Sciencemadness Discussion Board

Processing BaSO4 to either carbonate or sulfide

RogueRose - 15-2-2018 at 06:35

I've been reading over the processes of processing barium sulfate into some version that is soluble in water or acid and it seems that the only options are to process with carbon at orange/yellow heat or to boil with excess Na2CO3. Both seem to have drawbacks with the whole process of heating with carbon and then eventually dealing with the H2S evolution upon hydrolysis, so I was wondering about the Na2CO3 option.

Some of the posts stated they use 12-15x stoichiometric amounts of Na2CO3 (so I'm guess LOTS of excess water??) and then boiled for long periods 3-12 (though some said they only boiled for 30-90 mins). I'm wondering if processing under pressure would increase the efficiency of this process. By pressure I'm talking about 3-15 bar, possibly even more.

I have some old air tanks that are rated for 3200lbs that have gone out of date. They are steel so I think they should handle this heat and pressure but I would need a way to figure out the pressure regulation, possibly something similar to a pressure cooker steam vent with a heavier weight? The only problem I could see is the pressure being released (weight coming off) and the water flashing to steam - not a good thing...

RawWork - 15-2-2018 at 06:49

Doesn't make sense. What is your plan after that? You'll get two soluble salts, which you again have to separate. You want pure Ba salt? Not mixed with something else?

[Edited on 15-2-2018 by RawWork]

ninhydric1 - 15-2-2018 at 07:52

I would go with the carbon reduction method, simply because you wouldn't introduce cationic contaminants. H2S isn't bad to deal with if you do it outside or in a well ventilated area. The main problem is the CO produced, so you might also want to do the reduction outside.

clearly_not_atara - 15-2-2018 at 08:14

RawWork: Barium carbonate is not soluble; the solution is simply filtered post-rxn. Not that it works; I've only heard of this working with CaSO4, and the solubility of BaSO4 is much lower afaik.

RawWork - 15-2-2018 at 08:25

Quote: Originally posted by clearly_not_atara  
RawWork: Barium carbonate is not soluble; the solution is simply filtered post-rxn. Not that it works; I've only heard of this working with CaSO4, and the solubility of BaSO4 is much lower afaik.


Well, I checked and looks like you are right. He said he needs to process Ba into some soluble salt, like carbonate, so i believed it's soluble without checking. He's wrong, because his plan is to make some soluble barium salt by reacting Ba sulfate with Na carbonate. Except if Barium bicarbonate exists, which i have not heard yet.

[Edited on 15-2-2018 by RawWork]

RogueRose - 15-2-2018 at 09:45

I had planned to use HCl or HNO3 to dissolve the carbonate from the sulfate/carbonate mix

RawWork - 15-2-2018 at 09:51

That's impossible as both chlorides or nitrates are soluble. Moreover, neither HCl nor HNO3 will react with sulfate. Also I think you don't wanna lose precious barium atoms, so my advice is to not use aqueous method, but distillation or something else.

clearly_not_atara - 15-2-2018 at 12:49

It sounds like you're not familiar with the method, because your objections still don't make sense.

First the sulfate is boiled with a soluble carbonate. Because the carbonate has an even lower solubility than the sulfate, the tiny amount of sulfate which dissolves is converted to insoluble carbonate and precipitates. This prompts more sulfate to dissolve and precipitate as carbonate again, so on until all of the sulfate is converted to carbonate.

Then the carbonate is separated from the reaction mixture and added to acid. The very small amount of carbonate which dissolves reacts with the acid, releasing carbon dioxide, which allows more carbonate to dissolve, releasing more CO2 until the whole thing is converted to the chloride/acetate/etc.

This works okay with calcium sulfate, because it is about a hundred times more soluble than calcium carbonate. But both barium sulfate and barium carbonate have such low solubility I'm not sure how practical it is here. Regardless experiment is king. The method is feasible in a purely mechanistic sense, though.

EDIT: Experiment is king, not kind. Experiment is a tyrannical and demanding king who will not be crossed.

[Edited on 16-2-2018 by clearly_not_atara]

RogueRose - 15-2-2018 at 16:48

So what about doing this under increased pressure. I'm wondering if the solubility of the BaSO4 would increase at all as well as maybe speed up the conversion either by increase in sulfate solubility or by "other factors?".

RawWork - 15-2-2018 at 17:50

Here's solution if dissolving barium sulfate is all you want.
Just add sulfuric acid to it. You'll get soluble barium bisulfate.
As for your method of reacting it with sodium carbonate, forget it, it doesn't work.

As Handbook of Inorganic Chemicals says: "It does not undergo double decomposition reactions in aqueous phase".
That's what I thought.

