Further things which may be of interest to members
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The role of the HCl is to provide a chemical removal of metals from the gold particles to then allow gold solvents such as cyanide and aqua regia to access the gold.
It is not there as a diluent.
The size of the gold particles left in the slag after gravity separation on a table is effectively all less than 10 microns, good luck in getting any form of concentrator to efficiently operate on them.
As a special bonus the gold particles at this sizing have a strong bonding effect with the slag, they are not floating around as free particles.
You thus have a lot of slag particles with ultra fine gold attached, this is a leaching proposition not a gravity separation proposition.
Deano
It is not there as a diluent.
The size of the gold particles left in the slag after gravity separation on a table is effectively all less than 10 microns, good luck in getting any form of concentrator to efficiently operate on them.
As a special bonus the gold particles at this sizing have a strong bonding effect with the slag, they are not floating around as free particles.
You thus have a lot of slag particles with ultra fine gold attached, this is a leaching proposition not a gravity separation proposition.
Deano
cuchugold
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- Oct 25, 2017
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This explains a lot. Thanks Deano. So, for example one could have a 100 gr per Ton (about 3 Oz) gold in ore, and if the gold is in minus 10 microns sizes, it'd be both difficult to detect properly in classical fire assays, and even more difficult to recover, especially if a lot of clay is present. Correct?.
Do not confuse the gold residual in slag with similarly sized gold particles in an ore.
The gold in slag was formed in an environment of heavy base metal contamination during the smelt and was thus contaminated with metal coating.
The gold in an ore was formed in a much less metallic environment, even ores with high metal levels do not have the concentration range of metals in slag.
It is obviously possible to have an ore which is full of base metals which will greatly affect the fire assay but over the centuries methods have been devised to modify these assays for better gold recoveries.
Unfortunately there is now financial pressure on assay labs so that to do any assay apart from a standard fire assay is very expensive and the knowledge base is shrinking rapidly.
Carrying out these assay methods on slag will not get you much return, the damage has been done during the smelt.
Recovery of less than 10 micron sized gold particles is purely a leaching proposition.
You will always recover some gold particles by gravity no matter what method you use, what becomes important is what percentage of gold you have recovered.
You do not find any of the gravity device sellers offering a bulk cyanide leach on your gravity tailings so that you can get precise numbers on your percentage recovery.
Deano
The gold in slag was formed in an environment of heavy base metal contamination during the smelt and was thus contaminated with metal coating.
The gold in an ore was formed in a much less metallic environment, even ores with high metal levels do not have the concentration range of metals in slag.
It is obviously possible to have an ore which is full of base metals which will greatly affect the fire assay but over the centuries methods have been devised to modify these assays for better gold recoveries.
Unfortunately there is now financial pressure on assay labs so that to do any assay apart from a standard fire assay is very expensive and the knowledge base is shrinking rapidly.
Carrying out these assay methods on slag will not get you much return, the damage has been done during the smelt.
Recovery of less than 10 micron sized gold particles is purely a leaching proposition.
You will always recover some gold particles by gravity no matter what method you use, what becomes important is what percentage of gold you have recovered.
You do not find any of the gravity device sellers offering a bulk cyanide leach on your gravity tailings so that you can get precise numbers on your percentage recovery.
Deano
In a totally different topic which may have relevance with the northern hemisphere summer approaching, here is an experiment which someone may wish to try.
Get access to a hedge or similar of English lavender, what you are wanting is a location where you can put a pot plant and have the pot plant surrounded with the lavender, it is important that the pot plant is immediately adjacent to the lavender, not one or two metres away.
Plant strawberries in the pot plant, the varieties appear to not matter.
When the strawberries are ripe they will have a pleasant subtle taste of lavender.
I presume that the taste comes from scent molecules transferring from the lavender to the berries, not from cross pollination by the many bees present.
Deano
Get access to a hedge or similar of English lavender, what you are wanting is a location where you can put a pot plant and have the pot plant surrounded with the lavender, it is important that the pot plant is immediately adjacent to the lavender, not one or two metres away.
