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Comment by kragen | Hacker News Reader

Headline is a lie: as we finally find out halfway through the article, it's not soap but lye, sodium hydroxide. The solvent is the fairly nontoxic dimethyl sulfoxide, so both of these are safe to release into the environment. In https://news.ycombinator.com/item?id=32515659 sbierwagen reports that the reaction requires 120-degree temperatures so this isn't suitable for in-situ remediation.

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The reaction doesn't "require" 120C, that was simply the first experiment they described. They began by confirming that this reaction actually takes place and discovering which PFAs were neutralized by it. To that end they boiled a mixture of the stuff for 24 hours.

The reaction can occur at more moderate temperatures. There is more analysis (with experimental results) further down in the paper:

> Substantial defluorination still occurred when the isolated PFOA degradation product (perfluoro-1H-heptane 2) was subjected to degradation conditions but heated to only 40°C (table S3).

Okay, but you can't, for example, heat up large masses of contaminated dirt to 40° without killing everything in them. And you probably can't even saturate them with DMSO, both because even though it's relatively nontoxic it's not that nontoxic, and because it's expensive.

I was (totally) wrong, but can't delete or edit the comment.

Totally wrong how? Their mix doesn't break down perfluorinated stuff at 40 degrees?

Ummm... What? 120C NaOH does *not* sound safe "to release". I've worked with similar solutions. That stuff eats through so much and it's a pretty scary solution, if at high concentration.

As with everything, It very much depends on the concentration.

NaOH is only unsafe because it's highly alkaline, but it doesn't stay highly alkaline after it encounters buffers like bicarbonate or hydrogenphosphate, which are abundant in the natural environment. After it's been neutralized in this way, it's just sodium ions, and while enough of those will indeed cause environmental damage (witness salinization-induced desertification in much of the Middle East) it takes truly massive quantities.

Well if we coat the earth in lye global warming will take care of the rest. Problem solved.

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