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Suggested Citation:"1 Introduction." National Academies of Sciences, Engineering, and Medicine. 2019. A Research Agenda for Transforming Separation Science. Washington, DC: The National Academies Press. doi: 10.17226/25421.
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Suggested Citation:"1 Introduction." National Academies of Sciences, Engineering, and Medicine. 2019. A Research Agenda for Transforming Separation Science. Washington, DC: The National Academies Press. doi: 10.17226/25421.
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Suggested Citation:"1 Introduction." National Academies of Sciences, Engineering, and Medicine. 2019. A Research Agenda for Transforming Separation Science. Washington, DC: The National Academies Press. doi: 10.17226/25421.
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Suggested Citation:"1 Introduction." National Academies of Sciences, Engineering, and Medicine. 2019. A Research Agenda for Transforming Separation Science. Washington, DC: The National Academies Press. doi: 10.17226/25421.
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Suggested Citation:"1 Introduction." National Academies of Sciences, Engineering, and Medicine. 2019. A Research Agenda for Transforming Separation Science. Washington, DC: The National Academies Press. doi: 10.17226/25421.
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Suggested Citation:"1 Introduction." National Academies of Sciences, Engineering, and Medicine. 2019. A Research Agenda for Transforming Separation Science. Washington, DC: The National Academies Press. doi: 10.17226/25421.
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Suggested Citation:"1 Introduction." National Academies of Sciences, Engineering, and Medicine. 2019. A Research Agenda for Transforming Separation Science. Washington, DC: The National Academies Press. doi: 10.17226/25421.
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Suggested Citation:"1 Introduction." National Academies of Sciences, Engineering, and Medicine. 2019. A Research Agenda for Transforming Separation Science. Washington, DC: The National Academies Press. doi: 10.17226/25421.
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Suggested Citation:"1 Introduction." National Academies of Sciences, Engineering, and Medicine. 2019. A Research Agenda for Transforming Separation Science. Washington, DC: The National Academies Press. doi: 10.17226/25421.
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Suggested Citation:"1 Introduction." National Academies of Sciences, Engineering, and Medicine. 2019. A Research Agenda for Transforming Separation Science. Washington, DC: The National Academies Press. doi: 10.17226/25421.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

  1 Introduction Separation, as the term is used in this report, is the division of a chemical mixture (a mixture of mol- ecules or colloidal particles) into its constituent or distinct elements. The purpose of a chemical separation process is usually to enrich a product stream in one or more of the components of the original mixture. In some cases, the purpose of the separation process is to divide the mixture fully into its pure components. At the simplest level, a chemical separation might involve boiling and condensing water to eliminate salts or preferentially evaporating a more volatile component from a mixture. At a more sophisticated level, a chemical separation might involve passing a mixture through a specialized membrane that interacts with specific constituents to affect their permeabilities and thus separates them. Separations are an integral component of a wide array of technologies that are necessary to meet so- cietal needs. The goal can vary from dividing a complex mixture into thousands of fractions to extracting a single chemical from a highly dilute solution. The scale of a separation process can vary from less than a microgram to megatons of material. Regardless of the goal and the scale, separation processes are vital to numerous industries, including the oil and gas industry, chemical and pharmaceutical manufacturing, biotechnology, food production, water desalination and purification, and waste management and treat- ment. They are critical for providing clean water and air to the world’s population, extracting natural re- sources for energy storage and use, and delivering effective and affordable health care. Although separation processes are used throughout many industries, there are challenges, and cur- rent methods are often costly. For example, most industrial separations are energy-intensive (see Box 1-1, Figure 1-1) and by some estimates account for about half the energy used in U.S. industry and 10–15% of total U.S. energy consumption (Humphrey and Keller, 1997; ORNL, 2005). Many traditional separation processes use larger amounts of energy than emerging technologies that do not rely on the vaporization of one or more of the chemical components and instead rely primarily on separation materials (see Figure 1-2). Although design and operation improvements have reduced the energy use of distillation processes, energy-intensive separations are reported to account for 80% of industrial separations (ORNL, 2005). Some separation processes generate large waste streams that are expensive to manage. For those reasons, advances in separation science are critical both for future U.S. economic competitiveness and for improv- ing living standards globally. Given the scientific and technological advances that have occurred in the decades since the publica- tion of Separation and Purification: Critical Needs and Opportunities (NRC, 1987), the Department of Energy (DOE), the National Science Foundation (NSF), and the National Institute of Standards and Tech- nology (NIST) recognized that there are important opportunities for improving separation processes and asked the National Academies of Sciences, Engineering, and Medicine (the National Academies) to de- velop an agenda for fundamental research in separation science. As a result of that request, the National Academies convened the Committee on a Research Agenda for a New Era in Separation Science, which prepared this report. Prepublication Copy 9

