Desalination of seawater ion complexes by MFI-type zeolite membranes: Temperature and long term stability

Abstract

Desalination of seawater ion complexes by MFI-type zeolite membranes: temperature and long term stability, Journal of Membrane Science, http://dx.doi.org/10.1016/j.memsci. 2013.10.071 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 2 high rejection (>93%) for all major seawater ions including Na + (except for K + , 83%) at an applied pressure of 700 kPa and room temperature (22 °C), but showed a continuous decrease in ion rejection when increasing the temperature from 22 °C and 90 °C. Permeation flux of the zeolite membrane significantly increased with increasing in temperature. Upon closer observation of the major cations, size selective diffusion in the zeolite membrane was observed over the temperatures tested. Larger ions Ca 2+ and Mg 2+ were less responsive to temperature than smaller ions Na + and K + . No changes in membrane structure were observed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) after 180 days seawater exposure. However, energy-dispersive X-ray spectroscopy (EDS) mapping on the surface of the membrane revealed a small quantity of tightly bound divalent cations present in the structure, which appear to have penetrated the zeolite, accelerated by temperature. They were suspected to have altered the permstructure, explaining why original high rejections at room temperature were not reversed after heat exposure. The work has shown that zeolite membranes can desalinate seawater, but other unusual effects such as ion selective diffusion as a function of temperature indicate a unique property for desalination membrane materials.

Structural effects on SAPO-34 and ZIF-8 materials exposed to seawater solutions, and their potential as desalination membranes

“…Desalination performance of the prepared membranes was carried out in the desalination test system similar to that used in our previous work [10]. The desalination experiments were conducted in a cross-flow setup with the feed solution (deionised water or 3,000 mg/L NaCl) being fed under pressure on the inside and permeating to the outside of the membrane.…”

“…Materials which possess these properties and have already been demonstrated for desalination are silica [2,3] and zeolites [4][5][6][7][8][9]. Seawater desalination was demonstrated in reverse osmosis mode on MFI type zeolite membranes, which have an intrinsic crystal pore size of 0.55nm [10]. In saline waste water desalination, MFI type zeolite membranes were shown to produce high quality water suitable for reuse, and exhibited strong tolerance to cleaning with high strength chlorine [11].…”

Synthesis of graphene oxide/polyimide mixed matrix membranes for desalination

“…5,6 In comparison with organic polymer membranes, the inorganic membranes are more stable under harsh separation condition. So far, various inorganic membranes, such as carbon membrane, 7,8 zeolite membranes, [9][10][11] and metal organic frameworks membrane 12 have been developed for seawater desalination. Despite much progress in the development of membranes for seawater desalination, it is still highly desired to develop a novel membrane with high stability and high ions rejection for seawater desalination.…”

Graphene-Based Membrane Technology: Reaching Out to the Oil and Gas Industry

“…Interesting results have been obtained by working with inorganic nanomaterials used as fillers of the polymeric layer to allow the formation of composite thin films with enhanced permeability. Alternative structures and materials with respect to polyamide membranes have also been reported such as layer-by-layer assembled active layers, zeolite-based thin films [22][23][24][25][26][27][28], and graphene-based nanomaterials [29,30] which perform separation by size exclusion of hydrated ions.…”