Mining metals: wastes

[Tero]

A mine in Finland isolating nickel and copper managed to leak uranium from gypsum ponds.
http://www.stoptalvivaara.org/fi/newsstream.html
Canadian mine wants to pollute lake:
http://www.minesandcommunities.org/arti ... a=8730&l=1

Chinese dump tailings into sea.

How are the new processes better or safer than smelting? Smelting uses carbon to reduce metal oxides under heat.

[klr]

A mine in Finland isolating nickel and copper managed to leak uranium from gypsum ponds.
http://www.stoptalvivaara.org/fi/newsstream.html
Canadian mine wants to pollute lake:
http://www.minesandcommunities.org/arti ... a=8730&l=1

Chinese dump tailings into sea.

How are the new processes better or safer than smelting? Smelting uses carbon to reduce metal oxides under heat.

Uranium as a by-product? That will likely please some people, and enrage others.

Ah, I see Finland has nuclear power plants. At least the Uranium will get a good home.

And I thought the Chinese would have more sense by now.

[Tero]

Finland has no refining, so it probably goes to russia for that, as yellow cake.

Smelting has assorted wastes, SO2 etc
http://www1.ifc.org/wps/wcm/connect/469 ... 6a6515bb18

[Jason]

How are the new processes better or safer than smelting? Smelting uses carbon to reduce metal oxides under heat.

I don't know about 'safer', but the chemical process for gold is more efficient, or so I'm told. For instance, using aqua regia, you extract and refine in one process and you're left with 99.something% pure gold and a bunch of gravel. No muss, no fuss, no massive energy input required. The acids used in the process are reusable afaik as well.

[Tero]

Acids are not reusable. A large amount of industrial chemistry makes acids and bases
http://en.wikipedia.org/wiki/Sulfuric_acid#Manufacture

In 2004, world production was estimated at 60 million dry metric tonnes of sodium hydroxide
http://en.wikipedia.org/wiki/Sodium_hyd ... Production

[Jason]

I'll have to look it up, and I don't feel inclined atm, but it seems to me that the acids were said to be reusable when I was researching this stuff a few months back. Also it's not sulfuric acid or sodium hydroxide I'm talking about, but nitric and hydrochloric (when mixed the create aqua regia - the only acid that will dissolve gold I believe).

[Tero]

HCl production is the same. See wiki. When you neutralize HCl with NaOH you get NaCl. Not a useful chemical for mining. But you can dump it in the ocean.

[Jason]

Yeah, you're right.

[pErvinalia]

One of the problems with acid use in gold mines is that they need to store the acidic waste water in storage ponds. Fine in principle, but in practice the things can leak, and overflow in heavy rains. Acid mine drainage is a huge problem in the metals mining industry.