NaOH and increase the volume of material in solution

[yasin1987]

Hi
My English is not good. And I apologize for that.

I'm dealing with a rock mine and I came across something strange in my experiments.
Samples taken contain about 1 gram per kilogram of gold up to 40 ppm.
The ore contains Galena, pyrite, chalcopyrite and so on.
It can be said that it is a sulfide rock and it has many problems in this regard ...
We usually use sodium cyanide for initial testing. NaOH and lime are used to increase the pH. The initial pH is in the range of 6. Unlike other places, to increase the pH, more than normal NaOH should be consumed.
If used less, the pH remains in the same range of 6.

As NaOH increases, the volume of the soil suddenly increases and the solution suddenly turns into a paste.
I have not had this problem before.
What substances have I encountered?

 

[Deano]

Hard to tell from a description from a distance but it reads like you have a mix of clays and sulphates in your ore.

As the clays hydrate the addition of caustic will separate the platelets and cause an increase in soil volume.

This effect can be enhanced by gypsum formation from the sulphates and caustic.

The giveaway is the need for high caustic levels to increase pH, the soil is buffering the solution.

Assuming that the above is what is actually causing your problem you can minimise the effect by adding a crystal growth modifier at around the rate of 50 ppm to your solution before starting testing and pH control.

Go to a chemical supplier and see what he has in stock, you will not need much and it is fairly cheap, I do not know what brands you will have available but a decent chemical supplier should be able to help you.

Deano

 

[yasin1987]

Hard to tell from a description from a distance but it reads like you have a mix of clays and sulphates in your ore.

As the clays hydrate the addition of caustic will separate the platelets and cause an increase in soil volume.

This effect can be enhanced by gypsum formation from the sulphates and caustic.

The giveaway is the need for high caustic levels to increase pH, the soil is buffering the solution.

Assuming that the above is what is actually causing your problem you can minimise the effect by adding a crystal growth modifier at around the rate of 50 ppm to your solution before starting testing and pH control.

Go to a chemical supplier and see what he has in stock, you will not need much and it is fairly cheap, I do not know what brands you will have available but a decent chemical supplier should be able to help you.

Deano

Thanks for your helps.
I had read something about clay soils, but it was a mineral so I thought it was unlikely.

I did not understand the full name or chemical composition of this substance. Or the builder.
can you give more threads :G

 

[Deano]

Crystal growth modifiers are sold under that title by companies such as Nalco and Solvay who have a range under their Cyquest brand.

Contact your nearest chemical supply store and ask them for their recommendations from suppliers, try to stay with products from major companies as they will have the largest range to try.

Prices are cheap, if you can get samples to try in small scale you can always get larger amounts later.

Deano