An Initial Study of Polysulfone-Nanodiamond Mixed Matrix Membranes for Oxygen/Nitrogen Separation
Open Access
- Author:
- Han, Andrew
- Area of Honors:
- Chemical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Hee Jeung Oh, Thesis Supervisor
Michael John Janik, Thesis Honors Advisor - Keywords:
- Polysulfone
Mixed Matrix Membrane
Nanodiamond
Contact Angle
Gas Separation
Coefficient of Thermal Expansion
Scanning Electron Microscopy
Polymers - Abstract:
- One of the biggest challenges for polymer membranes in the gas separation field today is the separation of oxygen from air due to the similar atomic properties of the major constituents, oxygen and nitrogen. Membranes are typically characterized by low permeability and selectivity. A proposed solution to address this challenge is a polymeric mixed matrix membrane (MMM) composed of polysulfone (PSF) loaded with various concentrations of functionalized nanodiamonds (NDs). The goal of this initial work is to study mechanical and surface affinity effects NDs may have on PSF. In order to probe how NDs interact with the PSF and if functionalized NDs affect the hydrophilicity of the polymer, thermal and contact angle analyses were employed to address these questions. Using thermomechanical analysis (TMA), PSF-ND MMMs showed little change in the coefficient of thermal expansion with increasing ND loading. Thermogravimetric analysis (TGA) revealed residual solvent in PSF films; however, no other impacts were seen that could be correlated to ND loading. Also, differential scanning calorimetry (DSC) resulted in little difference in glass transition (Tg) temperatures between pure PSF and PSF-ND membranes. Water contact angle goniometry revealed that increasing the ND concentration resulted in lower contact angles, presumably because of greater hydrophilicity. However, this finding was only seen on one surface of the film which suggests that the ND distribution may not be homogenous across the membrane thickness. The increase in inhomogeneity correlated with ND loading can be shown visually with scanning electron microscopy (SEM) as ND concentrations greater than 2% resulted in ND agglomeration in the PSF films. Overall, ND loading in PSF to form a ND-PSF MMM does not affect many mechanical properties of pure PSF. However, the distribution of NDs throughout PSF is inhomogeneous as increasing ND loading results in a greater asymmetrical distribution which potentially causes membrane phase separation and ND agglomeration. These findings may provide insight into determining an ideal membrane for separating oxygen from air which can lead to environmental benefits in the future.