POLYMERS Vol.65　No.4 April 2016

POLYMERS　Vol.65　No.4

COVER STORY
Membrane Separation for the Next Generation

COVER STORY: Highlight Reviews

Innovative Water Treatment by Forward Osmosis Membrane Process

Hideto MATSUYAMA, Masahiro YASUKAWA

<Abstract> The rapid increase in the global population and acceleration of urbanization will lead to further serious shortage of available water in the world. Membrane separation technology is one of the effective ways to solve this water shortage problem. Recently, the forward osmosis (FO) membrane process has gained much research attentions because of its potential usage in both water and energy applications. FO enables the spontaneous water transfer through a selectively semi-permeable membrane from a solution with lower concentration, for example, sea water to one with higher concentration, known as the draw solution (DS), by an osmotic pressure gradient. Since the conventional RO membranes can not be used as the FO membrane, innovative FO membranes must be developed for the commercialization of this process. In addition, a development of DS, which can be easily recovered, is also of great importance
Here, we briefly introduce research development and future prospective in FO membrane process including our recent works
Keywords: Forward Osmosis Membrane / Water Treatment / Draw Solution / Zero Liquid Discharge / Pressure Retarded Osmosis

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Bio-Inspired Membrane

Hiroshi UMAKOSHI

<Abstract> It is important to establish a methodology to design and develop a “Bio-Inspired Membrane”, which can be defined as an “Artificial Membrane” inspired by structures and functions observed in “Biomembrane”. Several approaches relating to this research area are reviewed based on a hierarchical view about the structures and characteristics of the above membranes. A “Membranome” research utilizing a gel membrane immobilizing liposome membrane at high concentration is herewith introduced as one of several approaches to create the “Bio-Inspired Membrane”.
Keywords: Bio-Inspired Membrane / Artificial Membrane / Biomembrane / Membranome / Liposome / Self-Assembly

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Past, Present, and Future of Polymer Membranes for Gas Separation Applications

Kazukiyo NAGAI

<Abstract> A gas separation polymer membrane is required to have either a small molecule permselective property or a large molecule permselective property. The transport of gases in a dense polymer membrane is thought to obey the solution-diffusion mechanism. The total permeability is a product of the solubility and the diffusivity. Hence, the permselectivity is a product of the solubility selectivity and the diffusivity selectivity. The dominant factor to determine the permselectivity is the diffusivity selectivity for small molecule permselective polymer membranes and the solubility selectivity for large molecule permselective polymer membranes. The control of the polymer-gas interaction and/or the size and distribution of the fractional free volume produces a wide variety of gas separation properties in polymer membranes. This review article describes past, present, and future of polymer membranes for gas separation applications.
Keywords: Polymer Membranes / Gas Separation / Gas Purification / Solution-Diffusion Mechanism / Solubility Selectivity / Diffusivity Selectivity / Molecular-Sieving

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COVER STORY: Topics and Products

Development of Low Water Production Cost Desalination Technology

Hideaki KUROKAWA

<Abstract> For decreasing the water production cost, two types of low cost desalination systems were developed. One is the integrated sea water reverse osmosis and Sewage reuse system, the other is the high recovery RO system. Integrated system was developed at Kitakyusyu Water Plaza and supported by NEDO. The feature of this system is to mix the treated sewage with the sea water for the feed of desalination system. This system can reduce the salinity of the feed water and the energy of RO system can be reduced. As the results of the verification, about 30% of water production cost could be reduced in comparison with conventional RO desalination system. High recovery RO system is also proposed for reducing the water production cost using optimum plant configuration. This system can increase the water recovery from 40% to 60%. By the trial calculation, approximately 15% of OPEX and CAPEX are reduced respectively. We will pursue to reduce the water production cost by the system optimaization.
Keywords: Desalination / Reverce Osmosis / High Recovery / Low Water Production Cost / Sewage Reuse / System Optimization / Membrane

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1/f Fluctuation and Water Permeation of Aquaporins

Eiji YAMAMOTO, Kenji YASUOKA

<Abstract> Aquaporins (AQPs) are transmembrane water channels that exclusively transport water molecules across the plasma membranes. Using all-atom molecular dynamics simulations for a system of AQP1/water molecules/lipid bilayer, we investigated the effects of conformational fluctuations of amino acids on water pemeation within AQP1. We found that the amino acids exhibit 1/f fluctuations, indicating possession of long-term memory. In this case, water molecules crossing the ar/R region obey a non-Poisson process. Moreover, we performed restrained MD simulations of AQP1. In restrained MD simulations, the fluctuations of amino acids show white Gaussian fluctuation, and water molecules crossing the ar/R region obey a Poisson process. These results suggest that 1/f fluctuations of amino acids generate the non-Poisson water permeation within AQP1.
Keywords: Aquaporin / Molecular Dynamics Simulation / 1/f fluctuation / Non-Poisson Process / Water Molecules / Cell Membrane

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CO₂ Separation Membranes and Carbon Capture and Storage (CCS)

Ikuo TANIGUCHI

<Abstract> An explosive increase of atmospheric concentration of greenhouse gas, particularly CO₂, causes global warming and climate change. One of the effective solutions should be mitigation of CO₂ emission through the air by Carbon Capture and Storage, CCS. CO₂ is separated over other gaseous components at the mass emission sources, such as thermal power plants, and then stored under ground or seabed after transportation by pipeline or tanker truck. For implementation of CCS, the capture cost should be drastically reduced, which is equivalent to develop novel CO₂ capture technologies with much lower energy consumption. Among various CO₂ capture technologies, membrane separation is promising because difference in pressure or chemical potential between feed and permeate sides drives the separation, and basically additional energy, such as heating in liquid amine scrubbing technology, is not required at all. A number of CO₂ separation membranes have been investigated, and herein, the recent progress and the potentiality of membrane separation in CO₂ capture are reviewed.
Keywords: Carbon Capture and Storage / CO₂ / Gas Separation / Membrane / Permeability

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Polymer Science and I: A Personal Account

Can I Believe Myself ?

Yukiko KAMIYA

<Abstract> A variety of ups-and-downs experiences in my research on biopolymer such as protein, oligosaccharide, and nucleic acids make my research life fruitful. This personal account describes the author's own experience including the research topics and episodes.

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Front-Line Polymer Science

Visualization of Membrane Fouling

Tatsuo MARUYAMA

<Abstract> Although polymeric membranes have been widely used as separation and purification techniques in various industries, the membrane separation technique still suffers from a severe problem, “membrane fouling”. Recent progess in microscopy and fluorescent labeling allows visualization of membrane (bio)fouling and provides the microscopic information. A confocal laser scanning microscope is a powerful tool for the visualization of a cake layer in membrane fouling, especially in membrane biofouling. Membrane-internal fouling caused by soluble foulants can be visualized by fluorescent microscopy with fluorescent labeling of foulants. These microscopic analysis provides the spatial, time-dependent and component information of membrane fouling, which helps our understanding for membrane fouling and also leads to an effective strategy to clean a fouled membrane.
Keywords: Membrane Fouling / Biofouling / Polymeric Membrane / Visualization / Protein / Polysaccharide

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