Date of Defense
20-11-2025 11:15 AM
Document Type
Thesis Defense
Degree Name
Doctor of Philosophy in Chemical Engineering
College
COE
Department
Chemical and Petroleum Engineering
First Advisor
Prof. Sulaiman Al Zuhair
Second Advisor
Prof. Bart Van der Bruggen
Keywords
Enzymatic Membrane Reactors, MOFs, Nanomaterials, Pharmaceutical Pollutants, Wastewaters.
Abstract
Emerging pollutants (EPs), such as pharmaceuticals and personal care products, are increasingly detected in municipal wastewater due to household discharge and improper industrial disposal. Their persistence and ecological risks pose major challenges to conventional treatment technologies. Among advanced options, membrane filtration, particularly microfiltration and ultrafiltration, has gained prominence for its efficiency and scalability. However, membrane fouling, especially biological and chemical fouling, remains a critical barrier, accounting for nearly half of total energy consumption and requiring frequent use of harsh chemical cleaning agents that further burden the environment.
This PhD research addresses these challenges by developing and evaluating hybrid bioactive enzyme-active membranes (EAMs) as a sustainable and effective solution for EP removal, using ibuprofen as a model contaminant. The work introduces a novel approach by immobilizing the biocatalyst Aspergillus oryzae peroxidase onto a PVDF membrane and integrating it with structured nanomaterials, including metal-organic frameworks (MOFs) such as ZIF-8 and ZIF-L. MOFs provide a high surface area, tunable pore structures, and improved enzyme–substrate interactions, thereby enhancing mass transfer and catalytic efficiency.
A series of hybrid membranes were fabricated and systematically characterized to evaluate their mechanical stability, chemical resistance, and antifouling properties under realistic operating conditions. Enzyme encapsulation within MOFs proved superior to surface adsorption, as it preserved enzyme conformation, increased active surface area, and enhanced pollutant degradation. A diffusion–reaction model was developed to analyze internal transport dynamics, while adsorption kinetics and thermodynamics were modeled to optimize fixed-bed continuous operation.
Further advancements included the co-immobilization of peroxidase with redox mediators, including ABTS, γ-Fe₂O₃, and kraft lignin. The peroxidase/ZIF-8/ABTS/PVDF membrane achieved high ibuprofen degradation, strong reusability, and excellent antifouling resistance, with ABTS•⁺ radicals playing a key role in boosting electron transfer and catalytic activity. Machine learning (ML) models were employed to support performance prediction and process optimisation. Linear regression models achieved high predictive accuracy, demonstrating the potential of AI-driven tools for forecasting membrane performance. The peroxidase/γ-Fe₂O₃/ZIF-8 hybrid membrane removed over 90% of ibuprofen under mild conditions without added H₂O₂, maintaining both permeability and catalytic activity over five cycles and 40 days. Incorporating kraft lignin further enhanced pollutant affinity and sustainability, with the peroxidase/lignin/ZIF-8/PVDF membrane achieving up to 99% ibuprofen removal, alongside excellent reusability and long-term stability for 5 cycles and 40 days, respectively. Addressing the environmental persistence and potential toxicity of fluorinated polymers, PVDF underscores the necessity of long-term sustainability in membrane materials, emphasizing the necessity of future development of eco-friendly alternatives and mitigation strategies.
The versatility of the hybrid bioactive system was validated across PES membranes, which successfully integrated catalytic components without surface modification. This environmentally friendly processing method highlights adaptability to different polymer platforms while delivering strong pollutant degradation efficiency, improved antifouling resistance, and reliable reusability across multiple operational cycles.
Finally, an economic assessment was conducted to evaluate scalability and complement the technical validation. The results indicate that the proposed approach is economically viable and technically feasible for large-scale implementation. This thesis demonstrates enzyme-active and hybrid bioactive membranes as promising alternatives to conventional pollutant removal technologies. By combining the catalytic power of enzymes with the structural advantages of MOFs, nanoparticles, and renewable biopolymers, the research establishes a new pathway for advanced water treatment systems. The findings provide a solid scientific and practical foundation for scalable, eco-friendly, and cost-effective technologies that directly address emerging pollutants' challenges. Beyond its scientific contributions, the research supports national and global goals for sustainable water management and environmental protection, offering innovative solutions to safeguard water security for the future.
