Solar technology purifies water in under 30 minutes

Technology uses sunlight to purify water

For millions of people around the world, clean drinking water is still hard to find. Traditional desalination methods consume a significant amount of energy and chemicals. Researchers at Monash University have come up with a water purification technique that uses only sunlight to turn dirty water into safe drinking water in less than 30 minutes.

The new technology uses solar energy and special materials called metal-organic frameworks (MOFs) to get rid of harmful particles in brackish water and seawater. Each kilogram of MOF material can make 139.5 liters of clean water every day. This provides hope to communities that lack access to traditional water treatment systems.

How the “solar sponge” works

Metal-organic frameworks are a type of compound made up of metal ions that form crystals with the largest surface area of any known material. MOFs are so porous that a teaspoon can hold the whole surface of a football field.

The research team made a special type of MOF called PSP-MIL-53 by putting poly(spiropyran acrylate) into the pores of MIL-53. In the dark, this material quickly picks up a lot of cations and anions from water, with high ion adsorption loadings of up to 2.88 mmol per gram of sodium chloride.

When the sun hits the material, the magic happens. The neutral isomer quickly releases these adsorbed salts when exposed to sunlight, which regenerates the MOF so it can be used again right away. This process makes a cycle that lasts without needing any chemicals other than the MOF material at the start.

Sustainability and better performance go hand in hand

The World Health Organization says that good drinking water should have a total dissolved solid (TDS) level of less than 600 parts per million (ppm). In just 30 minutes, researchers were able to get the TDS down to less than 500 ppm.

Professor Huanting Wang, who led the study from Monash University’s Department of Chemical Engineering, talked about how important this was. “Desalination has been used to deal with the growing lack of water around the world.” “Because there is brackish water and seawater available, and because desalination processes are reliable, treated water can be added to existing aquatic systems with very little risk to health,” he said.

This solar-powered method is much more efficient than thermal desalination or other water purification systems, which use a lot of energy, or reverse osmosis, which uses chemicals. When desalinating 2,233 ppm synthetic brackish water, the technology uses very little energy—only 0.11 Wh per liter.

Wider uses and effects

The effects go far beyond just cleaning water. Professor Wang said, “These MOFs that respond to sunlight could be further functionalized for low-energy and environmentally friendly ways to extract minerals for sustainable mining and other related uses.”

Recent improvements in solar water purification technologies have shown promising progress in a number of different areas. Solar-powered water purification systems are changing the way people get clean, safe drinking water in many parts of the world. Researchers are working on ways to make the systems better, get more energy out of them, and come up with integrated solutions.

For families who want to improve the quality of their water right away, established filtration systems like those from Waterdrop Filter are good options while these new technologies are still being developed for commercial use.

Benefits for the environment and the economy

“Sunlight is the most plentiful and renewable energy source on Earth.” Professor Wang said, “Our development of a new adsorbent-based desalination process that uses sunlight for regeneration is an energy-efficient and environmentally friendly way to desalinate water.”

There are a lot of problems with traditional desalination methods. Thermal processes require a significant amount of energy, and reverse osmosis necessitates a substantial amount of chemicals to clean the membranes and remove chlorine. This solar-responsive technology addresses both issues while maintaining reliable operation.

The MOF material is durable, which means it will last for a long time. The adsorbent is very stable and works well in cycles. When it is exposed to sunlight, it can be regenerated for reuse in four minutes.

Future implications and progress

“This study has successfully demonstrated that the photoresponsive MOFs are a promising, energy-efficient, and sustainable adsorbent for desalination,” Professor Wang concluded. “Our work opens up a new and exciting way to design functional materials that use solar energy to cut down on energy use and make water desalination more environmentally friendly.”

Solar energy technologies are always getting better, which has made water purification and treatment applications much more efficient and cost-effective. For example, solar panels with higher conversion rates and new materials for desalination membranes have changed the field.

As researchers keep improving this technology for use on a larger scale, the chances of solving the world’s water shortage problems get better and better. A sustainable way to make sure everyone has access to clean drinking water is to use a lot of solar energy and new materials science.

The study was published in the journal Nature Sustainability.

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