# Pretreatment of gold sulfide cons



## montanacreations (Nov 25, 2015)

Hello all,
I have a couple questions I am needing help with. The cons I am wanting to pretreat is the courser part of my concentrates, +60 mesh, the smaller fraction will be going to another company for leaching. Separating the +60 mesh free gold from the sulfides has proven very difficult, the sulfides are really heavy and difficult to make a complete separation on a table. I would prefer to not crush these cons further do to sliming. I have experimented with roasting and acid pretreatment, but would prefer to avoid roasting if possible. Dilute sulfuric 30% or so seems to break down the sulfides well but need to treat fumes (hydrogen sulfide). I am not talking about large volumes, only a couple pounds at a time. The question I have is will cold 30% sulfuric convert silver sulfide to a sulfate and the same with the lead sulfide. If the sulfuric does convert sulfides to sulfates what would be a good temp to roast at to convert back to oxides, or is there a better way. Also would bubbling the off gasses through sodium hydroxide take care of the hydrogen sulfide. 

The make up of the cons from ICP-MS in ppm for just the larger %, I can list all if needed, Ag 1060, Al 2970, As 987, Bi 1580, Fe 117000, Pb 449000, S 108000, Te 397, Ti 40700, Zn 21100. I haven't had the larger mesh cons assayed, the -150 and smaller runs about 24oz gold. This ICP-MS result was from the smaller mesh cons,-150 mesh. I can have another run on the larger fraction if I need to. 

I would like to get these cons cleaned up enough to smelt is my goal, as you can see from the ICP-MS I have a lot of base metals that interfere with the smelt. I have experimented with direct smelting but not happy with the results, roasting before hand also and using different collector metals, silver, lead, Pbo etc. and several different flux recipes. I would prefer to not smelt with Pbo, cuppeling I would like to stay away from but can if I have to.
Thank you,
Cliff


----------



## Lou (Nov 25, 2015)

What's the head ore FIRE assay at?


Looking at your results I question the ICP-MS report because of the dilution required to get those numbers.

Of the opinion that given the As/Te levels roasting is indicated to remove those and at least most of the sulfur.
The high titanium levels (if your assay is to be believed, it's really kind of inappropriate to use MS for this work) will make smelting difficult, as TiO2 only really goes into CaF2 and cryolite.

My advice, get it homogenous and have inspectorate come sample it, then send the material overseas. If you talk to the nice Aussie chap at Legend Mining Supply, they might be able to broker this.


----------



## montanacreations (Feb 6, 2016)

Thanks for the reply Lou, sorry for the delay getting back to you, hit the books a little more. At this time we are not driving on the vein, just cleaning up tons of ore left by the old timers do to its very limited access back in the day. This was a un-oxidized free milling gold deposit and they left the bulk of the sulfides which a lot of the gold was associated with. The assays done on the ore varied greatly, probably do to the course gold. We have spent more time assaying our concentrates which are running about 24oz gold and about the same in silver on -100 mesh using a table. At this time not producing enough larger cons to justify sending overseas.
As far as further testing what would you recommend rather than icp-ms if the titanium levels are high, we have done a couple of different samples with similar high ti levels, these samples were done by two separate companies and run through a splitter etc., pretty representative of the cons. Is it the small amount used in a icp-ms that isn't a good representation? 
Have done more testing on the cons larger than 100 mesh, trying a reduction roast at around 1000f and following up with a oxidative roast at 1350f. That seemed to get rid of most the sulfur as it didn't react with a dilute sulfuric treatment. 
My goal I guess is trying to clean these cons up enough to either smelt or leach, am I thinking correctly as far as the roasting and sulfuric pretreatment to at least get rid of part of the iron and zinc etc., Or would a hcl pretreatment work better to also help remove some of the pbo. Not sure of exact reactions I am getting roasting say the lead sulfides, would the reduction roast take it to lead sulfate and then to lead oxide after oxidative roast? I also just tried treating some cons after roasting and sulfuric treatment with oxalic which seemed to remove a bunch of iron oxides, not sure if that's a real good idea or not, wasn't planning on using any nitric at this time, wasn't sure if the silver would be a problem as far as creating silver oxalate.
Any help from anyone on this would be greatly appreciated.
Thanks,
Cliff


----------



## Deano (Feb 6, 2016)

What you need to do first is to look at the treatment options available to you.

