Decrease Size Increase Size Print Comment Separation Processes
By Mary Page Bailey | July 1, 2022
A new membrane for separating emulsions is being fabricated using recycled carbon-fiber production scraps from aerospace manufacturing. “We think this is the first membrane of its type to be constructed from recycled carbon fibers,” explains Shuaifei Zhao, senior research fellow in the Institute for Frontier Materials (IFM) at Deakin University (Victoria, Australia; www.deakin.edu.au), where the new membrane was developed.
In order to prepare the scrap carbon fibers for use in the membranes, the IFM team applied a specialized recycling process involving pyrolysis, thermal oxidation and ball milling. “Typically, the spent composite was heated in a nitrogen atmosphere at high temperatures to degrade the polymer resin, forming a char on the fibers. Then, the material is heated again in air, which provides an oxidizing atmosphere to completely degrade any residual char and oxidize residual char from the fiber surface,” says Zhao. Once these treatment steps are complete, the reclaimed fibers undergo ball milling and sieving to obtain the desired fiber length.
To fabricate the membrane, a dip-coating method was used wherein the substrate membrane was dipped into a dispersion of functionalized carbon fibers in tannic acid (a common crosslinking substance), in the presence of a 3-aminopropyl triethoxysilane (APTES) solution. “The key novelty is the functionalization of the reclaimed carbon fibers to construct a special hierarchical structure, which increases the membrane’s surface roughness and improves the reaction between the fibers, tannic acid and APTES, providing the membrane with its superhydrophilic and underwater superoleophobic properties,” adds Zhao.
The carbon-fiber-recycling process has been scaled up for industrial production by Gen2 Carbon Ltd. (West Midlands, U.K.; www.gen2carbon.com). IFM is working to demonstrate the membrane’s performance in industrial conditions, focusing on long-term stability, cleaning requirements and replacement frequency. The team expects that the membrane could have wide-ranging applications with favorable economics, since the use of recycled materials lowers overall membrane-construction costs and the fabrication process can be readily automated.
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