# Stock pot Lime alternative



## MarcoP (Aug 25, 2014)

Hi all,

Agricultural Lime in not available, or easy to find, in my area as our water/soil's PH is already high so it is getting way too long for me to finish my first stock pot.

I guess what makes the Lime work for this job are the oxidizing agents in it, so would that means that calcium oxide alone or magnesium oxide alone will still do the job? Or do I need a mix of them.

What else could I use after scrap iron has been digested in a spent HCl solution to drop copper out?
Would caustic soda push the remaining BMs out of solution while neutralizing it?

I'm sure it has been answered already and my bad I didn't take note of it as I was sure I was able to find some Lime, or similar, locally.

In Italy, most of your easily locally available products are not available and if so under a different name thus ending up with extra work.

Basic question if you have it all sorted, not so basic when even simple products cause you to read a lot more because their unavailability messing up my already little knowledge.

Thank you.


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## MarcoP (Aug 25, 2014)

:idea: 
Looking at the reactivity series Mg or Al will work, but I want to be sure to end up with the cleanest solution as far I can.


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## butcher (Aug 25, 2014)

We do not use lime in the stock pot, where we are trying to recover traces of values, and would like to leave most of the other metals in solution, here we will normally use a metal like copper or iron to cement values.

It is in the waste treatment where we use the lime to neutralize the acidic solution, where its main purpose is to make a neutral salt of the acids, this is used after we replace most of the more dangerous metals from solution, usually using a metal like iron to cement the more dangerous metals from solution, then decanting the solution from those metal powders, and neutralizing the acidic waste, with a neutralizing agent like sodium hydroxide, lime, or another strong basic chemical, to form insoluble hydroxides, carbonates of many of the other metals which were left in solution. bringing the pH up to 9 to 9.5 where most of these metals are less soluble, and precipitate these from solution, after decanting we will, then use a little acid to bring our waste solutions pH back to down to 7, because some metal hydroxides are soluble, and this will again make these less soluble so we can then precipitate these out of solution, now we can decant our salt water solution from these metal powders, this gives us a salt water solution at pH7 with most all of the dangerous metals removed from solution that we can dispose of properly, we still have to be careful where we dump this salt water, so we do not pollute or destroy a water supply or soil, the sewer water treatment plants can deal with this salt water.

MarcoP,
it is not the metal of sodium, potassium, calcium, magnesium, aluminum, or other very reactive metals that we use to do this work with, but the basic salt of these metals, metal hydroxide salt, the metal carbonate, or oxide... of these metals, which we use for their acid neutralizing property's.

There are several different basic, alkali, or carbonate chemicals that can be used, some work better than others, some you will need to add a lot more to get the job done, some cost more or are easier to find...


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## MarcoP (Aug 25, 2014)

Thanks for taking the time to write such detailed infos.

I'll have to pay more attention to the terms I use. I've just learned that when all metals of interest are cemented out, Stock Pot becames Waste Solution.
Said this, a Copper sheet was used to drop any PMs left, decanted, and scrap Iron was used to recover Copper back, sorry if I didn't take the time to fully describe the process as you did with me.
At this point I'll have to use NaOH [sodium hydroxide salt, very strong alkali base (see I'm learning already)] as I already have a stock of it for soap makings.

Thank you very much.


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## etack (Aug 25, 2014)

Don't wast any money on chemicals to neutralize your waste unless it needs to be done quick. Use limestone marble or anything like that for it. takes more time but you can get them cheap or free.

Eric


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## MarcoP (Aug 25, 2014)

For limestone marble do you mean finely grinded marble http://en.m.wikipedia.org/wiki/Marble ?
I've looked that up too when I was reading about Lime, but it seemed too easy to be true.
If that is the case, yes, I could probably get it for free!


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## Irons (Aug 25, 2014)

MarcoP said:


> For limestone marble do you mean finely grinded marble http://en.m.wikipedia.org/wiki/Marble ?
> I've looked that up too when I was reading about Lime, but it seemed too easy to be true.
> If that is the case, yes, I could probably get it for free!



