Is it possible to generate sulfuric acid from sodium sulfate without special membranes or special processes?

[realflow100]

Is it possible to generate sulfuric acid from sodium sulfate without special membranes or special processes?
The first thing that comes to mind is similar to using clay pots as one would with magnesium sulfate.
Would something similar work for sodium sulfate?
if possible, what if one fills both compartments with the sodium sulfate. would one also generate sodium hydroxide at the same time? Could any sort of practical concentrations be achieved? How long would the process take?

[exchemist]

5 hours ago, realflow100 said:

Is it possible to generate sulfuric acid from sodium sulfate without special membranes or special processes?
The first thing that comes to mind is similar to using clay pots as one would with magnesium sulfate.
Would something similar work for sodium sulfate?
if possible, what if one fills both compartments with the sodium sulfate. would one also generate sodium hydroxide at the same time? Could any sort of practical concentrations be achieved? How long would the process take?

What process are you referring to, involving clay pots and MgSO4?

[realflow100]

There are youtube videos on preparing sulfuric acid from magnesium sulfate with clay pots in a larger container. in the clay pot is where the sulfuric acid is said to be formed. and in the other container magnesium hydroxide forms.
I was thinking what about a similar or different possibility for sodium sulfate?

Edited July 19 by realflow100

[exchemist]

10 minutes ago, realflow100 said:

There are youtube videos on preparing sulfuric acid from magnesium sulfate with clay pots in a larger container. in the clay pot is where the sulfuric acid is said to be formed. and in the other container magnesium hydroxide forms.
I was thinking what about a similar or different possibility for sodium sulfate?

I’m not going to trawl through the crap on YouTube to find what may or may not be what you are referring to. Can you not describe the process in your own words? I presume you must have a fairly clear idea of it, if you propose to copy or adapt it. 

[realflow100]

In the video. it is proposed that an aqueous solution of magnesium sulfate is put into the container and a micro porous clay pot (with no drain hole) is inserted. filled with a more dilute concentration of magnesium sulfate (presumably for initial conductivity)
Carbon electrodes (or alternatively lead/lead dioxide) electrodes may be used. and inserted into the container and clay pot separately
A voltage and current is applied. The negative being in the container. and the positive being in the clay pot to the electrodes
Over several hours, potentially days, sulfuric acid is generated in the clay pot. while magnesium hydroxide forms in the container.
There is still water in both the clay pot and container. that may need to be topped up regularly. The solutions that form are dilute.
It proceeds slowly over time.
This seems to be an inefficient way to do it though. and I'm fairly sure a more efficient and compact setup could be made. and I was wondering if sodium sulfate could be used instead of magnesium sulfate.

Also I am not interested in concentrating to extreme hazardous concentrations. as that serves me no purpose. focusing more on the core idea and dilute concentrations.

Edited July 20 by realflow100

[exchemist]

8 hours ago, realflow100 said:

In the video. it is proposed that an aqueous solution of magnesium sulfate is put into the container and a micro porous clay pot (with no drain hole) is inserted. filled with a more dilute concentration of magnesium sulfate (presumably for initial conductivity)
Carbon electrodes (or alternatively lead/lead dioxide) electrodes may be used. and inserted into the container and clay pot separately
A voltage and current is applied. The negative being in the container. and the positive being in the clay pot to the electrodes
Over several hours, potentially days, sulfuric acid is generated in the clay pot. while magnesium hydroxide forms in the container.
There is still water in both the clay pot and container. that may need to be topped up regularly. The solutions that form are dilute.
It proceeds slowly over time.
This seems to be an inefficient way to do it though. and I'm fairly sure a more efficient and compact setup could be made. and I was wondering if sodium sulfate could be used instead of magnesium sulfate.

Also I am not interested in concentrating to extreme hazardous concentrations. as that serves me no purpose. focusing more on the core idea and dilute concentrations.

OK thanks for the description. I think I understand what they are doing. Electrochemistry is not my strong suit but I can see that the anode can generate oxygen and hydronium ions:

2H₂O -> O₂ + 4 H+ + 4e-  https://www.chemguide.co.uk/inorganic/electrolysis/solutions.html

while the cathode generates hydrogen and hydroxide:

4H₂O +4e- -> 2H₂ +4OH-   

However what I struggle with is that the implication of the clay pot setup as described seems to be that you would end up with a charge separation, with surplus H+ inside the pot, with no counterion to neutralise the +ve charge, and similarly surplus OH- outside, also with nothing to neutralise the -ve charge. If this started to happen the potential produced would rapidly stop current flowing, bringing the process to a halt. Or, if the permeability of the pot were sufficient to allow the metal cation and SO₄²⁻  to diffuse through it to preserve electrical neutrality, why would it not also allow H+ and OH- to diffuse through, preventing the accumulation of acidity and alkalinity on either side?  So at the moment I have difficulty seeing how this setup can produce the effect claimed. But maybe someone with more electrochemical knowledge will comment.

