Graphene based barrier membrane for gas separation processes

Author

• Cheng Peng, New Jersey Institute of Technology

Document Type

Dissertation

Date of Award

8-31-2020

Degree Name

Doctor of Philosophy in Materials Science and Engineering - (Ph.D.)

Department

Committee for the Interdisciplinary Program in Materials Science and Engineering

First Advisor

Kamalesh K. Sirkar

Second Advisor

Zafar Iqbal

Third Advisor

N. M. Ravindra

Fourth Advisor

Boris Khusid

Fifth Advisor

Ken Keunhyuk Ahn

Abstract

Novel graphene oxide (GO) flake-based composite lamellar membrane structure is being developed as a potential component of a garment for protection against chemical warfare agents (CWAs) represented here by simulants, dimethyl methyl phosphonate (DMMP) (a sarin-simulant) and 2-chloroethyl ethyl sulfide (2-CEES) (a simulant for sulfur mustard), yet allowing a high moisture transmission rate. GO flakes of dimensions 300-800 nm, 0.7-1.2 nm thickness and dispersed in an aqueous suspension are formed into a membrane by vacuum filtration on a porous polyethersulfone (PES) or poly (ether-ether-ketone) (PEEK) support membrane for noncovalent π-π interactions with GO flakes. After physical compression of such a membrane, Upright Cup tests indicate that it can block toluene for 3-4 days and DMMP for 5 days while exhibiting excellent water vapor permeation. Further, they display very low permeances for small molecule gases/vapors. The GO flakes undergo crosslinking later with ethylenediamine (EDA) introduced during the vacuum filtration followed by physical compression and heating. With a further spray-coating of polyurethane (PU), these membranes can be bent without losing barrier properties vis-a-vis the CWA simulant DMMP for 5 days; a membrane not subjected to bending blocks DMMP for 15 days. For the PEEK-EDA-GO-PU compressed membranes after bending, the separation factors of 1120 over other species for low gas flow rates in the dynamic moisture permeation cell (DMPC) are: α_H2O-He is 42.3; α_H2O-N2 is 110; α_H2O-ethane is 1800. At higher gas flow rates in the DMPC, moisture transmission rate goes up considerably due — to reduced boundary layer resistances and exceeds the threshold water vapor flux of 2000 g/m2-day that defines a breathable fabric. This membrane displays considerable resistance to permeation by 2-CEES as well. The PES-EDA-GO-PU compressed membrane shows good mechanical property under tensile strength tests.

The GO-MOF composite membrane is a brand-new membrane structure. It blocks DMMP for at least 7 days, while it has a good moisture permeability. This composite membrane still allows smaller molecules to get through, like He and N2. In the test of 2-CEES permeation, the time lag for GO membrane by itself is 16 2 min, and even after 2-CEES went through, the concentration is extremely low. It is predictable that with the GO cutting down the leakage to a very low level with 2-CEES, the bottom MOF membrane could hold it back for quite a while.

The P84-rGO membrane with PEEK substrate shows its possibility in separation of ethane and ethylene. The separation factor of ethylene over ethane is: α_{ethylene-ethane} = 3.15. Although other researchers were able to achieve higher selectivity using P84 membranes without graphene, it is still a satisfactory result, considering that they were using propane and propylene. Their kinetic diameters and size difference are both larger than those of ethane and ethylene. This membrane can also be cast without any substrate, but it must be with a lower thickness to obtain higher permeances and selectivity.

Recommended Citation

Peng, Cheng, "Graphene based barrier membrane for gas separation processes" (2020). Dissertations. 1908.
https://digitalcommons.njit.edu/dissertations/1908