Although Earth is known as the water planet, about 97.5% of the Earth's water is seawater, which people cannot drink. If the large amount of seawater can be converted into fresh water, collecting water resources wouldn't be difficult. Recently, Australian scientists have brought in a new high-efficiency solar steam generation system that claims to remove nearly 100% of salt and provide clean water to off-shore areas of the countryside.
There are two current solutions to water resource problems, desalination and wastewater recovery, but the factories for these solutions are expensive to build, and how to deal with by-products such as high concentrations of salt water is a major problem. As they are based on the combustion of fossil fuels, they are also not very environment friendly, and there are fuel transportation problems. All of these factors have made them difficult to implement in low-development countries or rural areas.
In order to solve the problems, many scientists are now looking for sustainable and efficient ways to minimize the burden on the environment and the local economy; for example, the research teams from King Abdullah University of Science and Technology in Saudi Arabia and the University of Maryland in the US have been involved in related research. Recently, a research team from Monash University in Australia has also invested in research to launch high-efficiency solar steam generation systems. Efforts are being made to remove the salt of seawater through photothermal materials and near-endless solar energy.
How did the scientists at Monash University turn seawater into pure water without salt? The team first used super-hydrophilic filter paper and carbon nanotubes to create a "disc" that absorbs light, and then used a 1-millimeter diameter cotton line as a water channel, like the cotton line suction method of pot, using the siphon phenomenon to suck salt water into the upper disc.
The carbon nanotube can not only adsorb salt, pollutants and pathogens, but also let pure water pass through, so after the salt water is sucked into the disc, water and salt will gradually separate, and the filter paper will gather pure water and push the salt to the edge of the disc, as shown in the film in the following link.
The team's experiment also pointed out that the solar steam generation system's light absorption rate has reached 94%, and after the sun exposure, regardless of whether the disc is dry or wet, evaporation performance has been good. For the dry state, after exposure, the temperature can rise from 25℃ to 50℃in 1 minute; for the wet state, the temperature can increase from 17.5℃ to 30℃.
The study suggested that the new solar evaporation technology can be used in desalination, industrial wastewater recovery, sludge dehydration, mining tailings disposal and resource recovery. Xiwang Zhang, a professor at the ARC Research Hub for Energy-efficient Separation at Monash University, said the team hopes the study will succeed in providing millions of people with clean, safe fresh water in the future, while reducing the environmental impact of wastewater and waste recycling.
(Collaborative media: TechNews; Photo courtesy of Monash University)