Modification of polyacrylonitrile ultrafiltration membranes to enhance the adsorption of cations and anions

Ion adsorbing ultrafiltration membranes provide an interesting possibility to remove toxic ions from water. Furthermore, it is also possible to recover valuable elements. In this work, we demonstrate two easy strategies to modify polyacrylonitrile membranes with anion and cation adsorbing groups. The membranes were modified to have positively charged amine groups or negatively charged carboxyl groups. The success of the reactions was confirmed using IR spectroscopy and zeta-potential measurements. The membranes carrying negatively charged groups provided a negative zeta-potential and had an isoelectric point at pH 3.6, while the membranes carrying positively charged groups had a positive zeta-potential in the analyzed pH range. Since only the surface of the polymer was modified, the pore size and permeance of the membranes were not drastically affected. The membranes prepared by both modification strategies had a pure water permeance higher than 1000 L/(m2 h bar) and a water contact angle of 44.3 and 57.2°, respectively. Therefore, the membranes can be operated at low pressures with reasonable flux. Additionally, SEM images showed that the membranes were still open-pored. Adsorption tests using a positively and a negatively charged dye as well as a toxic cation and an anion were performed to analyze the adsorption behavior. Both membranes were able to adsorb the oppositely charged dyes as well as the copper and chromate ions. Therefore, these membranes are good candidates to purify water streams containing hazardous ions.

Subjects

membrane post-modification

PAN membranes

ion adsorption

water purification

adsorptive ultrafiltration membranes

DDC Class

530: Physik

540: Chemie

Funding(s)

Selective Oxy-anion Removal from Drinking Waters by modified Hollow Fiber Membranes

Funding Organisations

Helmholtz-Zentrum Hereon

More Funding Information

This work was financially supported by Helmholtz Zentrum Hereon through the technology transfer project program. This research was also funded by the i3 project Selmo-HF of the Hamburg University of Technology.

Publication version

publishedVersion

Lizenz

https://creativecommons.org/licenses/by/4.0/

Name

membranes-12-00580-v2.pdf

Size

5.92 MB

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Adobe PDF

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Modification of polyacrylonitrile ultrafiltration membranes to enhance the adsorption of cations and anions