Scientists Develop Environmentally Friendly Method for Removing Chemicals from Water

The newly-invented method, named the matrix assembly cluster source (MACS), involves no solvent and is a step change in the approach to water treatment and other catalytic processes.

Cai et al demonstrate the catalytic activity of Ag and Au clusters physically deposited onto titanium dioxide (TiO₂) powders with the MACS in the catalytic ozonation of nitrophenol; compared to traditional catalysts reported in the literature, the catalysts produced by the MACS exhibit at least comparable activities and show excellent reusability without evident degradation after five cycles: (a) photograph and (b) schematic diagram of the MACS system; (c) photograph of the Ag cluster on TiO₂ powder catalyst produced (1 g), showing the color change from white to brown. Image credit: Cai et al, doi: 10.1021/acsami.0c05955.

Harmful organic molecules are destroyed by a powerful oxidizing agent, e.g. ozone, which is boosted by a catalyst.

Usually such catalysts are manufactured by chemical methods using solvents, which creates another problem — how to deal with the effluents from the manufacturing process?

The MACS technique manufactures the catalyst by physical methods, involving no solvent, and therefore no effluent.

“Our new approach to making catalysts for water treatments uses a physical process which is vacuum-based and solvent free method,” explained senior author Professor Richard Palmer, a researcher in the College of Engineering at Swansea University.

“The catalyst particles are clusters of silver atoms, made with the newly invented MACS machine.”

“It solves the long-standing problem of low cluster production rate — meaning, for the first time, it is now possible to produce enough clusters for study at the test-tube level, with the potential to then scale-up further to the level of small batch manufacturing and beyond.”

“The clusters are approximately 10,000 times smaller than the width of a human hair and have been of significant interest to researchers because of their unique properties. However, due to the inadequate rate of cluster production, research in this area has been limited.”

The MACS method has changed this — it scales up the intensity of the cluster beam to produce enough grams of cluster powder for practical testing.

The addition of ozone to the powder then destroys pollutant chemicals from water, in this case nitrophenol.

“The MACS approach to the nanoscale design of functional materials opens up completely new horizons across a wide range of disciplines — from physics and chemistry to biology and engineering,” Professor Palmer said.

“Thus, it has the power to enable radical advances in advanced technology — catalysts, biosensors, materials for renewable energy generation and storage.”

“It seems highly appropriate that the first practical demonstration of our environmentally friendly manufacturing process concerns something we are all concerned about — clean water.”

The new method is described in a paper in the journal Applied Materials and Interfaces.

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Rongsheng Cai et al. 2020. Scale-Up of Cluster Beam Deposition to the Gram Scale with the Matrix Assembly Cluster Source for Heterogeneous Catalysis (Catalytic Ozonation of Nitrophenol in Aqueous Solution). ACS Appl. Mater. Interfaces 12 (22): 24877-24882; doi: 10.1021/acsami.0c05955