Solid, aqueous, and gaseous: functional materials and advancements to reduce pollution in three forms
Authors:   , Siercks Ian C. 
Published: February 2023

Growing environmental concerns require new and novel materials to combat the glut of anthropogenic pollution produced. Solid waste polymer pollution chokes the planet and, concerningly, has been found to generate a new class of pollutant in microplastics; these microplastics, and also waste pharmaceuticals and dyes, accumulate in our water with deleterious effects on animal life. Simultaneously, CO2 and other greenhouse gases threaten us with climate change causing loss of habitable land, destroyed ecosystems, and prevalent extreme weather events. For a sustainable future, pollution in all three forms must be combatted. In this dissertation, I present works related to the pursuit of this goal. In all cases, I have striven to produce research and materials that are creative and multifunctional. In as much as possible, I have given thought to the feasible real-world applicability of this work. Firstly, I have produced and characterized an extensive series of activated carbons using waste plastics in proportions that mimic those found in real world mixed plastic recycling. The carbons were activated by tube furnace pyrolysis at three different temperatures with both common and atypical activating agents. The materials were rigorously characterized and their abilities to adsorb both three aqueous compounds - a cationic dye, an anionic dye, and a neutral pharmaceutical - and gaseous CO2 were investigated. It was found that the materials were extremely diverse with materials activated with KOH and citric acid being the most performant at capturing CO2 (1.86 and 1.91 mmol CO2/g sorbent, respectively). As far as the adsorption of aqueous pharmaceuticals or dyes is concerned, the materials tested displayed differing capacities for each adsorbate that appeared mostly independent of surface area and activating agent. For cationic methylene blue (MB), Sodium Citrate-600 was the most performant, capturing a maximum of 89.59 mg/g; for anionic methyl orange (MO), Zinc Chloride-500 performed best and captured a maximum of 123.8 mg/g; for neutral tetracycline (TC), Zinc Chloride-500 was again the most effective and captured a maximum of 189.7 mg/g. Further, a series of amine-loaded silica materials were created using a variety of silica supports (SBA-15, PE-MCM-41, COK-19, HPS, and fumed silica) and one amine (Jeffamine T-403) to elucidate the most crucial support property on the overall CO2 capacity of the loaded material. Results suggest that surface area is the most important predictor of CO2 capacity for these materials. It was also found that pore expanded MCM-41 performed the best, capturing 1.81 mmol CO2/g sorbent under atmospheric pressure of 100 percent CO2 at 45 degreesC. This support was additionally co-loaded with a different -- high capacity but poorly regenerating -- amine to optimize the low temperature regeneration of the material; the resultant co-loaded material displayed the favorable regenerable capacity of 2.04 mmol CO2/g sorbent under the same conditions as above. Finally, a recently published procedure for the low-cost removal of microplastics from water using calcium carbonate co-precipitation was expanded by testing the method using common polystyrene microspheres and found to be 56.59 percent and 91.66 percent effective when using 1 µm and 25 µm spheres, respectively. To add to this method, a novel procedure exploring the use of CO2 to release captured microplastics was explored. Overall, it is my hope that these works as a whole will help pave the way for the feasible reduction of pollution in solid, aqueous, and gaseous forms.