If you can get the cons toll treated at a smelter this is the easiest and cheapest way to go.

Selling the cons to a smelter is the next best option, you will just loose some of your profit.

Doing your own smelting is a recipe for every governmental agency to take a strong interest in what you are doing apart from the start-up and running costs of the smelter.

Add on the environmental and health factors and smelting is best left to a professional operator.

If you can get a cyanide permit it would be next on the list of treatment options.

Many sulfides will direct leach well with cyanide, a test should be carried out at a commercial metallurgical lab.

The standard test is a 24 hour bottle roll with a fire assay on the residue carried out on both milled and unmilled splits of the concentrate.

Assuming a positive leach result with cyanide, if you cannot get commercial access to cyanide or do not wish to cyanide process yourself the next option is to find someone who is doing cyanide leaching elsewhere.

The grade of your cons is high enough that you can send them a long way for treatment, the options are the same as for smelting above.

If neither smelting nor cyanide leaching are your treatment preference then the only alternative is non-cyanide leaching of some form.

The cheapest, simplest and safest of these leaches is neutral pH saline/hypochlorite leaching in a vat leach with carbon adsorbent, cyanide can also be run in such a vat.

Note that the above leach will be more expensive than a cyanide leach as hypochlorite will be expended on digestion of the sulfides.

It is still a lot cheaper than the iodine, bromine or thiocyanate leaches recommended by people who have not had to run them commercially and successfully themselves.

If you want I can detail for you how to set-up and run such a vat leach.

The problem with the titanium assays is that the multiplication factors are so high for the levels you have the the results really should be rated as indicative rather than precise.


Deano


----------



## montanacreations (Feb 6, 2016)

Thanks for the info Deano, it is appreciated. We do have a company in Idaho we are going to take the bulk of the cons to if it proves leachable with cyanide but they only want 60-70 mesh and down cons. Cyanide is banned here in Montana. We are just looking for preferably a means of leaching the larger cons 30-70 mesh or so, unless we can find someone to take them. If you know of any smelters that take smaller lots I would be very interested, just haven't heard of any. I need to get a few assays on the larger cons as it would run pretty high. We had just been testing small scale smelts but haven't been happy with consistent results and knew it would be a problem scaling up.
I would very much appreciate info on the saline/hypochlorite vat leach setup, that sounds very doable. We don't need a large setup, we are very limited to the tonnage we can remove from the property do to its location and time of year.
Thanks again,
Cliff


----------



## Deano (Feb 7, 2016)

You can easily turn your larger sized cons into smaller sized cons by just milling them.

It is standard practice to mill sulfide cons before cyaniding to improve recovery assuming that the cyanide is being run as CIP or CIL.

Get a lab to run the bottle roll tests on milled and unmilled cons for a range of milling sizes, this will tell you all that you need to know about cyanide recovery on your cons.

Standard milling sizes would be 100% passing 50 mesh, 100 mesh, 200 mesh, 300 mesh.

Preferably wet ball milled rather than ring milled to both minimise surface oxidation effects and replicate the method most likely to be used in full scale.

Deano


----------



## montanacreations (Feb 7, 2016)

Thanks Deano, I will check into a lab to run the tests. My concern has been over milling the free gold, there is a lot of free gold in the 30 to 70 mesh and have had trouble separating that from the sulfide. We currently are using a jaw and roll mill with a wave table with tight classification, and a small rod mill to regrind oversized, its looking like we need to go with another style of table to make a better separation I guess and a ball mill at some point. Its just me and my father and funds are tight, the wives think they need to see more gold before spending more money for some reason! 
Thanks again,
Cliff


----------



## Deano (Feb 8, 2016)

If you are wanting to separate free gold from sulfides on a well sized feed you need a Wilfley or similar type table.