Plant strawberries in the pot plant, the varieties appear to not matter.
When the strawberries are ripe they will have a pleasant subtle taste of lavender.
I presume that the taste comes from scent molecules transferring from the lavender to the berries, not from cross pollination by the many bees present.
Deano
An area which people who are performing electrowinning are often not familiar with is that DC power sources can give an incorrect readout under some conditions. These conditions usually, but not always, involve the presence of chelates in the electrowinning liquor.
The digital readouts can be up to 2v below true voltage across the plates, around 0.5 volts is common.
The only way to ensure that the wanted voltage is actually applied is to use a multimeter as a check source.
Note that when the voltage is reading incorrectly the amperage will also read incorrectly, you have to actually put the multimeter inline to get the true amperage value.
Nothing worse when thinking you are applying 1volt to the plates and you see massive bubbling from the plates, this indicates water splitting on a large scale and is not going to happen at a true 1 volt output.
Deano
The digital readouts can be up to 2v below true voltage across the plates, around 0.5 volts is common.
The only way to ensure that the wanted voltage is actually applied is to use a multimeter as a check source.
Note that when the voltage is reading incorrectly the amperage will also read incorrectly, you have to actually put the multimeter inline to get the true amperage value.
Nothing worse when thinking you are applying 1volt to the plates and you see massive bubbling from the plates, this indicates water splitting on a large scale and is not going to happen at a true 1 volt output.
Deano
Thank you Deano for this observation.
Would cyanide be among the chelants demonstrating this effect?
Seeing as electrical circuitry is not my strong suit please allow me to ask for clarification. This is a typical sketch off the internet of an electroplating circuit. Electrowinning may exhibit more anodes and cathodes but the principle is the same.
Where would you place the multimeter on this sketch for the check?
Would cyanide be among the chelants demonstrating this effect?
Seeing as electrical circuitry is not my strong suit please allow me to ask for clarification. This is a typical sketch off the internet of an electroplating circuit. Electrowinning may exhibit more anodes and cathodes but the principle is the same.
Where would you place the multimeter on this sketch for the check?
There are no hard and fast rules regarding the types of chelates which show this effect, you actually have to check each solution type in use as the effect also has variability according to the metals present.
Most of the commercial type EW power sources are designed to avoid this effect giving false readings but some of the cheaper units are susceptible.
Smaller lab type units are much more susceptible, even more so if EW direct from a pulp is practiced.
In the sketch shown you just have to put the multimeter probes across the anode and cathode bus bars and compare the reading with that shown on the power source readout.
Deano
Most of the commercial type EW power sources are designed to avoid this effect giving false readings but some of the cheaper units are susceptible.
Smaller lab type units are much more susceptible, even more so if EW direct from a pulp is practiced.
In the sketch shown you just have to put the multimeter probes across the anode and cathode bus bars and compare the reading with that shown on the power source readout.
Deano
One of the more useful bits of lab equipment is a vacuum filter.
The one I use was put together by a commercial engineering workshop but anyone who has access to a lathe or is willing to part this out can put together a unit similar to this.
Mine was made from a length of 200mm diameter 316 stainless steel pipe and the flange was made from a piece of 20mm thick 316 ss plate.
These dimensions were chosen because the bulk of my filtrations use a 250mm diameter filter paper.
Smaller diameter pipe can be directly scaled for smaller diameter filter papers however filters larger than 200mm pipe will require a centre support for the stainless punched plate.
I use this filter for all filtrations except where active aqua regia or hot slow filtering hydrochloric acid liquors are involved.
10 years use has shown little corrosion however I do take care to rinse out the base with water after using chloride liquors.
The main thing about this unit is the ease of use, you can change filter papers in seconds and the upper section which contacts the pulp can be simply rinsed off under a tap.
There are many designs which can be used to locate the upper section centrally over the bottom section, I prefer the 4 pillar system but others have used angled outer locaters with success.
If anyone is interested I will put the dimensions in another post.
Side view of the unit showing the vacuum system from the filter through a vacuum flask and a vacuum pump.