BaSO4 + H2SO4 => Ba(HSO4)2

[Edited on 16-2-2018 by RawWork]

ninhydric1 - 15-2-2018 at 21:12

RawWork, I don't think you understand what OP is trying to do. OP wants to convert BaSO4 to other salts, so he wants to convert to carbonate. If BaSO4 is more soluble than the carbonate, the equilibrium will be shifted to the right very slightly, forming BaCO3. Because the small amount of BaSO4 that was dissolved was consumed, more dissolves and more reacts and precipitates as carbonate. This can be filtered out. It might work, but very, very slowly.

Of course this is only if the difference in solubilities is high, i.e. at a specific temperature.

If you still don't get it RawWork, look into solubility equilibria and chemical equilibrium more. Theory is important after all.

EDIT 1: grammar.

[Edited on 2-16-2018 by ninhydric1]

RawWork - 16-2-2018 at 05:50

Quote: Originally posted by RogueRose  
processing barium sulfate into some version that is soluble in water or acid


No, OP is trying to dissolve Ba sulfate, but he thought that was the only option. Working with slightly soluble and insoluble salts is very shady, as it's time consuming and heating is needed. BaSO4 is soluble in H2SO4(aq).
Quote: Originally posted by ninhydric1  
If BaSO4 is more soluble than the carbonate, the equilibrium will be shifted to the right very slightly, forming BaCO3

Never heard for that theory, although I know equilibriums. Which part of lesson am I missing?
Are you saying that BaSO4 WILL react with Na2CO3? Explain that example of solubility equilibrium please.

But even if it's right, it is probably one very very slightly. And even if he uses no matter how strong pressure he won't change the equilibrium even a bit, as both salts are becoming more soluble. :(

[Edited on 16-2-2018 by RawWork]

RogueRose - 16-2-2018 at 07:39

Quote: Originally posted by ninhydric1  
RawWork, I don't think you understand what OP is trying to do. OP wants to convert BaSO4 to other salts, so he wants to convert to carbonate. If BaSO4 is more soluble than the carbonate, the equilibrium will be shifted to the right very slightly, forming BaCO3. Because the small amount of BaSO4 that was dissolved was consumed, more dissolves and more reacts and precipitates as carbonate. This can be filtered out. It might work, but very, very slowly.

Of course this is only if the difference in solubilities is high, i.e. at a specific temperature.

If you still don't get it RawWork, look into solubility equilibria and chemical equilibrium more. Theory is important after all.

EDIT 1: grammar.

[Edited on 2-16-2018 by ninhydric1]


You are correct. I was looking to see how BaCO3 could be made from the sulfate. If it could be turned into a soluble salt, then it could be neutralized with Na2CO3 or if the sulfate would dissolve some in boiling Na2CO3 solution, I thought some BaCO3 would precipitate.

There are at least 2 threads on the forum that report various successes with this but they are a little unclear as to how effective the boiling Na2CO3 solution with BaSO4 would be. That is why I thought a pressurized vessel may help increase solubility.

ninhydric1 - 16-2-2018 at 08:01

BaSO4 (s) <--> Ba2+(aq) + (SO4)2-(aq)

Ba2+(aq) + (CO3)2- (aq) --> BaCO3 (s)

If BaSO4 is considerably more soluble than BaCO3, the equilibrium shifts to the right for the two eqs and therefore the overall net reaction also shifts to the right. This will take time though because the Ksp of BaSO4 is still small. It also needs a specific temperature because this won't happen at room temperature due to difference in Ksps.

If you really don't know anything about this, RawWork, I recommend looking into it. Equilibrium is an important part of fundamental chemistry.

[Edited on 2-16-2018 by ninhydric1]

RawWork - 16-2-2018 at 08:16

Quote: Originally posted by ninhydric1  
It also needs a specific temperature because this won't happen at room temperature due to difference in Ksps.


That's explanation I needed, but not maybe exactly correct.
It should go like "It also needs a specific temperature because this won't happen at room temperature due to thermodynamics."

It's thermodynamics stability. It determines what will react with what at what temperature. Not Ksp or concentration. Sodium can be formed from it's compounds in presence of carbon only at higher temperatures because at these temperatures it becomes more favorable/stable/existant (although is may still be less favorable than reverse reaction, it at least begins to exist with some percent). It's not removal of sodium by distillation that enables sodium carbonate to react with carbon, but temperature! Removal only speeds up or allows reaction to proceed.

I know that at certain temperature compounds decompose and equilibrium can shift to opposite side than at normal temperature. I think equilibrium shifts to right not due to some concentration of some ions, but only due to temperature??? Temperature changes everything. It's not concentration or pressure or something else I think. For example if we put sodium carbonate + carbon together and no matter how much pressure we reduce, no sodium will form. But at certain temperature, law is saying "hey, sodium can exist at this temperature". Same is true for cells (electrochemistry).

And if that temperature which will change side into which equilibrium will shift is above boiling temperature of water with dissolved salts, it means it MUST be done under pressure!