Wave tables will not give you the clean separation you are looking for but you can very slowly and with minimal water pass the cons from a wave table over a Wilfley for clean separation.

The jaw and roll mill are what I would choose for milling in your circumstance.

The small rod mill is usually used for two stages of regrind for a small gravity circuit.

For the initial regrind the rods are single sized, this minimises the slimes produced and lost on tabling.

It is usual to then repass the feed through the rod mill with a set of graded rods to liberate the finer sulfides.

You then have to pass this material very slowly through your gravity circuit.

If you do not cost your time then this is usually worth doing.

It is usual for cons to be riffle split and have multiple assays done before being either sold to a leach plant owner or toll treated by same.

If the sulfides are cyanide leachable then the assays which show all of the gold in the cons are taken, with a recovery factor, to represent the cyanide recoverable gold whether this gold is free or in sulfides.

It may be easier to just have a bulk con leached and accept that the return will be lower in total rather than try to take out the free gold and just leach the sulfides.

Get the bottle rolls done so that you know what options you have.

Deano


----------



## montanacreations (Feb 8, 2016)

Much appreciated Deano, will get the tests done and go from there. When you say graded rods is that a mix of different sized rods? I have a lot to learn!
Thanks again,
Cliff


----------



## Deano (Feb 9, 2016)

A set of graded rods is a mix of different diameters.

Usually run as 1/2 largest rods, 1/4 half sized rods and 1/4 quarter size rods.

The above is indicative only, generally the finer you want to mill the more smaller rods are put in.

You may be OK with 2/3 full sized and 1/3 half sized, it all depends on the material and how fine you want to mill it.

You have to actually run a sample to see what you need.

Deano


----------



## montanacreations (Feb 9, 2016)

Thanks Deano, that makes a lot of sense, I had been running a mix and over sliming, had to really slow down the feed and was still loosing. Figured I would have to go to floatation to get it all and have saved the tailings. A lot to learn, I hadn't studied up on rod mills, just had an old one and put it to work with what rods we had, more science involved than I realized. Do you have an opinion on the MSI mining table, similar to a Gemeni , or is the wilfley the best option. I had been looking into the wilfley tables but was needing to talk with someone as far as best deck for what I am working with. A friend here just got in a small lab size and had the raised tapered riffles but hasn't got it set up to run yet.
Thanks again,
Cliff


----------



## Deano (Feb 9, 2016)

Flotation is fairly easy to do once someone has set up the circuit for you.

Small cells are usually available second hand, if you want to get all of the sulfides this is the way to go.

If you are happy with getting most of the sulfides then a very slowly fed table will do the job.

The Gemini type tables will get you a good con as far as recovery is concerned but they will not give you a clean con.

They are not good for recovery of fine sulfides, you cannot slow the flow rates down enough.

Always keep in mind that when flotation was invented there was a total shift from gravity to flotation.

This was mainly due to the large number of tables required to treat the fine end of a sulfide feed.

If you are sliming the sulfides then you need to both size your table feed carefully and run very low rates of ore over the fines table.

Control of the wash water is critical for the slimes fraction, I wrote a detailed description of how to apply wash water in my "Things that may be of interest to members" thread.

The raised tapered riffle type lab table deck is OK, there are hundreds of designs all of about similar ability to recover slimes.

The best deck I ever saw was made of a single piece of shot blasted glass, I was not sure that the high performance was worth the worry about it breaking.

