You're asking the right questions! Even a few PPM of the diamine left in the water is going to be an issue either due to toxicity or if non-toxic, water quality (i.e. taste and perception of potability).

The "switchable" chelating agent is pretty interesting, but I haven't been close enough to know if this is groundbreaking or just an advancement of an exiting phenomenon.

I might be a major cynic here, but my guess is that this is really cool science and like a lot of cool, basic science, the researchers need to find a practical use for it. That helps translate "cool basic science" into "existing new technology".

My PI did it when I was in graduate school - we always talked about our new molecules as being potential cancer treatments when really the focus was on the basic organic chemistry. It's a lot easier to win grants saying you're developing "new anti-cancer compounds" than being honest and saying your research is focused on the development of "novel chalcogen compounds that undergo pericyclic rearrangements to form strained heterocycles".

A lot of deep groundwater (associated with gas, oil) is both salty, and gassy. If this technique is about converting mine waste to semi-potable for use in agriculture, or mining, and also uses the CO2 on-hand, and salt on-hand, its a virtuous industrial circle.

I'd hate it since it would be monetizing part of the mining industry I don't like, but it makes economic sense in the narrow. If diamine is bad, and gets into the food chain this wreaks longterm harm. If the liberated salt is bad, likewise.

I tend to "stop the mining" but understanding the pressure of water issues on mining and farming, there may be huge upsides here.

> salty, and gassy

Deep groundwater passes the vibe check.

Most of water is used for technical purposes, not for drinking. Like washing hands, body or dishes. If it's safe for that, that would be huge achievement is this process is cheaper than conventional methods.

I'm not sure how practical it is to have two classes of water for different purposes though, given most buildings come with only one set of pipes.

There's also other non-domestic uses that could greatly benefit from cheap large-scale desalination: Agriculture in arid regions. Sea water is not an option, but taste is not a primary concern.

Indeed, domestic uses account only for 11% of the global fresh water usage. Main uses are agricultural and industry (http://www.fao.org/aquastat/en/overview/methodology/water-us...)

Taste might not be a concern, but toxicity would be even more if a concern if the crops bioconcentrate the chemical.

Taste might be a concern if the chemicals pass in the edible parts of the plants.

In large parts of the world we can't drink water out of the tap. So we buy drinking water separately. I don't think it is that big a deal.