated Carbon- (AC-) Epoxy Vitrimer Biocomposite: Thermomechanical and Self-Healing Performance

Vitrimeric materials have emerged as fascinating and sustainable materials owing to their malleability, reprocessability, and recyclability. Sustainable vitrimeric materials can be prepared by reinforcing polymeric matrix with bioderived fillers. In the current work, a sustainable vitrimer is prepared by incorporating biomass-derived activated carbon (AC) filler into the epoxy matrix to achieve enhanced thermal and mechanical properties. Thus, prepared biocomposite vitrimers demonstrate a lower-temperature self-healing (70°C for 5 min) via disulfide exchanges, compared to the pristine epoxy vitrimers (80°C for 5 min). Significantly, the self-healing performances have been studied extensively with the flexural studies; and changes in material healing efficiency have been demonstrated based on the observed changes in modulus

Fundamentals of mercury transformations in coal combustion flue gas - A theoretical and modeling study

The emission of trace metals such as mercury and arsenic from fossil fuel combustion for electric power generation has become increasingly important because of the potential health risks associated with the presence of elevated concentrations of such species in the environment. Once emitted, the mercury compounds deposit in aquatic systems and transform into organic (methylated) mercury, which gets bioaccumulated and its concentration magnified in the aquatic food chain. Methyl mercury is a neurotoxin and the U.S. EPA estimates that each year nearly 300,000 children in the U.S. face an elevated risk of developing disabilities associated with exposure to elevated levels of mercury arising out of consumption of mercury contaminated fish. In the U.S., coal-fired electric utilities account for 48% of the approximately 110 tons of annual anthropogenic mercury emissions. A fundamental understanding of Hg transformations in combustion systems is required for developing Hg emission control technologies because the different forms of Hg have distinct removal characteristics. While elemental mercury (Hg0) is relatively transparent to capture in pollution control devices installed on power plants, the oxidized (Hg 2+) and particulate (Hg(p)) forms are easily captured in devices such as ESP (for particulate control) and FGD (for SO2 control). A comprehensive study of the chemical kinetic transformation pathways of various mercury species under postcombustion conditions of utility coal power plants was therefore conducted in this thesis. ^ A complete chemical kinetic mechanism was developed that consisted of gas phase Hg reactions with Cl species (Cl, Cl2, HCl, HOCl) coupled to heterogeneous reactions of Hg/Cl with unburned carbon in fly ash. The model also included an Hg oxidation mechanism on SCR catalysts (Ti/V) installed on power plants for the control of NO emissions, and an equilibrium analysis for predicting Hg retention in FGD systems. This model was used to predict mercury speciation and capture data from full-scale power plants for a broad range of conditions. Both measurements and predictions showed that power plants with SCR and FGD achieved the greatest reduction in air emissions of Hg and tests with high Cl and high levels of unburned carbon in fly ash correlated with higher extents of Hg oxidation. ^ To refine rate constants of the Hg oxidation mechanism, rate constants of homogeneous gas phase reactions between Hg and Cl species were calculated using theoretical tools of quantum chemistry and transition state theory. Such rate constants eliminate empiricism and allow for the development of a complete heterogeneous reaction set and associated rate constants. Several quantum calculation methods (HF, MP2, MP4, B3LYP, QCISD, QCISD(T)) were used for the electronic structure calculations by employing ECP basis sets for Hg and extensive all-electron basis sets for Cl, O, and H. Transition state for each reaction was determined by using the method/basis set combination that provided the best agreement (within 4% relative error) with experimentally measured properties of bond length, vibration frequency and reaction enthalpy. The QCISD/QCISD(T) methods were found to provide an incorrect temperature dependence for the three body Hg/Cl recombination reaction. The theoretical rate constants for the eight reactions were typically lower in magnitude than the corresponding empirical rate constants and were within the collision limit for all reactions.

Bio-Vitrimers for Sustainable Circular Bio-Economy

The aim to achieve sustainable development goals (SDG) and cut CO2-emission is forcing researchers to develop bio-based materials over conventional polymers. Since most of the established bio-based polymeric materials demonstrate prominent sustainability, however, performance, cost, and durability limit their utilization in real-time applications. Additionally, a sustainable circular bioeconomy (CE) ensures SDGs deliver material production, where it ceases the linear approach from production to waste. Simultaneously, sustainable circular bio-economy promoted materials should exhibit the prominent properties to involve and substitute conventional materials. These interceptions can be resolved through state-of-the-art bio-vitrimeric materials that display durability/mechanical properties such as thermosets and processability/malleability such as thermoplastics. This article emphasizes the current need for vitrimers based on bio-derived chemicals; as well as to summarize the developed bio-based vitrimers (including reprocessing, recycling and self-healing properties) and their requirements for a sustainable circular economy in future prospects

