pH is stuck, better caustic?
pH is stuck, better caustic?
(OP)
Question: I have a 1000 Gallon waste treatment tank that has spent nitric acid, hydrofluoric acid, ammonia hydroxide, hydrogen peroxide and lots DI water. It is a sludge tank being treated to go out to the state. The problems which I am having are: the pH has not raisen much at all. I have been adding Sodium Hydroxide to bring it up, but it doesn't seem to be working very well. I was sitting at a pH of 2.5 for the better half of the day. Adding the caustic at a regular rate, but slow enough not to over heat. I got the tempurature around 33C and the pH started to climb but now that I am at a pH of 4.5, it is stuck and holding. Every time I add more Sodium Hydroxide, the pH drops a little. If I leave it to mix, it comes back up to 4.5 and holds. The temp. however goes up. So I let it sit over night to cool off. Starting again at the pH of 4.5 and 19C its stuck. I have gotten the temp. to 26C and still holds at 4.5. So the problem is the same. So does the acid take the caustic better at a higher temp? Is there a better base to neutralize this mix better? And is the heat a factor I should be taking into consideration?





RE: pH is stuck, better caustic?
Yes, pH is affected by temperature. The reaction that is going on is essentially instantaneous, so it shouldn't be affected by temperature that you would notice.
Good luck,
Latexman
RE: pH is stuck, better caustic?
Using a hand-held pH meter? It's probably not all that well compensated for temperature. Make sure you take the readings when the tank is cool prior to discharge.
If by "the state" you mean a publicly owned treatment works, remember that they tend to like pH in the range of 6-9: they'd prefer it a little alkaline to a little acidic.
If you value your time more than your money, you can use magnesium hydroxide for the last bit- it's tough to over-dose. If you value the latter more than the former, calcium hydroxide (lime) is cheaper than NaOH.
RE: pH is stuck, better caustic?
Thanks
RE: pH is stuck, better caustic?
RE: pH is stuck, better caustic?
RE: pH is stuck, better caustic?
RE: pH is stuck, better caustic?
I can't recall what the secondary treatment was but will try to get the information