The potential of zeolite membrane for forward osmosis operation was demonstrated. Na–ZSM–5, an aluminosilicate zeolite, membrane was used for fruit juice concentration and the purification of contaminated water with heavy metals. In these applications, Na–ZSM–5 membrane exhibited superior rejection and antifouling performances. In addition, the influence of support structure on water flux in FO operation was studied. The structure of support, namely the thickness, strongly affected water flux, indicating that the water flux through zeolite membrane will be improved by using thin supports, such as hollow fibers and anodized alumina filter.

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Distillation is widely used for concentration of aqueous organic solvent solutions, but it consumes large amounts of energy. Membrane separation is energy–efficient for concentration, but conventional reverse osmosis (RO) method has limitations in the degree of concentration because of high osmotic pressure of concentrated solution. Osmotically Assisted Reverse Osmosis (OARO) is a method that enables high concentration at relatively low pressure. We applied the OARO method to the high concentration of aqueous organic solvent solutions. Dilute solutions of organic solvents such as isopropanol (IPA) and N,N–dimethylformamide (DMF) were successfully concentrated to 20 ～ 40 wt% by OARO with a high yield. OARO is useful for energy–efficient concentration and recovery of organic solvents from industrial wastewater containing organic solvents.

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Seawater desalination has long been used as a solution to the global water shortage. The water recovery ratio of seawater desalination is about 40 ～ 45%, with the remainder being discharged into the ocean as concentrated brine. In recent years, there has been increasing attention on the resource recovery of substances such as sodium chloride and magnesium from concentrated brine. By separating and recovering these substances from concentrated brine, it becomes possible to resourcefully utilize concentrated brine. On the other hand, high concentration is essential for the resource recovery of concentrated brine. One of the high–efficiency concentration technologies developed in recent years is the osmotically assisted reverse osmosis (OARO) method. OARO is a membrane concentration technology that allows for high concentration with low energy consumption, and its development is progressing from the demonstration stage to commercialization. In this paper, in addition to the features of the OARO process, we will introduce examples of its practical application.

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Non–heated concentration membrane system has been developed by using FO (Forward Osmosis) and MD (Membrane Distillation) membrane. FO mainly removes water with osmotic pressure difference between Feed Solution (FS) and Draw Solution (DS). On the other hand, MD mainly removes solvent such as acetonitrile with vapor pressure difference between FS and Cooling Water (CW). This system is applied to pharmaceutical manufacturing processes that are sensitive to heat and pressure such as peptides and oligonucleotides. This is the only one technology which can concentrate the liquids without heat and pressure, and control liquid composition at the same time. This review includes the test results with the cyclic peptide solution, which demonstrates the potential of the FO–MD system in pharmaceutical manufacturing processes.

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Elucidating the fouling phenomena on polymeric biomaterial surfaces promotes the development of antifouling membrane materials. Recently, we have investigated the microscopic mechanisms of the excellent antifouling properties of nonionic poly(2–methoxyethyl acrylate) (PMEA) and zwitterionic betaine polymers by using molecular dynamics simulations. Here, we evaluated the interactions between the side chains of polymers and model organic foulants. We clarified that the suppression of the hydrophobic interactions is essential for enhancing antifouling properties. We believe that our studies contribute to the molecular design of polymeric membrane materials with excellent antifouling properties.

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Machine learning (ML) is a methodology for uncovering patterns and principles hidden within empirical measurement data. Among these, generative modeling using a variational autoencoder (VAE) is a powerful technique for generating new data based on learned ML model, and it has demonstrated success in accurately generating molecular structures. If membrane permeation property can be evaluated from molecular structures in a non–empirical manner, it would enable the design of novel, high–performance separation membranes. This paper focuses on providing an overview of applications of the VAE generative model, along with the characteristics and utilization of the latent space. As a concrete example of its application, research on the molecular structure design of carbon dioxide separation membranes was presented.

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Membrane separation technologies are becoming increasingly important in meeting water shortages and pollution, as well as in the efficient treatment of chemical production and waste solvents. In particular, technologies such as reverse osmosis (RO) and forward osmosis (FO) are gaining attention, and an understanding of membrane structure and performance is important. The advancement in membrane technology requires membrane design at the molecular scale, and molecular simulation is expected to play an important role. Membrane modeling and permeation simulation methods were reviewed for membrane permeation studies of liquid phase using classical molecular simulations, and recent examples of molecular design of membranes with graphene oxide and new diamines were presented. For the relationship between the microscopic structure and membrane performance, valuable insights have been provided by molecular simulations.

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CO₂ capture is considered as an essential technology in a carbon–neutral society. For the time being, amine– based methods will contribute to the widespread use of CO₂ capture. Computational chemistry is expected to be utilized to accelerate the development of this technology. In this paper, we discuss the reaction analysis of amine–CO₂ systems, and the design of new amine molecules based on theoretical calculations.

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Energy optimization in Membrane Bioreactors (MBRs) is essential to facilitate the widespread adoption of this technology for wastewater treatment. This research examined various operating conditions and commonly employed fouling mitigation techniques to assess their impact on the lifespan of porous alumina microfiltration membranes and energy consumption over the operation cycles in MBRs with backwashing. Parameters studied include frequency of backwashing t_cycle (30 to 120 min), backwashing duration t_backwashing (1 to 10 min), backwash flow rate Q_backwashing (1 to 5 mL/min), filtration flow rate Q_filtration (1 to 3 mL/min), air circulation flow rate Q_{air, module} (0 to 300 mL/min), and MLSS (2000 to 8000 mg/l). Filtration resistance, measured over the operation time, exhibited a typical two–stage behavior. Membrane fouling rates varied under different conditions. Operations showing lesser fouling rates were not always found to be the most energy efficient. Energy consumption during the filtration period E_filtration is the major contributor to the total energy consumption E_total.

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Membrane separation is widely used in various industries, but is mainly for processing aqueous solution and suspension, and we have developed solvent–resistant hollow fiber membrane module, WINSEP®. WINSEP® show stable performances in a variety of organic solvent including aprotic polar solvent. We demonstrated separation tests of organic solvent by using WINSEP ®, for example, separation and classification of quantum–dots, removal of water in w/o emulsion, polymer purification and regeneration of waste solvent from electronics industry.

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