A Research Agenda for Transforming Separation Science BOX 1-1 Ethylene Production via Steam Cracking The expansion of natural-gas capacity in the United States has led to a generous availability of ethane (and propane), which in turn has led to an increase in ethylene production of about 50% from 2016 to 2019. The production process uses steam cracking in which steam acts as a diluent to in- crease conversion (see Figure 1-1). A typical cracker comprises three main sections: steam cracking, fractionation and compression, and separation. That description, however, masks the complexity of a process that contains 12–14 unit operations (Moulijn et al., 2001). Although the energy intensity of ethylene production has improved greatly (from about 17–21 to about 12–14 GJ/tonne) through im- plementation of efficient process design, energy recovery, and the use of advanced materials (Gulf, 2010; Neelis, 2008; Worrell, 2017), the use of steam still causes substantial energy waste and impos- es a huge capital burden. An energy analysis of the ethane-to-ethylene process indicates that 24% of the process energy is lost through the steam-cracking section (DOE, 2015). Furthermore, the use of conventional distillation for product separation is highly energy-intensive; the separation process ac- counts for about 30% of the energy used in ethylene production. A challenge for the separations community is to develop technology for critical aspects of hydrogen and hydrocarbon (C1, C2, and C3) separations that not only saves energy in product recovery but allows the design of ethane-to-ethylene processes that are free of steam. FIGURE 1-1 Steps for ethylene production that uses steam cracking. SOURCE: Chemical Engineering, see https://www.chemengonline.com/ethylene-production-via-cracking-ethane-propane/. FIGURE 1-2 Examples of thermal separation processes (higher energy use) and nonthermal separation processes (lower energy use). Thermal processes are energy-intensive because they are based on the enthalpy of vaporization of at least one component. MOTIVATIONS There were several compelling reasons to undertake the committee’s task; some are described below. 10 Prepublication Copy

Introduction Developing a Sustainable Chemical Enterprise to Drive the Economy. Advances in separation sci- ence and technology are critical for developing a sustainable chemical enterprise. As noted, separations in industrial processes can be extremely energy-intensive. Reducing energy consumption in industrial sepa- ration processes was identified as one of the grand challenges in Sustainability in the Chemical Industry: Grand Challenges and Research Needs (NRC, 2006, p. 86), which stated the following: The energy efficiency of chemical separations is a key research component of this grand challenge. Finding effective alternatives to distillation are especially needed. While membrane separations, ad- sorption, and extractions tend to be less energy intensive, significant technical challenges must be overcome in the development of these alternatives in order to realize any significant reductions in the energy intensity of the [chemical processing industry]. More energy-efficient chemical separations in U.S. industry could save an estimated $4 billion in energy costs a year (DOE, 2015) and make industry more sustainable. Creating a more sustainable chemical enterprise will also require optimizing separations so that use- ful materials can be recovered and waste generation minimized. For example, rare-earth metals are im- portant resources that are used regularly in magnets, in renewable-energy technologies, and as catalysts in petroleum refining. However, separation of rare-earth metals from ores or used electronic components is inefficient and produces large amounts of waste and unwanted byproducts. New approaches would im- prove recovery of these valuable materials. Likewise, more mass- and energy-efficient separations are needed for a wide variety of chemical recycling applications. For instance, depolymerization of mixed plastics followed by easy separation into purified monomer streams could contribute to a more sustainable chemical enterprise. Reducing Adverse Effects of Industrial Activities. Some industrial activities result in the discharge of pollutants and have adverse effects on human health and the environment. An integral component of developing a sustainable chemical enterprise is reduction of those effects. Creation of more efficient and selective separation processes can play a key role in this endeavor. For example, minimization of solvent use in separations, use of more sustainable solvents, and removal of heavy metals and other contaminants from wastewater before discharge all hold tremendous potential for reducing the amount of toxic and waste substances generated or released and thus reducing effects on human health and the environment. Another grand challenge identified by the National Academy of Engineering (NRC, 2008, updated 2017) is the development of carbon-sequestration methods. The most energy-intensive and capital- intensive part of carbon sequestration is separation of carbon dioxide from a gas mixture or potentially separation of oxygen from air for use in oxyfuel combustion. In both cases, the main difficulty is to sepa- rate compounds that are extremely similar in size. More energy-efficient separations could reduce carbon dioxide emissions by 100 million tons a year (Sholl and Lively, 2016)—an important reduction in carbon emissions relative to climate-change initiatives. Improving Human Health. Separation science is key to many aspects of improvement of the stand- ard of living and quality of life of billions of people. For example, one-sixth of the world’s population do not have access to potable water. There is no lack of water on the planet, but only 3% is freshwater. Providing access to clean water is one of the 14 grand challenges identified by the National Academy of Engineering (NAE, 2008, updated 2017) and constitutes a separation challenge. Improved separation technologies are also critical for other aspects of human health. For example, monoclonal antibodies (mAbs) are the most widely produced and most important biopharmaceutical products. Numerous types of separation methods are necessary in the production of these compounds. Their commercial-scale manufacture is based on batch processing in which each unit operation is com- pleted in sequence, and a long-term challenge is to convert batch processing to continuous synthesis and purification (Zydney, 2016). To be used as pharmaceuticals, mAbs have to be safe for patients, and multi- ple quality attributes must be maintained. For example, the removal of compounds of lower and higher molecular weight than a given pharmaceutical mAb is important. Higher-molecular-weight species might cause unwanted immunogenic responses, such as anaphylaxis, and lower the efficacy of the drug. Lower- Prepublication Copy 11

