Aeon13
Well-known member
Good day to all the members of this helpful forum.
I would like to thank this forum and the members for the valuable knowledge that is being shared here.
I learned so much already and I am still learning so much every time I come and read.
I have come again to seek knowledge from you guys. I apologize for this will be a long post because I will try to explain every detail for you guys to understand.
Lately, I tried the Carbon In Leach process to recover gold from very finely ground ores.
Let me explain why these ores are very fine. In the process of milling, the ores here are ground for about 100 microns. It is done by milling it in a rod mill with water for more than an hour. When the miners here take the ground ore out, it goes to container but the water with it goes to another.
The water has with it the very fine ores and after some time they will settle and these are the ones that I bought to process it in a Carbon In Leach tank.
The CIL tanks here I suppose are not industry standards because they were build by small scale miners by the help of someone who has knowledge.
This is how the CIL process works here:
1. we put the ore with water and quicklime in the tank. The tank is mechanically agitated with air purged inside using air compressor.
2. we let the lime, ore and water mix for about 4 hours without cyanide for what they say as "oxidation".I don't know if this is really required but I was not able to read anything about this step. Still I followed what they say.
3. we add cyanide and let the mix run for about 48 hours. Then add again additional cyanide after 48 hours.I think we are putting so much cyanide here because they are not titrating. I tried to titrate using the method I read here and If I am correct the concentration was 3 g/L NaCN.
4. then activated carbon is added and let it mix for about 48 hours also.
5. the tank will be released and the carbon will be recovered using a screen.
6. carbon elution is not used here. Instead, ashing is the processed used. the carbon will be ashed which will take about 12 hours or more.
7. the ash will then be mixed with borax and will be smelted using a torch (compressed air- LPG set up).
8. the metals will all combine in a button and will be refined further for the pure gold.
I decided to read about the CIL process here in the forum as well as the internet because I was not contented with the explanations and the steps in the process done here. I started reading about cyanide concentrations, titration, activated carbon loading,leach time,proper pH, oxygen concentration ,size of ground ore,temperature and much more. I understood these are the factors for a successful leach.
These are the ideas which I understood with my readings and I am adding some questions about them for me to have a much clearer understanding.
1. The ores are very fine that they flow with water and has a consistency of a mud when concentrated, Is it better this way for the cyanide to liberate gold particles?
2. I read that the pH must be in the range of 10.5 - 12. Is this the proper range of pH of the solution with cyanide already mixed? Adding lime or caustic soda will increase the pH, what if I added too much and had the pH higher than I want, how can I decrease the ph?
3. I did titrate the solution but this is my first time and I am not that sure of my readings. I followed the titration using silver nitrate and potassium iodide as an indicator. I understood the unit will be g/L. That is grams per Liter of the whole solution(whole CIL tank?)?
I read somewhere that the concentration used is 0.05 to 1.25 g/L cyanide. My reading here is 3 g/L. this is too much but is there an effect on the leaching?
4. After cyanide leaching, carbon is added. Is it safe to say that there are no gold/silver remaining if the concentration of free cyanide is not changing? Adding carbon will not affect the free cyanide concentration right?
5. Is there any other test in the solution if gold is still present except for stannous test?
6. I find ashing very lengthy and I feel that small gold particles might fly with the air blown. Do you think elution using hydrochloric acid and precipitating with zinc dust is much better? ( I have not read about this HCL elution thoroughly but I am on my way)
7. I read about proper oxygen concentration and how important oxygen in the reaction of leaching. I also searched on how to measure oxygen concentration using titration but I am having a difficult time finding these chemicals that is required, do you have any other options on measuring dissolved oxygen or is it safe to say that the air purged by the compressor is enough supply?
8. I read that many CIL processes use 50% solid slurry density. How can I practically measure this state of density? (I don't have any instruments for this measurement) What will happen if I added too much liquid and made it 30-40% solid?
Any answers/suggestions/recommendations will be greatly appreciated.
I believe that many heads are better than one or two. This is the reason for me asking questions here because I know that many of the members have ideas about any questions herein.
