Apr. 2020: Congratulations!
Fangzhou Liu successfully defend his master's thesis.
Explore the Nano World
Apr. 2020: Congratulations!
Leqi Lin successfully defend her master's thesis.
Wen's Research Group
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i. Nanoscale physicochemical characterization of Surface Modified Membranes
Wanyi Fu's research statement
This work involved the use of AFM and AFM-IR to acquire surface topography, hydrophobicity and chemical distribution at nanoscale on chemically modified polymeric membranes. Firstly, AFM was used to obtain the topography images, showing the pore size, porosity and also surface roughness of the polymeric membranes. Secondly, AFM chemical force mode was applied to probe nanoscale hydrophobicity on modified membranes. I established a linear correlation (R2=0.994) between the measured adhesion force and water contact angles. Moreover, I tested this technique for nanoscale hydrophobicity measurements on engineered nanoparticles and carbon-based nanomaterials successfully. Thirdly, the hybrid AFM-IR offers accurate chemical identifications and distribution of additives on modified membranes based on their characteristic IR peaks. The IR mapping images showed the inhomogeneous modifiers’ distribution on membrane surface, which could not be resolved by regular FTIR due to the diffraction limit. The hybrid AFM techniques are believed to be critical for revolutionizing the nanoscale characterization for material properties in a wide spectrum of applications ranging from surface contamination or fouling process, material weathering process, capsules coating in pharmaceutical engineering, to antifouling surface design (e.g., eye contact lenses and sanitary coating).
ii. Experimental and Modeling Assessment of Membrane Fouling Kinetics
In this work, I studied the effects of surface properties (i.e., hydrophobicity, surface charge) of membranes on membrane fouling during filtration with BSA and HA as model foulants. The experimental results for different membrane–foulant systems showed that the hydrophilized membranes yielded smaller flux decline rates. Further, the EDLVO theory analysis indicated that the electrostatic (EL) and acid-base (AB) components were both main contributors to the total interaction energy for BSA-membrane system, while the EL interaction energy was a primary contributor for HA-membrane system. Positive correlations (R2=0.74-0.99) were obtained between the fouling rates and the foulant deposition rates on different membrane-foulant systems. This correlation could be used for further developing predictive models of membrane fouling.
iii. Microwave-assisted Antifouling Membrane Filtration Technologies
Overview of Research
My research interests focus on development of membrane-based technologies for sustainable water treatment and investigation of the microplastic pollution in surface waters. Since membrane fouling and insufficient removal efficiency for dissolved organic matters remain big challenges for membrane filtration, I am working on means to (i) design antifouling membrane filtration system for enhanced treatment efficiency for persistent organic pollutants, (ii) design novel membrane distillation system for high efficient desalination and (iii) investigate the membrane surface properties for better understanding of membrane fouling mechanisms. Apart from membrane technologies, I am also working on understanding the environmental levels, chemical compositions, effects, fates and transport pathways of microplastic pollutants.
As a Ph.D. student, my doctoral dissertation research focuses on antifouling membrane filtration technologies for water treatment and mechanisms of membrane fouling. Specifically, three major topics were studied: (i) nanoscale physicochemical characterization of the chemically modified polymeric membranes; (ii) quantitative model between membrane properties and membrane fouling kinetics; and (iii) developing microwave-assisted antifouling membrane filtration technologies.
Membrane fouling and insufficient ability for pollutant removal are two major challenges in the wide industrial applications of membrane filtration technology. In this project, I designed a microwave-enhanced membrane filtration process that uses microwave (MW) irradiated and catalyst-coated ceramic membranes to achieve efficient removal of persistent organic pollutants (i.e., 1,4-dioxane) and significant mitigation of fouling. MW irradiation is selectively absorbed by catalysts and hydrogen peroxide to produce ‘‘hotpots” on membrane surface that promoted generation of radicals and nanobubbles. These active species enhance pollutant degradation and further prevented membrane fouling. In contrast to ultrasound and ultraviolet radiations, MW could efficiently penetrate membrane housing materials and selectively dissipate energy to membrane-impregnated catalyst nanoparticles. This innovative technology could mitigate the membrane fouling as well as enhancing the treatment efficiency of pollutants in the water/wastewater. The MW-assisted membrane filtration processes may open new avenues toward next-generation antifouling and high-efficiency separation techniques.