Included in
BIOACTIVE MEMBRANE SYSTEM FOR EFFICIENT EMERGING POLLUTANTS TREATMENT
Emerging pollutants (EPs), such as pharmaceuticals and personal care products, are increasingly detected in municipal wastewater due to household discharge and improper industrial disposal. Their persistence and ecological risks pose major challenges to conventional treatment technologies. Among advanced options, membrane filtration, particularly microfiltration and ultrafiltration, has gained prominence for its efficiency and scalability. However, membrane fouling, especially biological and chemical fouling, remains a critical barrier, accounting for nearly half of total energy consumption and requiring frequent use of harsh chemical cleaning agents that further burden the environment.
This PhD research addresses these challenges by developing and evaluating hybrid bioactive enzyme-active membranes (EAMs) as a sustainable and effective solution for EP removal, using ibuprofen as a model contaminant. The work introduces a novel approach by immobilizing the biocatalyst Aspergillus oryzae peroxidase onto a PVDF membrane and integrating it with structured nanomaterials, including metal-organic frameworks (MOFs) such as ZIF-8 and ZIF-L. MOFs provide a high surface area, tunable pore structures, and improved enzyme–substrate interactions, thereby enhancing mass transfer and catalytic efficiency.
A series of hybrid membranes were fabricated and systematically characterized to evaluate their mechanical stability, chemical resistance, and antifouling properties under realistic operating conditions. Enzyme encapsulation within MOFs proved superior to surface adsorption, as it preserved enzyme conformation, increased active surface area, and enhanced pollutant degradation. A diffusion–reaction model was developed to analyze internal transport dynamics, while adsorption kinetics and thermodynamics were modeled to optimize fixed-bed continuous operation.
Further advancements included the co-immobilization of peroxidase with redox mediators, including ABTS, γ-Fe₂O₃, and kraft lignin. The peroxidase/ZIF-8/ABTS/PVDF membrane achieved high ibuprofen degradation, strong reusability, and excellent antifouling resistance, with ABTS•⁺ radicals playing a key role in boosting electron transfer and catalytic activity. Machine learning (ML) models were employed to support performance prediction and process optimisation. Linear regression models achieved high predictive accuracy, demonstrating the potential of AI-driven tools for forecasting membrane performance. The peroxidase/γ-Fe₂O₃/ZIF-8 hybrid membrane removed over 90% of ibuprofen under mild conditions without added H₂O₂, maintaining both permeability and catalytic activity over five cycles and 40 days. Incorporating kraft lignin further enhanced pollutant affinity and sustainability, with the peroxidase/lignin/ZIF-8/PVDF membrane achieving up to 99% ibuprofen removal, alongside excellent reusability and long-term stability for 5 cycles and 40 days, respectively. Addressing the environmental persistence and potential toxicity of fluorinated polymers, PVDF underscores the necessity of long-term sustainability in membrane materials, emphasizing the necessity of future development of eco-friendly alternatives and mitigation strategies.
The versatility of the hybrid bioactive system was validated across PES membranes, which successfully integrated catalytic components without surface modification. This environmentally friendly processing method highlights adaptability to different polymer platforms while delivering strong pollutant degradation efficiency, improved antifouling resistance, and reliable reusability across multiple operational cycles.
Finally, an economic assessment was conducted to evaluate scalability and complement the technical validation. The results indicate that the proposed approach is economically viable and technically feasible for large-scale implementation. This thesis demonstrates enzyme-active and hybrid bioactive membranes as promising alternatives to conventional pollutant removal technologies. By combining the catalytic power of enzymes with the structural advantages of MOFs, nanoparticles, and renewable biopolymers, the research establishes a new pathway for advanced water treatment systems. The findings provide a solid scientific and practical foundation for scalable, eco-friendly, and cost-effective technologies that directly address emerging pollutants' challenges. Beyond its scientific contributions, the research supports national and global goals for sustainable water management and environmental protection, offering innovative solutions to safeguard water security for the future.