March 3, 2024

The need to avoid highly toxic hydrogen fluoride

Chemists may have found a way to avoid the use of one of the most widely used toxic substances: hydrogen fluoride.

Made from the mineral fluorspar (CaF2), hydrogen fluoride (HF) is used in both gaseous and liquid form.

A small splash of HF on the skin is enough to be fatal – and contact with the gas can cause blindness, severe burns, and serious lung damage.

But hydrogen fluoride is the only effective way to make fluorine-containing substances. These fluorochemicals are vital in a range of products including refrigerants, lithium batteries, pharmaceuticals, agrochemicals, and non-stick materials.

A team of chemists from the UK have found a way to make fluorochemicals with direct fluorspar, which is less dangerous.

“Direct use of CaF2 for fluorination is a Holy Grail in the field, and a solution to this problem has been sought for many years,” says Professor Véronique Gouverneur, a chemist at the University of Oxford and senior author of a paper describing the research, published in Science.

“This study is an important step in this direction as the method developed at Oxford has the potential to be applied anywhere in academia and industry.”

Her method, inspired by the biomineralization that nourishes teeth and bones in nature, involves grinding CaF2 in a ball mill for three hours with salt – powdered potassium phosphate.

This generates a powder containing fluorine and potassium, which they call Fluoromix.

Using high-precision techniques, such as X-ray diffraction, the researchers discovered key insights into the composition of Fluoromix and the structures of the fluorinated species. This diagram shows the structures of the crystalline components of Fluoromix, which act as fluorinating reagents. Credit: Professor Michael Hayward.

The researchers showed that their fluorspar-based Fluoromix can create more than 50 different fluorochemicals, and potentially many more.

Gouverneur says the method could also minimize carbon emissions by shortening supply chains, since it skips a step in the fluorspar-to-fluorochemical pipeline.

The ball milling technique, which is a hallmark of a field called mechanochemistry, avoids the sulfuric acid and high energy cost required to turn CaF.2 into HF.

“This seemingly simple process is a very effective solution to a complex problem; However, there were still big questions about how this reaction worked,” says co-author Calum Patel, a PhD student at the University of Oxford.

“The collaboration was critical to answering these questions and advancing our understanding of this new and unexplored area of ​​fluorine chemistry.”

The researchers have spun off a company called FluoRok, which is commercializing their technology.

Read more: What is ‘green chemistry’, and why are Australian scientists so excited about it?

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