Date of Award
1-11-2022
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Population growth and development in the forms of urbanization and industrialization have made the availability of clean water a critical global issue. As we face this reality, continued advancements in water purification technologies are necessary. Membrane technologies have been extensively employed for wastewater treatment and reuse, seawater desalination, and drinking water production. Generally, membrane treatment processes are relatively easy to operate, stable, environmentally friendly, and can be energy saving; however, fouling issues and the trade-off between permeability and selectivity remain critical technological challenges. Over the past decade, nanotechnology has rapidly advanced from basic research and development to commercial applications and is now a cornerstone approach to improve conventional ceramic and polymeric water treatment membranes. Recently, a number of engineered carbon nanomaterials (CNMs) and their derivatives, such as carbon nanotubes, fullerenes C60, and graphene oxide (GO), have attracted significant interest as novel materials for the water treatment. Compared to traditional analogs, these nanomaterials, with rapidly decreasing costs, have demonstrated superior and even unique physical and chemical properties for water treatment technologies, including membranes for advanced separations. Among all these materials, graphene oxide (GO) has become a focus of attention recently for its unique two-dimensional single-layer thickness structure, outstanding chemical properties (rich oxygen-containing functional groups), excellent mechanical stiffness, and potential engineering possibilities. Such features make graphene oxide an excellent platform candidate towards improving membrane properties such as permeability, anti-fouling, and antimicrobial properties. Interestingly, the traditional 2D graphene oxide nanosheets can be crumpled into 3D balls which shows excellent anti-aggregation and anti-compression properties, while allowing for the effective encapsulation and incorporation of other functional materials. This thesis is mainly focused on the development and characterization of membrane assemblies that are either comprised of, or enhanced by, engineered carbon nanomaterials, including fullerol, 2D GO nanosheets, 3D ‘crumpled’ GO balls and its functional nanocomposites. For the first time, we have prepared and characterized polysulfone (PSF) ultrafiltration membranes via a phase inversion method which incorporate oxidized fullerenes. When the ratio of fullerol is optimized, the incorporation of fullerol breaks the traditional trade-off between membrane permeability and selectivity, as both are improved concurrently. We have also conducted a comprehensive study, including membrane structure, surface chemistry, performance (permeability, selectivity, and antimicrobial ability) of the GO membrane assemblies as a function of material morphology and surface chemistry. Results reveal that the employment of advanced 3D CGO provides a broader platform for water treatment membranes to concurrently achieve high permeability, satisfactory rejection, and excellent antimicrobial properties. Furthermore, we engineer CGO with nanomagnetite into the crumpled structures. The membrane surface modified by this material can be cleaned and reformed in situ under magnetic field manipulation after each period of use, providing a novel approach to future methods of membrane cleaning and fouling control. We also explore the environmental behavior (aggregation, deposition, and release) of GO/CGO materials, illustrating new knowledge of how the physical and chemical transformations of GO can change its transport behaviors, which is important for its applications, potential environmental implications, and disposal management.
Language
English (en)
Chair
John Fortner