The solution-diffusion model for water transport in reverse osmosis: What went wrong?

In this review, previous researches related to water transport in PEMFC are comprehensively reviewed. The state and transport mechanism of water in different components are elaborated in detail. The water transport in anion exchange membrane fuel cell (AEMFC) and the novel bipolar membrane fuel cell (BPMFC) are also discussed based on the cases in PEMFC. The water transport mechanism in AEMFC and BPMFC are similar to that of PEMFC, while the water management would be much difficult since the limitation properties of anion exchange membrane. In another hand, the difference between electrode reactions and membrane interface reactions for BPMFC make the transport of water more complicated. Fully understand the water transport in membrane electrode assembly is important in the develop of novel self-humidification fuel cells. As a result, the attractive cell configuration of BPMFC would make it a potential candidate for smart self-humidification fuel cells.

Activity-derived model for water and salt transport in reverse osmosis membranes: A combination of film theory and electrolyte theory

Membrane technologies using reverse osmosis (RO) and nanofiltration (NF) have been widely implemented in water purification and desalination processes. Separation between species at the molecular level is achievable in RO and NF membranes due to a complex and poorly understood combination of transport mechanisms that have attracted the attention of researchers within and beyond the membrane community for many years. Minimizing existing knowledge gaps in transport through these membranes can improve the sustainability of current water-treatment processes and expand the use of RO and NF membranes to other applications that require high selectivity between species. Since its establishment in 1949, and with growing popularity in recent years, Eyring's transition-state theory (TST) for transmembrane permeation has been applied in numerous studies to mechanistically explore molecular transport in membranes including RO and NF. In this review, we critically assess TST applied to transmembrane permeation in salt-rejecting membranes, focusing on mechanistic insights into transport under confinement that can be gained from this framework and the key limitations associated with the method. We first demonstrate and discuss the limited ability of the commonly used solution-diffusion model to mechanistically explain transport and selectivity trends observed in RO and NF membranes. Next, we review important milestones in the development of TST, introduce its underlying principles and equations, and establish the connection to transmembrane permeation with a focus on molecular-level enthalpic and entropic barriers that govern water and solute transport under confinement. We then critically review the application of TST to explore transport in RO and NF membranes, analyzing trends in measured enthalpic and entropic barriers and synthesizing new data to highlight important phenomena associated with the temperature-dependent measurement of the activation parameters. We also discuss major limitations of the experimental application of TST and propose specific solutions to minimize the uncertainties surrounding the current approach. We conclude with identifying future research needs to enhance the implementation and maximize the benefit of TST application to transmembrane permeation.

True driving force and characteristics of water transport in osmotic membranes

A mechanistic model for salt and water transport in leaky membranes: Implications for low-salt-rejection reverse osmosis membranes

Comparison of water and salt transport properties of ion exchange, reverse osmosis, and nanofiltration membranes for desalination and energy applications

Treatment of cauliflower processing wastewater by nanofiltration and reverse osmosis in view of recycling

Reverse osmosis (RO) is a very well-established technology for water desalination. Commercial RO systems are composed of several numbers of RO passes with auxiliary equipment such as high-pressure pumps and pressure-exchanger units to facilitate the separation, and to deliver clean water. Available design models for the RO network represent mixed integer nonlinear programming (MINLP) formulations. In addition, the existing RO design MINLP models are static in nature. These models are not suitable for RO network design under time-variant constraints. In this study, a multiperiod MINLP model is detailed for the RO network design. High-level design decision variables are related to the RO network configuration and equipment sizing, which are independent of time. These decisions are modeled by discrete and continuous variables. Low-level time-variant decision variables are related to the RO network operation and modeled by continuous variables. The operation decision variables are constrained by the design variables through different time periods to satisfy water-demand constraints. In addition, several correlations are considered in this study to estimate water and RO transport properties during the separation process. Case studies are analyzed to show the application of the mathematical programming model.

Dynamics of water and solute transport in polymeric reverse osmosis membranes via molecular dynamics simulations

Effects of water matrix on the rejection of neutral pharmaceutically active compound by thin-film composite nanofiltration and reverse osmosis membranes

The transport mechanism of water molecules on the surface of single-layer [Formula: see text]-graphyne is investigated from the first-principles calculations. The result indicates that when water molecules are adsorbed in different stances, their corresponding transport paths are different. When N atoms are doped with sp carbon atoms, the transport pathway of water molecules is opposite to that of intrinsic [Formula: see text]-graphyne, which is due to the charge transfer between atom s. Consequently, this study is conducive to understand the mechanism of nanoscale water transport on the graphyne surface and provides a theoretical basis for exploring the interaction between water and graphyne.

Chapter 4 - Mechanisms of Water Transport Across Cell Membranes and Epithelia

Early applications of desalination were small-scale plants deploying a range of technologies. However with the technological developments in Reverse Osmosis, most new plants use this technology because it has a proven history of use and low energy and capital costs compared with other available desalination technologies. This has led to the recent trend for larger seawater desalination plants in an effort to further reduce costs, and 1000 MLD seawater desalination plants are projected by 2020.Efficient Desalination by Reverse Osmosis recognises that desalination by reverse osmosis has progressed significantly over the last decades and provides an up to date review of the state of the art for the reverse osmosis process. It covers issues that arise from desalination operations, environmental issues and ideas for research that will bring further improvements in this technology.Efficient Desalination by Reverse Osmosis provides a guide to best practice from pre-treatment to brine management.ISBN: 9781780405049 (eBook)ISBN: 9781780405056 (Print)

Four release tests exhibit variable silver stability from nanoparticle-modified reverse osmosis membranes

Life cycle cost of a hybrid forward osmosis – low pressure reverse osmosis system for seawater desalination and wastewater recovery