Or simply said all of this above: Solubility equilibrium is only valid if thermodynamics equilibrium is valid.

Now even I am confused. There are many factors.
Theoretically said: "First thermodynamics then solubility equilibrium."

This is challenging topic. Not only example with Ba, but generally, what can be done with equilibriums. Reverse reaction probably. Nobody has even done reduction of sodium using carbon which is based on this principle.

Nobody produced sodium on youtube using these methods, not to talk about other missing videos/experiments. Yet these processes were discovered and done long time ago:
"Gay Lussac and Thenard obtained metallic sodium by chemical reduction of caustic soda with iron at elevated temperatures. Deville, in 1854, prepared the metal by reduction of sodium carbonate and lime with charcoal at a temperature above the boiling point of sodium. Castner, in 1886, improved the chemical reduction process preparing the metal by heating sodium hydroxide with iron carbide at high temperature." - Handbook of Inorganic Chemicals

Only experiment will prove this.
Subscribe to my channel. You don't want to miss it before spring comes.
https://www.youtube.com/channel/UCPmTPa2-8PM2lDdIt9SHw0g

Actually maybe I am half-wrong about all of this. That's why I hate complicated theory. Experiment allows me to verify and do something without almost any (all but simple) theory. Through only experiments and simplest theories we can know everything. After all it's all about Yes or No, True or False. Youtube is the king for doing experiments. :cool:

[Edited on 16-2-2018 by RawWork]

ninhydric1 - 16-2-2018 at 10:25

Nope, your sodium carbonate and carbon reaction was never thermodynamically favorable.

G=H-TS (with corres. deltas)

The Gibbs free is positive regardless. Not all reactions are thermodynamically stable at a specific temperature.

Temperature is not the only factor of equilibrium. It provides the AE for the rxn and is part of it, but molecules and the presence of them still shifts the equilibrium.

RawWork - 16-2-2018 at 10:35

That's why I hate theory, could get old and die while learning. And even then not know the truth how will practically everything end up. Sometimes experiment is easier and quicker, and leads to truth, solution, survival, gain.

The main thing I see success in is SIMPLICITY. Once things become complicated, it's too late. And they start being complicated when many things accumulate, like many equilibriums. One thing at a time is smart!

I do not need complicated things to live or survive. Luckily things can only be complicated in our minds. They are not complicated for themselves, but our thoughts about it.

That's the border along which i'm gonna walk. Never immerse myself in many things, in complications. Things get complicated by quantity, by division.

Word equilibrium extends to words:
Sedimentation equilibrium
Punctuated equilibrium
Genetic equilibrium
Mechanical equilibrium
Radiative equilibrium
Hydrostatic equilibrium
Partition equilibrium
Thermal equilibrium
Donnan equilibrium
Chemical equilibrium
...

Human mind can't think so many things at once, even if previously learned all. Confusion arises. One things can oppose others...
Although many things at once can work by themselves.

I'll stick to experiment side and avoid complicated discussions. :mad:
Complicated stuff demotivates me, and I believe everyone. Then chemistry is not what i imagined it to be. It's only beautiful in it's simple form, at beginning, in order, when things are organized, just like it's true with all other sciences and stuff.

Best example is organic chemistry. Only 2-3 elements make so many compounds. Luckily even organic chemistry may be simplified and can be liked then. Best proof that things easily get complicated is wikipedia's disambiguation pages. Also pages that contain words "list of", "category:", "template:", "index of", and similar. References too. One article refers to 1000 others. Start reading one article, end up reading 1000. :mad:

As one song says: "The simplicity is numbing genius is dumbing down the situation to a manageable level".

Things can be simplified through experiment through ELIMINATION.

As Ross Horne said in book Health and Survival in 21st Century: "Other information follows as well, of course, and as Sherlock Holmes said to his friend Dr Watson (or words to the same effect): "When you have eliminated all that is false then whatever remains must be the truth.""

Or as Bert said to me: "Best of all, come with the data FROM the experiment, it matters not if it seems to confirm your idea or not- An apparently negative result is still valid data".

[Edited on 16-2-2018 by RawWork]

clearly_not_atara - 16-2-2018 at 11:37

To be clear: Wikipedia gives Ksp for [Ba2+][SO4(2-)] as 1.08 * 10^-10, and Ksp for [Ba2+][CO3(2-)] as 2.58 * 10^-9. Based on these data, it is not possible to efficiently transform barium sulfate to the carbonate by hearing with carbonate salts unless the solubility of the sulfate increases significantly at high temperatures.

For [Ca2+][SO4(2-)], Ksp is 4.93*10^-5 and for [Ca2+][CO3(2-)], Ksp = 3.3*10^-9. So it is possible to convert calcium sulfate to the carbonate by this method, because calcium sulfate is much more soluble than the carbonate, even though both are poorly soluble.

