March /2016
(STRATEGIC PROPOSALS)
Innovations in Separation Engineering - Separation Science and Technology for a Sustainable Society -/CRDS-FY2015-SP-04
Executive Summary

The natural is composed of diverse mixtures comprising various substances, where numerous chemical reactions occur simultaneously. The similar situation holds true in the living organisms, where countless mingled substances flow in the blood. Such is the inevitable consequence of the nature which progresses inexorably toward entropy maximization. Thus, in order for human begins to achieve a sustainable society and survive, it is our important task to sort and extract useful substances from mixture, as well as to remove unwanted matter. This work represents a decrease in entropy, which requires input of energy.

The process for precise separation of desired substances with minimum energy consumption is a basic process in chemistry comparable to material synthesis and occupies an extremely important position in industry, as well. In fact, separation technologies are indispensable in wastewater treatment and seawater desalination, for example, in order to cope with the significant shortage of water resources associated with the expected population rise of world. Shale gas and shale oil have shown great promise as an energy source, but the large amount of contaminated water produced when mining shale is a serious environmental concern, where an effective separation technology is required. There has also been an emphasis placed on separation processes that produce great social and industrial merits, including the separation of radioactive material from the massive amount of contaminated water produced from the Fukushima Daiichi nuclear disaster, and the dehydration of microalgae in biofuel refining performed to extract compounds expected to serve as renewable energy. To date, distillation processes have been heavily used in the separation of liquids, but such distillation processes account approximately 40% of the total energy consumption in the petrochemical industry, requiring new low-energy separation technologies.

Industry is also facing many challenges with gases, including the need to separate air pollutants such as PM2.5 and to separate and recover greenhouse gases (CO2) generated in large quantities by thermal power plants, as well as the importance of separating and storing high-purity hydrogen for the coming hydrogen society. The separation technologies of solid mineral resources are basically the dressing, smelting, and refining processes. However, due to the declining number of quality mines in resource-rich countries, we are now forced with having to mine low-grade ore that includes many harmful substances, such as arsenic and, hence, need to develop technologies for separating target substances with less energy and low environmental impact. Human beings industrially produce and consume wide variety of products based on the resources obtained from this mineral processing. The massive amounts of products discarded after use can then be treated as artificial mixtures, as opposed to the natural occurring mixtures like ore, and can once again be subjected to separation in order to recycle these products. This material cycle is now an important issue confronting humankind. Although great technological and economic hurdles exist at present in achieving the separation of both naturally occurring mixtures and artificial mixtures, it is a challenge for humankind to overcome, since establishment of a sustainable material cycle will be extremely important in the future society.

In terms of living organisms, high-speed and high-precision separation processes are needed for separating specific cells, proteins, and other biomaterials to realize early diagnosis and treatment of diseases, minimally invasive procedures, and the production of pharmaceutical ingredients. Technical development of separation processes for biological material must also be integrated with analyses. Moreover, unlike separation technologies for gases, liquids, and solids described earlier, separation and analysis on biological material must be performed on infinitesimal quantities either to reduce the impact on the patient or simply because the body inherently includes only small amount of such materials.

The innovations in separation engineering addressed by this proposal are targeting at a marked improvement of conventional separating technologies with reduced energy consumption and improved precision in separating operations, such as the extraction of desired materials or the removal of unwanted substances from mixtures consisting of diverse substances in a mixed state. This proposal proposes drastic efforts to innovate separation engineering by reconsideration of processes and functions formulated by existing science and technology, represented by chemical engineering. This proposal is based on future demands of society and industry from a modern perspective of innovation in science and technology, and based on knowledge and skills acquired through the merging and integration of technologies of other fields. In order to solve various important social and industrial issues in which separation is crucial, innovation is strongly required that realizes separation of target substances by means of engineering methods while returning to the basic scientific principles that governs the separation processes.

The basic principles of separation can roughly be divided into three categories; mechanical separation, equilibrium separation, and speed-difference separation. This proposal aims at achieving energy-saving, high-precision operations of separation by making use of dramatic advances in recent nanotechnology, state-of-the-art measuring technologies, and simulation technologies to control at the atomic and molecular level these basic principles of separation, as well as agents of the separating operations such as materials, devices, and processes. The goal of this innovation is to achieve a required separation throughput per unit energy of separated substance while maintaining a high performance, despite there is generally a trade-off relationship between performance and throughput. In this proposal, separation problems that cannot be solved by individually developed technologies will be surpassed drastically by merging different technologies, introducing new materials and devices, and combining reactions. In other words, the goal of this proposal is to systematically organize separation engineering to create a direct path from cross-disciplinary efforts to innovation.

The challenges for separation addressed in this proposal can be divided into three major requirements or directions: (1) gas-liquid separation, (2) separation of mineral resources and solid wastes, and (3) separation in biological, pharmaceutical, agricultural, and food systems. The basic issues that intersect these three categories are also important. Some of these issues that will require contributions from academia in particular include the establishment of an in-situ measuring technologies for elucidating and learning how to control crystallization mechanisms and phase separation processes in mixed solutions, and simulation models for identifying unmeasurable phenomena. The required scale and precision differs greatly among the three directions described above and, hence, the separation technology or combination of technologies and the system employed will differ according to the objective. Requirements for separation performance are also determined based on the application. Accordingly, it will be necessary to develop new separation technologies and processes and separating materials with consideration for cost in order to achieve these requirements of performance.

For (1) gas-liquid separation, this proposal discusses the various R&D challenges in adsorption, absorption, and membrane separation. These fields have seen the emergence of new materials, such as zeolites, metal-organic frameworks (MOF), and nanocarbons, and next-generation separation technologies employing ionic liquids and supercritical fluids. However, the barrier to finding replacements for conventional separation technologies such as distillation is high and may not be overcome by depending solely on new technologies. It is important that we greatly improve separation performance in the overall process and system by combining new separation technologies with existing technologies.

For (2) separation of mineral resources and solid wastes, this proposal describes metal recycling and the basic theory of smelting. Smelting is often regarded as a mature field owing to its long history, but there are still many important element pairs that are difficult to separate. We have the potential to greatly transform this field by incorporating recent advances in nanofabrication and evaluating technologies, computational science and modeling, and data science.

For (3) separation in biological, pharmaceutical, agricultural, and food systems, this proposal describes the isolation and simplified testing for causative agents of infectious diseases, for example, the thorough examination of disease-related components, and the separation of active constituents in plants and foods. Living organisms possess numerous unexplained functional molecules whose interaction is not sufficiently understood. Therefore, we need to develop technologies for specifically separating and analyzing classes of molecules that are functionally related, while preserving their functions and states, and to consolidate the analysis results and analyze these results using the latest information science.

As described above, the scale of the apparatus and equipment needed in the separation process ranges widely from an enormous case weighing more than one ton to an ultramicro scale of picoliters or femtoliters, depending on the subject of separation, but the fundamental principles are shared among all methods in that separation is achieved based on the shape of molecules at the nanometer level and differences in their physical, chemical, and electrical properties. Thus, we can prepare a physical structure that corresponds to the physical shape and size of the target substance and separate the target substance using its difference in chemical affinity. This shows the importance of establishing intersecting basic technologies common to all separation processes in order to understand these separation processes at the molecular level and develop new technologies and new materials that can bring about innovation in separation engineering, and therefore academia is expected to play an important role in this endeavor. This proposal describes the heightened need for industry and academia to share roles and collaborate, as well as how such collaboration can be implemented.