A Research Agenda for Transforming Separation Science molecular-weight fragments often have lower activity than the original mAb, and immune responses might be elicited by exposure to unique epitopes. The exact glycosylation distribution and charge-state distribution of an approved mAb also must be maintained, and post-translation modifications might in- duce changes. New and Challenging Separations. Many industrial processes—such as in the electronics, solar en- ergy, and pharmaceutical and biotechnology industries—have much higher purity requirements than in past decades. The constant pressure to produce higher-purity products creates a demand for new separa- tion processes or technologies. Furthermore, scientists are identifying challenging separations that could yield valuable products or resources. For example, although uranium concentrations in seawater are ex- tremely low (parts per billion), some estimate that more than 4 billion tons of uranium could be extracted from seawater and used for nuclear power if efficient separation techniques could be developed (Sholl and Lively, 2016). Opportunities for a Paradigm Shift. As will be described in Chapter 3, important advances have occurred in the last 30 years in molecular modeling and simulation, machine learning and data analytics, analytical techniques, and characterization, especially for short time and length scales. Those advances tantalize us with the prospect of a greatly improved theoretical and mechanistic understanding of separa- tion processes, improved modeling and prediction of chemical behaviors, and the exploration and devel- opment of new chemicals, materials, and approaches. Thus, separation science is poised for a paradigm shift in which the brightest minds in chemistry, chemical engineering, materials science, and other fields will be vying to achieve the breakthroughs in the next generation of separation science, and conventional separation technology will be replaced with high-throughput, energy-efficient, and exquisitely selective separation systems. THE 1987 REPORT Given the motivations described above, it is time for a compelling vision and strategy for separation science. Such a vision was last offered in Separation and Purification: Critical Needs and Opportunities (NRC, 1987).1 That report highlighted several key technological challenges: commercializing biotechnol- ogy, reducing dependence on foreign sources of critical and strategic metals, protecting the environment, meeting the demands for ultrapure materials, and developing alternative energy sources and feedstocks. The report noted that those endeavors had many features in common, such as the need to isolate products or contaminants from dilute solutions, the need to separate complex mixtures, and the need to replace en- ergy-intensive processes. Given the commonalities, the report concluded that separations could be sub- stantially improved by focusing on six generic research themes in which concentrated efforts could “lead to clearer insights into fundamental principles and major opportunities for technological innovations” (NRC, 1987, p. 44); the research themes are listed in Box 1-2 and discussed in more detail in Chapter 2 of the present report. The 1987 report highlighted the idea that research activities are fragmented and that better commu- nication, idea exchange, and technology transfer among the disciplines engaged in separation science re- search are needed. The report recommended a conference on separation science or formation of a new professional society for separation research to facilitate collaborative efforts. It also recommended modi- fication of educational courses in traditional undergraduate disciplines (chemical engineering, chemistry, and biochemistry) and development of a cross-disciplinary curriculum in separation science and technol- ogy. And it recommended increased efforts to collect, evaluate, correlate, and disseminate physicochemi- cal data so that more powerful predictive models could be developed. The report concluded that “the im- portance and pervasiveness of separations throughout the U.S. economy indicate that a federal program of generic research… will have significant benefits to our economic competitiveness… A timely response is required if these opportunities are not to slip from our grasp” (NRC, 1987, p. 6). 1 Separation and Purification: Critical Needs and Opportunities is referred to hereafter as the 1987 report. 12 Prepublication Copy

