A Review on the Morphology and Material Properties of the Gas Separation Membrane: Molecular Simulation

Bimetallic PdPt Nanoparticles Decorated PES Membranes for Enhanced H2 Separation

Hydrogen separation has significant importance in diverse applications ranging from clean energy production to gas purification. Membrane technology stands out as a low-cost and efficient method to address the purpose. The development of efficient gas-sensitive materials can further bolster the membrane's performance. In this pursuit, bimetallic PdPt nanoparticles were synthesized using a wet chemical approach and were strategically decorated onto poly(ether sulfone) (PES) membranes. The fibrous morphology of the PES membranes provided an ideal platform for the decoration of nanoparticles, promising enhanced gas transport properties. Prior to the attachment of nanoparticles, the membranes were pretreated under UV light to enhance their surface properties and facilitate improved adhesion. The synthesized bimetallic nanoparticles were characterized by using transmission electron microscopy and X-ray photoelectron spectroscopy for their morphological and elemental analysis. Furthermore, the engineered membranes were characterized using various techniques, such as Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy (FESEM) with rigorous scrutiny to ensure a comprehensive understanding of their structural, chemical, and morphological properties. The membranes were examined for their separation performance using pure H2, N2, and CO2 gases, and the results revealed a 30% increment in H2 permeability and 40 and 42% increments in H2/CO2 and H2/N2 selectivity, respectively. These findings confirmed the critical role of tailored material design and synthesis strategies in advancing membrane technologies for H2 separation applications.

Biogas Upgrading Using a Single-Membrane System: A Review

In recent years, the use of biogas as a natural gas substitute has gained great attention. Typically, in addition to methane (CH4), biogas contains carbon dioxide (CO2), as well as small amounts of impurities, e.g., hydrogen sulfide (H2S), nitrogen (N2), oxygen (O2) and volatile organic compounds (VOCs). One of the latest trends in biogas purification is the application of membrane processes. However, literature reports are ambiguous regarding the specific requirement for biogas pretreatment prior to its upgrading using membranes. Therefore, the main aim of the present study was to comprehensively examine and discuss the most recent achievements in the use of single-membrane separation units for biogas upgrading. Performing a literature review allowed to indicate that, in recent years, considerable progress has been made on the use of polymeric membranes for this purpose. For instance, it has been documented that the application of thin-film composite (TFC) membranes with a swollen polyamide (PA) layer ensures the successful upgrading of raw biogas and eliminates the need for its pretreatment. The importance of the performed literature review is the inference drawn that biogas enrichment performed in a single step allows to obtain upgraded biogas that could be employed for household uses. Nevertheless, this solution may not be sufficient for obtaining high-purity gas at high recovery efficiency. Hence, in order to obtain biogas that could be used for applications designed for natural gas, a membrane cascade may be required. Moreover, it has been documented that a significant number of experimental studies have been focused on the upgrading of synthetic biogas; meanwhile, the data on the raw biogas are very limited. In addition, it has been noted that, although ceramic membranes demonstrate several advantages, experimental studies on their applications in single-membrane systems have been neglected. Summarizing the literature data, it can be concluded that, in order to thoroughly evaluate the presented issue, the long-term experimental studies on the upgrading of raw biogas with the use of polymeric and ceramic membranes in pilot-scale systems are required. The presented literature review has practical implications as it would be beneficial in supporting the development of membrane processes used for biogas upgrading.

Graphene in Polymeric Nanocomposite Membranes—Current State and Progress

One important application of polymer/graphene nanocomposites is in membrane technology. In this context, promising polymer/graphene nanocomposites have been developed and applied in the production of high-performance membranes. This review basically highlights the designs, properties, and use of polymer/graphene nanocomposite membranes in the field of gas separation and purification. Various polymer matrices (polysulfone, poly(dimethylsiloxane), poly(methyl methacrylate), polyimide, etc.), have been reinforced with graphene to develop nanocomposite membranes. Various facile strategies, such as solution casting, phase separation, infiltration, self-assembly, etc., have been employed in the design of gas separation polymer/graphene nanocomposite membranes. The inclusion of graphene in polymeric membranes affects their morphology, physical properties, gas permeability, selectivity, and separation processes. Furthermore, the final membrane properties are affected by the nanofiller content, modification, dispersion, and processing conditions. Moreover, the development of polymer/graphene nanofibrous membranes has introduced novelty in the field of gas separation membranes. These high-performance membranes have the potential to overcome challenges arising from gas separation conditions. Hence, this overview provides up-to-date coverage of advances in polymer/graphene nanocomposite membranes, especially for gas separation applications. The separation processes of polymer/graphene nanocomposite membranes (in parting gases) are dependent upon variations in the structural design and processing techniques used. Current challenges and future opportunities related to polymer/graphene nanocomposite membranes are also discussed.