Obesity has consistently presented a significant challenge, with excess body fat contributing to the development of numerous severe conditions such as diabetes, cardiovascular disease, cancer, and various musculoskeletal disorders. In this study, different methods are proposed to study substrate utilization (carbohydrates, proteins, and fats) in the human body and validate the biomarkers enabling to investigation of weight management and monitor metabolic health. The first technique to study was Indirect calorimetry, which assessed Resting Energy Expenditure (REE) and measured parameters like oxygen consumption (VO2) and carbon dioxide production (VCO2). A validation study was conducted to study the effectiveness of the medical device Breezing Med determining REE, VO2, and VCO2. The results were compared with correlation slopes and regression coefficients close to 1. Indirect Calorimetry can be used to determine carbohydrate and fat utilization but it requires additional correction for protein utilization. Protein utilization can be studied by analyzing urinary nitrogen. Therefore, a secondary technique was studied for identifying urea and ammonia concentration in human urine samples. Along this line two methods for detecting urea were explored, a colorimetric technique and it was validated against the Ion-Selective method. The results were then compared by correlation analysis of urine samples measured with both methods simultaneously curves. The equations for fat, carb, and protein oxidation, involving VO2, VCO2 consumption, and urinary nitrogen were implemented and validated, using the above-described methods in a human subject study with 16 subjects. The measurements included diverse diets (normal vs. high fat/protein) in normal energy balance and pre-/post interventions of exercise, fasting, and a high-fat meal. It can be concluded that the indirect calorimetry portable method in conjunction with urine urea methods are important to help the understanding of substrate utilization in human subjects, and therefore, excellent tools to contribute to the treatments and interventions of obesity and overweighted populations.

Pervaporation is a membrane process suited to complex and highly contaminated wastewaters. Pervaporation desalination is an emerging area of study where the development of high-performance membranes is necessary to propel the field forward. This research demonstrated that sulfonated block polymer membranes (Nexar™)show excellent permeance (water passage normalized by driving force) of as much as 135.5 ± 29 kg m-2 hr-1 bar-1, with salt removal values consistently equal to or greater than 99.5%. Another challenging water management scenario is in spaceflight situations, such as on the International Space Station (ISS). Spaceflight wastewaters are highly complex, with low pH values, and high levels of contaminants. Current processes produce 70% wastewater recovery, necessitating the handling and processing of concentrated brines. Since recoveries of 85% are desired moving forward, further efforts in water recovery are desirable. An area of concern in these ISS water treatment systems is scalant deposition, especially of divalent ions such as calcium species. Zwitterions are molecules with localized positive and negative charges, but an overall neutral charge. Zwitterions have been used to modify the surface of membranes have shown to decrease fouling. Building a copolymer between zwitterions and other polymers, creates zwitterion layer on top of previously studied Nexar™ membranes. This coating demonstrates great promise to combat scaling, as it increases the hydrophilicity of the membrane surface measured via contact angle. The zwitterion membranes experienced reduced scaling, with the greatest difference being between 1617 ± 241 wt% on control membranes, to 317 ± 87 wt% on zwitterion coated membranes in the presence of CaCl2. In treating spaceflight wastewater, these zwitterion membranes are effective at retaining the acid in the feed, going from a pH value of 2 to 7 and reducing the contamination level of the feed, with a removal value of 99.3 ± 0.4%, measured through conductivity. These membranes also perform well in separation processes that do not require extreme vacuum and can be operated passively. By optimizing both membrane material properties and process conditions, achieving increased high levels of water recovery from spaceflight wastewaters is attainable.

Freshwater as the resource for the survival of humans and all lives on earth is very precious but scarce. The shortage of the original freshwater resources and the interfering activities by human and other natural factors form this issue together. To reduce the water supply pressure and deterioration of freshwater systems (for example, river, wetland, and groundwater), the quantity-increase and the quality-increase strategies should be implemented at the same time. Therefore, corresponding membrane technologies have been developed to achieve water purification with high efficiency and low cost. For desalinating seawater and other types of saline water, pervaporation has been proved that has the potential to complete desalination with salt rejection rate over 99 % when dealing with high salinity water that reverse osmosis (RO) cannot handle. In this dissertation, except the discussion of commonly used materials to synthesize pervaporation membranes, two types of novel pervaporation desalination membranes (nanophotonic-enhanced membrane and free-standing sulfonated membrane) have been presented and discussed. The novel membranes were tested to see the potential of pervaporation to desalinate seawater and saline water with more complex ionic composition, and the possibility of achieving zero liquid discharge in the desalination field when having pervaporation as the assistance. For mitigating polluted water that is caused by human activities, especially agricultural activities, electrodialysis is an effective method to remove specific ions from water, and it does not require extra chemical cost or regeneration. A type of anion exchange membranes inspired by ion exchange resins was synthesized and tested, and the performance on nitrate removal has been evaluated in this dissertation.