Introduction BOX 1-2 Generic Research Themes Proposed in the 1987 Report  Generating improved selectivity among solutes in separation.  Concentrating solutes from dilute solutions.  Understanding and controlling interfacial phenomena.  Increasing the rate and capacity of separation systems.  Developing improved process configurations for separation equipment.  Improving energy efficiency in separation systems. SOURCE: NRC, 1987. CURRENT LANDSCAPE OF SEPARATION SCIENCE Since publication of the 1987 report, separation science and technology have seen substantial ad- vances. Perhaps the most dramatic example is the widespread commercial adoption of membrane-based separations for water desalination. Salt can be removed from water by evaporation, but that process re- quires enormous amounts of energy. Reverse-osmosis technology lowers the energy requirement substan- tially and therefore now dominates new commercial desalination installations (Elimelech and Phillip, 2011). Thousands of facilities now use that technology. A remarkable observation about modern reverse- osmosis membranes for desalination is that they require only twice the thermodynamic minimum energy. That implies that additional improvements in the technology will need to focus on such issues as the lon- gevity of membranes, particularly with respect to fouling, pretreatment, and post-treatment conditions (Imbrogno et al., 2017). A second example of commodity-scale separations in which nonthermal methods are becoming widespread is the use of adsorption or membranes for separating oxygen or nitrogen from air. Cryogenic distillation is still the most economically competitive technology for these separations at the largest scales and highest purities, but nonthermal separation methods are now favored in many set- tings, such as preservation of fruits, vegetables, and flowers and oxygen enrichment for health applica- tions. Important advances in separation technologies have occurred in applications in which the total feed volume is modest by commodity chemical standards but exquisite selectivity and the ability to manage extremely complex feeds are critical. An example is the tailoring of materials to capture trace radionu- clides from nuclear waste (Wilmarth et al., 2011). It is characterized by radionuclides at trace concentra- tions in competition with bulk ions at 100,000-fold higher concentrations—which demands recovery re- quirements of greater than 99.9975% for Cs-137—and by extreme environments with high radiation fields and highly corrosive conditions. Designer solvents that use calixarene-crown molecules as highly specific sequestering agents (Dozol and Ludwig, 2010) reject almost all competing ions and deliver a nearly pure cesium borate product stream from the complex waste for vitrification in borosilicate glass (Moyer et al., 2005). Regardless of the important advances that have occurred over the last few decades, there is a con- cern that the United States is losing a competitive edge in science and technology to China and India and this trend also is a concern for separation science. Among many possible metrics, the number of publica- tions focused on separations2 by U.S. researchers has increased modestly. From 1990 to 2006, the United States outnumbered most countries in number of publications, but China has been the leading country in publications focused on separations since 2006 (see Figure 1-3). The U.S. loss of leadership in number of publications in the separation field might be caused by the number and size of programs that clearly target separations research. 2 Key search terms used in SCOPUS were gas separations, liquid separations, separations and adsorption, sepa- rations and chromatography, separations and extraction, separations and purification, and separations and mem- branes. Prepublication Copy 13

