Key Takeaways & Executive Findings
- •• A new evaluation framework using radar charts with five dimensions (water permeance, water/NaCl selectivity, membrane cost, scale of development, and stability) is proposed to assess desalination membranes. • Novel membrane materials (e.g., aquaporins, artificial water channels, graphene oxide, carbon nanotubes) show high theoretical performance but face practical challenges such as large-scale fabrication, mechanical strength, and chemical stability. • Thin film nanocomposite (TFN) membranes and membranes from novel materials are compared with state-of-the-art thin film composite (TFC) membranes, revealing critical deficiencies that guide future development. • The review identifies prospects and challenges for next-generation reverse osmosis membranes, providing a comprehensive reference for designing high-performance desalination membranes.
Abstract
Membrane desalination is an economical and energy-efficient method to meet the current worldwide water scarcity. However, state-of-the-art reverse osmosis membranes are gradually being replaced by novel membrane materials as a result of ongoing technological advancements. These novel materials possess intrinsic pore structures or can be assembled to form lamellar membrane channels for selective transport of water or solutes (e.g., NaCl). Still, in real applications, the results fall below the theoretical predictions, and a few properties, including large-scale fabrication, mechanical strength, and chemical stability, also have an impact on the overall effectiveness of those materials. In view of this, we develop a new evaluation framework in the form of radar charts with five dimensions (i.e., water permeance, water/NaCl selectivity, membrane cost, scale of development, and stability) to assess the advantages, disadvantages, and potential of state-of-the-art and newly developed desalination membranes. In this framework, the reported thin film nanocomposite membranes and membranes developed from novel materials were compared with the state-of-the-art thin film composite membranes. This review will demonstrate the current advancements in novel membrane materials and bridge the gap between different desalination membranes. In this review, we also point out the prospects and challenges of next-generation membranes for desalination applications. We believe that this comprehensive framework may be used as a future reference for designing next-generation desalination membranes and will encourage further research and development in the field of membrane technology, leading to new insights and advancements.
1. Introduction
Water scarcity is an unavoidable challenge due to the global population explosion, industrialization, and climate change [1, 2]. To mitigate this crisis, desalination and water reuse by reverse osmosis (RO) technology [3, 4] have been increasingly adopted. RO technology relies on membrane materials that can selectively remove small solutes, even monovalent salts, from aqueous solutions [5]. Currently, the thin-film composite (TFC) membranes being used in RO processes are predominately composed of polyamide-based materials. These polyamide membranes are limited by permeance selectivity trade-off [6–9], chlorine attack [10–12], and membrane fouling [12–14], which can be attributed to the inherent material properties of polyamide chemistry. Therefore, alternative advanced membrane materials are highly desired to further develop RO membranes.
A wide variety of novel materials have been explored for making high-performance RO membranes. For example, the naturally occurring aquaporins (AQPs), when incorporated into amphiphilic triblock-polymer vesicles, exhibited a water permeance of 167 μm s−1 bar−1, which is two orders of magnitude higher than the water permeance of the current polyamide-based TFC membranes [15]. Inspired by AQPs, artificial water channels (AWCs) constructed by simpler synthetic compounds when embedded in the polyamide layer demonstrated their effectiveness in improving separation performance and fouling resistance of membranes [16, 17]. Many other materials, such as graphene oxide (GO), carbon nanotubes (CNTs), metal-organic frameworks (MOFs), and covalent-organic frameworks (COFs), have also been investigated for their potential in desalination membranes.
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Siqi Wu, Lu Elfa Peng, Zhe Yang, Pulak Sarkar, Mihail Barboiu, Chuyang Y. Tang, Anthony G. Fane (2024). Next-Generation Desalination Membranes Empowered by Novel Materials: Where Are We Now?. Nano-Micro Letters. https://doi.org/10.1007/s40820-024-01606-y
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Frequently Asked Questions
What is the main focus of this review?
This review focuses on next-generation desalination membranes empowered by novel materials, providing a holistic evaluation using a five-dimensional framework (water permeance, water/NaCl selectivity, membrane cost, scale of development, and stability) to compare state-of-the-art and newly developed membranes.
What are the five dimensions used to evaluate membranes in this study?
The five dimensions are water permeance, water/NaCl selectivity, membrane cost, scale of development, and stability. These are visualized using radar charts to assess the advantages, disadvantages, and potential of different desalination membranes.
What are the main challenges for novel membrane materials in real applications?
Despite high theoretical performance, novel membrane materials face challenges such as large-scale fabrication, mechanical strength, and chemical stability, which impact their overall effectiveness in practical desalination applications.
How does this review compare thin film nanocomposite (TFN) membranes with thin film composite (TFC) membranes?
The review compares TFN membranes and membranes developed from novel materials with state-of-the-art TFC membranes using the five-dimensional framework, highlighting critical deficiencies and guiding future development of next-generation reverse osmosis membranes.
What is the significance of the evaluation framework proposed in this review?
The proposed framework provides a comprehensive and systematic method to evaluate desalination membranes, bridging the gap between different membrane types and serving as a future reference for designing next-generation desalination membranes.
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