Researchers identify effective ways to tackle the global water crisis

Laser etching an easy way to deal with the global water crisis

In the coronavirus pandemic, people in developed countries have sufficient clean water to wash their hands as often as necessary to protect themselves from illness.

Yet, almost one-third of the world’s population does not even guarantee clean, drinkable water.

Researchers at the University of Rochester have found a way to address this problem by evaporating and purifying contaminated water with an efficiency of more than 100%, which is sunlight that everyone can use.

How is this possible?

In the paper Natural sustainabilityLab researchers at Chunlei Guo, a professor of optics, show how a burst of femtosecond laser pulses etches the surface of a regular aluminum sheet into a super-hygroscopic (attracting water), super-energy absorbing material. I am.

When placed in water at an angle facing the sun, the surface looks like this:

• Draw a thin film of water upwards on the surface of the metal
• Holds almost 100% of the energy absorbed from the sun and heats water quickly
• At the same time, it alters the intermolecular bonds of water, further increasing the efficiency of the evaporation process.

“These three factors enable the technology to operate at 100% efficiency and outperform the ideal device,” says Guo, who works in the University’s Physics and Materials Sciences program. ..

“This is a simple, durable, and inexpensive way to deal with the global water crisis, especially in developing countries.”

Laboratory experiments have shown that this method reduces all common pollutants such as detergents, dyes, urine, heavy metals, and glycerin to safe levels for drinking.

Guo says the technology may also help developed countries in mitigating water scarcity in drought-stricken areas and for water desalination projects.

Easy to clean and aim

Boiling using sunlight has long been recognized as a way to eliminate microbial pathogens and reduce death from diarrhea infections.

However, boiling water does not remove heavy metals or other contaminants.

However, solar-based water purification can significantly reduce these pollutants, as almost all impurities are left behind when the evaporated water becomes gaseous and condenses and collects.

The most common method of solar-based water evaporation is to heat large amounts of water, but volumetric heating where only the top layer can be evaporated.

This is clearly inefficient, as Guo says, because only a small portion of the heating energy is used.

A more efficient method, called interfacial heating, places a floating, multilayered absorbent and wicking material on top of the water, so only the water near the surface needs to be heated.

However, all available material must float horizontally above the water and cannot face the sun directly, Guo says.

Therefore, this approach is less energy efficient. In addition, the available wicking material quickly becomes clogged with contaminants left over after evaporation, requiring frequent material replacement.

The panel developed by Guo’s lab avoids these inefficiencies by drawing a thin layer of water from the reservoir and heating it directly to the surface of the solar absorber for evaporation.

The open grooved surface makes it easy to clean by just spraying. The biggest advantage is that “the angle of the panel can be continuously adjusted to face the sun directly as the sun rises and then move across the sky before setting”-maximizing energy absorption .. What can I do here?”

Chunlei Guo, Professor, Faculty of Optics, University of Rochester

The latest set of applications

The project was funded by the Bill and Melinda Gates Foundation, the National Science Foundation, and the US Army Research Office.

“Because the Army and its fighters run over the water, I’m particularly interested in researching basic materials that could lead to advanced technologies for producing drinking water,” says the Army, a component of US Army combat capability. Said Evan Lannastrom, Program Manager at the Research Department. Army Institute of Development Command.

“The super-hygroscopic and light-absorbing properties of these aluminum surfaces allow for passive or low-power water purification, improving the durability of fighters on the battlefield.

In addition to using Femtosecond Laser Etching Technology to create superhydrophobic (water repellent), superhydrophilic (water-attracting), superenergy-absorbing metals, Guo Labs is often pressed Created a metal structure that won’t sink even water or how much damage or puncture it was.

Before making water-repellent metals, Guo and his assistant, Anatolyy Borobiev, demonstrated using femtosecond laser pulses to blacken almost all metals.

The surface structure created on the metal was very effective in trapping incident radiation such as light. But they also captured light over a wide range of wavelengths.

Later, his team used a similar process to change the colors of different metals to different colors such as blue, gold and gray.

Applications include the production of color filters and optical spectrum devices that use a single laser to manufacture different colored cars in a car factory. Or suggest a gold engagement ring that matches the blue color of your fiance.

The lab is also using early black and tinted metal technology to create a unique array of nanoscale and microscale structures on the surface of regular tungsten filaments that will allow the bulb to glow brighter using the same energy. I chose