A Research Agenda for Transforming Separation Science FIGURE 1-3 Number of publications from the United States and China that focused on separation methods and technology, 1990-2018. Separation science is not highlighted in many chemistry and chemical engineering courses; thus, fewer scientists are exposed to the fundamentals of separation science and how the fundamentals can be applied. In a survey conducted by the American Institute of Chemical Engineers in 2018, respondents in- dicated that U.S. chemical engineering programs typically offer a dedicated class in separations to their undergraduates but that the class focuses primarily on distillation and other traditional separation technol- ogies rather than on newer separation methods (such as use of membranes) or on the fundamental princi- ples needed to understand separations.3 That approach might lead students to view separations as estab- lished technology and devoid of opportunities for exciting research advances. That idea is supported by the fact that only a minority of the top 10 chemical engineering PhD programs in the United States have any research efforts in separations. Graduate chemical engineering courses related to separations tend to be very specific (for example, bioseparations or use of membranes) and in many cases are not offered regularly. Chemists in the United States usually take a separation course as part of the graduate curricu- lum but only if the school has a sufficiently large and active analytical chemistry program. The courses typically begin by studying equilibrium driving forces and thermodynamics, then move to studying flow and mass transport, and conclude by studying chromatography. Additional separation courses are normal- ly not available or offered to chemistry students. Furthermore, the number of academic chemists who have separation science as a major portion of their research portfolio has dropped by nearly 40% since the 1987 report4; this demonstrates that there is a 3 The survey was conducted by the AIChE Education Division. Data were solicited from 166 chemical- engineering programs in the United States that are accredited by the Accreditation Board for Engineering and Tech- nology, Inc. The response rate was 36%, and the data are posted on the AIChE web site (see https://www.aiche.org/ community/sites/divisions-forums/education-division/how-we-teach-surveys). 4 These data were collected by committee members by identifying separation scientists and engineers in analytical chemistry and chemical engineering departments as listed in the 1987 American Chemical Society Directory of Graduate Research and current departmental Web sites. Separation scientists at all R1 (highest research activity) analytical chemistry programs were counted. Chemical engineering departments considered were those listed in 2018 by US News & World Report as the top 20 chemical engineering graduate programs. 14 Prepublication Copy

Introduction strong need to attract young colleagues to the field. Likewise, the number of chemical engineering faculty in top departments who can be clearly identified as separation researchers has decreased by 30% despite the large increase in the total number of faculty in those departments. The publication trends in separation science, the results of the AIChE survey, and the number of faculty currently in the field raise questions about whether the training and exposure of students to the fundamentals of separations needs to be re- evaluated and restructured and about whether current funding is sufficient for separation science. Those questions and others are discussed further in Chapter 6 of this report. THE COMMITTEE AND ITS TASK Given the need to provide a fresh vision for separation science, DOE, NIST, and NSF asked the National Academies to develop an agenda for fundamental research in separation science. Box 1-3 pro- vides the verbatim statement of task. The committee convened as a result of the request included experts in chemistry and chemical engineering with specialties in materials science, analytical chemistry, compu- tational and theoretical chemistry, interfacial chemistry, liquid and gas-phase separations, and industrial separation processes (see Appendix A for biographic information on the committee). COMMITTEE’S INTERPRETATION OF ITS TASK To accomplish its task, the committee held six meetings, including three data-gathering sessions during which it heard from experts and stakeholders in government agencies, industry (including trade associations), and the academic community. Topics explored during the data-gathering sessions included synthesis of new materials, external field effects, instrumentation, computational chemistry, and educa- tional and societal needs. The committee also met with AltSep representatives during one of the data- gathering sessions; AltSep is an initiative created to accelerate industrial adoption of less energy-intensive BOX 1-3 Statement of Task The National Academies of Sciences, Engineering, and Medicine will convene an ad hoc committee of experts and scientific leaders to develop an agenda for fundamental research in separations science. The committee will write a report that will:  Assess recent and ongoing research efforts to advance science that underpins separations of chemical mixtures and identify priority areas of research that will transform the field of separa- tions science;  Identify advances in chemical transformations, chemical and materials in-situ and operando char- acterization, computation and theory, and synthesis capabilities that can be employed to advance separations sciences and illustrate how they can be utilized to advance separations science;  Address the intersections between chemistry, biochemistry, materials, physics, engineering, and information science that will be essential for scientific progress;  Identify needs and opportunities for novel instrumentation and tools that will advance our under- standing of separations processes, including laboratory scale to mid-scale to large scale, such as synchrotron light sources or neutron facilities;  Identify the educational and human resource needs (including cross-sections of academia and industry) to enable advances in separations science; and  Assess the potential impacts that fundamental research in separations can have on technologies and practices in industry. The report will provide guidance to research sponsors, as well as to the research communities in aca- demia and industry. The report’s recommendations will focus on science needs and priorities rather than specific funding or organizational aspects. Prepublication Copy 15

