Abstract
Herein we present a two-stage phase inversion method for the preparation of nanocomposite membranes for application in ultra-low-pressure reverse osmosis (ULPRO). The membranes containing DA-stabilized xGnP (xGnP-DA-) were then prepared via dry phase inversion at room temperature, varying the drying time, followed by quenching in water. The membranes were characterized for chemical changes utilizing attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The results indicated the presence of new chemical species and thus, the inclusion of xGnP-DA in the polyethersulfone (PES) membrane matrix. Atomic force microscopy (AFM) showed increasing surface roughness (Ra) with increased drying time. Scanning electron microscopy (SEM) revealed the cross-sectional morphology of the membranes. Water uptake, porosity and pore size were observed to decrease due to this new synthetic approach. Salt rejection using simulated seawater (containing Na, K, Ca, and Mg salts) was found to be up to stable at <99.99% between 1–8 bars operating pressure. After ten fouling and cleaning cycles, flux recoveries of <99.5% were recorded, while the salt rejection was <99.95%. As such, ULPRO membranes can be successfully prepared through altered phase inversion and used for successful desalination of seawater.
Highlights
Desalination using reverse osmosis membranes is a costly process due to the high operating pressure required; this drawback currently affects the rate at which various countries adopt the process.As such, many approaches are being investigated to lower these costs, and they include feed water pre-treatment, membrane material modification, and proper plant maintenance
This work envisaged the development of a new fabrication method and the development of ultra-low-pressure reverse osmosis (ULPRO) membranes for simulated seawater desalination
Two-stage phase inversion is used to prepare gas filtration membranes, and this study reports on the preparation of ULPRO membranes using this approach
Summary
Desalination using reverse osmosis membranes is a costly process due to the high operating pressure required; this drawback currently affects the rate at which various countries adopt the process. Many approaches are being investigated to lower these costs, and they include feed water pre-treatment, membrane material modification, and proper plant maintenance. Regarding these RO membranes, it is important to note that these should be developed with favorable properties such as chemical stability, low-fouling, high throughput, high permeability, and low operating pressure [1,2,3]. Ultra-low-pressure reverse osmosis (ULPRO) takes this principle a step further by reducing the operating pressures used during desalination.
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