·¬ÇÑÉçÇø

Topic

Advances in Reverse Osmosis Membrane Engineering and Alginate Recycling: Covalent Surface Modifications for Membrane Performance and Analysis of Molecular Changes and Calcium Crosslinker Removal for Alginate sustainable practices

Department of Civil Engineering

Date & location

• Tuesday, November 12, 2024

• 9:00 A.M.

• Engineering Computer Science Building

• Room 467

Reviewers

Supervisory Committee

• Dr. Heather Buckley, Department of Civil Engineering, ·¬ÇÑÉçÇø (Co-Supervisor)

• Dr. Onita Basu, Department of Civil Engineering, UVic (Co-Supervisor) 

External Examiner

• Dr. Samira Gharehkhani, Department of Mechanical Engineering, ·¬ÇÑÉçÇø 

Chair of Oral Examination

• Dr. Christopher Eagle, Department of Mathematics and Statistics, UVic

   

Abstract

The increasing demand for potable water and the environmental impact of conventional plastics present significant global challenges that require innovative solutions. Addressing these issues effectively involves advancements in both water purification technologies and material sustainability. This thesis explores these challenges through two complementary projects: enhancing reverse osmosis (RO) membrane technology and improving the sustainability of alginate-based bioplastics.

Reverse osmosis is a critical water purification technology used to produce fresh water from diverse sources, including seawater and brackish water. Central to this technology are RO membranes, which are predominantly made of polyamide. Despite their effectiveness, these membranes face performance limitations due to biofouling and chemical degradation. Biofouling, caused by microorganisms forming biofilms on the membrane surface, reduces water flux, increases operational pressure, and raises energy consumption. Chemical degradation affects membrane longevity and performance, leading to frequent cleaning and replacement. These issues contribute to significant economic costs and environmental waste. 

Chapter 1 explores the attachment of PEI-diazirine onto PET surfaces, with the hypothesis that successful cross-linking in these trials could also be applied to polyamide-based reverse osmosis (RO) membranes due to the reactivity between polyamides and carbenes. The objective was to develop a method for covalent modification of RO membranes using diazirine moieties, which could serve as a foundation for further functionalization. Covalent bonding offers advantages such as improved stability, durability, and compatibility, making it a favorable approach for RO membrane surface modification. In conclusion, the study introduced an innovative approach to enhancing the surface properties of RO polyamide-based membranes by incorporating covalently bonded diazirine-containing molecules. While direct evidence of covalent attachment was not confirmed, indirect observations—such as results from dye and water angle tests, DSC, and FTIR—support the presence of activated diazirine on the surface. These tests disproved the idea that diazirine molecules react exclusively with each other rather than with the surface. This groundwork sets the stage for future functionalization processes to impart foul-release properties to RO membranes. 

Chapter 2 focuses on advancing the sustainability of alginate-based bioplastics, particularly those derived from kelp. The study investigates the recycling potential of alginate, aiming to enhance sustainable practices. Recycling alginate helps preserve resources by reintegrating used materials into the production cycle, reducing the need for fresh raw materials. Additionally, recycling alginate-based products reduces waste volume, supports waste reduction goals, and minimizes the environmental impact of landfill disposal.

The research in Chapter 2 builds on optimized sodium alginate extraction methods and evaluates the recycling potential of alginate films produced by these methods. It proposes and assesses a recycling protocol for its effectiveness in terms of yield and purity, focusing on calcium crosslinker removal and structural changes in alginate films. This study provides valuable insights into sustainable alginate recycling, promoting a circular economy by extending the life cycle of materials and reducing waste generation. 

Although each chapter addresses different material types and applications, they share a common theme: enhancing material performance while mitigating environmental impact. Improving RO membrane fouling resistance and chemical stability directly contributes to reducing waste and energy consumption in water treatment. For alginate bioplastics, optimizing recycling processes ensures effective material reuse, decreasing plastic waste and the demand for new raw materials. 

These projects reflect a broader commitment to sustainability by tackling critical issues in material performance and environmental responsibility. The outcomes from these chapters offer practical solutions that align with global efforts to conserve resources and minimize ecological footprints. Through the development of advanced membrane technologies and sustainable bioplastics, this thesis contributes to a more sustainable future, demonstrating that innovation in material science can drive significant improvements in both industrial applications and environmental stewardship.

In conclusion, this thesis bridges the gap between technological advancement and environmental sustainability. By addressing the challenges of water purification and plastic waste management, it provides valuable insights and practical solutions that enhance material performance and promote a more sustainable approach to resource use.