Moisture permeable barrier membranes for toxic gases and vapors

Author

• Yufeng Song, New Jersey Institute of Technology

Document Type

Dissertation

Date of Award

8-31-2020

Degree Name

Doctor of Philosophy in Chemical Engineering - (Ph.D.)

Department

Chemical, Biological and Pharmaceutical Engineering

First Advisor

Kamalesh K. Sirkar

Second Advisor

Boris Khusid

Third Advisor

Piero M. Armenante

Fourth Advisor

Xianqin Wang

Fifth Advisor

Wen Zhang

Abstract

Defense against small molecule toxic gases is an important aspect of protection against chemical and biological threat as well as chemical releases from industrial accidents. Current protective respirators/garments cannot effectively block small molecule toxic gases and vapors and retain moisture transmission capability without a heavy burden.

Metal organic frameworks (MOFs) have been used as highly effective adsorbents and catalysts to remove ammonia, cyanogen chloride, and sulfur dioxide from air. A nanopacked bed of nanoparticles of MOF by synthesizing them in the pores of microporous membranes is developed in the study. The submicron scale size of membrane pores ensures a large surface area of MOF nanoparticles which can capture/adsorb and react with toxic gas molecules efficiently. HKUST-1 (Hong Kong University of Science and Technology-1) MOF is synthesized in polyvinylidene fluoride (PVDF) membrane first. Since stability of HKUST-1 MOF in air is not ideal, UiO-66-NH₂ MOF is subsequently synthesized in microporous membranes.

It is demonstrated that the microporous expanded polytetrafluoroethylene (ePTFE) membrane with UiO-66-NH₂ MOF grown inside and around the membrane can defend against ammonia for a significant length of time while allowing passage of moisture and nitrogen. It is also demonstrated that the MOF-loaded ePTFE membrane could provide significant protection from Cl₂ intrusion as well intrusion from 2-chloroethyl ethyl sulfide (CEES) (a simulant for sulfur mustard). Such MOF-filled membranes exhausted by NH₃ breakthrough experiments are regenerated conveniently by heating at 60°C for one week under vacuum for further/repeated use; a single regenerated membrane can block NH₃ for 200-300 min. The moisture permeability of such a membrane/nanopacked bed is considerably above the breathability threshold value of 2000 g/m² -day. The results suggest that microporous membranes filled with reactive MOF nanoparticles could be designed as protective barriers against toxic gases/vapors, e.g., NH₃ and Cl₂ and yet be substantially permeable to H₂O and air.

To optimize the process, the mixed reactant-containing solution is pushed into the pores of hydrophobic microporous ePTFE membranes by high pressure nitrogen gas. In addition to saving processing time, the size of MOF crystals formed in the optimized process is smaller which improves the performance of defense to ammonia gas. To simplify the process, microporous Nylon membrane is used as the base membrane instead of ePTFE membrane since Nylon membrane can be wetted by the mixed reactant-containing solution directly.

A method for incorporating MOF nanoparticles into microporous membrane is also studied in this project. Since the MOF nanoparticles are unavailable, silica nanoparticles are used as simulated MOF particles for incorporation into the microporous membranes. This method can circumvent the limitations of the physical and chemical properties (melting point, resistance to organic solvents, e.g., dimethyl formamide (DMF)) of the porous membrane.

Recommended Citation

Song, Yufeng, "Moisture permeable barrier membranes for toxic gases and vapors" (2020). Dissertations. 1910.
https://digitalcommons.njit.edu/dissertations/1910