The world is running out of clean water.
By the end of the century more than 11 billion people are predicted to be sharing the planet. Climate change and sea-level rise will bring salinization of coastal aquifers, the disappearance of the glaciers and snowpack that provide water in dry summer months, and unpredictable shifts in rainfall that will result in both droughts and floods.
Currently, four billion people live with severe water scarcity at least one month of the year. Half a billion people face severe yearround water shortages. In many arid regions of the world, economic development and population growth will stress existing water supplies, leading to less water to drink and less water for crops.
Chemistry professor Omar Yaghi knows something about life in a dry climate. He grew up in Amman, Jordan, where fewer than 10 inches of rain falls in most years. To the east and south lie deserts so arid and austere that they served as a double for the planet Mars in the Ridley Scott movie, “The Martian.”
One of the world’s most highly cited chemists, Yaghi is using his skills to help provide water to arid regions of the globe. Along with his colleagues and students, Yaghi has developed a new field in chemistry, reticular chemistry. Researchers in this new field have created new materials—intricately structured nanoporous metalorganic frameworks (MOFs), covalent-organic frameworks (COFs) and zeolitic imidazolate frameworks (ZIFs).
These molecular frameworks can be tuned to create materials with specific pore sizes and unique chemical activity. Yaghi has developed MOFs with numerous applications, including capturing carbon dioxide from smokestacks and storing methane for clean-burning trucks. He is now turning his attention to trapping yet another gas, water vapor.
Capturing water from air is nothing new. The Incas were capturing water from fog high in the Andes centuries ago. Both air conditioners and dehumidifiers condense water vapor by passing humid air around a refrigerated coil. Atmospheric water generators, devices that pull drinking water out of the air, use similar techniques, but then purify and store the condensed water. Like refrigerators, all these modern devices require a big share of the electricity used by households.
A new generation of atmospheric water generators, produced by several companies (including Ecoloblue in the Bay Area), have brought down energy requirements. But producing a gallon of water for home use still requires more than one kilowatt hour of electricity. The units typically cost more than a thousand dollars and require expensive filters that must be replaced regularly.
Atmospheric water generators range in size from household units to industrial-scale models that fit on a large truck. These machines work fine in places like the Bay Area where the relative humidity is often 60 percent or greater. Home versions can even be powered by solar panels. However, they are not practical for arid regions where the relative humidity is less than 20 percent.
Yaghi is working to overcome these limitations with a powdered MOF material that will selectively adsorb water from air at low relative humidity and release it when heated. At 30 °C. (86 °F.) and 20 percent relative humidity, there are only six grams of water vapor per cubic meter of air. In those conditions, you would have to wring out every water molecule in a cube of air 5.5 meters (18 feet) on a side to collect just one liter of liquid water. Yaghi’s MOF can act as a water vapor concentrator to raise the relative humidity of the air before it is processed to extract drinking water.
To build a proof-of-concept device, Yaghi enlisted the help of MIT mechanical engineering professor Evelyn Wang. The device contained a five-centimeter square layer of powdered MOF. Left on a rooftop at MIT, the device adsorbed water overnight that was released the next morning by the warmth of the sun and then condensed to liquid water. Says Yaghi group member Eugene Kapustin, co-author of a recent Science magazine paper on the topic, “For now our proof-of-concept device is small and creates a few milliliters of water every cycle. It does not require a condenser—simple air cooling is enough.
“Because of its nanoscale pore size, the MOF may be able to keep out bacteria and other contaminants. These contaminants must be filtered out of the water produced by conventional atmospheric water generators. Further testing of our MOF is ongoing.”
Notes Yaghi, “My group does basic research to discover new materials and develop their interesting properties. Our MOFs can increase the efficiency of atmospheric water generators for use where clean water is scarce. So far the results are encouraging. Perhaps in the next few years we’ll see bolt-on MOF-based vapor concentrators that will allow us to push atmospheric water generators further out into the desert.”
The world has taken interest in Yaghi’s work. In Jordan, Princess Sumaya bint El Hassan, a science advocate and the president of Jordan’s Royal Scientific Society (RSS), is keen on developing this technology. In a recent visit to UC Berkeley, she was awarded a Chancellor’s Citation by Chancellor Nicholas Dirks. This citation is awarded to distinguished visitors, alumni and friends whose great achievements the university salutes and whose presence honors and benefits the campus.
Yaghi, who is the founding director of the Berkeley Global Science Institute, has worked closely with Princess Sumaya over the past five years to re-engage the Jordanian diaspora community in scientific research to address global problems. A delegation from the institute has met with the Princess to discuss plans for building a reticular foundry, a joint UC Berkeley-Royal Scientific Society research institute that will serve as a hub of scientific research attracting top talent from throughout Jordan and the Middle East region. Says Yaghi, “It is my hope that this joint partnership will train the next generation of problem-solvers, innovators and scientific leaders.”
Princess Sumaya also serves as chair of the World Science Forum (WSF), which will be hosted by Jordan in November 2017. The WSF is a leading forum for science and policymaking, and this will be the first time it is held in the Middle East. The theme for the 2017 WSF is “Science for Peace,” and she hopes that the event will inspire young people and give policymakers renewed appreciation for science and the scientific method.
In the Spring of 2017, Yaghi also met with Jordan’s King Abdullah II bin Al-Hussein to discuss plans for the Global Science Reticular Foundry. Says Yaghi, “The King enthusiastically accepted the proposal for the new building in Amman.”
Adds Yaghi, “The scientific focus will be on the basic science of new materials with an emphasis on applications in food, food security, energy and water. A third goal is popularizing science and creating research opportunities for emerging scholars.”
As the director of the Berkeley Global Science Institute, Yaghi has helped create Centers of Global Science in Japan, Vietnam, Korea and Saudi Arabia. Their mission is to partner with institutions of learning, foundations, government and industry, in the United States and abroad, to create centers of research in foundational sciences to address global problems and build a culture of science.
Says Yaghi, “I am extremely encouraged by the potential of the international science centers the Berkeley institute has helped create in solving global problems such as water scarcity.”