Membrane fouling, especially inorganic fouling, is a significant obstacle to treatinghighly saline brine using membrane distillation (MD). In this study, microbubbles (MBs) were injected into the feed tank of a lab-scale direct contact membrane distillation (DCMD) system, and its effect on permeate flux over time was examined. A synthetic inland reverse osmosis (RO) brine with a high scaling tendency was used as a feed solution. Results showed a sharper flux decline in the absence of MBs compared to when MBs are continuously injected into the feed tank. The introduction of MBs reduced the formation of salt precipitations on the membrane surface, which was the primary cause of the decline in flux. The use of intermittent MBs injection instead of continuous MB injection was evaluated as a way to reduce energy consumption; with a 15 min MBs injection every 2h, similar benefits were found for intermittent injection compared to continuous injection, indicating that providing MBs continuously is not needed to mitigate scale formation. These results show that MBs can be a potential chemical-free method to prevent scaling in desalination systems treating high saline solutions.

Hospital wastewater usually contains high concentrations of pharmaceuticals and other hazardous materials, depending on how waste is disposed of in a hospital. This poses potential health concerns for both the surrounding ecosystem and the contamination of drinking water. Membrane bioreactors (MBRs) are at the forefront of treating hospital wastewater due to their efficiency in dealing with high concentrations of pharmaceuticals and the relatively small size of the MBR system. Although MBRs are typically the best method of dealing with pharmaceutical-containing wastewater, an MBR is just one of many methods for treating wastewater. Engineers should be consulted to determine which water treatment systems are best for a hospital, depending on the total water usage, required size of the system, and the duration of operation for the system. Sustainable water practices can be implemented in hospitals to reduce the cost and consumption of water. Treating and reusing hospital wastewater with membrane bioreactors significantly reduces the concentration of pharmaceuticals, making hospital wastewater reusable in various parts of a hospital, which lowers the consumption of water. Furthermore, other practices can be used to minimize costs for both MBRs and total water usage within a hospital.

Membrane based technology is one of the principal methods currently in widespread use to address the global water shortage. Pervaporation desalination is a membrane technology for water purification currently under investigation as a method for processing reverse osmosis concentrates or for stand-alone applications. Concentration polarization is a potential problem in any membrane separation. In desalination concentration polarization can lead to reduced water flux, increased propensity for membrane scaling, and decreased quality of the product water. Quantifying concentration polarization is important because reducing concentration polarization requires increased capital and operating costs in the form of feed spacers and high feed flow velocities. The prevalent methods for quantifying concentration polarization are based on the steady state thin film boundary layer theory. Baker’s method, previously used for pervaporation volatile organic compound separations but not desalination, was successfully applied to data from five previously published pervaporation desalination studies. Further investigation suggests that Baker’s method may not have wide applicability in desalination. Instead, the limitations of the steady state assumption were exposed. Additionally, preliminary results of nanophotonic enhancement of pervaporation membranes were found to produce significant flux enhancement. A novel theory on the mitigation of concentration polarization by the photothermal effect was discussed.

Nanoporous materials, with pore sizes less than one nanometer, have been incorporated as filler materials into state-of-the-art polyamide-based thin-film composite membranes to create thin-film nanocomposite (TFN) membranes for reverse osmosis (RO) desalination. However, these TFN membranes have inconsistent changes in desalination performance as a result of filler incorporation. The nano-sized filler’s transport role for enhancing water permeability is unknown: specifically, there is debate around the individual transport contributions of the polymer, nanoporous particle, and polymer/particle interface. Limited studies exist on the pressure-driven water transport mechanism through nanoporous single-crystal nanoparticles. An understanding of the nanoporous particles water transport role in TFN membranes will provide a better physical insight on the improvement of desalination membranes.

