Salt partitioning in ionized, thermo-responsive hydrogels: perspective to water desalination

Abstract

Charged hydrogels are capable of swelling in aqueous salt solutions, whereby part of the salt ions is repelled due to the presence of fixed charged groups inside the hydrogel. This effect creates a concentration gradient between the absorbed solution and the surrounding fluid known as salt partitioning, offering a potential for these materials to be employed to desalinate saltwater. If the charged hydrogels are thermo-sensitive as well, then the purer, absorbed solution can be recovered by shrinking the hydrogels upon temperature change. To tailor that potential in water-purification and desalination applications, the main parameters influencing the salt partitioning, the deswelling of the hydrogels, and the recovery of water must be understood. In this paper, we analyze these factors based on equations derived from the Donnan theory. In addition, hydrogels composed of N-isopropyl acrylamide and acrylic acid are synthesized, and their salt rejection efficiency in a model desalination experiment is studied. A comparison of the experimental and the theoretical results demonstrates that the charge density of the hydrogels at their equilibrium swelling and the degree of water recovery are two parameters controlling the salt rejection efficiency. These parameters are individually controlled by the content of the ionic groups and the degree of cross-linking of the gel polymer network. In addition, the prediction of the theory and the experimental results demonstrate that the salt rejection efficiency can be significantly improved if a second water recovery step is performed by a secondary increase in the temperature in the deswelling process.

Autoren

Amir Jangizehi
Sebastian Seiffert

DOI

10.1063/5.0044376

eISSN

1089-7690

ISSN

0021-9606

Ausgabe der Veröffentlichung

14

Zeitschrift

The Journal of Chemical Physics

Sprache

en

Online publication date

2021

Datum der Veröffentlichung

2021

Status

Published

Herausgeber

AIP Publishing

Herausgeber URL

http://dx.doi.org/10.1063/5.0044376

Datum der Datenerfassung

2023

Titel

Salt partitioning in ionized, thermo-responsive hydrogels: perspective to water desalination

Ausgabe der Zeitschrift

154

Datenquelle: Crossref

Abstract

Charged hydrogels are capable of swelling in aqueous salt solutions, whereby part of the salt ions is repelled due to the presence of fixed charged groups inside the hydrogel. This effect creates a concentration gradient between the absorbed solution and the surrounding fluid known as salt partitioning, offering a potential for these materials to be employed to desalinate saltwater. If the charged hydrogels are thermo-sensitive as well, then the purer, absorbed solution can be recovered by shrinking the hydrogels upon temperature change. To tailor that potential in water-purification and desalination applications, the main parameters influencing the salt partitioning, the deswelling of the hydrogels, and the recovery of water must be understood. In this paper, we analyze these factors based on equations derived from the Donnan theory. In addition, hydrogels composed of N-isopropyl acrylamide and acrylic acid are synthesized, and their salt rejection efficiency in a model desalination experiment is studied. A comparison of the experimental and the theoretical results demonstrates that the charge density of the hydrogels at their equilibrium swelling and the degree of water recovery are two parameters controlling the salt rejection efficiency. These parameters are individually controlled by the content of the ionic groups and the degree of cross-linking of the gel polymer network. In addition, the prediction of the theory and the experimental results demonstrate that the salt rejection efficiency can be significantly improved if a second water recovery step is performed by a secondary increase in the temperature in the deswelling process.

Addresses

Department of Chemistry, Johannes Gutenberg University Mainz, D-55128 Mainz, Germany.

Autoren

Amir Jangizehi
Sebastian Seiffert

DOI

10.1063/5.0044376

eISSN

1089-7690

Externe Identifier

PubMed Identifier: 33858157

Open access

false

ISSN

0021-9606

Ausgabe der Veröffentlichung

14

Zeitschrift

The Journal of chemical physics

Sprache

eng

Medium

Print

Paginierung

144902

Datum der Veröffentlichung

2021

Status

Published

Datum der Datenerfassung

2021

Titel

Salt partitioning in ionized, thermo-responsive hydrogels: perspective to water desalination.

Sub types

Journal Article

Ausgabe der Zeitschrift

154

Datenquelle: Europe PubMed Central

Abstract

Charged hydrogels are capable of swelling in aqueous salt solutions, whereby part of the salt ions is repelled due to the presence of fixed charged groups inside the hydrogel. This effect creates a concentration gradient between the absorbed solution and the surrounding fluid known as salt partitioning, offering a potential for these materials to be employed to desalinate saltwater. If the charged hydrogels are thermo-sensitive as well, then the purer, absorbed solution can be recovered by shrinking the hydrogels upon temperature change. To tailor that potential in water-purification and desalination applications, the main parameters influencing the salt partitioning, the deswelling of the hydrogels, and the recovery of water must be understood. In this paper, we analyze these factors based on equations derived from the Donnan theory. In addition, hydrogels composed of N-isopropyl acrylamide and acrylic acid are synthesized, and their salt rejection efficiency in a model desalination experiment is studied. A comparison of the experimental and the theoretical results demonstrates that the charge density of the hydrogels at their equilibrium swelling and the degree of water recovery are two parameters controlling the salt rejection efficiency. These parameters are individually controlled by the content of the ionic groups and the degree of cross-linking of the gel polymer network. In addition, the prediction of the theory and the experimental results demonstrate that the salt rejection efficiency can be significantly improved if a second water recovery step is performed by a secondary increase in the temperature in the deswelling process.

Autoren

Amir Jangizehi
Sebastian Seiffert

Autoren-URL

https://www.ncbi.nlm.nih.gov/pubmed/33858157

DOI

10.1063/5.0044376

eISSN

1089-7690

Ausgabe der Veröffentlichung

14

Zeitschrift

J Chem Phys

Sprache

eng

Country

United States

Paginierung

144902

Datum der Veröffentlichung

2021

Status

Published

Titel

Salt partitioning in ionized, thermo-responsive hydrogels: perspective to water desalination.

Sub types

Journal Article

Ausgabe der Zeitschrift

154

Datenquelle: PubMed

Salt partitioning in ionized, thermo-responsive hydrogels: perspective to water desalination

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