Article pubs.acs.org/IECR
High Pervaporation Dehydration Performance of the Composite Membrane with an Ultrathin Alginate/Poly(acrylic acid)−Fe3O4 Active Layer Cuihong Zhao,†,‡ Zhongyi Jiang,†,‡ Jing Zhao,†,‡ Keteng Cao,†,‡ Qian Zhang,†,‡ and Fusheng Pan*,†,‡ †
Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China; ‡ Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China ABSTRACT: Poly(acrylic acid)−Fe3O4 nanoparticles (PAA−Fe3O4) with a size of 50 nm were synthesized by a one-pot method and then blended with sodium alginate matrix to prepare an ultrathin hybrid active layer of composite membrane for pervaporation dehydration of ethanol solution. The in situ modification of Fe3O4 nanoparticles by PAA improved the nanoparticle dispersion in the membrane. PAA−Fe3O4 nanoparticles not only interfered the ordered packing of polymer chains, but also enhanced the membrane structure stability and the diffusion selectivity. Compared with the membrane blended with Fe3O4 nanoparticles, the membrane blended with PAA−Fe3O4 nanoparticles displayed a much higher separation factor. When the PAA−Fe3O4 nanoparticle content was 8 wt %, the hybrid membrane acquired the optimal pervaporation performance with a separation factor of 1044 and a permeation flux of 1634 g/m2 h for 90 wt % ethanol aqueous solution at 350 K. Furthermore, the hybrid membrane possessed good long-term operation stability. nanoparticles in solutions.20,21 However, presently there is only sporadic research on formation of the ultrathin and defect-free hybrid active layer embedded with the small-size and welldispersed inorganic filler for dense membrane-based separation.22,23 Recently, Fe3O4 nanoparticles have been promising materials for many applications, such as magnetic fluids, biotechnology, environmental remediation, and membrane separation.24−26 Fe3O4 nanoparticles smaller than 100 nm can be prepared by many facile approaches, such as chemical coprecipitation, hydrothermal reaction, and sol−gel synthesis.27,28 Meanwhile, easy modification endows them with the potential to ease agglomeration. The most common modification strategy is coating Fe3O4 nanoparticles with organic compounds (including surfactants and polymers) or inorganic components (such as silica and carbon).29 In the fabrication of hybrid membranes, Fe3O4 nanoparticles coated by polymers more easily possess higher affinity toward the polymeric matrix and contribute to eliminating the defects at the interface between the polymeric matrix and fillers. The polymers can be coated by a postsynthesis coating method (nanoparticles are fabricated first and then coated by polymers)21,30 or an in situ one-pot synthesis method (nanoparticles are fabricated and modified simultaneously).31−34 In comparison, the latter is facile, economical, and scalable. Poly(acrylic acid) (PAA), as a weak polyelectrolyte, is often chosen for changing the surface properties of inorganic particles, due to the strong chelation of its numerous carboxyl groups with metal ions. Yang et al.31 and Si et al.32 prepared in situ modified Fe3O4 nanoparticles
1. INTRODUCTION Polymer−inorganic hybrid membranes have found important applications in dense membrane-based separation processes such as pervaporation,1−4 gas separation,5,6 and proton exchange membranes.7 The synergy between polymeric and inorganic phases often wins a high separation performance and desirable thermal and chemical resistances.8,9 Moreover, polymer−inorganic hybrid membranes provide the promising solution to overcoming the limitation of the trade-off between permeability and selectivity in polymeric membranes.10,11 Depositing an ultrathin polymeric−inorganic hybrid layer (usually
