- Menachem Elimelech
- Roberto Goizueta Professor
- Department of Chemical and Environmental Engineering
- Yale University
- New Haven, Connecticut
- 29 May, 2013
Published Online: 27 SEP 2013
Copyright © 2013 John Wiley & Sons, Inc. All rights reserved.
Encyclopedia of Membrane Science and Technology
How to Cite
Elimelech, M. 2013. Foreword. Encyclopedia of Membrane Science and Technology. xiii–xv.
- Published Online: 27 SEP 2013
Membrane separation processes play a central role in a variety of industries and scientific disciplines that impact our daily life. Examples include indoor air filtration, separations in the food and beverage industries, drinking water purification, domestic and industrial waste treatment, analytical separations in the chemical and life sciences, and artificial kidney dialysis. As an active researcher in the field of membrane science and technology since the mid-1990s, I have witnessed with great satisfaction the increasing trend of membranes replacing traditional separation processes, capitalizing on the higher separation efficiency, lower use of energy, smaller footprint, and modular design of membrane systems.
This revolution in membrane science and technology has been influenced by developments in other fields, particularly materials and polymer sciences, some of which are covered in this Encyclopedia of Membrane Science and Technology. The ability to create materials with tunable properties to selectively separate components from a mixture has been one of the key factors for the emergence of membrane technology. Large-scale production of membranes and the development of robust membrane modules with large surface areas have enabled the use of these new membrane materials in large-scale membrane systems that have had an immense impact on society.
One example of a large-scale membrane system that greatly impacted the lives of millions worldwide is seawater reverse osmosis technology. Over 50 years ago, United States President John F. Kennedy believed seawater desalination could change the world. In 1961, he told the Washington press corps that “if we could ever competitively, at a cheap rate, get freshwater from saltwater, that would really dwarf any other scientific accomplishments.” President Kennedy was indeed a visionary. The global production of water by desalination for 2016 is projected to be over 38 billion cubic meters per year, twice the rate of global water production by desalination in 2008, with the vast majority of the new desalination plants being based on reverse osmosis membrane technology rather than energy intensive thermal distillation technologies. Spain, which has the largest desalination capacity in the Mediterranean region, is producing 1 billion cubic meters of desalinated water annually, more than doubling its desalination capacity of 2005. Singapore, under a national plan to reduce its reliance on imported water from Malaysia, has embarked on the construction of a second large seawater reverse osmosis desalination plant that brings the country's desalination capacity to 165 million cubic meters per year, meeting nearly 30% of its demand for potable water. Another example is Israel, where population growth, droughts, and depletion and degradation of available water resources have prompted the development of a national desalination plan to augment water supply. This plan, which is near completion at this writing, involved the construction of five large-scale desalination plants along the Mediterranean, with an annual total water production of over 500 million cubic meters.
Recent advances in nanotechnology may herald the next revolution in membrane science and technology. Nanomaterials can be manipulated into membranes that exhibit higher solute selectivity and solvent permeability—two key intrinsic properties of any high performance membrane—than current generation membranes. Some of these ideas, like nanotube membranes, are described in this reference book. However, we should be cautious when attempting to relate such intrinsic membrane properties to membrane system performance and energy efficiency. One example is ultrahigh flux membranes made of carbon nanotubes or graphene, which were claimed to have the potential to significantly reduce the energy of desalination in reverse osmosis. Careful analysis of the reverse osmosis seawater desalination process suggests that the water flux is governed by the solution osmotic pressure rather than the membrane permeability, which results in negligible impact of ultrahigh flux membranes on the energy consumption in desalination. While carbon nanotube membranes will not have an impact on the energy of desalination by reverse osmosis, they can improve the selectivity of reverse osmosis membranes as the separation mechanism is likely to be by molecular sieving rather than a solution–diffusion mechanism. This separation mechanism by molecular sieving represents a significant advance as current membranes are constrained by the permeability–selectivity tradeoff, where improving membrane selectivity results in reduction of solvent permeability, and vice versa, attempts to increase membrane solvent permeability result in reduced solute selectivity.
Membranes also play an important role in addressing the global challenge for energy supply. Current global energy demand far exceeds our capacity for sustainable production. Although the development of a broad range of alternative energy technologies is making progress in increasing sustainable energy production, we still rely heavily on fossil fuels to meet our needs. To satisfy the energy demands of the present and future, existing alternative energy production technologies must be advanced beyond their current limitations, and additional sources of sustainable energy must be found. This reference book discusses membrane-based processes for sustainable power production and energy-related applications, such as in fuel cells, capture of carbon dioxide, power generation from salinity gradients by the emerging processes of pressure retarded osmosis and reverse electro dialysis, and energy efficiency of seawater reverse osmosis desalination.
Water, energy, and food in modern society are intrinsically linked. Water and energy shortages have motivated the development of a diverse suite of technologies to support our growth beyond the traditional limitations of natural resources. These technologies are diverse not only with regard to method and use, but also in the anticipated consequences of their operation. Our capability to desalinate billions of cubic meters of seawater daily to meet a global water demand that exceeds accessible freshwater resources can be viewed as a technological triumph. However, we also realize that long-term solutions for energy and water shortages cannot rely on provision of one through excessive utilization of the other. In this reference book, the authors address several membrane-based technologies at the water–energy–food nexus, including emerging processes such as forward osmosis and membrane contactors, applications of membranes in the food industry, and wastewater reuse through membrane bioreactors.
This Encyclopedia of Membrane Science and Technology provides the most comprehensive coverage of membrane processes. This invaluable reference book covers the underlying fundamentals of liquid and gas membrane separation processes, membrane materials, and membrane fabrication techniques as well as current and emerging applications. I am confident it will be an indispensable reference for generations of students, engineers, practitioners, and researchers in a variety of fields of science and technology. This comprehensive reference will also be an inspiration for students and young scientists entering the rapidly expanding field of membrane science and technology. The authors of this important reference book can be assured that there will be many appreciative readers who will have gained a broader perspective of the discipline of membrane separations as a result of their insightful coverage and elegant writing.