Lots of limestone in Italy.

It doesn't need to be finely ground. Small particle size means the reaction will be quick and it will likely foam-up. Size like fine gravel is better. It will fizz like Soda Water and likely take a few days to finish, but you won't have to waste time watching it.


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## MarcoP (Aug 30, 2014)

Thank you all for your replies making me saving money as I've find unlimited free supplies of limestone! Thanks you again!

I'm still waiting for my PH test strips and as soon as they come in I will start the process but while reading I've noticed that adding an excess of sodium metabisulfite into a chloride solution CuCl will precipitate, and CuCl at PH 5-7 will precipitate Pd from solution.
If this is correct, is this a possible way to recover any Pd from waste solution if any made it to it?

So basically add few grams of SMD, start using limestone till PH7, harvest any sediment (possible Pd), keep adding limestone and proceed as suggested?

Is there any catch that I don't know about?


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## butcher (Aug 30, 2014)

MarcoP,
It sounds like there are a lot of catches that you do not know about yet.

Save the limestone for treating the waste solution.

Keep studying before you begin, it sounds like you need to do a lot more study before you are ready.


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## MarcoP (Aug 30, 2014)

butcher, sure you are right, I wont disagree with that. I have a lot to learn yet to be just 1/100 of what many of you are.

My post implied an already correct (as I believe) recovery from stock pots and it was a simple idea about any possible Pd left on waste solutions.


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## butcher (Aug 30, 2014)

If you intend to recover dissolved values from the stock pot I would use copper metal.

In any case I would not use lime or pH adjustment to recover values from most any solution, which would precipitate unwanted metals...

It does look like you are doing a good job studying, but it also sounds like you have a lot more to do, keep up the good work, the more you study the less messes you will make the safer and more successful you will be when you do begin.


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## MarcoP (Jan 7, 2015)

I still couldn't find limestone in my area (I must be looking in the wrong places).
I've tried different types of what I believed to be limestone, some would frizzle but not for long, others are just be inert.

So I've got some calcium hydroxide and it does works for hydrochloric acid I then tried on a small sample of sulfuric acid but PH doesn't want to change at all. Am I doing something wrong or sodium hydroxide is the only way to neutralize sulfuric acid?

I have hold all my HCl liquids ready to be processed and finally I'll be able to do a little clean up, I'm just looking ahead for proper disposal of sulfuric acid.


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## g_axelsson (Jan 7, 2015)

MarcoP said:


> So I've got some calcium hydroxide and it does works for hydrochloric acid I then tried on a small sample of sulfuric acid but PH doesn't want to change at all. Am I doing something wrong or sodium hydroxide is the only way to neutralize sulfuric acid?


Do you add it dry or dissolved in water? If you add it dry I think it will be covered in calcium sulfate (or gypsum) which is not soluble in water so it will passivate the calcium hydroxide and the neutralization will go extremely slowly.

The same problem would appear if you mix limestone (CaCO3) with sulfuric acid. Gypsum will form and protect the rock, it has to be crushed fine to work with sulfuric acid.

The Ragusa plateau (Hyblean plateau) in south eastern Sicily is made up from carbonates. 10 km west of Palermo is another large carbonate area. More or less all the blue areas consists of mainly carbonates. (Marble is another form of lime stone and that should be a common building material in your part of the world.)






I might come and visit you, there is a lot of interesting geology on Sicily, here everything is covered in snow and it's cold outside. :mrgreen: 

Göran


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## MarcoP (Jan 7, 2015)

Will have to try to dissolve it in water first!

I'm probably walking in top of it as I live near Siracusa... on Hydrochloric acid I've tried marble (frizzes but then it stop) and other samples of limestone but they had no reaction at all. Before I'll finish my 25Kg of calcium hydroxide I'll have to find free source of limestone.

You, Dave and others are most welcome in my house, not kidding! Sicily has a lot to offer come and get it


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