EDIT: One interesting possibility is to heat barium sulfate with sulfur, anticipating the reaction:

2 BaSO4 + 1/8 S8 >> SO2 + 2 BaSO3

Unlike carbon, sulfur will not reduce barium sulfite further, but if you get lucky it might reduce the sulfate. Barium sulfite can then be acidified without fear of H2S release, although (less) toxic SO2 is emitted.

[Edited on 16-2-2018 by clearly_not_atara]

nezza - 16-2-2018 at 12:52

Boiling BaSO4 with Sodium or potassium carbonate does indeed work. I have done this in the past. You need to boil a suspension of BaSO4 with tha carbonate for a while. The reaction does not go to completion, but I managed to get a reasonable amount of Barium Carbonate formed which can then be dissolved in dilute nitric or hydrochloric acid. The boiling can be repeated for any unreacted sulphate.

ave369 - 16-2-2018 at 13:17

> Boiling BaSO4 with Sodium or potassium carbonate does indeed work.

Not just barium, it works with radium as well. Marie Curie used this reaction to make radium salts.

Melgar - 18-2-2018 at 10:21

Barium sulfate is famous for its insolubility in water. The thing with carbonates does not seem practical at all.

The hydrogen sulfide and carbon monoxide produced are both flammable, you know, and they're not really even that toxic as long as your ventilation is decent. Really though, you can just burn off the gases as they form, which is a good test to make sure the reaction is proceeding as expected.

unionised - 18-2-2018 at 11:44

Quote: Originally posted by Melgar  
The thing with carbonates does not seem practical at all.

It seems odd to say that after someone else says they have done it.
I have also done that reaction, you need very finely powdered BaSO4 for it to work better than badly.

I have also tried the reduction to sulphide which works better but still isn't great.

Hydrogen sulphide is about as toxic as hydrogen cyanide.
A litre of carbon monoxide is plenty to kill you.

RawWork - 18-2-2018 at 11:52

Hope somebody will show, before I do (before spring).

Melgar - 21-2-2018 at 16:33

Quote: Originally posted by unionised  
Quote: Originally posted by Melgar  
The thing with carbonates does not seem practical at all.

It seems odd to say that after someone else says they have done it.
I have also done that reaction, you need very finely powdered BaSO4 for it to work better than badly.

I have also tried the reduction to sulphide which works better but still isn't great.

Hydrogen sulphide is about as toxic as hydrogen cyanide.
A litre of carbon monoxide is plenty to kill you.

Note that I said "practical", not "possible". Because then you went on to say that, in fact, it was not very practical.

Hydrogen sulfide has a very strong, unpleasant odor at low concentrations. That thing about it "deadening" your sense of smell doesn't actually happen unless you're a complete idiot and try your hardest to ignore it, or are trying to commit suicide.

Carbon monoxide is odorless and deadly, but its main danger is that it renders you unconscious, in an area where you're presumably breathing an atmosphere with carbon monoxide in it.

Neither of these is a major concern if it's done outside, or with adequate ventilation. It's not in the same category as, say, phosgene or sarin.

happyfooddance - 21-2-2018 at 17:49

A while ago, I had a bunch of calcium sulfate but I needed calcium carbonate, and I wondered how I could easily convert it. A web search brought me to a few references about a metathesis reaction with ammonium carbonate. This stuck me as strange, because I was thinking that CaSO4 was practically insoluble. I read that the reaction depended on the "limited" solubility of calcium sulfate. The more I thought about it, I couldn't see why the same reaction wouldn't work with sodium carbonate rather than ammonium carbonate. Sodium sulfate is very soluble, calcium carbonate isn't...

So I added an excess of sodium carbonate to my calcium sulfate, put it on a hotplate for a few hours (maybe less time would be ok?), filtered, washed with several large portions of water, near quantitative yield of CaCO3.

I don't know if it will work with barium, but it sounds really similar to what you guys are talking about so I thought I'd mention it.

teodor - 9-7-2019 at 07:31

Quote: Originally posted by RogueRose  
I've been reading over the processes of processing barium sulfate into some version that is soluble in water or acid and it seems that the only options are to process with carbon at orange/yellow heat or to boil with excess Na2CO3.


Some people don't believe me, but I have no problems with dissolving BaSO4 in the chromic acid prepeared by Vogel's procedure (dissolving K2Cr2O7 in 98% H2SO4 at 100 degrees C). It undoubtedly removes BaSO4 strains and also can dissolve large amount of BaSO4 at cold. Well, the question is only how much and I plan to check that with pure BaSO4 and compare with pure H2SO4 (the known solvent of BaSO4).

So, you definitely can dissolve BaSO4 in H2SO4 presence, the question is how to get soluble Ba ions from this solution - and SO42- anion is very stable.