Dissertation Defence: A Geotechnical Permeable Reactive Barrier Based on a Novel Metal Organic Framework (MOF) Magnetic Polymer Composite for Microplastics Interception in Complex Matrices

Mahmoud Babalar, supervised by Dr. Sumi Siddiqua, will defend their dissertation titled “A Geotechnical Permeable Reactive Barrier Based on a Novel Metal Organic Framework (MOF) Magnetic Polymer Composite for Microplastics Interception in Complex Matrices: Synthesis, Characterization, Adsorption, Regeneration, and Breakthrough Studies” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering.

An abstract for Mahmoud Babalar’s dissertation is included below.

Examinations are open to all members of the campus community as well as the general public. Please email sumi.siddiqua@ubc.ca to receive the Zoom link for this exam.

Abstract

Microplastic (MPs) contamination is an emerging environmental and geotechnical problem because persistent polymeric particles can migrate through landfill leachate, soils, drainage systems, and groundwater pathways while interacting with other contaminants. Conventional barriers, adsorbents, and filtration systems are often limited by incomplete retention, fouling, clogging, poor durability, and weak compatibility with subsurface flow. This thesis develops an integrated treatment pathway for microplastic interception through five connected research chapters that progress from geotechnical review to material synthesis, membrane filtration, and permeable reactive barrier application. The second research chapter reviews geotechnical approaches for microplastic mitigation, including permeable reactive barriers, geotextiles, landfill liners, hydraulic barriers, vegetative systems, monitoring methods, and smart detection tools, and identifies the need for reactive media that can retain MPs while maintaining hydraulic performance. The third research chapter develops PMACZ, a polymer-coated magnetic activated biochar zeolite composite, as the central reactive material. PMACZ is characterized using SEM, EDS, BET, zeta potential, VSM, XRD, FTIR, and TGA, then tested for adsorption of fluorescent polystyrene MPs with particle sizes of 2 µm and 15 µm. The adsorption results show maximum capacities of 736 mg/g and 769 mg/g for 2 µm and 15 µm particles, respectively. Kinetic modelling follows a pseudo-second-order model with R² of 99%, while isotherm analysis shows agreement with the Langmuir model with R² values of 80% and higher. Optimization indicates maximum adsorption near pH 4, with optimum temperatures of 28 °C and 24 °C for 2 µm and 15 µm particles, respectively, and regeneration is maintained for at least four cycles. The fourth research chapter translates PMACZ into modified PES membrane systems for microplastic and PCB 209 removal from synthetic landfill leachate, achieving complete microplastic rejection in tested conditions and PCB 209 removal up to 99.67%. The fifth research chapter advances the membrane design into a dual-layer architecture using PMACZ, MOF functionality, and self-assembled mesoporous silica, improving smaller particle rejection, repeated cycle stability, and fouling resistance. The sixth research chapter converts PMACZ into a granular permeable reactive barrier medium and evaluates breakthrough behaviour, longitudinal retention, hydraulic response, and barrier scale stability under column flow. Overall, this thesis demonstrates that PMACZ can function as a multifunctional reactive platform across adsorption, membrane filtration, and permeable reactive barrier systems, linking microplastic removal with hydraulic durability and geotechnical applicability.