Application of robust MFI-type zeolite membrane for desalination of saline wastewater

Abstract

a b s t r a c tZeolites are potentially a more robust desalination alternative as they are chemically stable and possess the essential properties needed to reject ions. This work proposes to use zeolite membranes for desalination of saline recycled wastewater for the possibility of avoiding the costly pre-treatment needed for polymeric reverse osmosis membranes. The MFI-type zeolite membrane was developed on a tubular α-alumina substrate by a combined rubbing and secondary hydrothermal growth method. The prepared membrane was characterised by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and single gas (He or N 2 ) permeation, and underwent desalination tests with saline wastewater under different conditions. When saline wastewater was fed at 7 MPa to the zeolite membrane it showed a salt rejection of 80% based on electrical conductivity (EC) and a flux of 4 L m À 2 h À 1 . A 254 (organics absorption at the wavelength of 254 nm measured by a HACH DR5000 spectrophotometer) removal exceeded 90%. Slightly lower salt removal and A 254 results were observed when operating at a lower pressure of 3 MPa. During batch concentration runs on the saline wastewater, the EC of the feed water increased from the initial value of 1770 mS cm À 1 to 3100 mS cm À 1 over the 48 h test time which indicates that a 43% water recovery was achieved. EC reduction remained 470% and flux was maintained at around 2 L m À 2 h À 1 throughout the test period, indicating that the membrane resisted organic fouling. Chlorine stability studies showed that a long-term (7 days) strong hypochlorite clean did not significantly alter the flux or rejection confirming the chemical stability of zeolite membranes. Overall, the zeolite membrane showed excellent chemical resilience and produced a desalinated product suitable for reuse applications (e.g. irrigation, residential or industrial). Fluxes, however, need to be improved to be competitive with current polymeric membranes as do rejections for higher purity water applications.

Zeolite membranes – a review and comparison with MOFs

“…[31][32][33][34][35][36][37] Recently, Hedlund and co-workers extended the manual assembly technique to nanocrystals by controlling the humidity of the environment during the coating process. 38 The authors proposed, as shown in Fig.…”

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

“…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]. Zeolite HS has also been considered for reverse osmosis desalination, having cavity diameters of 0.66nm separated by apertures of 0.3nm and 0.22nm [12].…”

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.…”