This dissertation investigates water permeation through single-crystal molecular sieve zeolite A particles in TFN membranes in four steps. First, the meta-analysis of nanoporous materials (e.g., zeolites, MOFs, and graphene-based materials) in TFN membranes demonstrated non-uniform water-salt permselectivity performance changes with nanoporous fillers. Second, a systematic study was performed investigating different sizes of non-porous (pore-closed) and nanoporous (pore-opened) zeolite particles incorporated into conventionally polymerized TFN membranes; however, the challenges of particle aggregation, non-uniform particle dispersion, and possible particle leaching from the membranes limit analysis. Third, to limit aggregation and improve dispersion on the membrane, a TFN-model membrane synthesis recipe was developed that immobilized the nanoparticles onto the support membranes surface before the polymerization reaction. Fourth, to quantify the possible water transport pathways in these membranes, two different resistance models were employed.

The experimental results show that both TFN and TFN-model membranes with pore-opened particles have higher water permeance compared to those with pore-closed particles. Further analysis using the resistance in parallel and hybrid models yields that water permeability through the zeolite pores is smaller than that of the particle/polymer interface and higher than the water permeability of the pure polymer. Thus, nanoporous particles increase water permeability in TFN membranes primarily through increased water transport at particle/polymer interface. Because solute rejection is not significantly altered in our TFN and TFN-model systems, the results reveal that local changes in the polymer region at the polymer/particle interface yield high water permeability.

Nanomaterials (NMs), implemented into a plethora of consumer products, are a potential new class of pollutants with unknown hazards to the environment. Exposure assessment is necessary for hazard assessment, life cycle analysis, and environmental monitoring. Current nanomaterial detection techniques on complex matrices are expensive and time intensive, requiring weeks of sample preparation and detection by specialized equipment, limiting the feasibility of large-scale monitoring of NMs. A need exists to develop a rapid pre-screening technique to detect, within minutes, nanomaterials in complex matrices. The goal of this dissertation is to develop a tiered process to detect and characterize nanomaterials in consumer products and environmental samples. The approach is accomplished through a two tier rapid screening process to screen likely presence/absence of elements present in common nanomaterials at environmentally relevant concentrations followed by a more intensive three tier characterization process, if nanomaterials are likely to occur. The focus is on SiO2 and TiO2 nanomaterials with additional work performed on hydroxyapatite (Ca5(PO4)3(OH)). The five step tiered process is as follows: 1) screen for elements in the sample by laser induced breakdown spectroscopy (LIBS) and X-ray fluorescence (XRF), 2) extract nanomaterials from the sample and screen for extracted elements by LIBS and XRF, 3) confirm presence and elemental composition of nanomaterials by transmission electron microscopy paired with energy dispersive X-ray spectroscopy, 4) quantify the elemental composition of the sample by inductively coupled plasma – mass spectrometry, and 5) identify mineral phase of crystalline material by X-ray diffraction. This dissertation found LIBS to be an accurate method to detect Si and Ti in food matrices (tier one approach) with strong agreement with the product label, detecting Si and Ti in 93% and 89% of the samples labeled as containing each material, respectively. In addition XRF identified Ti, Si, and Ca in 100% of food samples TEM-confirmed to contain Ti, Si, and Ca respectively. As a tier two approach, LIBS on the 0.2 micrometer filter identified nano silicon in 42% of samples confirmed by TEM to contain nano Si and 67% of TEM-confirmed samples to contain Ti. XRF identified Si, Ti, and Ca loaded on to a 0.1 µm filter and Ti in the surfactant rich phase of CPE of water and water with NOM.

Membranes are a key part of pervaporation processes, which is generally a more

efficient process for selective removal of alcohol from water than distillation. It is

necessary that the membranes have high alcohol permeabilities and selectivities.

Polydimethylsiloxane (PDMS) based mixed matrix membranes (MMMs) have

demonstrated very promising results. Zeolitic imidazolate framework-71 (ZIF-71)

demonstrated promising alcohol separation abilities. In this dissertation, we present

fundamental studies on the synthesis of ZIF-71/PDMS MMMs.