General side view
Closer side view showing the slope of the bottom section.
Top view of the bottom section showing the o ring and circle of ss punched plate
View of the base with the ss punched plate removed
Deano
The one I use was put together by a commercial engineering workshop but anyone who has access to a lathe or is willing to part this out can put together a unit similar to this.
Mine was made from a length of 200mm diameter 316 stainless steel pipe and the flange was made from a piece of 20mm thick 316 ss plate.
These dimensions were chosen because the bulk of my filtrations use a 250mm diameter filter paper.
Smaller diameter pipe can be directly scaled for smaller diameter filter papers however filters larger than 200mm pipe will require a centre support for the stainless punched plate.
I use this filter for all filtrations except where active aqua regia or hot slow filtering hydrochloric acid liquors are involved.
10 years use has shown little corrosion however I do take care to rinse out the base with water after using chloride liquors.
The main thing about this unit is the ease of use, you can change filter papers in seconds and the upper section which contacts the pulp can be simply rinsed off under a tap.
There are many designs which can be used to locate the upper section centrally over the bottom section, I prefer the 4 pillar system but others have used angled outer locaters with success.
If anyone is interested I will put the dimensions in another post.
Side view of the unit showing the vacuum system from the filter through a vacuum flask and a vacuum pump.
General side view
Closer side view showing the slope of the bottom section.
Top view of the bottom section showing the o ring and circle of ss punched plate
View of the base with the ss punched plate removed
Deano
That's because you live in Australia. It's a well known fact that it's upside down. After all, it's called Down under. :mrgreen:Deano said:
Göran
Nice design,
A few questions.
The filter paper is sealed by sandwiching it between two O rings rather than having suction pull it to the plate? If that is the case it allows for more filtration area because the smooth area on a Buchner funnel is where the paper seals but makes the effective diameter less. Your holes for filtration extend all the way to the edge of the inside diameter.
One thing I like about this design is the filter paper is actually clamped in place which prevents solids from sneaking under the paper to porcelain seal on a typical Buchner, which happens all too often. The down side is it takes longer to change a paper because it needs to be disassembled and re-assembled. A small price to pay for only having to filter once!
Where is the outlet for suction, I don't see it on the pictures? Do you actually draw from the bottom of the slope so all the filtered liquid is sucked into the flask? Or is the flask a trap to prevent liquid from entering the vacuum pump?
I would think off the shelf PVC flanges like these, https://www.usplastic.com/catalog/item.aspx?itemid=26315 would also work. They have an O ring groove as well and with PVC construction they would be good to filter acids. A tabletop Buchner is pricey, even the plastic ones, this seems an affordable alternate.
Thanks for posting this.
A few questions.
The filter paper is sealed by sandwiching it between two O rings rather than having suction pull it to the plate? If that is the case it allows for more filtration area because the smooth area on a Buchner funnel is where the paper seals but makes the effective diameter less. Your holes for filtration extend all the way to the edge of the inside diameter.
One thing I like about this design is the filter paper is actually clamped in place which prevents solids from sneaking under the paper to porcelain seal on a typical Buchner, which happens all too often. The down side is it takes longer to change a paper because it needs to be disassembled and re-assembled. A small price to pay for only having to filter once!
Where is the outlet for suction, I don't see it on the pictures? Do you actually draw from the bottom of the slope so all the filtered liquid is sucked into the flask? Or is the flask a trap to prevent liquid from entering the vacuum pump?
I would think off the shelf PVC flanges like these, https://www.usplastic.com/catalog/item.aspx?itemid=26315 would also work. They have an O ring groove as well and with PVC construction they would be good to filter acids. A tabletop Buchner is pricey, even the plastic ones, this seems an affordable alternate.
Thanks for posting this.
I was thinking the same as 4metals, before I read his post. That funnel is genius and I want one. I have some 4 inch pvc and some 10 inch, just nothing in between. I will be shopping tomorrow though. I would appreciate all the info I can get on it.
There is only one o ring which is permanently set in the groove in the base.
