Advancing Materials and Technologies for Water Purification
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and Technologies for Water Purification
Mark A. Shannon and Raphael Semiat, Guest Editors Abstract Worldwide, 1.2 billion people lack access to sufficient amounts of clean water, and 2.6 billion lack adequate sanitation. Also, industry relies on large quantities of water during manufacturing, which is then returned to the environment. Having adequate water supplies, and removing pathogens, chemicals, and other contaminants with high throughput at a low cost is a growing challenge around the world. This issue of MRS Bulletin examines how materials research, through the development of membranes, catalysts, nanoparticles, and other materials, is addressing these needs.
Introduction Access to clean water is increasingly becoming the most important issue facing people around the world. Worldwide, 1.2 billion people lack access to sufficient amounts of clean water, and 2.6 billion lack adequate sanitation.1 The combination of poor sanitation and unhealthy water quality accounts for the single largest cause of disease and death in the world.2 Clean water, according to the World Health Organization (WHO), is water that has less than the allowed concentrations of dissolved matter—a different amount depending on the constituent. Salted or polluted water contains suspended matter such as dust, algae, bacteria, viruses, and silt; organic matter such as solvents, fuel traces, pesticides, and herbicides; various salt ions above the recommended concentration; and heavy metals and more. No other problem today is remotely close in magnitude to the need for clean water, and yet problems with water are expected to grow rapidly due to population growth imposing larger demands on the water supply for domestic use, agriculture, and energy. Moreover, water supplies are increasingly threatened due to the contamination of aquifers, the largest source of fresh water in the world, from toxic compounds to salts intruding from sea and saline sources. Salting and contamination of fresh water sources drives
the need for new supplies of clean water and more extensive water treatment. As the glaciers on continents throughout the world disappear, major rivers that currently supply fresh water year-round may become intermittent, forcing the hunt for new supplies.3,4 Current water purification methods in wide use employ chemically intensive treatment that is relatively expensive, increases stress on watersheds and the environment, and is not translatable to the non-industrialized world. Water touches every aspect of human activity, from food, health, and the environment to local and global economies. Clearly, the staggering importance of water cries out for solutions to be found and enacted. All is not bleak, however. Many current water treatment methods are far from the thermodynamic limits. Biological disinfection, decontamination, filtering, and ion transport stand as examples of optimized systems in energetically efficient, self-cleaning, and renewable purification. A hallmark of these systems is that the interaction of species in water occurs
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