A submicrometer-thick molecular sieve zeolite nanosheet laminated (ZNL) membrane has been synthesized on macroporous polyvinylidene fluoride (PVDF) substrate via the simplistic vacuum filtration-coating method. The membrane has been demonstrated with extraordinary water flux (∼11 kg/m2·h) and salt rejection (∼99.9%) in pervaporation (PV) desalination of a multicomponent brine with 22 wt % of total dissolved salts (TDS) including Li+, Na+, K+, Mg2+, Cl–, and SO4 2–, etc. The desalination of high-salinity brines is critical to treatment and beneficial use of many industrial produced waters. The large aspect ratios (>100) and preferable b-orientation of the densely layered nanosheets make the solution dewatering rate surpass the ion diffusion rates in the nanoscale internanosheet spaces. This unique transport behavior effectively prevents the dissolved salts from migrating through the ZNL layer and stabilizes the water flux and ion rejection rates. The supported multilayered ZNL membrane, which is interlocked by the substrate-type PVDF binder, exhibits structure and performance stability in PV desalination of high-TDS brines.

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Single crystalline ZSM-5 ZNs with thicknesses around 6 nm were obtained by secondary growth of silicalite nanoparticles using diquaternary bis-1,5(tripropyl ammonium) pentamethylene diiodide (dC5) as a structure-directing agent (SDA). The dC5 could be effectively removed from the ZN pores by either high-temperature calcination or UV irradiation in air at room temperature but not by the piranha solution treatment. Ultrathin ZN-laminated membranes (ZNLMs) were fabricated by sandwiching a UV-activated multilayered ZN film between two recast Nafion® layers (ZNLM-Nafion) and by filtration coating from a suspension of thermally activated ZNs on a nonionic porous PVDF (ZNLM-PVDF). The ZNLMs on both supports demonstrated the ability of highly proton-selective ion conduction with low resistances in aqueous electrolyte solutions. The ZNLM-PVDF with PVDF binder was structurally stable, and it achieved a comparably low ASR but much higher proton selectivity compared with a Nafion membrane of same overall thickness. However, detachment between the ZNLM and Nafion layers occurred when the ZNLM-Nafion operated in aqueous electrolyte solutions. Results of this study show the potential for developing ZNLMs as efficient proton-conducting membranes without using expensive ionic polymer matrices. However, the development of polymer-supported ZNLMs is hindered by the current inefficiency in preparing well-dispersed suspensions of open-pore ZNs. Future development of efficient methods for synthesizing open-pore ZNs in dispersed states is key to realizing high-performance ZNLMs on polymers.