Reverse osmosis (RO) is widely used for water reuse and desalination. Although RO membranes are known for their high salt rejection and practical permeate flux, their performance can be impaired by fouling, and their removal of some disinfection byproducts and their precursors (e.g., bromide, N-Nitrosodimethylamine [NDMA]) does not meet drinking water standards. RO membrane modifications have been widely studied to overcome these limitations. In this research, RO membranes were grafted with cationic polymers to induce a positive charge on the RO membrane surface. This modification aimed at enhancing the rejection of negatively charged bromide ions by removing them from solution by binding them to the membrane surface. The results showed that the modified (positively charged) RO membranes achieved lower rejection (82% rejection) for bromide ions compared to the unmodified ones (94.5% rejection). This behavior was likely a result of increased concentration polarization of the bromide ions at the membrane surface and/or increase in porosity of the modified membranes. Calculations based on the film theory indicate that the concentration of bromide ions at the surface of the modified membrane was 1371 ppm compared to 1307 ppm at the surface of the unmodified membrane. Evidently, the polymer attraction energy was not sufficient to keep the bromide ions attached to the membrane surface and prevent their diffusion across the membrane. Although the goal of the modification in the current study (i.e., enhancing removal of bromide ions) was not met, the permeate flux of the modified membrane was improved compared to the unmodified one. The literature suggests that increasing flux after modification is likely a result of increase in membrane pore size and hydrophilicity. In addition to the experimental work conducted in this study, a multi-criteria decision analysis was performed to prioritize research on surface modifications of reverse osmosis membranes. It was found that surface modifications have been mainly focused on reducing membrane fouling and to a much lower extent on removal of disinfection byproducts and their precursors. The RO membrane modification alternatives for fouling reduction and N-Nitrosodimethylamine (NDMA) removal were ranked based on multiple criteria using the Analytical Hierarchy Process (AHP) and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). This multi-criteria decision analysis process resulted in the identification of the top five promising modifications to reduce fouling and improve NDMA rejection. Grafting and coating the RO membranes with complex polymeric salts were the highest ranked modification approaches to reduce fouling. Heat-treatment of RO membranes achieved the highest NDMA rejection (98%); however, this technique was the second highest ranked modification approach for NDMA removal because it scored lower for other evaluation criteria.

The air conditioning systems currently utilized in automobiles are the vapor compression systems. This type of system has many disadvantages: the refrigerant used is not environmentally friendly, the compressor is in competition with the engine coolant system, and the compressor uses a significant portion of the engine power. A waste heat driven absorption refrigeration system is one alternative to the current systems that could address these problems. The absorption refrigeration system uses solutions for the absorbent-refrigerant pair that do not harm the environment. This investigation includes a theoretical analysis of the feasibility of absorption air conditioning system in automotive applications. Also, a comparison of the power requirements of the proposed system and the vapor compression system is performed.

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<p>In this research, ozone hydrodynamics and disinfection by-products formation in a novel hybrid ozonation-ceramic membrane filtration system was studied to minimize membrane fouling while also ensuring that the system meets regulatory criteria for disinfection by-products. The influence of important operating parameters including inlet ozone mass injection rate, initial bromide concentration, membrane molecular weight cut off (MWCO), membrane coating, hydroxyl radical scavenger (<em>t</em>-butanol), pH, and temperature on bromate concentration in the absence and presence of natural organic matter (NOM) was examined. Experiments were also conducted under various operating conditions to investigate the formation of total trihalomethanes (TTHMs) and halo-acetic acids (HAAs) in the water distribution system due to post chlorination. Moreover, variations in the TOC, UV₂₅₄, color and turbidity with respect to operating parameters were monitored.</p> <p>Bromate and TTHMs formation increased with increasing ozone mass injection rate, and initial bromide concentration. An increase in the bromate concentration was observed with decreasing membrane MWCO. Less bromate and TTHM was formed with the coated membrane and <em>t</em>-butanol significantly reduced bromate and TTHM formation. Bromate formation decreased significantly with decreasing pH. Increasing the temperature resulted in enhanced bromate formation. NOM exerted a favorable effect on bromate formation as the bromate concentration was observed to decrease as the NOM content was increased.</p> <p>Experimental results indicated that ozonation can greatly reduce color and turbidity of water and can be used to overcome membrane fouling. Ensuring a minimum ozone residual in the system enables the continuous treatment of water at a relatively high permeate flux (up to 85% of the clean water flux) and eliminates the need for membrane cleaning procedures.</p> <p>An empirical model was developed to predict bromate formation in the hybrid ozone- membrane system (R²=0.903). Theoretical models were developed to estimate the rate of bromate formation and to describe the ozone mass transfer in a hybrid system. In all cases, good correlation between the model predictions and the experimental data was achieved.</p> / Doctor of Philosophy (PhD)