On the separate matter of substituting Na₂SO₄ for MgSO₄, I should not think the change of cation will make any difference. As both elements have an electrode potential, E₀ considerably more -ve than hydrogen, it will in both cases be H₂ that is generated at the cathode, the metal cation being unaffected. 

 

 

[realflow100]

I tried creating a similar setup but without having access to a clay pot I decided on a different smaller scale setup. with just a pair of rectangular tall narrow containers. and a bit of folded paper towel draped across from one to the other allowing the sodium sulfate solution to soak through the paper towel from both containers..
I started with sodium sulfate in distilled water with a near-saturated solution. about 2M
Added a pair of carbon plate electrodes. Started with about 1.5 watts of power. Oxygen and hydrogen evolution could be seen as small bubbles coming off of the electrodes. After about 12 hours the ph of the positive electrode side dropped to a very strong 2. while the negative electrode side increased to a very strong 13.5
Approximately 0.01M sulfuric acid concentration might be present in the positive electrode container. and I'm guessing that a similar concentration of sodium hydroxide might of formed in the negative electrode container
It was confirmed that sulfuric acid was indeed created. I extracted a drop. put it on a slide and sprinkled a little baking soda on it. it immediately fizzed vigorously for about a second before stopping. releasing carbon dioxide. Indicating a clear neutralization reaction.
The current flow or voltage required did not seem to change over time. both solutions remained conductive in the two containers.
At 0.01M sulfuric acid concentration. there still remained 1.98 to 1.99M concentration of sodium sulfate. which is a very dilute concentration.

Edited July 21 by realflow100

[exchemist]

3 hours ago, realflow100 said:

I tried creating a similar setup but without having access to a clay pot I decided on a different smaller scale setup. with just a pair of rectangular tall narrow containers. and a bit of folded paper towel draped across from one to the other allowing the sodium sulfate solution to soak through the paper towel from both containers..
I started with sodium sulfate in distilled water with a near-saturated solution. about 2M
Added a pair of carbon plate electrodes. Started with about 1.5 watts of power. Oxygen and hydrogen evolution could be seen as small bubbles coming off of the electrodes. After about 12 hours the ph of the positive electrode side dropped to a very strong 2. while the negative electrode side increased to a very strong 13.5
Approximately 0.01M sulfuric acid concentration might be present in the positive electrode container. and I'm guessing that a similar concentration of sodium hydroxide might of formed in the negative electrode container
It was confirmed that sulfuric acid was indeed created. I extracted a drop. put it on a slide and sprinkled a little baking soda on it. it immediately fizzed vigorously for about a second before stopping. releasing carbon dioxide. Indicating a clear neutralization reaction.
The current flow or voltage required did not seem to change over time. both solutions remained conductive in the two containers.
At 0.01M sulfuric acid concentration. there still remained 1.98 to 1.99M concentration of sodium sulfate. which is a very dilute concentration.

OK that's interesting. I was thinking more about this yesterday afternoon after my original post. I suppose the porous clay pot is in effect a "salt bridge" with MgSO₄(aq) as the bridging solution. At the start, the counterions that move through the pores to preserve electrical neutrality will be Mg²⁺and SO₄²⁻ and it will only be as the acidity and alkalinity build up that a proportion of the moving counterions will start to be H⁺ and OH⁻. So yeah, I think I see how it works now. (It's been half a century since I did this stuff.)

 

[realflow100]

Well it's at least been proven "potentially possible". Is there any ideas what sort of concentrations could actually be achieved with such a setup?
With my "up and over" bridge it seems that the longer it ran. the more the ph would decrease in the acidic container and the more it would increase in the basic container. but I stopped at ph of 2 since it was getting late and i needed to sleep and couldn't sit up keeping an eye on it all night.

