Is CuFeS2 or CuFeSO4 harmful???????

[Comon]

Hello all.

 

Some friends of mine are concerned about a future potential mining operation in their forest and near their country town via copper iron sulfide. This ore is going to be extracted and trucked through the town and pristine forest. The concern stems from someone's assertion that CuFeS2 can be oxidised to CuFeSO4. I'm concerned that in acidic moist air, hydrogen sulfide may evolve.

 

I don't understand this in terms of oxidation numbers because it seems to me that copper's oxidation number doesn't change in going from the CuFeS2 to CuFeSO4.

 

Is it because of the aquisition of oxygen that copper iron sulfide is considered to oxidise into copper iron sulfate?

 

More importantly what enviromental chemical issues would be created by the introduction of the CuFeS2 as airborne dust and spillage and the dissolvable "oxidised form" of CuFeSO4 into a forest and nearby township?

 

Any useful comments, chemically based or in terms of consequences to a forest (eucalypt)environment and a township of people through which the trucks will roll would be appreciated.

 

Thank you again.

[YT2095]

Simple answer Yes!

 

all copper salts are toxic at a certain dosage.

[John Cuthber]

Everything is toxic, to some extent. Copper and iron compounds are unusual in that they are needed by the body in relatively large amounts ( a few grams of iron and a few centigrams of copper) but are quite toxic when present in excess.

 

Anyway, you are right in thinking that the oxidation state of the copper and iron son't change, but look at the sulphur.

As for the effect on the environment it will depend greatly on how the stuff is worked with. Obviously, if it's transported carefully in sealed trucks then there's less of a problem than if it's left to blow about the place.

[Comon]

What could change CuFeS2 to CuFeSO4 in the environment, and how could I determine both of their solubilities please?

[YT2095]

well SO4 is a -2 oxidation state and so the Copper and Iron would both have to be +1 oxidation state.

 

now I must admit I have never hears of such a metal complex as a Sulphate either.

 

you used S2 so that says that both the Iron and Copper are both in the +2 oxidation state.

 

as for a Mechanism to alter this???

 

Hydrolysis of the sulphides would Probably go some way towards it, but I can`t really say from there, sorry.

 

also quite a few D block metal sulphides are nearly insoluble, so that would show quite easily, your CuFe complex as a sulphate should dissolve reasonably well, but the problem then is that the Fe+ and Cu+ and the SO4- belong to nothing in particular, so you would probably get a mixture of Copper(ii) sulphate and Iron(ii) sulphate if you tried to re-crystalise it.

[insane_alien]

http://www.mindat.org/min-955.html

 

there isn't any data on it's toxicology. doubt it's soluble as well.

 

why don't you give it a shot an see try dissolving some of it in hot water.

 

it oxidises in air but i can't find any reference to H2S evolving from it.

 

from the looks of it the most severe damage is going t obe caused by the actual act of excavation rather than the excavated materials.

 

i can't find any references to ecological damage from CuFeS2 dust from any other quarries either.

[YT2095]

I just googled the CuFeSO4 you mentioned (I`ve never heard of it before) and it Does give some hits here: http://www.google.co.uk/search?q=cufeso4&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-GB:official&client=firefox-a

[John Cuthber]

I think FeCuSO4 should be written as (Cu/Fe)SO4 ie a mixed Fe and Cu sulphate (both as 2+ ions). Made by oxidation of the similar mixed sulphide/ pyrites mineral. The most likely oxidising agent is a mixture of water and air. If I'm right about that then it's soluble in water. The sulphide isn't.

[Comon]

Insane Alien, I don't have any access to the ore but I know that metal sulfides evolve H2S in acidic conditions. Is that too simplistic a view?

[YT2095]

if you wanted to make H2S from a metal sulphide then yes, dropping it in some acid would be a good place to start

[Comon]

Would CuFeS2 dust, that comes off the trucks, react with slightly most and acidic soils to evolve H2S?

 

I'm interested in how CuFeS2 can be oxidised (S in a moist and slightly acidic environment (from 2- to 6+ ?)

 

I'm not sure of the half equations.

 

however for S2 to SO4,

 

S24-(s) +8H2O(l) → 2SO42-(aq) +16H+(aq) +16e-

 

and

 

2H2O +2e- → H2(g) + 2OH-(aq)

 

So overall,

 

Cu2+Fe2+S24-(s) +24H2O(l) → Cu2+Fe2+2SO42-(aq) +16H+(aq) +8H2(g) + 16OH-(aq)

 

With H+ not being mopped up completely H2S may be evolved in acidic moist soils, right?

 

Hypothesis: Cu2+ free ions enter the soil in moist conditions and H2S will be evolved if the soils are moist and acidic.

[insane_alien]

it may be evolved but i really doubt there will be any great quantity of it. acidic soil, isn't really all that acidic and CuFeS2 is pretty insoluble. it woud take a LOT of dust and a LOT of soil and a LOT of time for a decent amount of H2S to evolve. since there is likely wind unless you are living at the bottom of a mine shaft the H2S will blow away. not to mention that most probably it will react with something in the process.

 

also, your equations are wrong, CuFeS2 is a single compound not a mixture of compounds.

[John Cuthber]

"CuFeS2 is a single compound a mixture of compounds."

Pardon?

[insane_alien]

should read 'CuFeS2 is a single compound not a mixture of compounds'

 

brain got ahead of my fingers there

[Comon]

I'm treating it as a single compound; I'm just showing oxidation numbers for most of the critical species in the overall equation.

[John Cuthber]

Actually I'm not sure about CuFeS2. I think it's a single (though probably non stoichiometric) compound.

http://en.wikipedia.org/wiki/Chalcopyrite

Iron pyrites is FeS2. I think you could get substitution of Fe(II) by Cu(II).

 

And I'm not offering to give a balanced equation for oxidation of that in air. Some H2S will be lost, some SO2 probably would be too. I'm not ruling out S8 as a possible product.....