The filter paper is clamped between the bottom of the top section steel edge and the o ring in the base.
The clamping is purely by gravity so the disassembly is quick and easy.
You would need a larger piece of plastic pipe on the top section to provide the weight for clamping.
The weight of the top section is 5 kg.
Keep in mind that you will need a support for the filter paper, my rationale for using stainless steel throughout was that if I was using a piece of punched ss sheet for the paper support I might as well use ss throughout.
I have pushed a lot of samples through the unit and there is very little evidence of corrosion anywhere.
Filter paper changes take around 5 seconds, certainly no longer than changing a Buchner funnel.
The suction outlet is at the bottom of the slope, the flask is to prevent liquids entering the vacuum pump.
I use 250mm papers so the o ring diameter is 210mm, this allows around 15mm of paper outside the outer edge of the o ring for easy gripping for removal.
If you want I will detail the dimensions, this is the last of a line of prototypes.
Deano
The filter paper is clamped between the bottom of the top section steel edge and the o ring in the base.
The clamping is purely by gravity so the disassembly is quick and easy.
You would need a larger piece of plastic pipe on the top section to provide the weight for clamping.
The weight of the top section is 5 kg.
Keep in mind that you will need a support for the filter paper, my rationale for using stainless steel throughout was that if I was using a piece of punched ss sheet for the paper support I might as well use ss throughout.
I have pushed a lot of samples through the unit and there is very little evidence of corrosion anywhere.
Filter paper changes take around 5 seconds, certainly no longer than changing a Buchner funnel.
The suction outlet is at the bottom of the slope, the flask is to prevent liquids entering the vacuum pump.
I use 250mm papers so the o ring diameter is 210mm, this allows around 15mm of paper outside the outer edge of the o ring for easy gripping for removal.
If you want I will detail the dimensions, this is the last of a line of prototypes.
Deano
I have a very old tabletop Buchner funnel a client gave me years ago. It is heavy porcelain with a 32 cm plate and the mass of the thick porcelain ring seals the paper the same way. It has proven useful over the years for small leach test lots because the top of the old beast holds about 5 gallons of liquid. The guy's logic for giving it away was he didn't want to buy 32 cm papers just for that funnel. Worked for me!
So all of the liquid exits the funnel and is captured in the flask, making the flask both the receiver and a trap before the vacuum pump.
If you take apart one of the larger Bel Art tabletop Buchners, the big plate is supported by a bunch of short lengths of plastic pipe, the ends are cut so the liquid flows above and beneath them trapping as little of the filtered liquid as possible, and they fill the entire void to support the plate. A 50 cm funnel probably has 50 or 60 of these things filling the bottom. The bottom is flat though so they are all the same length. Every once in a while you have to remove the plate and rinse it out or just use a lot of rinse water without the paper in place. The point is the supports do hold up the plate which is more flexible than Deano's stainless plate so a larger diameter is do-able.
One consideration for members designing their own funnel is to check availability of the filter papers you prefer and make the ID of the top smaller than the paper and the base big enough so the paper fits inside the bolts. Then you will have an easy time changing paper. Nobody likes having papers too big for a funnel and having to break out the scissors! How do I know that???
So all of the liquid exits the funnel and is captured in the flask, making the flask both the receiver and a trap before the vacuum pump.
If you take apart one of the larger Bel Art tabletop Buchners, the big plate is supported by a bunch of short lengths of plastic pipe, the ends are cut so the liquid flows above and beneath them trapping as little of the filtered liquid as possible, and they fill the entire void to support the plate. A 50 cm funnel probably has 50 or 60 of these things filling the bottom. The bottom is flat though so they are all the same length. Every once in a while you have to remove the plate and rinse it out or just use a lot of rinse water without the paper in place. The point is the supports do hold up the plate which is more flexible than Deano's stainless plate so a larger diameter is do-able.
One consideration for members designing their own funnel is to check availability of the filter papers you prefer and make the ID of the top smaller than the paper and the base big enough so the paper fits inside the bolts. Then you will have an easy time changing paper. Nobody likes having papers too big for a funnel and having to break out the scissors! How do I know that???
