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MXenes are a newer class of 2D materials, possess with desirable properties such as large specific surface area, conductivity, and hydrophilicity, making them attractive for various environmental applications, including remediation and as membranes for water treatment. Until recently, the practical implementation of MXenes was hindered by their instability in water, although improved synthesis procedures have largely addressed this issue. Consequently, it is now important to assess the stability of MXenes in engineered environments relevant to drinking water and membrane operation (e.g. backwashing). In this study, Ti3C2Tx MXenes were found to remain stable upon exposure to an aqueous environment saturated with oxygen and to UVC and UVA light at circumneutral pH, but were transformed upon exposure to Fe(III) chloride and free chlorine. The chlorination reaction kinetics are 1st order with respect to Ti3C2Tx and free chlorine concentration, with a rate constant that increased at pH ≤ 7.5, implicating HOCl as the reactive species. We propose that MXene reactions with HOCl occur by an electrophilic attack of Cl+, forming TiO2 and degrading the MXene. AFM data shows that transformations are initiated at the edges of the MXene sheets and localized areas on the MXene, suggesting that the initial sites for Cl+ attack are defect sites and/or uncoordinated Ti atoms. During the initial stages of the oxidative degradation, the sheet-like structure of colloidal MXenes is preserved, although prolonged chlorine exposure leads to three-dimensional crystalline (anatase) TiO2 formation. The degradation of MXenes during chlorinationThis contrasts with the inertness of nanoscale TiC, highlighting the need to devise surface modification processes that will allow MXenes to resist the oxidative conditions associated with membrane regeneration/backwashing.
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A perspective on MXene-enhanced biofiltration-membrane water reuse treatment systems: A review and experimental validation
As the demand for sustainable and efficient water treatment solutions grows, the integration of advanced nanomaterials has become a focal point in enhancing membrane technologies. The purpose of this review is to provide a comprehensive and critical analysis of the current state of research on Ti3C2Tx MXenes, highlighting their unique properties, the challenges they address, and the potential they hold for MXene-enhanced biofiltration-membrane systems. The perspective systematically examines how Ti3C2Tx MXenes, with their exceptional electrical conductivity, hydrophilicity, and tunable surface chemistry, can be integrated into biofiltration-membrane systems to improve key performance metrics such as water flux, contaminant rejection, and fouling resistance. Various processes, including biofiltration, adsorption, and nanofiltration, are discussed, where Ti3C2Tx MXenes have been shown to have a potential application. In addition to synthesizing existing literature, experimental validations are presented that demonstrate how MXene incorporation can alter membrane morphology and structure, leading to improved antibacterial properties and enhanced overall performance. These findings underscore the transformative potential of Ti3C2Tx MXenes in developing next-generation biofiltration-membrane technologies that are not only more efficient but also more sustainable. Through this perspective, the key challenges that remain, such as cost implications and long-term stability, are identified, and future research directions are proposed to address these issues. This in-depth analysis highlights the critical role MXenes can play in advancing water treatment technologies, particularly in the context of water reuse, and encourages further interdisciplinary research in this rapidly evolving field.
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- PAR ID:
- 10552588
- Publisher / Repository:
- Desalination
- Date Published:
- Journal Name:
- Desalination
- Volume:
- 593
- Issue:
- C
- ISSN:
- 0011-9164
- Page Range / eLocation ID:
- 118198
- 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/10.1016/j.desal.2024.118198
