Sciencemadness Discussion Board - Obtain different sulfates from gypsum?

Obtain different sulfates from gypsum?

Alquimia - 11-10-2017 at 08:33

Perhaps the title confuses you, I will explain better:

I want to obtain copper sulphate, nickel sulphate and sulfo-aluminate (alum) of any metal, from gypsum, since gypsum is calcium sulphate.

I would like to know if there is any more or less simple method (based on ion exchange or something similar) to obtain these sulfates.

The methode of manufacture that I search should not make use of non-commercia usuall substances (such as nitric acid, etc), since the objective of making different sulfates from gypsum is to avoid the use of sulfuric acid or others substances hard to obtain/manufacture.
Electrolysis is accepted.

[Edited on 11-10-2017 by Alquimia]

MrHomeScientist - 11-10-2017 at 08:54

I'd expect pulling the sulfate ion off CaSO4 to be very difficult. It's extremely insoluble, and tough to get it back into solution. I think CaCO3 is even more insoluble, so you could try mixing finely powdered gypsum with a carbonate solution and stirring for several hours. Some of the sulfate will go into solution over a long time. It'll be hard to tell, though, since the carbonate and sulfate are both white powders. Test the liquid after a while by adding a drop of calcium chloride solution and seeing if anything precipitates.

Alquimia - 11-10-2017 at 09:25

Carbon is more electropositive than sulfur (and calcium is more electropositive than nickel, copper, aluminium...).

I would say that the reaction will be extremelly slow (if endothermic) or non-spontaneus, since calcium will go where there is more electronegativity (to sulphur).
Will it work really?

Could I use copper, nickel and aluminium chlorides instead of carbonates (it is easier of obtain for me)?

[Edited on 11-10-2017 by Alquimia]

MrHomeScientist - 11-10-2017 at 09:57

I think solubility will be the main driver here, not electronegativity. I haven't found exact values, but CaS is commonly cited as "slightly soluble" which I infer is more soluble than CaSO4's known very low solubility. Meaning nothing would happen when mixing gypsum with a soluble sulfide. But if you have the reagents, feel free to experiment.

The point of using carbonates is that calcium carbonate is very insoluble, so the sulfate ion will go into solution.
CaSO4(s) + CO32- == CaCO3(s) + SO42-

Chlorides won't have any effect. You would need a soluble carbonate salt, or a way to gas the solution with CO2. Either way, it's going to take a while.

Depending on what exact sulfates you are trying to make, some can be found in common products. Root killer for septic tank systems, for example, is copper sulfate.

violet sin - 11-10-2017 at 19:56

gypsum + steel. I know from continued occurrence, drywall mud will turn green/black around the steel mixing spade overnight. When you pull it up to break clumping before a mix in the morning, it's always colored. I had assumed it was iron sulfate and iron oxide. The spade/paddle get superficial corrosion easily when pulled out and dried, indicating abrasive and chemical reactions attack freshly exposed iron. They are galvanized, so that probably has an impact.

This probably helps very little, but it's a common sight to me, perhaps the green coloration is promising. It doesn't stay green if the mud dries. Wonder what copper powder would do overnight in some? Would it be leachable? After boiling with Epsom salt? Pretty low tec but that just means easy to check.

j_sum1 - 11-10-2017 at 21:52

There are easier sulfate sources than gypsym.
Epsom salt is available everywhere.
Copper sulfate is not too hard to come by - root killer or pottery supplies.
Manganese sulfate is an (unusual) otc item in the fertiliser aisle of my hardware store.
You can also make it by reaction of sulfur dioxide with battery paste. SO2 from burning sulfur.

Any of these would be a better start point.

ave369 - 11-10-2017 at 23:52

Boiling gypsum with sodium carbonate totally works, though you have to boil it for a long time, preferably under reflux. However, car battery acid is a much more convenient source of the sulfate ion, and it is available in any car parts shop. It is 36% sulfuric acid.

[Edited on 12-10-2017 by ave369]

MrHomeScientist - 12-10-2017 at 05:59

Quote: Originally posted by violet sin

gypsum + steel. I know from continued occurrence, drywall mud will turn green/black around the steel mixing spade overnight. When you pull it up to break clumping before a mix in the morning, it's always colored. I had assumed it was iron sulfate and iron oxide. The spade/paddle get superficial corrosion easily when pulled out and dried, indicating abrasive and chemical reactions attack freshly exposed iron. They are galvanized, so that probably has an impact.

I'd hypothesize that's just the iron rusting due to the moisture in the mud. To know for sure, of course, you'd have to test the colored substance for sulfates.

violet sin - 12-10-2017 at 12:17

Challenge accepted.

NEMO-Chemistry - 12-10-2017 at 12:25

Sorry for being stupid, but what is drywall mud?

unionised - 12-10-2017 at 12:48

If you reflux gypsum in a solution of ammonium carbonate (you will need a good condenser) you will convert at least some of it to ammonium sulphate and calcium carbonate.
If you filter off the calcium salts and then dry down the solution the excess ammonium carbonate will sublime and you will get ammonium sulphate.
If you heat that with iron oxide you should get ammonia and iron sulphate.

This is vastly more trouble than it is worth, since iron sulphate can be obtained as a moss killer.

violet sin - 12-10-2017 at 16:33

Mud used in the construction field for seamwork on drywall. Aka, gypsum mud for use on gypsum board. The panels come 4' x 8' and are taped together on the joints with the mud.

It is corrosive, abrasive and not much fun. Now, when I say corrosive, I mean it will rust metals at least superficially. Dust left after sanding will settle on clean copper pipes causing a patina when it absorbs moisture from the air. It will cause rust spots on exposed nailheads, brackets, non-stainless steel. The nails we use are galvanized, or phosphated as well as oiled usually. When a nail is sunk to depth with a hammer, the resulting scuff through that coating will rust.

Point is we use a lot of stainless and aluminum tools. There is more than gypsum in the mud and board, so it's not a strictly fair comparison to the accessible mineral. My idea was to use snack sized sandwich bags to test small amounts of copper scrap and metal bits from the bottom of our tub of screws. Maybe a piece of standard steel.

I'm fairly certain there is some free sulfate in the mix, and that more is involved in this corrosion from the bulk material. I have access to calcium chloride, to check for sulfate. Figure mud plus water mixed and decanted after settling will show a cloudy salute if the chloride is dropped in forming basically gypsum. Frankly, that seems like a waste of time but I'll try it. Not like the rest of this group here has the materials just sitting in the truck outside.

I'm not gonna race to get this done, busy guy. But I will throw a touch of time at it and report back with any observations. Remember I work~ 200mi from home so my equipment isn't just in the other room. Only have what my curiosity demands I bring with me... On the off chance of science

few chems and some electronics stuff.

vmelkon - 16-10-2017 at 18:38

I don't suppose you have an easy way of reaching high temperatures?
CaSO4 + SiO2 → CaSiO3 + SO3
That probably requires over 1000 °C.

Another one:
https://chemiday.com/en/reaction/3-1-0-3980
"Calcium sulfate react with carbon monoxide to produce calcium sulfide and carbon dioxide. This reaction takes place at a temperature of 600-800°C."

and probably this would work as well at high temp:
CaSO4 + 2 C → CaS + 2 CO2