A new filter is 99% efficient at removing microplastics from water in seconds

Daegu Gyeongbuk Institute of Science and Technology (DGIST)

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Researchers in Korea developed a new method to clean water that can quickly and effectively eliminate microplastics and other pollutants. This is a creative and important way to deal with the problem of microplastics in the environment, which is getting worse.

Given how common plastic is in modern society, it is not surprising that tiny pieces of plastic can be found almost everywhere on Earth, even in places that are supposed to be clean. From pole to pole, from the deepest ocean trenches to the highest mountain summits, microplastics have been found, and they are moving up the food chain all the way to us.

Some materials being looked into to help get rid of microplastics include nanocellulose, semiconductor wires, magnetic "nanopillars," and filtration columns made of sand, gravel, and biofilms.

A new design has now shown potential, according to experts at the Daegu Gyeongbuk Institute of Science and Technology (DGIST) in South Korea.

The substance known as a covalent triazene framework (CTF) is the key. Because this material is very porous and has a large surface area, it has a lot of space inside for storing molecules that it catches. Recent research has shown that similar compounds can eliminate organic dyes in industrial wastewater.

The team worked hard to make the molecules in the CTF more water-loving (called "hydrophilic"), and then they put the material through a mild oxidation process.

Over 99.9 percent of the contaminants were said to have been taken out of the water in just 10 seconds, thanks to how fast the filter worked. Additionally, the material can be recycled numerous times without losing its effectiveness.

In a different experiment, the scientists made a type of polymer that can absorb sunlight, turn it into heat, and then use that heat to clean up volatile organic chemicals (VOCs), which are also pollutants. Under the force of a single solar irradiation, this was able to eliminate more than 98 percent of VOCs.

Over 99.9 percent of both contaminants could be eliminated by a prototype that used both membranes.

"The technology we developed here is an unrivaled water purification technology with the world's highest purification efficiency, removing more than 99.9 percent of phenolic microplastics and VOC contaminants in water at ultra-high speeds," explained Professor Park Chi-Young, lead author of the study.

"We expected that it will be a universal technology with high economic efficiency that can purify contaminated water and supply drinking water even in areas where there is no power supply," he added.

You can view the full study for yourself in the Advanced Materials journal.

Study abstract:

"Freshwater shortage is becoming one of the most critical global challenges owing to severe water pollution caused by micropollutants and volatile organic compounds (VOCs). However, current purification technology shows slow adsorption of micropollutants and requires an energy-intensive process for VOCs removal from water. In this study, a highly efficient molecularly engineered covalent triazine framework (CTF) for rapid adsorption of micropollutants and VOC-intercepting performance using solar distillation is reported. Supramolecular design and mild oxidation of CTFs (CTF-OXs) enable hydrophilic internal channels and improve molecular sieving of micropollutants. CTF-OX shows rapid removal efficiency of micropollutants (>99.9% in 10 s) and can be regenerated several times without performance loss. Uptake rates of selected micropollutants are high, with initial pollutant uptake rates of 21.9 g mg−1 min−1, which are the highest rates recorded for bisphenol A (BPA) adsorption. Additionally, photothermal composite membrane fabrication using CTF-OX exhibits high VOC rejection rate (up to 98%) under 1 sun irradiation (1 kW m−2). A prototype of synergistic purification system composed of adsorption and solar-driven membrane can efficiently remove over 99.9% of mixed phenol derivatives. This study provides an effective strategy for rapid removal of micropollutants and high VOC rejection via solar-driven evaporation process."