A Research Agenda for Transforming Separation Science separation processes and is developing an industry-driven technology roadmap for separation alternatives to distillation.5 Agendas for the data-gathering sessions are provided in Appendix B. The committee also consulted published references from public sources, including the scientific literature and government reports. The main topics discussed in this report are chemical, analytical, and biological separations, includ- ing those involving proteins and nucleic acids but excluding organelles, cells, and viruses. The committee considers a variety of separation techniques in this report but excludes mechanical or physical separa- tions, such as centrifugation or depth filtration. The committee does not discuss distillation and evapora- tion in great detail because it considers those techniques to be mature technology and out of the scope of this research agenda. The committee emphasizes that it was specifically tasked with developing a fundamental research agenda as opposed to undertaking a focused empirical investigation of particular processes. Understand- ing the fundamentals will lead to increased knowledge of how complex mixtures can be separated in a controlled manner and, therefore, advance the science. Advancing separation science will then enable so- lutions to many vexing societal problems. Although the time lag between fundamental research discovery and industrial commercialization might be several decades, fundamental discoveries are likely to benefit all aspects of chemical separations. The use of separations spans many communities, each using a specific terminology. Accordingly, many of the key terms used in this report are defined in different ways by different communities. The committee notes that using different terminology to describe the same or similar phenomena creates road- blocks to translating advances from one field to another, and researchers need to improve understanding of terminology across the disciplines. In an effort to provide clarity to all readers, the committee defines in Box 1-4 key terms that it uses in this report. ORGANIZATION OF THE REPORT This report is organized into six chapters and three appendixes. Chapter 2 discusses the efforts to advance separation science in the last 30 years. The committee describes advances made in the six prima- ry research themes outlined in the 1987 report (see Box 1-2), discusses advances that were not anticipated by the 1987 report, and touches on workforce development and educational and industry needs. In a simi- lar manner, Chapter 3 discusses relevant advances in the last 30 years in intersecting disciplines; it de- scribes key fields of research that can provide insight and knowledge to advance separation science: mate- rials synthesis, systems engineering, responses to external stimuli, instrumentation and characterization tools, and data science and analytics. Although much progress has been made, gaps and challenges re- main, and Chapter 4 discusses the obstacles and sets the stage for the committee’s research agenda. Chap- ter 5 presents a research agenda that researchers and their funders can use to develop research programs in separation sciences. The committee’s research agenda outlines two high-priority research areas and two cross-cutting topics and describes the significance of moving research forward in those areas. Experi- mental, theoretical, and computational approaches and potential barriers are also discussed. Chapter 6 describes what it will take to implement the research agenda presented in Chapter 5. Specifically, it ad- dresses educational needs in separation science, the need to create collaboration opportunities, the im- portance of access to tools at the national level, and the influence that progress in the research agenda will have on industry. It emphasizes the need to repopulate and rejuvenate the separations community to ad- dress the challenges detailed in Chapter 4 by implementing the research agenda offered in Chapter 5. 5 AltSep is an initiative of the American Chemical Society Green Chemistry Institute Chemical Manufacturers Roundtable that was created with funding from the NIST Advanced Manufacturing Technology Consortia Program. See http://altsep.org/ for further details. 16 Prepublication Copy

Introduction BOX 1-4 Definitions of Key Terms Capacity is the ratio of the targeted species to the separation material. Chemical mixture refers to a mixture of molecules or colloidal particles the separation of whose com- ponents is based on intermolecular interactions (such as electrostatic interactions, dispersion, or hy- drogen bonding) or chemical reactions and not mechanical mechanisms, such as filtration. Electrostatic interactions are interactions between fixed charges, permanent dipoles, quadrupoles, other multipoles, and induced dipoles. Flux is throughput per area. Hierarchical structures are materials that have features on multiple scales. Hydrophobic interactions are interactions of nonpolar molecules in a polar solvent. Interface is the area of contact between a bulk phase and the interfacial region. Interfacial region is the domain between two bulk phases whose structure and extent are determined by the molecular interaction between the bulk phases. Robustness refers to stability of the separation material under action. Separation system is the entire process or procedure that effects a separation, which can include the separation material, the device, and other components. Separation materials interact directly with the targeted species in a mixture. Separation materials in- clude both hard and soft materials, which may be crystalline, amorphous, composite, or liquid. Selectivity is the ratio of the capacity, flux, or retention of two species. Throughput is capacity per time. Van der Waals interactions are interactions between nonpolar molecules that result from induced- dipole–induced-dipole interactions. They are also called dispersion interactions. Appendix A provides the biographic information on the committee members, Appendix B provides the agendas of the committee’s open sessions, and Appendix C provides further detail on characterization and instrumentation. REFERENCES DOE (Department of Energy). 2015. Bandwidth Study on Energy Use and Potential Energy Saving Opportunities in U.S. Petroleum Refining. Washington, DC: U.S. Department of Energy. Dozol, J.-F., and R. Ludwig. 2010. Extraction of radioactive elements by calixarenes. Ion Exchange and Solvent Extraction, edited by B. A. Moyer, Vol. 19. Boca Raton, Florida: CRC Press, 195–318. Elimelech, M., and W. A. Phillip. 2011. The future of seawater desalination: Energy, technology, and the environ- ment. Science 333(6043):712. doi: 10.1126/science.1200488. Gulf Publishing. 2010. Hydrocarbon Processing: Petrochemical Processes 2010. Houston, TX: Gulf Publishing Company. Humphrey, J., and G. E. Keller. 1997. Separation Process Technology. New York: McGraw-Hill. Prepublication Copy 17