Dear Mr Deano,
Before İ would like to ask a question about its reaction vessel at the neutral pH of saline /hypochlorite leaching. İ inform you that İ have been carefully reading all your posts for a long time. İf there is a god of leaching, you, Mr. Deano, must be prophet of leaching. Great Respects.
At neutral pH of saline/ hypochlorite leaching at atmospheric/ambient pressure conditions,
Does hypochlorous acid (HCOl) release the oxigen atom into solution at atmospheric conditions? İf yes, Must a reaction vessel be
something like a pressurized tank?
İ got a flotation concentrate of cu pb and zn which contains 65 ppm gold.
Best regards
Erdem
Before İ would like to ask a question about its reaction vessel at the neutral pH of saline /hypochlorite leaching. İ inform you that İ have been carefully reading all your posts for a long time. İf there is a god of leaching, you, Mr. Deano, must be prophet of leaching. Great Respects.
At neutral pH of saline/ hypochlorite leaching at atmospheric/ambient pressure conditions,
Does hypochlorous acid (HCOl) release the oxigen atom into solution at atmospheric conditions? İf yes, Must a reaction vessel be
something like a pressurized tank?
İ got a flotation concentrate of cu pb and zn which contains 65 ppm gold.
Best regards
Erdem
There are two things which are important regarding neutral pH saline/ hypochlorite leaching processes.
Firstly the pH must be kept in the range 6 to 8 to ensure that the active oxidant group is the HOCl radical.
If the pH is greater than 8 the majority of the oxidant is present as the OCl group , this has a much lower oxidation power than the HOCl group and will have difficulty keeping gold in solution.
If the pH is lower than 6 then the majority of the oxidant will be present as Cl gas, this group has high oxidation power but will want to evolve from the solution as chlorine gas. This means that you are going to be working with toxic fumes, not recommended. Also at the lower pH levels there will be large losses of the chlorine to the atmosphere, this will raise the cost of processing.
In the preferred pH range of 6 to 8 there is very little loss of chlorine gas and the smell test shows a similar chlorine level to that of a swimming pool. It does, however mean that good pH control is needed.
HOWEVER, if you are treating a float concentrate you will have two effects which are not good.
The high levels of metals present will consume a lot of the oxidant and will also try very hard to drop the solution pH below 6. This means that you will need to monitor the solution energy with a redox probe to ensure enough oxidant is present not just to leach all the base metals and gold but to keep the leached metals in solution.
If the redox or Eh level drops then gold will be lost from the leach solution.
This type of feed will very rapidly drop the solution pH so very close monitoring of pH is also required.
If I was processing this type of concentrates I would look at a cyanide leach at pH 11.
If permitting for such a leach type is not possible you have four alternatives.
Firstly sell the concentrates to a smelter or other type of commercial refiner or a mine which will toll treat them.
Secondly use a ferrocyanide leach at pH 11. If used under UV light it forms a cyanide leach but will get you around cyanide permitting regulations.
Thirdly carry out an acid leach of 10% HCl to remove the base metals before using any off the above leaches.
Keep in mind that a HCl leach will need to be carried out in all plastic equipment. The leach is slow, think weeks at ambient temperatures, intermittent agitation is needed. It can be sped up if heat is used, solar works well if the leach only contacts black poly solar tubing.
You will need to responsibly dispose off the metal laden solution, the easiest way is to use up the acid in leaching the metals, decant and/or filter the liquid off and then raise the pH of the liquor to 7. Let the metal hydroxides settle and decant and/or filter the liquid off again, let the solids dry and put them into appropriate storage.
Fourthly the gold grade of your concentrates will allow you to transport them to a location where cyaniding is permitted, this may be in a neighbouring country.
Deano
Firstly the pH must be kept in the range 6 to 8 to ensure that the active oxidant group is the HOCl radical.
If the pH is greater than 8 the majority of the oxidant is present as the OCl group , this has a much lower oxidation power than the HOCl group and will have difficulty keeping gold in solution.
