Abstract
Increasing demand to strengthen energy security has increased the importance of natural gas sweetening and biogas upgrading processes. Membrane-based separation of carbon dioxide (CO2) and methane (CH4) is a relatively newer technology, which offers several competitive advantages, such as higher energy-efficiency and cost-effectiveness, over conventional technologies. Recently, the use of graphene-based materials to elevate the performance of polymeric membranes have attracted immense attention. Herein, we do not seek to provide the reader with a comprehensive review of this topic but rather highlight the key challenges and our perspectives going ahead. We approach the topic by evaluating three mainstream membrane designs using graphene-based materials: (1) nanoporous single-layer graphene, (2) few- to multi-layered graphene-based stacked laminates, and (3) mixed-matrix membranes. At present, each design faces different challenges, including low scalability, high production cost, limited performance enhancement, and the lack of robust techno-economic review and systematic membrane design optimization. To help address these challenges, we have mapped out a technology landscape of the current graphene-based membrane research based on the separation performance enhancement, commercial viability, and production cost. Accordingly, we contend that future efforts devoted to advancing graphene-based membranes must be matched by progress in these strategic areas so as to realize practical and commercially relevant graphene-based membranes for CO2/CH4 separation and beyond.
Highlights
The strong demand for energy to meet the increasing population and economic growth has motivated a shift towards alternative energy resources to supplement the depleting conventional fossil fuels [1]
There are several etching techniques used to generate nanopores on single-layer graphene nanosheet to date, including ion bombardment followed by chemical oxidation [21], focus-ion beam (FIB) patterning [10], gold nanoparticle deposition followed by oxidation [22], oxygen plasma [23] with ozone etching [24], and ultraviolet-induced oxidative treatment [25]
We believe that by strategically optimizing membrane design from a data-driven approach, high-performance graphene-based thin-film nanocomposite membranes, especially those in the hollow fiber configuration, can be realized. This will be a game-changer, considering that the amount of graphene-based materials used will be relatively lower than the mixed-matrix membranes and this will give a low-cost competitive advantage over all the other membrane designs discussed in this article [80]
Summary
The strong demand for energy to meet the increasing population and economic growth has motivated a shift towards alternative energy resources to supplement the depleting conventional fossil fuels [1]. The competitive advantage of GO lies in its solution processability, which allows easy processing into continuous films [13], and seamless integration with existing membrane fabrication techniques [11]. For this reason, GO garners widespread attention from the membrane community and is one of the most extensively used graphene-based materials for designing membranes to date. The discussion closes off with useful insights from positive implementation in practice or problem-solving strategies that can be prospective solutions to help advance graphene-based membranes for CO2 /CH4 separation. Beyond CO2 /CH4 separation, these insights are of relevance to a wider community with interests in other gas separation and water treatment applications
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