Harnessing Filler Materials for Enhancing Biogas Separation Membranes

Abstract

Biogas is an increasingly attractive renewable resource, envisioned to secure future energy demands and help curb global climate change. To capitalize on this resource, membrane processes and state-of-the-art membranes must efficiently recover methane (CH) from biogas by separating carbon dioxide (CO). Composite (a.k.a. mixed-matrix) membranes, prepared from common polymers and rationally selected/engineered fillers, are highly promising for this application. This review comprehensively examines filler materials that are capable of enhancing the CO/CH separation performance of polymeric membranes. Specifically, we highlight novel synthetic strategies for engineering filler materials to develop high-performance composite membranes. Besides, as the matrix components (polymers) of composite membranes largely dictate the overall gas separation performances, we introduce a new empirical metric, the "Filler Enhancement Index" ( F), to aid researchers in assessing the effectiveness of the fillers from a big data perspective. The F systematically decouples the effect of polymer matrices and critically evaluates both conventional and emerging fillers to map out a future direction for next-generation (bio)gas separation membranes. Beyond biogas separation, this review is of relevance to a broader community with interests in composite membranes for other gas separation processes, as well as water treatment applications.

Composite membranes of graphene oxide for CO2/CH4 separation

“…The intensity ratio of these two peaks typically indicates the ratio of rigid structure from the crystal region to the flexible structure with high free volume from the amorphous phase. The crystalline degree or crystallinity can be estimated from the ratio between the crystalline phase and amorphous phase of the prepared membranes, as shown in Eqn (3).…”

“…Nowadays, there are many technologies applied to remove CO 2 from raw biogas, such as pressure swing adsorption, chemical absorption, water scrubbing and membrane separation. Among these technologies, membrane separation is considered one of the most environmental friendly and the least energy‐intensive systems . However, the separation performance of the membrane separation is highly dependent on the membrane materials used.…”

“…Graphene oxide (GO) is one of the promising fillers because its 2D structure can rearrange in the direction that blocks the pathway for diffusion of gas molecules and pronounce the gas separation. In addition, GO exhibits high thermal and mechanical stability and it is highly tunable and processable in solution . Many research studies have proved that GO can enhance CO 2 capture and separation .…”

“…Among these technologies, membrane separation is considered one of the most environmental friendly and the least energy-intensive systems. [1][2][3] However, the separation performance of the membrane separation is highly dependent on the membrane materials used.…”

“…In addition, GO exhibits high thermal and mechanical stability and it is highly tunable and processable in solution. 3 Many research studies have proved that GO can enhance CO 2 capture 2784 www.soci.org N Norahim et al and separation. 6,[8][9][10][11][12] Li et al reported that due to the high aspect ratio (>1000) of GO, it led to an increasingly tortuous path of gas diffusion in the polymer matrix and reduced the mobility of polymer chains.…”