A new way to fight antibiotic contamination in the water: Sun exposure

What is it about?

Spread and residue of antibiotics (the vast majority are beta-lactam) in the environment through a variety of water media are increasingly common, becoming an urgent global health crisis due to the generation of drug-resistant bacteria. How to economically and efficiently exterminate antibiotics in water remains a major challenge. Some metal ions (e.g. Cu2+, Zn2+, etc.) have been known for decades to precisely break down the biological toxicity of beta-lactam antibiotics in the water by their inherent ability to catalyze the hydrolysis of deadly amide bonds they share. However, this process is too slow to achieve at room temperature. It is financially foolish, of course, to heat the whole sewage bodies to accelerate this special reaction because the hateful antibiotic residue in general sewage is generally only a few parts per million. Even if it is only heated ten degrees higher than room temperature (the rate increases by a corresponding factor of 2-3 times), it is astronomical energy consumption for daily treatment of one million tons of general sewage plant. So, what is a feasible heating approach for this needle-in-the-haystack reaction? The answer is sunlight. To this end, the researchers utilized a bipyridine linker on covalent organic framework (COF) materials to anchor Cu2+, creating a novel Lewis acid hydrolysis catalyst. This new material not only can preserve the Lewis acid catalytic properties of Cu2+ but also can generate and accumulate heat on limited catalytic sites upon exposure to visible light via the so-called photothermal conversion effect. The Cu2+ sites on support could be locally heated to over 211 °C within 1 minute (gas/solid medium) using a 300 W Xe lamp. Even in an aqueous solution, the local temperature of catalytic sites on the support could also be elevated more than 40 degrees higher than the surrounding water body, significantly enhancing the catalytic hydrolysis of the spread of antibiotic molecules from the bulk solution. It means that only sunlight is needed to decompose antibiotics in water efficiently without any additional heat source.

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Photo by Bob Brewer on Unsplash

Photo by Bob Brewer on Unsplash

Why is it important?

Our Cu2+/COF aided by the light illumination not only brings the eradicating of trouble β-lactam antibiotics by the most classic but effective Lewis acid catalysis within the bounds of practical possibility, but also enables the degradation products fully decarboxylated, which have lower toxicity such as teratogenesis, carcinogenesis, and endocrine disruption, and significantly improve biodegradability.

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