An optimized mechanochemical process produces multifunctional composite particles that remove pollutants from water.
Scientists are increasingly turning to sunlight as a powerful ally in cleaning up polluted water. Photocatalysts can harness solar energy to break down harmful contaminants, while photothermal evaporation uses that same energy to rapidly heat and vaporize dirty water, which then condenses into clean, drinkable liquid. Despite their promise, both methods often rely on expensive or difficult-to-manufacture materials that limit their large-scale use. This has sparked a global effort to create a single, affordable, and efficient material capable of performing multiple purification tasks—ideally one made from resources that would otherwise go to waste.
In a groundbreaking development, researchers at the Nagoya Institute of Technology (NITech) in Japan have found a way to turn common plastic waste into a powerful new tool for producing clean water. Led by Associate Professor Takashi Shirai, the team—consisting of Dr. Kunihiko Kato, Dr. Yunzi Xin, and Mr. Yuping Xu—has created multifunctional composite particles that can both purify and desalinate water using sunlight.
Their work was recently published in ACS Applied Materials & Interfaces.
Mechanochemical Synthesis Using a Planetary Ball Mill
To create this innovative material, the researchers used a planetary ball mill and carefully optimized the milling process. They began with a simple mixture of molybdenum trioxide (MoO3) and polypropylene, a common plastic found in packaging and household goods.
Through precise mechanical processing, they converted this waste-derived mixture into composite particles containing hydrogen molybdenum bronze (HxMoO3–y), molybdenum dioxide (MoO2), and activated carbon—materials that work together to capture sunlight and drive multiple purification reactions.
“The proposed mechanochemical process surpasses other current approaches in terms of both energy efficiency and cost-effectiveness,” highlights Dr. Shirai.
Through extensive experimentation, the research team demonstrated the many remarkable capabilities of their composites. First, these particles exhibited broad light absorption over the entire near-infrared–visible–ultraviolet range, allowing the photocatalytic degradation of a model organic pollutant. Interestingly, the composites also functioned as Brønsted acid catalysts and removed water pollutants even in the absence of light.
Harnessing Plasmonic and Photothermal Effects
Additionally, the proposed catalyst exhibited plasmonic properties leading to a marked photothermal effect that enabled rapid heating using sunlight. This could be leveraged to drive the fast evaporation of water with exceptional photothermal conversion efficiency. Finally, oxygen-containing carbons that remained as milling byproducts could adsorb and remove heavy metal ions from wastewater.
The research team plans to refine their ball milling process to produce similar all-in-one catalysts for water remediation and other applications. “Our developed technology has the potential to be applied to a wide range of oxides and plastics, and we anticipate that it will have varied applications, including enhancing the functionality of existing materials and upcycling waste plastics, to secure the availability of drinking water,” concludes Dr. Shirai.
Reference: “Multifunctional HxMoO3–y–MoO2/Carbon Composite Particles for Water Remediation” by Kunihiko Kato, Yunzi Xin, Yuping Xu and Takashi Shirai, 1 October 2024, ACS Applied Materials & Interfaces.
DOI: 10.1021/acsami.4c09169
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