Deano


----------



## montanacreations (Feb 10, 2016)

Thanks Deano, I appreciate your time spent helping and your Knowledge!
Cliff


----------



## kurtak (Feb 11, 2016)

I have enjoyed reading this thread :!: 8) 

Thanks for asking the questions Cliff & thanks for answering them Deano :!: 

I look forward to any further info that may result as you move ahead with your project Cliff 8) 

Kurt


----------



## montanacreations (Feb 11, 2016)

Thanks Kurt, I am sure I will have plenty more questions. The people and info this forum has to offer is invaluable, guys like Deano taking the time to share their wealth of information is very appreciated!
Cliff


----------



## rhwhite67 (Jul 10, 2017)

Its a pain in the neck but it does work. You can kill the sulfide with excess nitric. fine grind and then place all of your cons into a 10% cold nitric solution slowly warm while stirring. The nitric will destroy the sulfides leaving behind all of your Au and the metal powder from your sulfides ore component. Rinse thoroughly and then leach with normal process as shown on the forum for separating the Au etc.
I've done it. It works. Make sure to do it in a good fume hood. Its nasty. 
P.S. Add a small amount of Hydrogen Peroxide to your nitric it will help suppress the fumes by oxidizing the Nitrous fumes back into Nitric while they are still in solution and it will also make your nitric go further. There is a post on the forum somewhere about doing this look it up and follow the info. it works and makes it a lot less nasty to do.
Rom


----------



## Kustommolds (May 14, 2019)

montanacreations said:


> Much appreciated Deano, will get the tests done and go from there. When you say graded rods is that a mix of different sized rods? I have a lot to learn!
> Thanks again,
> Cliff



I have access to cyanide and nitric. I can process your cons if needed


----------



## galenrog (May 14, 2019)

Montanacreations has not logged in since August, 2016. I do not think he is going to see your post.


----------



## ashir (Jun 5, 2020)

rhwhite67 said:


> Its a pain in the neck but it does work. You can kill the sulfide with excess nitric. fine grind and then place all of your cons into a 10% cold nitric solution slowly warm while stirring. The nitric will destroy the sulfides leaving behind all of your Au and the metal powder from your sulfides ore component. Rinse thoroughly and then leach with normal process as shown on the forum for separating the Au etc.
> I've done it. It works. Make sure to do it in a good fume hood. Its nasty.
> P.S. Add a small amount of Hydrogen Peroxide to your nitric it will help suppress the fumes by oxidizing the Nitrous fumes back into Nitric while they are still in solution and it will also make your nitric go further. There is a post on the forum somewhere about doing this look it up and follow the info. it works and makes it a lot less nasty to do.
> Rom



Will this not also take some pgms?


----------



## Paul goldbugg (Jan 1, 2023)

Kustommolds said:


> I have access to cyanide and nitric. I can process your cons if needed


You still processing cons


----------



## payamk903 (Jan 2, 2023)

rhwhite67 said:


> گردن درد دارد اما کار می کند. شما می توانید سولفید را با نیتریک اضافی از بین ببرید. خوب آسیاب کنید و سپس تمام مواد مضر خود را در محلول نیتریک 10 درصد سرد به آرامی گرم و در حین هم زدن قرار دهید. نیتریک سولفیدها را از بین می‌برد و تمام طلا و پودر فلز حاصل از جزء سنگ معدن سولفید را از بین می‌برد. همانطور که در انجمن برای جدا کردن طلا و غیره نشان داده شده است، کاملاً بشویید و سپس با فرآیند معمولی شستشو دهید.
> من انجامش داده ام. کار می کند. مطمئن شوید که این کار را در یک هود خوب انجام دهید. زشت است
> PS مقدار کمی پراکسید هیدروژن را به نیتریک خود اضافه کنید، با اکسید کردن دودهای نیتروژن به نیتریک در حالی که هنوز در محلول هستند، بخارات را سرکوب می کند و همچنین باعث می شود نیتریک شما جلوتر برود. یک پست در انجمن در جایی در مورد انجام این کار وجود دارد و آن را جستجو کنید و اطلاعات را دنبال کنید. کار می کند و انجام آن را بسیار کمتر تند و زننده می کند.
> رام


ممنون از مطالب مفیدتون


----------



## payamk903 (Jan 2, 2023)

Thank you for your useful content


----------

