Waste Treatment Question - pH 2.5 for acid waste ?

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K

kernels

Well-known member
Joined
Apr 14, 2016
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Hi guys, not sure if I'm in the correct category here, but have read the stock pot / waste treatment threads and have a question.

The thread instructed to increase the pH of waste acids to 2.5 before adding to the final treatment drum that contains solid iron. My understanding is that this drum is used to cement all metals below iron out of the solution so you are left with mostly iron in solution.

What is the reason for increasing the pH to 2.5 ?
 
Your correct but not correct. At least the way I read it.

It is the final stage used primarily to cement out the copper. The use of the term lower metals is counter intuitive to me.


When you look at the table of elements, for example Al is # 13 (lower number) then Fe at # 26, but Fe will not cement it out. So to me that's the counter intuitive part. My mind thinks in terms of mass which gets higher as you move further down or lower on the table.
 
joekbit said:
Your correct but not correct. At least the way I read it.

It is the final stage used primarily to cement out the copper. The use of the term lower metals is counter intuitive to me.


When you look at the table of elements, for example Al is # 13 (lower number) then Fe at # 26, but Fe will not cement it out. So to me that's the counter intuitive part. My mind thinks in terms of mass which gets higher as you move further down or lower on the table.
Click to expand...

Yes, my terminology was wrong / different there. When you look at the list, Cu is literally lower on the list than Fe, hence iron will displace it. I still haven't really figured out the pH2.5 part, when I look at the solubility graphs for Iron Hydroxide versus pH, there is nothing really special about 2.5, although, it looks like the solubility of Iron Hydroxide is maximized around pH3, so I can only assume that is where it came from.
 
joekbit said:
Your correct but not correct. At least the way I read it.

It is the final stage used primarily to cement out the copper. The use of the term lower metals is counter intuitive to me.


When you look at the table of elements, for example Al is # 13 (lower number) then Fe at # 26, but Fe will not cement it out. So to me that's the counter intuitive part. My mind thinks in terms of mass which gets higher as you move further down or lower on the table.
Click to expand...
Joe, you may be confusing the periodic table of elements with the reactivity series. They are very different. When we talk about cementing and waste treatment, and refer to metals that are higher or lower in the series, we're talking about the reactivity series.

Dave
 
if your PH is too acidic it will cause a reaction with the iron, this will cause or may cause your vessel to "boil over"
you do not ever want a spill, especially if you're not there to supervise it 24 hours a day.

i am sure there are more reasons for this, i just follow the rules most of the time, learning the science as i perform the tasks.
 

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