Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction 2017-04-04T06:57:36+00:00
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Oxide Copper Recovery (8 replies)

SDHILLBILLY
6 months ago
SDHILLBILLY 6 months ago

I have been experimenting with direct smelting and sulfuric acid leaching/electrowinning of oxide copper/silver ores on my property. My great grand father used direct smelt 150 tons per day. I Would like to setup a pilot process of 4 to 8 tons per day. With the cost of acid,electric,equipment etc. is it better to just direct smelt to produce dore? The ore averages 9.2% cu with lows of 3% and highs of 32% copper, depending on which type of ore and vein. Silver 5.75oz. average .08 gold. Here are some pics. of ore, assays and metal.

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AJNeale
6 months ago
AJNeale 6 months ago
1 like by David

How can I not resist replying to a question from someone called SD Hillbilly!!!  The difference between what you want to do, and what your grand-daddy did, is an inconvenient problem known as permitting.  Even in the backwoods of Montana (I'm guessing, based on the assay lab being based in Norris, MT) you'll need a permit or a series of permits, regardless of which processing option you choose.  Whether you go smelting or acid leach will depend on capital and operating costs, size of the deposit, etc.  One low-cost option you might consider is hand sorting to produce a high grade product that you can sell directly to a smelter.  This is assuming that the gold and silver is associated with the copper, then you can crush the material, lay it out on a picking table (a slow moving conveyor belt), and get a few of the locals to simply hand-pick the copper mineral from the rest of the rock.  The trick here is to find someone to buy your product.  There used to be lots of small smelters in MT, but I think most of them are shut down.  The big copper smelters (Kennecott, Freeport, etc.) usually aren't interested in taking small lots, and if they do they may not give you very good terms.  You should also keep in mind that direct smelting will make a copper matte which in turn needs to be sold to a copper refiner, and copper metal produced from leaching and electrowinning may not be saleable at full value because it won't be "four nines" certified, i.e. pure copper metal.  Also remember that the acid leaching won't recover the gold or silver.  So lots to think about.  Before you make too many decisions, make sure you can sell the product you are going to produce.  Good Luck - Andrew

SDHILLBILLY
6 months ago
SDHILLBILLY 6 months ago
1 like by David

Thanks for the reply I'm actually in the Black Hills of South Dakota. No assayers here. I just use Norris for gold,silver and copper( I've known him for 27 years), and ALS for 64 elements and pgms. I have a 5000 ton bulk sample permit. My family has been here since 1874 so I have good grandfather rights. Permits don't seem to be an issue.The ground was patented in 1900. There are around 97,000 tons at or near the surface (within 25 feet), so I'm just looking at cleaning up the dumps now. School of Mines here did preliminary feasibility study a few years back.They have been studying here off and on since 1888. I'm just trying to set up for a feasibility study. You're absolutely right...shipping raw ore to smelters is too complicated with the volume, min. grade, deductions etc. Yes, that test in my previous post is my copper matte from direct smelt. All of the smaller refiners so far don't want the copper, just the noble metals. 1 idea I've done a little testing with is direct smelt, pour anode, then electrorefine copper out, leaving slime to ship? But man that's slow. Another thing I've done is leach out oxides ( very quick reaction), and gravity the leach tails. It seems to clean up the native metals and gets the oxides out of the way. The oxide ore is mainly malachite,azurite,and chrysocolla. I also made copper sulfate. They will pay 50% to 70% of assay on that (?)...two ton minimum.  Here's a pic of the metal from that previous assay I posted.

metal pieces
https://www.911metallurgist.com/wp-content/uploads/2017/02/metal-pieces.jpg
Javier Ramirez
6 months ago
Javier Ramirez 6 months ago

Dear SdHillBilly,

An R&D company in Mexico has developed a gravity concentrator system that may work very well for separating your Cu/Ag values from your ore.

The idea is to crush/grind the ore in order to liberate the Cu and Ag oxides, then feed to a two-stage gravity conc system. The bulk concentrate, then subjected to acid leaching and Cu cementation; the tailings could then be washed and cyanided for Ag recovery, or else, directly smelting.

Best,

Javier Ramirez, Ph.D., M.Eng.

AJNeale
6 months ago
AJNeale 6 months ago
1 like by David

It's an interesting problem, not from a technical perspective, but from an economic perspective, i.e. can you make a saleable product that you can sell at a profit?  The bulk of the value is in the copper, so you need to go after that first.  One option is acid heap leaching and direct electrowinning (contact Ian Ewart at Electrometals to see if his system is applicable) to produce copper metal.  How you go after the silver is a function of how much residual copper is in the tailings as residual copper oxides will consume a lot of cyanide (if you go that route), and some silver minerals are not that amenable to gravity recovery (i.e. native silver is rarely found in nature, unlike gold), etc., etc.  Feel free to contact me by e-mail (see my profile) for some other ideas.  Best Regards - Andrew 

SDHILLBILLY
6 months ago
SDHILLBILLY 6 months ago

That has been and still is my biggest problem to solve: finding a buyer for small quantities. That's the main reason I haven't put together a system yet. Not sure what product to make that is profitable.  I don't know what type of silver it is, but it does show up in copper sulfate crystals, unless my testing got contaminated. It has been suggested that I add salt to preg. solution to drop silver. I did 5 gallons, but have not filtered it. I am starting with 40% to 60% sulfuric acid at room temp. Here's a test of copper sulfate crystals and electrowinning slimes. Thanks for info

 

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SDHILLBILLY
6 months ago
SDHILLBILLY 6 months ago

I went digging though some older tests.This might help. I think most of the silver is Ag2o.The thing that's funny about this test is the Au2o3. SDSM&T did four tests that showed pink Alunite, grey and purple Kaolinite, and white Halloylite. This type of rock is very abundant here.

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SDHILLBILLY
6 months ago
SDHILLBILLY 6 months ago

Just thought I'd put this up. It's a shipment report of the copper matte my great grandpa made.

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David
6 months ago
David 6 months ago

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