Free-standing ZIF-71/ PDMS membranes with 0, 5, 25 and 40 wt % ZIF-71

loadings were prepared and the pervaporation separation for ethanol and 1-butanol from

water was measured. ZIF-71/PDMS MMMs were formed through addition cure and

condensation cure methods. Addition cure method was not compatible with ZIF-71

resulting in membranes with poor mechanical properties, while the condensation cure

method resulted in membranes with good mechanical properties. The 40 wt % ZIF-71

loading PDMS nanocomposite membranes achieved a maximum ethanol/water selectivity

of 0.81 ± 0.04 selectivity and maximum 1-butnaol/water selectivity of 5.64 ± 0.15.

The effects of synthesis time, temperature, and reactant ratio on ZIF-71 particle

size and the effect of particle size on membrane performance were studied. Temperature

had the greatest effect on ZIF-71 particle size as the synthesis temperature varied from -

20 to 35 ºC. The ZIF-71 synthesized had particle diameters ranging from 150 nm to 1

μm. ZIF-71 particle size is critical in ZIF-71/PDMS composite membrane performance

for alcohol removal from water through pervaporation. The membranes made with

micron sized ZIF-71 particles showed higher alcohol/water selectivity than those with

smaller particles. Both alcohol and water permeability increased when larger sized ZIF-

71 particles were incorporated.

ZIF-71 particles were modified with four ligands through solvent assisted linker

exchange (SALE) method: benzimidazole (BIM), 5-methylbenzimidazole (MBIM), 5,6-

dimethylbenzimidazole (DMBIM) and 4-Phenylimidazole (PI). The morphology of ZIF-

71 were maintained after the modification. ZIF-71/PDMS composite membranes with 25

wt% loading modified ZIF-71 particles were made for alcohol/water separation. Better

particle dispersion in PDMS polymer matrix was observed with the ligand modified ZIFs.

For both ethanol/water and 1-butanol/water separations, the alcohol permeability and

alcohol/water selectivity were lowered after the ZIF-71 ligand exchange reaction.

Membrane technology is a viable option to debottleneck distillation processes and minimize the energy burden associated with light hydrocarbon mixture separations. Zeolitic imidazolate frameworks (ZIFs) are a new class of microporous metal-organic frameworks with highly tailorable zeolitic pores and unprecedented separation characteristics. ZIF-8 membranes demonstrate superior separation performance for propylene/propane (C3) and hydrogen/hydrocarbon mixtures at room temperature. However, to date, little is known about the static thermal stability and ethylene/ethane (C2) separation characteristics of ZIF-8. This dissertation presents a set of fundamental studies to investigate the thermal stability, transport and modification of ZIF-8 membranes for light hydrocarbon separations.

Static TGA decomposition kinetics studies show that ZIF-8 nanocrystals maintain their crystallinity up to 200○C in inert, oxidizing and reducing atmospheres. At temperatures of 250○C and higher, the findings herein support the postulation that ZIF-8 nanocrystals undergo temperature induced decomposition via thermolytic bond cleaving reactions to form an imidazole-Zn-azirine structure. The crystallinity/bond integrity of ZIF-8 membrane thin films is maintained at temperatures below 150○C.

Ethane and ethylene transport was studied in single and binary gas mixtures. Thermodynamic parameters derived from membrane permeation and crystal adsorption experiments show that the C2 transport mechanism is controlled by adsorption rather than diffusion. Low activation energy of diffusion values for both C2 molecules and limited energetic/entropic diffusive selectivity are observed for C2 molecules despite being larger than the nominal ZIF-8 pore aperture and is due to pore flexibility.

Finally, ZIF-8 membranes were modified with 5,6 dimethylbenzimidazole through solvent assisted membrane surface ligand exchange to narrow the pore aperture for enhanced molecular sieving. Results show that relatively fast exchange kinetics occur at the mainly at the outer ZIF-8 membrane surface between 0-30 minutes of exchange. Short-time exchange enables C3 selectivity increases with minimal olefin permeance losses. As the reaction proceeds, the ligand exchange rate slows as the 5,6 DMBIm linker proceeds into the ZIF-8 inner surface, exchanges with the original linker and first disrupts the original framework’s crystallinity, then increases order as the reaction proceeds. The ligand exchange rate increases with temperature and the H2/C2 separation factor increases with increases in ligand exchange time and temperature.