Contents lists available at ScienceDirect Journal of Membrane Science journal homepage: www.elsevier.com/locate/memsci Bundling strategy to simultaneously improve the mechanical strength and oxygen permeation flux of the individual perovskite hollow fiber membranes Ran An a , Jian Song a , Yuan Li a , Xiaoyao Tan a, ⁎ , Jaka Sunarso b , Chi Zhang b , Shaobin Wang b , Shaomin Liu b, ⁎ a Key Laboratory of Separation Membranes and Membrane Processes, Department of Chemical Engineering, Tianjin Polytechnic University, Tianjin 300387, China b Department of Chemical Engineering, Curtin University, Perth, WA 6102, Australia ARTICLE INFO Keywords: Perovskite oxide Gas separation O 2 separation Hollow fiber Inorganic membrane ABSTRACT A single chopstick can be broken easily while a tightly bundled collection of them can withstand much more mechanical stress. This is the case for the individual perovskite hollow fiber membranes for air separation where their inherently low mechanical strength limits their application. Here, several La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ hollow fibers have been bonded together to form a bundle, significantly improving the mechanical properties and the oxygen flux. The strategy for such improvement is the application of porous Ba 0.5 Sr 0.5 Co 0.4 Fe 0.6 O 3-δ perovskite as the binder. The perovskite binder not only plays the function of binding to increase the mechanical strength but also works as the catalyst attached on the exterior of the hollow fiber to improve the oxygen reduction surface reactions, thus leading to the higher oxygen flux. 1. Introduction Oxygen is highly essential to support life, environmental, and various industrial applications including glass, metals, chemicals, petrochemical production, and pulp/paper manufacturing; making it one of the largest selling chemicals in this planet. Oxygen is now becoming more and more important for cleaner energy production as the reduction of anthropogenic climate change impacts has become a global goal [1–7]. The possible technologies for this achievement is via oxy-fuel combustion or integrated gasification combined cycle (IGCC) plants where pure oxygen rather than air is used as the feed gas to burn or oxidize the coal or other biomass. Under such circumstances, the waste gas would be pure CO 2 that allows for facile capture as nitrogen is no longer present to be separated from the waste gas [1–3, 7–14]. Currently the tonnage O 2 production is based on cryogenic distillation, an expensive and energy intensive process. Dense mixed ionic and electronic conducting (MIEC) ceramic membranes can continuously deliver 100% pure O 2 under O 2 concentration gradient via the membrane surface oxygen exchange reactions and oxygen ionic bulk diffusion [1,4,12,15–27]. This ceramic membrane technology offers the potential to reduce the oxygen production cost by 30–50% compared to the conventional cryogenic distillation thus attracting much attention for a possible integration in clean energy plants [7,28–30]. Just like polymeric membranes, MIEC membranes can also be made in hollow fiber form that features the larger membrane area per unit volume and less sealing issue in this configuration, relative to the disk or tubular membranes [4,12,31–35]. In our previous project, 899 hollow fibers (OD 2.0 mm; ID 1.50 mm and Length 35 cm) were used to prepare a module with membrane area of more than 2.0 m 2 for air separation, which can deliver 7 kg oxygen day -1 with purity more than 99% [36]. However, one of the major challenges of MIEC hollow fiber membranes is their low mechanical strength due to the intrinsic brittleness of the ceramic fiber material. This problem hampers its large scale applica- tion. In this paper, we report the strategy of using a ceramic binder to bind a certain number of hollow fibers into a bundle to increase the mechanical strength. To our surprise, combining the individual hollow fiber membranes into a bundle does not affect its permeation flux values. On the contrary, the flux is actually enhanced. The trick here is the usage of a porous ceramic binder. Such a binder made from perovskite material can provide the role of not only binding but also as a catalyst to improve the surface oxygen exchange reactions thus contributing to higher mechanical strength and higher flux rate. The hollow fiber sample and perovskite binder demonstrated http://dx.doi.org/10.1016/j.memsci.2017.01.010 Received 2 November 2016; Received in revised form 12 December 2016; Accepted 7 January 2017 ⁎ Corresponding authors. E-mail addresses: tanxiaoyao@tjpu.edu.cn (X. Tan), shaomin.liu@curtin.edu.au (S. Liu). Journal of Membrane Science 527 (2017) 137–142 Available online 08 January 2017 0376-7388/ © 2017 Elsevier B.V. All rights reserved. MARK