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New membrane may solve fresh water shortages

Hiroshima University

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Credit: Hiroshima University

Researchers at Hiroshima University have developed a technology that improves the removal of salt from seawater, a breakthrough that may alleviate the increasing demand for fresh water in some countries.

"A global shortage of fresh water is a long-term challenge that mankind faces in this century," said the director of the ROBUST membrane project, Professor Toshinori Tsuru.

Professor Tsuru and his team have designed a new kind of ultra-thin layered membrane that acts as a sieve and separates salt from seawater to produce fresh water, a technique known as reverse osmosis. The membrane is partly made from silicon and overcomes several challenges of existing designs by tolerating the harsh conditions inside desalination plant equipment. The research has been published in the Journal of Membrane Science.

One practical problem of separation membranes is "biofouling", where biofilms form on the membrane surface. This slows the amount of water that can pass through the membrane. Sodium hypochlorite is commonly used to remove these biofilms; however, the chlorine can also damage the membrane.

Professor Tsuru, who is supported by CREST (Core Research for Evolutional Science and Technology) and is a member of the Center for Research on Environmentally Friendly Smart Materials at Hiroshima University's Institute of Engineering, said that the new membranes are more robust, which makes them resistant to chlorine. They are also heat resistant, meaning they can be used in desalination at a temperature of 80°C.

"We are developing ROBUST membranes using three materials: silicon-based, hydrocarbon, and chemical vapor deposition. First we have developed silicon-based ROBUST membranes," Professor Tsuru said.

"We expect Japan to continue to be one of the leading countries in membrane technologies and membrane-treatment systems," he said.

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About the ROBUST membrane project

The ROBUST membrane project is one of the CREST programs for promising research projects funded by the Japan Science and Technology Agency (JST). The purpose of this project is to develop ROBUST reverse osmosis (RO)/nanofiltration (NF) membranes that can be used in water containing chloride at a wide range of pH and/or at high temperatures. The project aims to examine the applicability of the ROBUST membrane for various types of water resources.

About the Center for Research on Environmentally Friendly Smart Materials

Launched in 2014 as one of the promising research initiatives at Hiroshima University, the Center aims to realize a sustainable society through the development of innovative and environmentally-friendly materials such as high performance organic semiconductors, photovoltaic materials, light-emitting materials, nano-particles and porous materials. The Center's members come from backgrounds ranging from basic chemistry, applied chemistry and chemical engineering.

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