[exchemist]

1 hour ago, realflow100 said:

Well it's at least been proven "potentially possible". Is there any ideas what sort of concentrations could actually be achieved with such a setup?
With my "up and over" bridge it seems that the longer it ran. the more the ph would decrease in the acidic container and the more it would increase in the basic container. but I stopped at ph of 2 since it was getting late and i needed to sleep and couldn't sit up keeping an eye on it all night.

I suppose in theory it must be limited by the amount of metal cation and sulphate available as counterions, to match the increasing H+ and OH- concentrations on either side. Though I still think there will come a point at which a significant proportion of the counterion movement through the bridge will be H+ and OH-, at which stage neutralisation will increasingly compete with the production of acid and base.   

[realflow100]

The thing is though. sodium sulfate is a neutral salt. and essentially doesn't react with sulfuric acid or sodium hydroxide directly. which is exactly what would be formed after any neutralization reaction essentially slowing down any neutralization after the sodium sulfate itself is formed.
If we consider a 3 compartment setup. and used two salt bridges. the center compartment would have a relatively neutral mixture of sodium sulfate in it maintaining even further separation from the outer two compartments.
Also depending on the construction of the compartments the efficiency and rate of diffusion of ions and the solution could be controlled.
essentially if you first filled the middle compartment with sodium sulfate. then filled the outer ones with dilute concentrations of sulfuric acid and sodium hydroxide. no reaction would occur right away. even through there is a path of ions between the three solutions (the reaction would be very slow and gradual. occurring over time as ions and the solution gradually diffuses through the salt bridges. this could take hours or even days to run to complete equilibrium.)

Edited July 22 by realflow100

[exchemist]

2 hours ago, realflow100 said:

The thing is though. sodium sulfate is a neutral salt. and essentially doesn't react with sulfuric acid or sodium hydroxide directly. which is exactly what would be formed after any neutralization reaction essentially slowing down any neutralization after the sodium sulfate itself is formed.
If we consider a 3 compartment setup. and used two salt bridges. the center compartment would have a relatively neutral mixture of sodium sulfate in it maintaining even further separation from the outer two compartments.
Also depending on the construction of the compartments the efficiency and rate of diffusion of ions and the solution could be controlled.
essentially if you first filled the middle compartment with sodium sulfate. then filled the outer ones with dilute concentrations of sulfuric acid and sodium hydroxide. no reaction would occur right away. even through there is a path of ions between the three solutions (the reaction would be very slow and gradual. occurring over time as ions and the solution gradually diffuses through the salt bridges. this could take hours or even days to run to complete equilibrium.)

Yes I suppose that’s right: you could reduce the diffusion of H+ and OH- into each other’s presence by an intermediate reservoir of sodium sulphate. Also by making it a saturated solution, you could provide a reservoir of counterions to allow higher concentrations of H+ and OH- to be eventually reached. 

Edited July 22 by exchemist

[realflow100]

i started with a near-saturated solution. Not quite. to prevent precipitation from occurring too much.
but I think if you wanted you could mix/stirring in additional sodium sulfate as the concentration of sodium sulfate decreases with further conversion to sulfuric acid/sodium hydroxide.
I don't think that would be too necessary though if you only wanted a low molar concentration. (ph 1-2 is seemingly trivial to achieve even with a crude setup)

Edited July 23 by realflow100

[exchemist]

2 hours ago, realflow100 said:

i started with a near-saturated solution. Not quite. to prevent precipitation from occurring too much.
but I think if you wanted you could mix/stirring in additional sodium sulfate as the concentration of sodium sulfate decreases with further conversion to sulfuric acid/sodium hydroxide.
I don't think that would be too necessary though if you only wanted a low molar concentration. (ph 1-2 is seemingly trivial to achieve even with a crude setup)

Yes. To get to a molar acid concentration, i.e. pH ~0, might be a challenge, though - and of course there would still be metal cations present so it would be far from pure.  But I suppose it depends on what you want to do with it. 

Edited July 23 by exchemist

[realflow100]

Possibly. it probably just depends if the sodium sulfate participates or not in whatever your doing with the sulfuric acid. and specifically what sort of concentrations your dealing with.

[KJW]

One difference between using sodium sulfate and using magnesium sulfate is that the product magnesium hydroxide has very low solubility whereas the product sodium hydroxide is very soluble.

 

[exchemist]

2 hours ago, KJW said:

One difference between using sodium sulfate and using magnesium sulfate is that the product magnesium hydroxide has very low solubility whereas the product sodium hydroxide is very soluble.

