This dissertation investigates the pressing issue of climate change, identifying carbon dioxide as its main driver and introduces Direct Air Capture (DAC) as a crucial technology for achieving significant reductions in net global emissions. Through an extensive review of existing literature on DAC, it examines various methods and materials developed for this purpose, highlighting the ongoing efforts, advancements, and potential for real-world application. A novel sorbent, quaternary ammonium-functionalized poly(arylene ether sulfone) is explored for DAC via the moisture swing process. This sorbent exhibited the ability to capture and release atmospheric CO2 by a swing in moisture. Effects of form factors of powder, free standing dense membrane and thin film composite membrane were also evaluated for DAC. Furthermore, the dissertation explores modifications to poly(arylene ether sulfones) – polymers primarily used in desalination processes – to enhance water scarcity solutions by improving desalination membrane hydrophilicity and reducing fouling. This enhancement is achieved through the incorporation of zwitterionic groups into the polymer structure. Additionally, it investigates the synthesis of polysulfone polymers from lignin-derivable monomers, offering a greener alternative to traditional polysulfones used in desalination due to their environmental and health concerns. Polysulfones derivable from lignin exhibited comparable thermal properties and enhanced hydrophilicity compared to petroleum-derived polymers, showing considerable promise. Lastly, this dissertation investigates a potential hybrid system for desalination and direct ocean capture by integrating redox-active compounds into desalination membranes. This aims to achieve a pH swing that facilitates the formation of dissolved CO2.

Electrolytes play a critical role in electrochemical devices and applications, and therefore design and development of electrolytes with tailored properties are much desired to accommodate variety of operation requirements. Extreme temperatures are considered as one of the challenging environmental conditions, especially for devices rely on liquid state electrolytes, rendering failure of operations once the electrolyte systems undergo phase transitions. This work focuses on development of low-temperature iodide-containing liquid electrolyte systems, specifically designed for the molecular electronic transducer (MET) sensors in space applications. Utilizing ionic liquids, molecular liquids, and salts, multiple low-temperature liquid electrolytes were designed with enhancements in thermal, transport, and electrochemical properties. Effects of intermolecular interactions were further investigated, revealing correlations between optimization of microscopic dynamics and improvements of macroscopic characteristics. As a result, three low-temperature electrolyte systems were reported utilizing ethylammonium/water, gamma-butyrolactone/propylene carbonate, and butyronitrile as solvent with ionic liquid, 1-butyl-3-methylimidazolium iodide, and lithium iodide salt. Consequently, the liquidus range of these systems have been extended to -108 ˚C, -120 ˚C, and -152 ˚C, respectively, marking the lowest liquidus temperature of liquid electrolytes to the author’s best knowledge. Moreover, transport properties of designed systems were characterized from 25 to -75 ˚C. Effects of selected cosolvent/solvent on evolutions of transport properties were observed, revealing interplay between two governing mechanisms, ion disassociation and ion mobility, and their dominance at different temperatures. Experimental spectroscopy characterization techniques validated the hypothesized intermolecular interactions between solvent-cation and solvent-anion, complimented by computational simulation results on the complex dynamics between constituent ions and molecules. To support MET sensing technology, the essential iodide/triiodide redox were investigated in developed electrolytes. Effects of different molecular solvents on electrochemical kinetics were elucidated, and steady performances were validated under a properly controlled electrochemical window. Optimized electrolytes were tested in the MET sensor prototypes and showcased adequate functionality from calibration. The MET sensor prototype has also successfully detected real-time earthquake with low noise floor during long term testing at ASU seismology facility. The presented work demonstrates a facile design strategy for task-specific electrolyte development, which is anticipated to be further expanded to high temperatures for broader applications in the future.

The continued reliance on fossil fuel for energy resources has proven to be unsustainable, leading to depletion of world reserves and emission of greenhouse gases during their combustion. Therefore, research initiatives to develop potentially carbon-neutral biofuels were given the highest importance. Hydrothermal liquefaction (HTL, a thermochemical conversion process) of microalgae is recognized as a favorable and efficient technique to produce liquid biofuels from wet feedstocks. In this work, three different microalgae (Kirchneriella sp., Galdieria sulphuraria, Micractinium sp.) grown and harvested at Arizona State University were hydrothermally liquefied to optimize their process conditions under different temperatures (200-375 °C), residence times (15-60 min), solids loadings (10-20 wt.%), and process pressures (9-24 MPa). A one-factor-at-a-time approach was employed, and comprehensive experiments were conducted at 10 % solid loadings and a residence time of 30 min. Co-liquefaction of Salicornia bigelovii Torr. (SL), Swine manure (SM) with Cyanidioschyzon merolae (CM) was tested for the presence of synergy. A positive synergistic effect was observed during the co-liquefaction of biomasses, where the experimental yield (32.95 wt.%) of biocrude oil was higher than the expected value (29.23 wt.% ). Co-liquefaction also led to an increase in the energy content of the co-liquefied biocrude oil and a higher energy recovery rate ( 88.55 %). The HTL biocrude was measured for energy content, elemental, and chemical composition using GC-MS. HTL aqueous phase was analyzed for potential co-products by spectrophotometric techniques and is rich in soluble carbohydrates, dissolved ammoniacal nitrogen, and phosphates. HTL biochar was studied for its nutrient content (nitrogen and phosphorous) and viability of its recovery to cultivate algae without any inhibition using the nutrient leaching. HTL biochar was also studied to produce hydrogen via pyrolysis using a membrane reactor at 500 °C, 1 atm, for 24 h to produce 5.93 wt.% gas. The gaseous product contains 45.7 mol % H2, 44.05 ml % CH4, and 10.25 mol % of CO. The versatile applications of HTL biochar were proposed from a detailed physicochemical characterization. The metal impurities in the algae, bio-oil, and biochar were quantified by ICP-OES where algae and biochar contain a large proportion of phosphorous and magnesium.

Fresh water is essential to the human population and is an integral component in global economics for its multiple uses, and population growth/development cause concern for the possible exhaustion of the limited supply of freshwater. A combined computational and experimental approach to observe and evaluate pervaporation membrane performance for brackish water recovery was done to assess its efficiency and practicality for real world application. Results from modeling conveyed accuracy to reported parameter values from literature as well as strong dependence of performance on input parameters such as temperature. Experimentation results showed improved performance in flux by 34%-42% with radiative effect and then additional performance improvement (9%-33%) with the photothermal effect from carbon black application. Future work will include improvements to the model to include scaling propensity and energy consumption as well as continued experimentation to assess quality of pervaporation in water recovery.