Browsing by Author "Getachew, Bezawit"
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Item Environmentally friendly microcapsule based self-healing materials using castor oil in lieu of chlorobenzene(2023-12-01) Nelson, Georgia; Getachew, BezawitSelf-healing materials are a class of smart materials which can recover from physical or chemical damage autonomously. One type of self-healing materials involves the use of microcapsules which are embedded within a substrate. The microcapsules contain a reactive healing agent that is exposed to the outside environment when the substrate is damaged. Upon exposure to the environment, the healant inside the microcapsules reacts quickly and solidifies in place, repairing the damage at the interface. While microcapsule-embedded self-healing materials hold promise for improving the resilience of many systems including infrastructure and water treatment systems, current development has been limited to proof-of-concept work that uses carcinogenic chemicals such as chlorobenzene. Solvents such as chlorobenzene are used to dissolve the healing agent during the encapsulation process. Replacing the solvent used during microcapsule fabrication with more environmentally friendly solvents, such as castor-oil could improve the sustainability and practical application of self-healing materials. Practical applications include embedding these microcapsules to the surface of membranes for water treatment or applying them as a protective self-healing coating in pipes. In this work, microcapsules were fabricated with both chlorobenzene and castor oil, and the size distribution and the microcapsule core content of each solvent were compared using Fiji image analysis and Thermographic analysis (TGA) respectively. Using castor oil as a solvent resulted in microcapsules with an average diameter of 153um, in contrast to the chlorobenzene microcapsules that had an average diameter of 107um. Despite the larger average diameter of the castor oil microcapsules, TGA analysis suggested that microcapsules fabricated with chlorobenzene contained a higher percentage of healing agent. The successful fabrication of environmentally friendly castor oil-based self-healing microcapsules indicates that they can be used as an alternative to their toxic chlorobenzene counterparts, but future research is needed to determine if the lower percentage of healing agent will impact their performance.Item Evaluating the Swelling/Degradation Behavior of Calcium Alginate Beads in Synthetic Wastewater Under Varied Environmental Conditions(2024-04-17) Cadena Semanate, Eliana Salome; Getachew, Bezawit; Stadler, Lauren; Verduzco, RafaelBacteria encapsulation has gained attention as a promising technique to enhance the biodegradation of contaminants in wastewater. While encapsulation offers substantial benefits, including enhanced biological stability, higher biomass concentration, enhanced symbiotic relationships, and partition advantages, 1 it also presents challenges such as mass transfer limitations and matrix instability. This research seeks to gain insight into the behavior of calcium alginate beads under conditions simulating real-world wastewater environments. Dynamic weight change of beads was measured over time considering varying crosslinking degrees of CaCl2 (0.1M, 0.3M, 0.5M), different wastewater strengths (NaCl concentrations of 0 g/L, 15g/L, and 35g/L), and high turbulence (shaking at 200rpm). Results suggest that higher crosslinker concentrations yield smaller beads, but this does not significantly alter the maximum water uptake in synthetic wastewater. Moreover, beads show varying swelling and degradation rates depending on the medium’s ionic composition, especially in the presence of Na+ ions. Water uptake increased, and bead stability decreased with high NaCl concentrations. Similarly, high turbulence conditions increased the water uptake ratio. Overall, all of the beads resisted degradation and didn’t dissolve completely for at least 78 days. The study suggests a crosslinker concentration of 0.3M or higher is promising for optimal stability in wastewater applications. This research provides insights into the chemical and physical factors that affect the stability of calcium alginate beads in synthetic wastewater. However, further research is required to develop more effective matrixes for bacteria encapsulation for wastewater applications.Item Solubility, Precipitation Kinetic, and Chemical Control of Iron Sulfide(2024-04-18) Wang, Xin; Tomson, Mason B; Chapman, Walter G; Getachew, BezawitThe iron sulfides (FeS) constitute a diverse group of solids and dissolved complexes, many of which play critical roles in the natural system, such as marine sedimentation and biochemical processes. It has also become a significant problem in various industrial processes, such as water and wastewater treatment, metal equipment corrosion by hydrogen sulfide, and oil and gas production. Extensive studies have been done in the past century to better understand, predict, and control the sulfide mineral precipitation, of which the importance can never be overstated. In this work, a systematic study of the solubility, precipitation kinetics, and the chemical dispersion control of iron sulfide is conducted to better understand iron sulfide scale prediction and control in industrial processes.