Increase pH

[goldscraphobby]

Hi,
Looking to treating some waste. Its been in a drum with steel for several month and appears all the copper has dropped. I put some into a 5 gallon bucket and to raise the pH I got some white lime from home depot.
I put it in and mix it in and repeat over several days but the pH hasn't gotten over 3-4. I poured it into another bucket and there is lime sitting on the bottom.
I thought I read the lime would work, What is an accessible and inexpensive material to raise the PH?
I'm using an electronic pH meter, when I rinse it off it goes go up to 6/7 so it appears to be working.
Thanks

 

[geedigity]

Lime works but is not as strong as NaOH. However, lime will work slowly and after you add it, it does take a day or two to raise the pH. Now that you are in the 3 to 4 pH range, the solution pH should start to quickly come up with the addition of less and less lime. Patience is good. As the pH comes up, you will start to drop out metal hydroxides. Once it is near neutral, then you can wick the water out of the mixture and allow the material to dry. NaOH works quicker, but can be harder for some to acquire. Lime is readily available and somewhat inexpensive.

 

[Martijn]

I use soda ash and raise to Ph 11. A lot more hydroxides form above Ph 7.
Lime produces faster settling hydroxides i've heard.

Pauzing and filtering in between at Ph 9 would keep Cu at a minimum.

 

[Platdigger]

If you raise the ph too fast, some metals won't have a chance to settle out
before they redissolve back into the solute.

 

[goldscraphobby]

Thanks for the info. Does cold weather impact the reaction?
Thanks

 

[Smack]

If I may chime in. In my experience it seems to make a difference in how quickly I raise the PH above 7. Doing it quickly seems to produce a better cleaner settling of Hydroxides. Material source may play a role as well. :?:

 

[etack]

I always use chunks of cement. Takes longer but super cheap.

Eric