Again thank you so much and more power to the members as well as the forum.
I would like to thank this forum and the members for the valuable knowledge that is being shared here.
I learned so much already and I am still learning so much every time I come and read.
I have come again to seek knowledge from you guys. I apologize for this will be a long post because I will try to explain every detail for you guys to understand.
Lately, I tried the Carbon In Leach process to recover gold from very finely ground ores.
Let me explain why these ores are very fine. In the process of milling, the ores here are ground for about 100 microns. It is done by milling it in a rod mill with water for more than an hour. When the miners here take the ground ore out, it goes to container but the water with it goes to another.
The water has with it the very fine ores and after some time they will settle and these are the ones that I bought to process it in a Carbon In Leach tank.
The CIL tanks here I suppose are not industry standards because they were build by small scale miners by the help of someone who has knowledge.
This is how the CIL process works here:
1. we put the ore with water and quicklime in the tank. The tank is mechanically agitated with air purged inside using air compressor.
2. we let the lime, ore and water mix for about 4 hours without cyanide for what they say as "oxidation".I don't know if this is really required but I was not able to read anything about this step. Still I followed what they say.
3. we add cyanide and let the mix run for about 48 hours. Then add again additional cyanide after 48 hours.I think we are putting so much cyanide here because they are not titrating. I tried to titrate using the method I read here and If I am correct the concentration was 3 g/L NaCN.
4. then activated carbon is added and let it mix for about 48 hours also.
5. the tank will be released and the carbon will be recovered using a screen.
6. carbon elution is not used here. Instead, ashing is the processed used. the carbon will be ashed which will take about 12 hours or more.
7. the ash will then be mixed with borax and will be smelted using a torch (compressed air- LPG set up).
8. the metals will all combine in a button and will be refined further for the pure gold.
I decided to read about the CIL process here in the forum as well as the internet because I was not contented with the explanations and the steps in the process done here. I started reading about cyanide concentrations, titration, activated carbon loading,leach time,proper pH, oxygen concentration ,size of ground ore,temperature and much more. I understood these are the factors for a successful leach.
These are the ideas which I understood with my readings and I am adding some questions about them for me to have a much clearer understanding.
1. The ores are very fine that they flow with water and has a consistency of a mud when concentrated, Is it better this way for the cyanide to liberate gold particles?
2. I read that the pH must be in the range of 10.5 - 12. Is this the proper range of pH of the solution with cyanide already mixed? Adding lime or caustic soda will increase the pH, what if I added too much and had the pH higher than I want, how can I decrease the ph?
3. I did titrate the solution but this is my first time and I am not that sure of my readings. I followed the titration using silver nitrate and potassium iodide as an indicator. I understood the unit will be g/L. That is grams per Liter of the whole solution(whole CIL tank?)?
I read somewhere that the concentration used is 0.05 to 1.25 g/L cyanide. My reading here is 3 g/L. this is too much but is there an effect on the leaching?
4. After cyanide leaching, carbon is added. Is it safe to say that there are no gold/silver remaining if the concentration of free cyanide is not changing? Adding carbon will not affect the free cyanide concentration right?
5. Is there any other test in the solution if gold is still present except for stannous test?
6. I find ashing very lengthy and I feel that small gold particles might fly with the air blown. Do you think elution using hydrochloric acid and precipitating with zinc dust is much better? ( I have not read about this HCL elution thoroughly but I am on my way)
7. I read about proper oxygen concentration and how important oxygen in the reaction of leaching. I also searched on how to measure oxygen concentration using titration but I am having a difficult time finding these chemicals that is required, do you have any other options on measuring dissolved oxygen or is it safe to say that the air purged by the compressor is enough supply?
8. I read that many CIL processes use 50% solid slurry density. How can I practically measure this state of density? (I don't have any instruments for this measurement) What will happen if I added too much liquid and made it 30-40% solid?
Any answers/suggestions/recommendations will be greatly appreciated.
I believe that many heads are better than one or two. This is the reason for me asking questions here because I know that many of the members have ideas about any questions herein.
Again thank you so much and more power to the members as well as the forum.