If the pH is lower than 6 then the majority of the oxidant will be present as Cl gas, this group has high oxidation power but will want to evolve from the solution as chlorine gas. This means that you are going to be working with toxic fumes, not recommended. Also at the lower pH levels there will be large losses of the chlorine to the atmosphere, this will raise the cost of processing.
In the preferred pH range of 6 to 8 there is very little loss of chlorine gas and the smell test shows a similar chlorine level to that of a swimming pool. It does, however mean that good pH control is needed.
HOWEVER, if you are treating a float concentrate you will have two effects which are not good.
The high levels of metals present will consume a lot of the oxidant and will also try very hard to drop the solution pH below 6. This means that you will need to monitor the solution energy with a redox probe to ensure enough oxidant is present not just to leach all the base metals and gold but to keep the leached metals in solution.
If the redox or Eh level drops then gold will be lost from the leach solution.
This type of feed will very rapidly drop the solution pH so very close monitoring of pH is also required.
If I was processing this type of concentrates I would look at a cyanide leach at pH 11.
If permitting for such a leach type is not possible you have four alternatives.
Firstly sell the concentrates to a smelter or other type of commercial refiner or a mine which will toll treat them.
Secondly use a ferrocyanide leach at pH 11. If used under UV light it forms a cyanide leach but will get you around cyanide permitting regulations.
Thirdly carry out an acid leach of 10% HCl to remove the base metals before using any off the above leaches.
Keep in mind that a HCl leach will need to be carried out in all plastic equipment. The leach is slow, think weeks at ambient temperatures, intermittent agitation is needed. It can be sped up if heat is used, solar works well if the leach only contacts black poly solar tubing.
You will need to responsibly dispose off the metal laden solution, the easiest way is to use up the acid in leaching the metals, decant and/or filter the liquid off and then raise the pH of the liquor to 7. Let the metal hydroxides settle and decant and/or filter the liquid off again, let the solids dry and put them into appropriate storage.
Fourthly the gold grade of your concentrates will allow you to transport them to a location where cyaniding is permitted, this may be in a neighbouring country.
Deano
Dear Deano,
Thank you very much for your valuable information in detailed. At your previous posts in this thread you described that it could run the saline/hypochlorite leach in a open Vat thats is attached to carbon column. As a hard obligation, and as long as pH by adjusting HCL must be kept between 6 and 8.and kept ORP above 1000 mV. The most active ingredient of chlorine compounds will be HOCl So running under this conditions with a close monitoring Can mentioned leaching especially in open Vat be easily carried out?
But in the most literature İ read, they say that HOCl in aqeous solution at atmospheric conditions (contact with air and sunshine) turn into HCL rapidly by loosing oxigen molecule.
As to concentrates i have 70 tonnes Pb, Zn and Cu. Chalcopyrite contains just gold with 65 ppm İf İ separate chalcopyrite via re-flotation. 280 kg of chalcopyrite will contain about 4 kg gold....
İf you were me under this circumtances what would you do Sir?
Any comments would be appreciated.
Erdem
Thank you very much for your valuable information in detailed. At your previous posts in this thread you described that it could run the saline/hypochlorite leach in a open Vat thats is attached to carbon column. As a hard obligation, and as long as pH by adjusting HCL must be kept between 6 and 8.and kept ORP above 1000 mV. The most active ingredient of chlorine compounds will be HOCl So running under this conditions with a close monitoring Can mentioned leaching especially in open Vat be easily carried out?
But in the most literature İ read, they say that HOCl in aqeous solution at atmospheric conditions (contact with air and sunshine) turn into HCL rapidly by loosing oxigen molecule.
As to concentrates i have 70 tonnes Pb, Zn and Cu. Chalcopyrite contains just gold with 65 ppm İf İ separate chalcopyrite via re-flotation. 280 kg of chalcopyrite will contain about 4 kg gold....
İf you were me under this circumtances what would you do Sir?
Any comments would be appreciated.