Fundamentals of Mercury Oxidation in Flue Gas

The objective of this project was to understand the importance of and the contribution of gas-phase and solid-phase coal constituents in the mercury oxidation reactions. The project involved both experimental and modeling efforts. The team was comprised of the University of Utah, Reaction Engineering International, and the University of Connecticut. The objective was to determine the experimental parameters of importance in the homogeneous and heterogeneous oxidation reactions; validate models; and, improve existing models. Parameters studied include HCl, NO{sub x}, and SO{sub 2} concentrations, ash constituents, and temperature. The results suggested that homogeneous mercury oxidation is below 10% which is not consistent with previous data of others and work which was completed early in this research program. Previous data showed oxidation above 10% and up to 100%. However, the previous data are suspect due to apparent oxidation occurring within the sampling system where hypochlorite ion forms in the KCl impinger, which in turn oxidized mercury. Initial tests with entrained iron oxide particles injected into a flame reactor suggest that iron present on fly ash particle surfaces can promote heterogeneous oxidation of mercury in the presence of HCl under entrained flow conditions. Using the data generated above, with homogeneous reactions accounting for less than 10% of the oxidation, comparisons were made to pilot- and full-scale data. The results suggest that heterogeneous reactions, as with the case of iron oxide, and adsorption on solid carbon must be taking place in the full-scale system. Modeling of mercury oxidation using parameters from the literature was conducted to further study the contribution of homogeneous pathways to Hg oxidation in coal combustion systems. Calculations from the literature used rate parameters developed in different studies, in some cases using transition state theory with a range of approaches and basis sets, and in other cases using empirical approaches. To address this, rate constants for the entire 8-step homogeneous Hg oxidation sequence were developed using an internally consistent transition state approach. These rate constants when combined with the appropriate sub-mechanisms produced lower estimates of the overall extent of homogeneous oxidation, further suggesting that heterogeneous pathways play an important role in Hg oxidation in coal-fired systems

Pachymeningeal metastasis from squamous cell carcinoma of the uterine cervix with involvement of the optic nerve: case report and review of the literature

This report describes the case of a 50-year-old woman with carcinomatous meningitis from squamous cell carcinoma of the uterine cervix. Ultrasound showed an irregular hypoechoic mass in the cervix. Contrast enhanced computed tomography imaging revealed intense linear enhancement along the falx cerebri suggestive of pachymeningeal metastasis with involvement of the optic nerve. To our knowledge this is the first reported case of imaging features of isolated metastatic dural involvement from cervical carcinoma. Moreover, this is the first case of its kind in which dural involvement was diagnosed at presentation in a locally confined tumour

A strain-promoted alkyne-azide cycloaddition (SPAAC) reaction of a novel EpCAM aptamer-fluorescent conjugate for imaging of cancer cells

For the first time, a novel EpCAM aptamer (SYL3C)-DIBO-AF594 fluorescent conjugate was synthesised by bioorthogonal chemistry utilizing a strain promoted alkyne-azide cycloaddition (copper free click) reaction (SPAAC). The ligation efficiency of SPAAC was improved by freeze-thaw cycles. The obtained conjugate showed target specific binding and aided in the imaging of various EpCAM positive cancer cell lines like MCF7, MDAMB453, Weri-RB1 and PC3

Fundamentals of Mercury Oxidation in Flue Gas

The objective of this project is to understand the importance of and the contribution of gas-phase and solid-phase coal constituents in the mercury oxidation reactions. The project involves both experimental and modeling efforts. The team is comprised of the University of Utah, Reaction Engineering International, and the University of Connecticut. The objective is to determine the experimental parameters of importance in the homogeneous and heterogeneous oxidation reactions; validate models; and, improve existing models. Parameters to be studied include HCl, NO{sub x}, and SO{sub 2} concentrations, ash constituents, and temperature. This report summarizes Year 2 results for the experimental and modeling tasks. Experiments in the mercury reactor are underway and interesting results suggested that a more comprehensive look at catalyzed surface reactions was needed. Therefore, much of the work has focused on the heterogeneous reactions. In addition, various chemical kinetic models have been explored in an attempt to explain some discrepancies between this modeling effort and others

A bibliometric survey of research trends in vitrimer

The recent trends of vitrimer studies enhance the thermoset material with superior properties, therefore, it is particularly important to address the critical scientific inquiries in this area using their research metrics. The reported vitrimer systems have been highly required for future real-time applications; however, the inquisitiveness of material exchange mechanisms extends the research studies further. Significantly, more scientific information's are required to achieve the evident prospective outcomes via these materials. This article highlights the trends and developments of the most relevant publications, authors, articles, countries, and keywords in the vitrimer research field over the past 10 years. The represented bibliometric survey would elevate the basic understanding of the current vitrimer research stats and also help follow the particular research community to learn and develop insight. To generate bibliometric networks, bibliometric data has obtained from Scopus and visualised in VOS-viewer; as an overview of that, the highest number of publications were from China, United States, France, United Kingdom, and Spain