Possibilities for increasing the upper limit of floatable particle sizs in the froth flotation process have been examined since the early beginnings of mineral flotation. The economic implications of such an incresae are far ranging; from decreased grinding costs and increased recoveries to simplified flow-sheet design and increased throughput, all leading to increased revenue. Bubble-particle detachment has been studied to better understand the factors influencing the strength of attachment and the energies involved. Direct measurements of bubble particle detachment were performed using a hanging balance apparatus (KSV Sigma 70 tensiometer) and using a submerged hydrophobic plate in water. Three experiments were used; direct force measurement of bubble-particle detachment, detachment force and energy of a bubble from a submerged hydrophobic plate, and detachment force and energy of a cetyltrimethylammonium bromide coated silica sphere from a flat bubble. Octadecyltrichlorosilane was used as a hydrophobic coating in the first two experimental methods. These experiments were recorded with a CCD camera to identify the detachment processes involved. Energies for both methods were calculated and divided into the two main steps of the detachment process: Three-Phase-Contact pinning and three phase contact line sliding. The first step represents the energy barrier which must be overcome before detachment can begin. It is directly related to contact angle hysteresis. Detachment occurs during the second step, where the solid-vapor interface is replaced by solid-liquid and liquid-vapor. This step corresponds to the work of adhesion. The effects of surface tension, contact angle and hysteresis were well demonstrated with the three experimental methods. Good correlation was found between theoretical work of adhesion and measured energies. / Master of Science

Because of the structural analogies between these compounds and several other physiologically active compounds, such as chloroamphenicol, 4,4'-diaminodiphenyl sulfone, and 2,2-bis-(p-aminophenyl)-1,1,1-trichloroethane, a more complete study of the reduction products and the sequence of catalytic reduction of N-(4-nitrophenacyl)-4-(1-hexyl)pyridinium bromide was made in this investigation.

The forest products industry significantly contributes to Virginia's economy, generating $23 billion annually, employing 109,000 individuals, and providing $345 million to timber landowners. Hardwood log exports are a crucial portion of this economic contribution, with major importers including China, Vietnam, and Canada. Most importing countries have specific requirements to prevent the movement of invasive organisms on the logs imported, of which chemical treatment is common. This study examines the feasibility and implications of transitioning from chemical-based treatments, such as methyl bromide, to a vacuum and steam treatment for hardwood log exports. Our investigation focuses on understanding the barriers to the adoption of this new technology, including industry awareness and perception, regulatory framework challenges, international acceptance, and economic viability. By addressing these areas, we aim to create a comprehensive manual for any company interested in adopting this technology. The manual will include a performance measurement system and a feasibility study to ensure successful implementation. Therefore, this thesis consists of two documents, the first provides background information, a problem statement and methods and results around the investigation of barriers to the adoption of this new treatment and a second document, the proposed manual to assist with implementation. To address the first objective, data were collected through interviews with technology developers, industry experts, and hardwood log importers in China and India. Quantitative data highlighted a 36.7% increase in US hardwood log exports to China in 2023, with species like alder and yellow poplar leading the market. Results indicate that China imports a significantly higher volume of hardwood logs monthly compared to India, highlighting a larger and more consistent demand. Commonly imported species include red and white oak, ash, and walnut. Both countries have strict fumigation requirements, primarily using methyl bromide, underscoring a global reliance on this method despite its environmental concerns. Awareness of alternative treatments such as vacuum and steam is limited, though there is interest in exploring cost-effective and efficient methods. However, adoption is hindered by regulatory approval and the need for proven effectiveness. To facilitate this transition, we created a comprehensive manual for companies to guide them through replacing methyl bromide and other chemical treatments with vacuum and steam technology. This study provides a comprehensive pathway for adopting vacuum and steam technology, addressing technical, regulatory, and economic considerations. The forest products sector can mitigate environmental impact by aligning industry practices with sustainable treatment methods while maintaining international trade relationships. / Master of Science / Virginia's forest industry is a major part of the state's economy, generating $23 billion each year and providing jobs to 109,000 people. Hardwood logs, particularly those exported to countries like China, Vietnam, and Canada, play a significant role in this economic impact. However, these countries require that imported logs be treated to prevent the spread of harmful pests. Traditionally, chemical treatments like methyl bromide have been used, but they pose environmental concerns. Our study explores the possibility of switching to a safer and more environmentally friendly method: vacuum and steam treatment. We looked into the challenges that might come with adopting this new technology, such as how aware the industry is of it, regulatory hurdles, whether international markets would accept it, and whether it's economically feasible. Our goal is to create a helpful guide for companies interested in making this switch, ensuring they have all the information needed to implement the new treatment successfully. To gather insights, we interviewed experts and key players in the industry, including log importers from China and India. We found that while there is interest in exploring new treatments, there are significant challenges, particularly related to getting regulatory approval and proving the effectiveness of the new method. Despite these challenges, our research outlines a clear path for adopting vacuum and steam treatment, which could help the forest products industry reduces its environmental impact while continuing to thrive in international trade.

This disertation thesis is focused on the study of physico-chemical interactions of hyaluronan (with molecular weights from 10 to 1750 kDa) with cationic surfactants measured using uncommon technique named high resolution ultrasonic spectroscopy. Densitometer was also used for the study of these interactions, in measuring of density and ultrasonic velocity of hyaluronan with different molecular weight in dependence on elevated temperature (25 50 °C). The aim is the determination of critical micelle concentration (CMC) and critical aggregation concentration (CAC) of the suractants in the absence and in the presence of hyaluronan with various molecular weights. Interactions in this system are important for the design of the systems for the targeted delivery, especially for the drugs. The experiments were made in water and sodium chloride solution. The significant breakpoint in the ultrasonic velocity showed changes in the system hyaluronan-surfactant.

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