Erdem
Most papers are not written by people who have to apply a practical aspect to a process, they usually are for the maintaining of grants or CV padding. The old publish or perish effect.
That said, you are correct in that there will be some loss of HOCl but this is minor in relation to the amount used in dissolving metals.
It is not absolutely necessary to have the mv above 1000, gold will be solubilised in a chloride matrix at Eh generally above 700mv. The important part is that the gold will not remain solubilised at this Eh so you end up in a cycle of gold getting dissolved, being precipitated from the solution and then getting redissolved.
This means that the gold level in solution will not, under these lower Eh conditions, continue to rise with time so that it will finally represent all of the available gold.
However if you provide the dissolved gold with somewhere to preferentially adsorb onto so that this adsorbent acts as a gold sink, then gold will continue to dissolve to replace the gold lost from the solution to the gold sink.
In an oxidising chloride matrix the best and cheapest gold adsorbent is activated carbon.
Regarding your concentrates, I am presuming that the numbers you give me are from actual assays and not just theoretical projections.
Your treatment options really are governed by two factors.
What ore reserves do you have and what treatment rate can you sustain.
If you have several years worth of reserves at a treatment rate which gives you 70 tons of float cons per 1 to 3 months then the obvious approach is to sell the float cons to a smelter.
There are many smelters which will pay for all the metals involved in your cons provided that you can offer them regular supply of product.
You will not get full LME price for these metals but you also do not have the cost of refining the cons.
I do not know what refiners/smelters there are near you but it would pay to approach some of the South Korean companies if you cannot come to an arrangement locally.
When talking to any company regarding your cons it is always advisable to be flexible regarding the product/s you can offer them.
Some companies will apply small penalties for lead contamination so a refloat to get a cleaner copper product could be very viable, especially as on your numbers most if not all of the gold reports to the chalco fraction.
It is always advisable to talk to several companies to see who will offer you the type of deal that financially best suits you.
I have yet to see a case where it gives an operator a better return to treat the float cons than to have them treated by a specialist smelter.
The only exception is when the ore reserves are small or the treatment rate is low.
Deano
That said, you are correct in that there will be some loss of HOCl but this is minor in relation to the amount used in dissolving metals.
It is not absolutely necessary to have the mv above 1000, gold will be solubilised in a chloride matrix at Eh generally above 700mv. The important part is that the gold will not remain solubilised at this Eh so you end up in a cycle of gold getting dissolved, being precipitated from the solution and then getting redissolved.
This means that the gold level in solution will not, under these lower Eh conditions, continue to rise with time so that it will finally represent all of the available gold.
However if you provide the dissolved gold with somewhere to preferentially adsorb onto so that this adsorbent acts as a gold sink, then gold will continue to dissolve to replace the gold lost from the solution to the gold sink.
In an oxidising chloride matrix the best and cheapest gold adsorbent is activated carbon.
Regarding your concentrates, I am presuming that the numbers you give me are from actual assays and not just theoretical projections.
Your treatment options really are governed by two factors.
What ore reserves do you have and what treatment rate can you sustain.
If you have several years worth of reserves at a treatment rate which gives you 70 tons of float cons per 1 to 3 months then the obvious approach is to sell the float cons to a smelter.
There are many smelters which will pay for all the metals involved in your cons provided that you can offer them regular supply of product.
You will not get full LME price for these metals but you also do not have the cost of refining the cons.
I do not know what refiners/smelters there are near you but it would pay to approach some of the South Korean companies if you cannot come to an arrangement locally.
When talking to any company regarding your cons it is always advisable to be flexible regarding the product/s you can offer them.
Some companies will apply small penalties for lead contamination so a refloat to get a cleaner copper product could be very viable, especially as on your numbers most if not all of the gold reports to the chalco fraction.
It is always advisable to talk to several companies to see who will offer you the type of deal that financially best suits you.
I have yet to see a case where it gives an operator a better return to treat the float cons than to have them treated by a specialist smelter.
The only exception is when the ore reserves are small or the treatment rate is low.
Deano
