>bubbling them through an alkali mixture Which turns the liberated halogens back to salt automatically, in a very favorable reaction which is so strongly favor

>bubbling them through an alkali mixture Which turns the liberated halogens back to salt automatically, in a very favorable reaction which is so strongly favored it is almost irreversible. Almost. But not if you carefully apply energy to the brine using an electrochemical process, especially one which has been improved for over a century after the patent expired, and you can't get much more efficient than that. Especially at the scale these operate at. These are not petrochemical plants since they were doing this before petrochemicals actually had plants. Crude oil wasn't even that popular yet. But who's going to need to do that, the spent alkali after scrubbing the halogens has no need for additional energy to be added. Unless you wanted to turn it back into full-strength alkali. Which wouldn't be cost-efective anyway, and nobody should be paying more than it's worth. Because there's planty of fresh material coming out of the caustic plants already. But you know how much energy it takes to produce that alkali originally from the virgin brine feedstock those plants use? More than it's worth. It a plain electrochemical reaction. No other raw materials needed. It's that "irreversable" reaction that's just a little too strong. So it takes a lot of energy to reverse. Kind of like trying to turn CO2 back into hydrocarbons. And if you want to try and capture CO2 from the atmosphere using alkali, fuggedaboutit. You're going to need a bigger caustic plant, and a lot more of them. There's a thing called material balance too, not just electrochemistry and thermodynamics at work.