Transport and structural properties of osmotic membranes in high-salinity desalination using cascading osmotically mediated reverse osmosis

Abstract

Management of high-salinity brines is a global environmental challenge. Recently, we proposed a novel cascading osmotically mediated reverse osmosis (COMRO) technology for energy-efficient hypersaline desalination. In this study, a transport model is established for COMRO. We investigate the impacts of hydraulic pressure and salinity on transport and structural properties of thin-film composite osmotic membranes in COMRO. Our results show that transport properties are not affected by transitory pressure changes on the order of hours. But on longer timescales, on the order of days, the membrane undergoes compaction/relaxation in response to pressurization/depressurization, with water and salt permeabilities declining/recovering accordingly. Importantly, the water and salt permeabilities change in the same proportion. We found that this is due to morphological changes of the active-support interlayer altering the effective membrane area. The membrane structural parameter is demonstrated to be consistent at different salinities. As salinity increases, both water and salt permeabilities increase, but salt permeability rises substantially more. Lastly, the presented transport model is validated by good agreement between experimental and predicted water fluxes. This study advances the understanding of membrane transport and structural properties in the emerging COMRO technology, and provides insights into water and salt transport for other osmotic membrane processes. inland desalination [7], landfill leachate [8], and flue gas desulfurization [9]. Prevailing desalination methods are all thermally-driven processes based on liquid-vapor phase change of water, which intrinsically requires intensive energy input (≈630 kWh/m 3) [10,11]. Reverse osmosis (RO) is the most energy-efficient method for seawater and brackish water desalination [12-14], but the current state-ofthe-art of RO is unsuitable for desalination of high-salinity brines. As

Zero Liquid Discharge of Ultrahigh-Salinity Brines with Temperature Swing Solvent Extraction

“…30 TSSE desalination is not restricted by feedwater salinity, unlike membrane-based reverse osmosis (RO) with hydraulic pressure (or, equivalently, osmotic pressure) limitation. 20,35,36 Because TSSE desalination does not require a phase change of water, the high energetic penalty of the vaporization enthalpy is inventively sidestepped and significantly higher energy efficiencies are attainable, specifically for hypersaline brines.…”

Selection of substrate manufacturing techniques of polyamine‐based thin‐film composite membranes for forward osmosis process

“…The RO test is not convenient to properly estimate the real A and B intrinsic parameters of FO membranes. [ 38,43,44 ] In RO, the applied pressure tends to compact the membrane which then alters the effective surface membrane. Unlike both active and support layers, any change in the active‐support interlayer structure may modify the A, B values and the overall membrane mass transport.…”

“…Unlike both active and support layers, any change in the active‐support interlayer structure may modify the A, B values and the overall membrane mass transport. [ 43 ] Chen et al [ 43 ] have shown that the active‐support interlayer is a crucial element. They also showed that the ratio of TFC membranes does not vary with changes in the interlayer morphology.…”

“…The surface structure and properties of the support layer are the most critical factors affecting the PA layer quality. Although the values of A and B are dominated by the active layer, Chen et al [ 43 ] have shown that they are strongly dependent on the morphology of the interface between the active and support layers. The pore structure and surface porosity of the support layer are crucial parameters determining the performance of PA‐TFC membranes.…”

“…It is worth mentioning that the surface porosity of the membrane's support layer is also a critical element [ 27,43,85 ] as surface and bulk porosities can be different. [ 48,85 ] The water flux can thus be also affected by porosity of the support's top surface.…”