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The removal of small molecular weight charged compounds from aqueous solutions using membrane remains a challenge. In this study, polysulfone (PSf)- and sulfonated polyether ether ketone (SPEEK)-based membranes were fabricated via non-solvent induced phase separation process (NIPS) using N-Methyl-2-Pyrrolidone (NMP) as solvent and water as non-solvent. Membranes were characterized structurally and morphologically, followed by toxicity assessment conducted before and after filtration, both with and without annealing at various pH values to evaluate potential leaching of trapped solvent from the membrane pores. Additionally, membrane performance was characterized using binary mixtures of cationic and anionic dyes. The results demonstrated selective filtration behavior, with cationic dyes being preferentially rejected due to size exclusion and electrostatic interactions. Additionally, a key focus of this work was the investigation of solvent leaching, framed within a Safe(r)-by-Design (SbD) approach aimed at enhancing functional performance while minimizing environmental toxicity. Toxicity assessments using a model organism, a nematode Caenorhabditis elegans, revealed that annealing reduced solvent leaching and thus permeate toxicity, particularly at neutral pH values, by facilitating trapped solvent release prior to membrane use. These findings provide insights for the importance of including an SbD approach during membrane casting to fabricate membranes with desirable properties while minimizing toxicity.
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Microcystin-LR Removal from Water via Enzymatic Linearization and Ultrafiltration
Microcystin-LR (MC-LR) is a toxin produced by cyanobacteria that can bloom in freshwater supplies. This study describes a new strategy for remediation of MC-LR that combines linearization of the toxin using microcystinase A, MlrA, enzyme with rejection of linearized byproducts using membrane filtration. The MlrA enzyme was expressed in Escherichia coli (E. coli) and purified via a His-tag with 95% purity. Additionally, composite membranes made of 95% polysulfone and 5% sulfonated polyether ether ketone (SPEEK) were fabricated and used to filter a solution containing cyclic and linearized MC-LR. Tests were also performed to measure the adsorption and desorption of MC-LR on polysulfone/SPEEK membranes. Liquid chromatography-mass spectrometry (LC-MS) was used to characterize the progress of linearization and removal of MC-LR. Results indicate that the MlrA was successful at linearizing MC-LR. Membrane filtration tests showed rejection of 97% of cyclic MC-LR and virtually all linearized MC-LR, with adsorption to the membranes being the main rejection mechanism. Adsorption/desorption tests indicated that methanol could be used to strip residual MC-LR from membranes to regenerate them. This study demonstrates a novel strategy of remediation of microcystin-tainted water, combining linearization of MC-LR to a low-toxicity byproduct along with removal by membrane filtration.
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- Award ID(s):
- 1922694
- PAR ID:
- 10350582
- Date Published:
- Journal Name:
- Toxins
- Volume:
- 14
- Issue:
- 4
- ISSN:
- 2072-6651
- Page Range / eLocation ID:
- 231
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/toxins14040231
