Development Of Reverse Osmosis Membranes Research Articles

Mechanisms and models for water transport in reverse osmosis membranes: history, critical assessment, and recent developments.

Water scarcity is one of the greatest societal challenges facing humanity. Reverse osmosis (RO) desalination, a widely used membrane-based technology, has proven to be effective to augment water supply in water-stressed regions of our planet. However, progress in the design and development of RO membranes has been limited. To significantly enhance the performance of RO membranes, it is essential to acquire a deep understanding of the membrane separation and transport mechanisms. In this tutorial review, we cover the pivotal historical developments in RO technology, examine the chemical and physical properties of RO membrane materials, and critically review the models and mechanisms proposed for water transport in RO membranes. Based on recent experimental and computational findings, we conduct a thorough analysis of the key transport models-the solution-diffusion and pore-flow models-to assess their validity for accurately describing water transport in RO membranes. Our analysis involves examining the experimental evidence in favor of the solution-diffusion mechanism. Specifically, we explain whether the water content gradient within the membrane, cited as evidence for the key assumption in the solution-diffusion model, can drive a diffusive transport through RO membranes. Additionally, we review the recent molecular dynamics simulations which support the pore-flow mechanism for describing water transport in RO membranes. We conclude by providing future research directions aimed at addressing key knowledge gaps in water transport phenomena in RO membranes, with the goal of advancing the development of next-generation RO membranes.

Development of reverse osmosis membranes by incorporating polyhedral oligomeric silsesquioxanes (POSSs)

Development of reverse osmosis membranes by incorporating polyhedral oligomeric silsesquioxanes (POSSs)

Preparation of low-fouling reverse-osmosis membranes on an Al2O3 carrier for desalination exploratory research

The surface of an α-Al2O3 carrier for semi-permeable zeolite membranes was modified with copper via an electroless plating process. Following hydrothermal synthesis, dense and highly organized zeolite membranes were obtained. Membrane thickness was confined to the nanoscale following layer-by-layer self-assembly of polyelectrolytes with opposite charges. This controllable and low-cost preparation method could drastically reduce the cost of fabricating reverse osmosis membranes, which is highly significant for the realization of large-scale seawater desalination through reverse osmosis. Understanding the influences of interactions between various ions and the zeolite pores, inter-crystalline gaps, membrane structure and surface chemical properties, transmembrane pressure, and temperature on the desalination process will help provide a theoretical basis and reference point for the development of reverse osmosis membranes.

Recent developments in reverse osmosis desalination membranes

Reverse osmosis (RO) desalination is one of the main technologies for producing fresh water from seawater and other saline water sources. The membrane properties greatly affect the water productivity and energy costs in the reverse osmosis desalinatin processes. Recent years have seen significant research efforts devoted to developing high-performance RO membranes. This article reviews recent activities in the development of RO membranes with improved flux and salt rejection, chlorine tolerance, fouling resistance and thermal stability. In particular, this review mainly focuses on the modification of current polymeric membrane materials, and synthesis and separation performance of new polymer membranes, inorganic membranes and mixed matrix membranes.

Progress in membrane science and technology for seawater desalination — a review

It is imperative to review the history of the past to provide a vision for the future. It is therefore the objective of this paper to review the history of the development of membranes and membrane processes for water production in general and seawater desalination in particular. The review highlights some new trends observable in the following four areas; membrane development, membrane characterization, membrane transport and membrane system design. The future prospects in the above four areas are discussed. Membrane development deals with recent progresses in the development of reverse osmosis membranes used for desalination. There are two different approaches, both based on in-situ polycondensation technique. One is to develop membranes for desalination of brackish water operable at ultralow pressures, and the other is to develop membranes operable at high pressure to achieve high pure water recovery in seawater desalination. In membrane characterization section, Atomic Force Microscopy (AFM) is featured as a new tool to investigate membrane surfaces. The effects of surface roughness, which can be measured by AFM, on membrane productivity and membrane fouling are discussed. Electron Spin Resonance (ESR) is another method, the application of which to investigate synthetic membranes has only begun. The potential of this method to investigate the structure of the membrane is discussed. Recent progresses in the measurement of pore sizes as small as one nanometer are briefly described. Membrane transport deals with transport models made primarily for charged membranes. Since most of nanofiltration membranes are electrically charged, the development of such transport models is useful in water treatment by nanofiltration membranes. Transport models in which pore sizes are included explicitly are particularly important since pore sizes of nanofiltration membranes are measurable. The section in membrane system design deals with various hybrid systems for seawater desalination in which membrane processes are incorporated. There is a great potential to reduce desalination cost by combining membrane processes with more conventional unit processes.

Effect of secondary additives in casting solution on the performance of porous cellulose acetate reverse osmosis membranes

The solution structure and evaporation rate constant can be varied by changing the temperature of the casting solution and the temperature of the casting atmosphere for a given film-casting solution composition. The effects of the two temperature changes can be simulated (without changing the two temperatures) by replacing a small part of the solvent (acetone) by a secondary additive in the casting solution. The effect of 20 different secondary additives in the batch 316-type casting solution has been studied and is discussed. Porous cellulose acetate reverse osmosis membranes, capable of giving a 20% to 25% increase in productivity at a 90% level of solute separation for a 3500 ppm NaCl–H2O feed solution at 250 psig, have been produced using 5 wt-% ethyl ether as the secondary additive in the above casting solution. The use of secondary additives offers a new flexibility in the choice of film-casting conditions and in the general development of reverse osmosis membranes.