Studies on Molecular and Ion Transport in Silicalite Membranes andApplications as Ion Separator for Redox Flow Battery

Studies on Molecular and Ion Transport in Silicalite Membranes andApplications as Ion Separator for Redox Flow Battery

Bibliographic Details
Main Author: Yang, Ruidong
Language:English
Published: University of Cincinnati / OhioLINK 2014
Subjects:
Chemical Engineering
Zeolite
Redox flow battery
Ion separation
Membrane separation
Composite membrane
Optical interferometer
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406820402
id ndltd-OhioLink-oai-etd.ohiolink.edu-ucin1406820402
record_format oai_dc
collection NDLTD
language English
sources NDLTD
topic Chemical Engineering
Zeolite
Redox flow battery
Ion separation
Membrane separation
Composite membrane
Optical interferometer
spellingShingle Chemical Engineering
Zeolite
Redox flow battery
Ion separation
Membrane separation
Composite membrane
Optical interferometer
Yang, Ruidong
Studies on Molecular and Ion Transport in Silicalite Membranes andApplications as Ion Separator for Redox Flow Battery
author Yang, Ruidong
author_facet Yang, Ruidong
author_sort Yang, Ruidong
title Studies on Molecular and Ion Transport in Silicalite Membranes andApplications as Ion Separator for Redox Flow Battery
title_short Studies on Molecular and Ion Transport in Silicalite Membranes andApplications as Ion Separator for Redox Flow Battery
title_full Studies on Molecular and Ion Transport in Silicalite Membranes andApplications as Ion Separator for Redox Flow Battery
title_fullStr Studies on Molecular and Ion Transport in Silicalite Membranes andApplications as Ion Separator for Redox Flow Battery
title_full_unstemmed Studies on Molecular and Ion Transport in Silicalite Membranes andApplications as Ion Separator for Redox Flow Battery
title_sort studies on molecular and ion transport in silicalite membranes andapplications as ion separator for redox flow battery
publisher University of Cincinnati / OhioLINK
publishDate 2014
url http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406820402
work_keys_str_mv AT yangruidong studiesonmolecularandiontransportinsilicalitemembranesandapplicationsasionseparatorforredoxflowbattery
_version_ 1719437042267455488
spelling ndltd-OhioLink-oai-etd.ohiolink.edu-ucin14068204022021-08-03T06:26:29Z Studies on Molecular and Ion Transport in Silicalite Membranes andApplications as Ion Separator for Redox Flow Battery Yang, Ruidong Chemical Engineering Zeolite Redox flow battery Ion separation Membrane separation Composite membrane Optical interferometer Microporous zeolite membranes have been widely studied for molecular separations based on size exclusion or preferential adsorption-diffusion mechanisms. The MFI-type zeolite membranes were also demonstrated for brine water desalination by molecular sieving effect. In this research, the pure silica MFI-type zeolite (i.e. silicalite) membrane has been for the first time demonstrated for selective permeation of hydrated proton (i.e. H3O+) in acidic electrolyte solutions. The silicalite membrane allows for permeation of H3O+ ions, but is inaccessible to the large hydrated multivalent vanadium ions due to steric effect. The silicalite membrane has been further demonstrated as an effective ion separator in the all-vanadium redox flow battery (RFB).The silicalite is nonionic and its proton conductivity relies on the electric field-driven H3O+ transport through the sub nanometer-sized pores under the RFB operation conditions. The silicalite membrane displayed a significantly reduced self-discharge rate because of its high proton-to-vanadium ion transport selectivity. However, the nonionic nature of the silicalite membrane and very small diffusion channel size render low proton conductivity and is therefore inefficient as ion exchange membranes (IEMs) for practical applications. The proton transport efficiency may be improved by reducing the membrane thickness. However, the zeolite thin films are extremely fragile and must be supported on mechanically strong and rigid porous substrates. In this work, silicalite-Nafion composite membranes were synthesized to achieve a colloidal silicalite skin on the Nafion thin film base. The “colloidal zeolite-ionic polymer” layered composite membrane combines the advantages of high proton-selectivity of the zeolite layer and the mechanical flexibility and low proton transport resistance of the ionic polymer membrane. The composite membrane exhibited higher proton/vanadium ion separation selectivity and lower electrical resistance than the commercial Nafion 117 membrane. The high proton transport selectivity is a result of the molecular sieving effect between the H3O+ and multivalent vanadium ions by the zeolitic pores; thus the zeolite particles significantly reduced the effective membrane surface area for vanadium ion permeation. The low resistance of the composite membrane can be attributed to the reduced thickness of the Nafion base film and the thinness of the colloidal silicalite top layer. The composite membrane outperformed the Nafion 117 membrane in the vanadium RFB operation in terms of the overall charge-discharge energy efficiency. Efforts have been made in further investigation of ion and molecular transport diffusivity in the polycrystalline silicalite film using zeolite-coated optical fiber interferometers. A physical model has been established for analyzing the molecular diffusivity in the zeolite layer based on the temporal responses of the optical interferometric signals during the transient process of molecular sorption. Experiments were first carried out to study the diffusivity of isobutane to evaluate the effectiveness of the proposed optical method. The isobutane diffusivities in silicalite measured by this method were in good agreement with the values reported in literature. The zeolite coated fiber optic interferometer was however ineffective in monitoring ion sorption or ion exchange in the silicalite films. It is suggested that more sensitive fiber optic devices are needed for studying the ion diffusion. 2014-10-10 English text University of Cincinnati / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406820402 http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406820402 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

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