A New Method for a Polyethersulfone-Based Dopamine-Graphene (xGnP-DA/PES) Nanocomposite Membrane in Low/Ultra-Low Pressure Reverse Osmosis (L/ULPRO) Desalination

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.

Progress for Co-Incorporation of Polydopamine and Nanoparticles for Improving Membranes Performance

“…Instead of using (PDA-f-GO) for modifying the surface of the membrane support layer as discussed before, it can be injected into or blended with the support polymer matrix via the phase inversion technique due to the high dispersion of rGO-PDA. The prepared PES nanocomposite membranes tested in ultra-low-pressure reverse osmosis (ULPRO) desalination application demonstrated that blending PDA-f-GO with polymer matrix can increase membrane salt rejection up to 99.9% [ 99 ]. Moreover, blending PDA-f-GO with the casting solution can greatly enhance the flux, hydrophilicity, pore structure, antifouling properties, and surface roughness of casted membrane more than the pristine membrane or GO-based membrane, as was proved by the fabricated UF membrane of PSF/rGO-PDA mixed matrix membranes (MMMs) [ 83 ].…”