 

That's an excellent point. So in the case of Mg there will be less tendency for the accumulating OH- ions to migrate through the pores and neutralise the accumulating acid. 

[realflow100]

Sodium hydroxide is also conductive. so the reaction can "continue" proceeding without needing to occasionally add more sodium sulfate. while magnesium hydroxide is essentially nonconductive.

Edited July 24 by realflow100

[exchemist]

3 minutes ago, realflow100 said:

Sodium hydroxide is also conductive. so the reaction can "continue" proceeding without needing to occasionally add more. while magnesium hydroxide is essentially nonconductive.

Yes but the ions will start migrating through and neutralising the the acid on the other side - unless you try your idea of the central reservoir of NaSO4 of course. 

But this is quite a fun thread. 👍

Edited July 24 by exchemist

[realflow100]

I didn't really notice any rapid reactions at the porous separator I used. I could leave the solution sitting and not much would happen. The ph did not really start to change with any significance on it's own even when I left it sitting for about an hour. it didn't really seem to undo any of my progress.
if there is any reaction it's probably quite slow. at least at these dilute concentrations. I imagine it might be more of an issue if someone tried to get higher concentrations.
The thing is. if sodium sulfate does form from neutralization. it stops reacting because sodium sulfate itself is a neutral salt and doesn't react with either sulfuric acid or sodium hydroxide. so depending on the size of the "neutralized" portion between the two compartments. it might slow down and stop reacting after some time. leaving the bulk of the two solutions relatively unchanged.
The way I set it up seemed to work as a fairly effective bottleneck in stopping or sufficiently slowing spontaneous reactions without an external force applied.

Edited July 24 by realflow100

[KJW]

On 7/24/2024 at 7:45 PM, realflow100 said:

Sodium hydroxide is also conductive. so the reaction can "continue" proceeding without needing to occasionally add more sodium sulfate. while magnesium hydroxide is essentially nonconductive.

But you need sodium sulfate or magnesium sulfate to be present for the reaction to continue because these provide the ions that are migrating across the salt bridge to electrically neutralise the hydrogen ions and hydroxide ions that are formed at the electrodes.

 

 

On 7/23/2024 at 11:29 PM, exchemist said:

That's an excellent point. So in the case of Mg there will be less tendency for the accumulating OH- ions to migrate through the pores and neutralise the accumulating acid. 

One other consequence of the low solubility of magnesium hydroxide is that the required voltage across the electrodes will be lower because the produced hydroxide ions will be removed from solution (Le Chatelier's principle).

 

 

Edited July 25 by KJW

[realflow100]

Sodium sulfate would likely constantly be replenished at the salt bridge because as sodium hydroxide and sulfuric acid meet. they form sodium sulfate again.
it could just be in an ever-tighter portion of the salt bridge as the concentrations rise?

Edited July 26 by realflow100

[exchemist]

1 hour ago, realflow100 said:

Sodium sulfate would likely constantly be replenished at the salt bridge because as sodium hydroxide and sulfuric acid meet. they form sodium sulfate again.
it could just be in an ever-tighter portion of the salt bridge as the concentrations rise?

I think this is a misunderstanding. The cations and anions move quite separately through the solution, in order to maintain electrical neutrality. You do not have “sodium hydroxide” meeting “sulphuric acid”. You have Na+, OH-, H+ and SO4- - ions, with different concentrations of each on either side, moving independently of one another. The 2 anions will migrate towards the anode in proportion to their concentration, ditto  the cations towards the cathode. The more H+ and OH- you generate, the greater the share they will take of the movement of ions needed to balance electric charge. So the more acid/base neutralisation you will get, as these ions meet.

[realflow100]

Theres no driving force between them though with a salt bridge dividing/separating them from one another? I dont see how I could be missing anything.
In my setup I didn't observe any sort of rapid neutralization between the two halves when the external supply was removed. They remained relatively stable even when sat for an hour while testing. the PH did not change significantly and I didn't observe any noticeable behavior at the salt bridge interface between the two compartments.
unless your trying to explain that the "salt bridge" would need to be enormous in length or size or something?
The two halves are not simply connected to one another directly. there is no easy path between them other than through the salt bridge.
Think of a typical cell using a salt bridge setup like zinc and copper salt solutions. No reaction occurs between them automatically because the salt bridge separates their charges preventing them from mixing/reacting with each other.
I don't see the problem with the setup.

Edited July 26 by realflow100

[realflow100]

Unless I've still completely missed something obvious. I don't understand.