Development of Novel High Temperature Mixed Matrix Membranes (MMMs) for Oil Sands Wastewater Treatment
Date
2022-04-25
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ORCID
Type
Thesis
Degree Level
Masters
Abstract
While oil sands production plays a significant role in Canada’s economy, the rise in oil sands production leads to increasing water abstraction and pollution. Effective treatment and reuse of oilsands process-affected water (OSPW) can be considered a strategical solution to addressing these issues. Membrane technology is a promising option for OSPW treatment due to its high removal efficiency, small footprint, facile operation, installation and scaleup. Mixed matrix membranes (MMMs) prepared by mixing super-hydrophilic zwitterionic materials and inorganic nanoparticles into the host membrane are anticipated as a next membrane generation for OSPW treatment by achieving multi-functionalities beyond excellent fouling resistance, such as, improved water permeability, selectivity and mechanical strength. Reproducibility and feasibility for large-scale industrial applications are major challenges in the production of MMMs for OSPW treatment. There remain difficulties in adopting lab-scale membranes into industrial practice, along with ensuring their efficiency, stability and durability. This study aims to provide new insight on the performance, and stability of MMMs, outlooking to the commercialization prospect of MMMs. Molecular dynamics simulation (MDS) will be employed to provide in-depth information about complex atomic interactions between the membrane and the additives used, thus allow better understanding about structural and physical properties of MMMs in relation to their performance, fouling, and stability.
This thesis examined three major classes of zwitterionic material including carboxybetaine (CB), phosphatidylcholine (PC) and sulfobetaine (SB) for the modification of poly (vinylidene fluoride) PVDF membrane. Based on simulated data, PC is the most preferable zwitterion that leads to a more stable and hydrophilic mixed matrix membrane with enhanced oil-antifouling capacity. In addition, the chemistry and structural properties of zwitterionic material in relation to the performance of resultant modified membrane were investigated. In total 12 different zwitterionic structures with different polymer backbone (PB), spacer length (SL) and spacer chemistry (SC) were examined and compared. The results suggest that all PB, SL and SC influence the resultant MMM performance with SL the most impactful structural parameter on MMM stability and hydrophilicity. Long SL was demonstrated to reduce the ionic association of charged groups and increase their partial charges, thus promote higher inter-molecular interactions, resulting in well-connected polymer network. Moreover, the performance of modified membrane was examined at high temperatures (i.e., 25, 50, 70 and 90oC). Overall, high temperatures seemed to reduce the stability of modified membrane but to a smaller extent as compared to pristine PVDF membrane. Although the membrane hydrophilicity was greatly altered at high temperatures, no considerable impacts on MMM’s oil-antifouling capacity was observed. While the research outcomes can provide valuable knowledge for the design and development of high-quality membranes with the required characteristics for OSPW treatment applications, experimental studies are needed to validate the simulated data presented.
Description
Keywords
Mix Matrixed Membrane, Membrane Fouling, Molecular Dynamics Simulation, Zwitterion, Membrane Modification
Citation
Degree
Master of Science (M.Sc.)
Department
Chemical and Biological Engineering
Program
Chemical Engineering