A Research Agenda for Transforming Separation Science Imbrogno, J., J. J. Keating IV, J. E. Kilduff, and G. Belfort. 2017. Critical aspects of RO desalination: A combina- tion strategy. Desalination 401:68–87. Moulijn, J. A., M. Makkee, and A. Van Diepen. 2001. Chemical Process Technology. Hoboken, NJ: John Wiley & Sons, Ltd., 109–123. Moyer, B. A., J. F. Birdwell Jr., P. V. Bonnesen, and L. H. Delmau. 2005. Use of macrocycles in nuclear-waste cleanup: A real-world application of calixcrown in technology for the separation of cesium. Macrocyclic Chemistry—Current Trends and Future, edited by K. Gloe. Dordrecht, Netherlands: Springer, 383–405. NRC (National Resource Council). 2008. Updated 2017. NAE Grand Challenges for Engineering. Washington, DC. Neelis, M., Worrell., and E. Masane. 2008. Energy Efficiency Improvement and Cost Saving Opportunities for the Petrochemical Industry. Berkeley, CA: Lawrence Berkeley National Laboratory. NRC (National Resource Council). 1987. Separations and Purification: Critical Needs and Opportunities. Washing- ton, DC: National Academy Press. NRC. 2006. Sustainability in the Chemical Industry: Grand Challenges and Research Needs. Washington, DC: The National Academies Press. ORNL (Oak Ridge National Laboratories). 2005. Materials for Separation Technologies: Energy and Emission Re- duction Opportunities. Sholl, D., and R. Lively. 2016. Seven chemical separations to change the world. Nature 532:435–437. doi: 10.1038/ 532435a. Wilmarth, W. R., G. J. Lumetta, M. E. Johnson, M. R. Poirier, M. C. Thompson, P. C. Suggs, and N. P. Machara. 2011. Review: Waste-pretreatment technologies for remediation of legacy defense nuclear wastes. Solvent Ex- traction and Ion Exchange 29:1–48. doi: 10.1080/07366299.2011.539134. Worrell, E., L. Price, M. Neelis, C. Galitsky, and Z. Nan. 2007. World Best Practice Energy Intensity Values for Selected Industrial Sectors Berkeley, CA: Lawrence Berkeley National Laboratory. Zydney, A. L. 2016. Continuous downstream processing for high value biological products: A review. Biotechnolo- gy and Bioengineering 113(3):465–475. doi: 10.1002/bit.25695. 18 Prepublication Copy

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Separation science plays a critical role in maintaining our standard of living and quality of life. Many industrial processes and general necessities such as chemicals, medicines, clean water, safe food, and energy sources rely on chemical separations. However, the process of chemical separations is often overlooked during product development and this has led to inefficiency, unnecessary waste, and lack of consensus among chemists and engineers. A reevaluation of system design, establishment of standards, and an increased focus on the advancement of separation science are imperative in supporting increased efficiency, continued U.S. manufacturing competitiveness, and public welfare.

A Research Agenda for Transforming Separation Science explores developments in the industry since the 1987 National Academies report, Separation and Purification: Critical Needs and Opportunities. Many needs stated in the original report remain today, in addition to a variety of new challenges due to improved detection limits, advances in medicine, and a recent emphasis on sustainability and environmental stewardship. This report examines emerging chemical separation technologies, relevant developments in intersecting disciplines, and gaps in existing research, and provides recommendations for the application of improved separation science technologies and processes. This research serves as a foundation for transforming separation science, which could reduce global energy use, improve human and environmental health, and advance more efficient practices in various industries.

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