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New Technology Uses Sunlight and Rice Straw to Desalinate Seawater

A novel desalination technology developed by Chinese researchers utilizes sunlight and rice straw to produce clean water.

It is believed that the generation of solar steam is a potential approach for purifying seawater and wastewater. Now, researchers from the Ningbo Institute of Materials Technology and Engineering have used waste rice straw to create an innovative solar steam-generation device.

The novel device is composed of water pumps and a photothermal membrane. While the lower culms of the straw are engineered as water pumps, the leaves of the rice straw are carbonized and then composited with bacterial cellulose to work as a photothermal membrane.

A daily clean water yield of 6.4 to 7.9 kg/m2 is achieved by the solar rice straw-derived desalination on sunny days and 4.6 to 5.6 kg on overcast days. In the water, thus produced, more than 99.9% of saline ions were removed, which means it has reached safe drinking water standards. In addition to desalination of seawater, the new device can even be utilized to extract clean water from different water-bearing areas like marshes, wetlands¸ and tidal flats.

The study has been reported in the journal ACS Applied Materials and Interfaces.

Since the scarcity of fresh water is one of the most major concerns in the world, researchers are looking for novel desalination technologies to boost water productivity and, at the same time, reduce the overall cost of desalination.

The leading researcher Liu Fu informed that there is a significant requirement to lower energy consumption in desalination technology, and the generation of solar-driven steam has attracted a great deal of interest.

As green and inexhaustible energy, solar energy can be harnessed in desalination and water purification, leading to low-cost and sustainable technologies that address the water crisis worldwide.

Liu Fu, Researcher¸ Chinese Academy of Sciences

Solar thermal materials are required to utilize solar energy. Preparing conventional solar thermal materials, like graphene-based materials, carbon nanotubes, and plasmonic materials, is a costly and complicated process, and hence they are not appropriate for large-scale applications.

Novel materials and new engineering designs are being studied by Liu’s group to not only enhance the efficiency of solar thermal conversion but also lower the overall desalination cost.

Emerging from the laboratory and discovering from nature, Liu found that the most appropriate candidate for photothermal desalination is rice straw, because not only does it have a high transpiration coefficient but it also has an excellent water delivery capability via its culms.

Rice straw is abundantly available in China. Normally, farmers in China burn straw following harvest, which results in air pollution and therefore, this practice has been forbidden in a majority of places.

If this agricultural waste can be used for extracting clean water, it will be an environmentally friendly and sustainable technology.

Liu Fu, Researcher¸ Chinese Academy of Sciences

According to the research team, the method can be applied to mountainous regions or distant islands that lack water. In addition, it can be utilized at the time of emergencies like earthquakes, floods, and adverse environments, for example, in the wilderness for achieving clean water.

Liu’s group is also investigating other kinds of solar thermal materials, which are anticipated to be commercialized in large-scale desalination projects in three years.

According to Professor Zhu Jia from Nanjing University and an expert in solar-thermal desalination, the study was a fresh and creative investigation of utilizing solar energy for desalination of seawater.

By using rice straw as solar thermal materials, the cost for desalination can be further reduced.

Zhu Jia, Professor, Nanjing University (Xinhua)


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