# Filtering



## timsiggins (Nov 10, 2021)

Hey Guys,

one thing about filtering that bugs me is that stuff gets caught in the filter, aka you are filtering gold foils and specks of gold get caught in the filter so you have to throw the filter into the AR and let it dissolve, has anybody found any type of membrane filters that you can use clean and use again. I would only use it when I know I have pure material, anything that I have question of it being dirty, I would use a reg filter and then just keep it. Then process them with the rest of my filters. what do you guys think?


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## FrugalRefiner (Nov 10, 2021)

A Büchner funnel with a sintered glass disc would work, but they can get pricey.

Dave


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## Deano (Nov 10, 2021)

Try a Buchner with calendered polypropylene clothe, usually sold as filter cloth. Go online to see who sells the cloth in your area. There are a lot of manufacturers of these cloths and they all have different pore sizes.

Cloths are rated in porosity by airflow rates through them, I have no idea what the relationship in the US is between airflow rates and porosity. I do know that they are rated in cubic feet/minute but the rest of the world only rates them in metric units.

These cloths will last virtually forever provided you do not put them into aqua regia.

Deano


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## cejohnsonsr1 (Nov 10, 2021)

I'm not sure I completely understand the problem. Filtering is done for different reasons at different stages of the recovery and refining processes. The main purpose of each stage, however, is to remove the solids from whatever you just dissolved. How you process the solution and the solids is just the next step in the process. If you have gold foils in the filter just thoroughly incinerate the filter and the solids. If you were dissolving gold and still have foils in the filter, then you didn't finish the dissolving process.


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## cejohnsonsr1 (Nov 10, 2021)

After reading it again I have to say I still don't see the problem. You mentioned putting the filter and solids in AR. That is the most effective way to put the gold into solution and dispose of the remaining solids (including the filter). The filter will be completely consumed by the AR.


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## timsiggins (Nov 14, 2021)

@FrugalRefiner thanks for the name I was looking at those on eBay but didn't know what they really where used for, ya they are expensive maybe I will put it on my Christmas list

Also Thanks @Deano I will look at that too


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## FrugalRefiner (Nov 14, 2021)

timsiggins said:


> maybe I will put it on my Christmas list


Santa has brought me a lot of my equipment over the years. I love Santa!

Dave


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## snoman701 (Nov 14, 2021)

FrugalRefiner said:


> A Büchner funnel with a sintered glass disc would work, but they can get pricey.
> 
> Dave


Be careful, as I tried using one for gold. I loaded it up with silver chloride without realizing what I was doing. Now its pretty much shot since it dried in there.


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## voidforged (Nov 14, 2021)

cejohnsonsr1 said:


> After reading it again I have to say I still don't see the problem. You mentioned putting the filter and solids in AR. That is the most effective way to put the gold into solution and dispose of the remaining solids (including the filter). The filter will be completely consumed by the AR.


I read it as they want to be able to re-use the filter rather than have it be consumed in AR or incineration.


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## cejohnsonsr1 (Nov 14, 2021)

voidforged said:


> I read it as they want to be able to re-use the filter rather than have it be consumed in AR or incineration.


I suppose that's possible, but probably not very cost-effective or efficient.


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## dpgold (May 19, 2022)

cejohnsonsr1 said:


> I'm not sure I completely understand the problem. Filtering is done for different reasons at different stages of the recovery and refining processes. The main purpose of each stage, however, is to remove the solids from whatever you just dissolved. How you process the solution and the solids is just the next step in the process. If you have gold foils in the filter just thoroughly incinerate the filter and the solids. If you were dissolving gold and still have foils in the filter, then you didn't finish the dissolving process.


I have a question, I am making a test and have dissolved some filtered gold from AP, together with the filter in AR, should the filter dissolve completely in AR? Also how long should I let it in, I have added nitric just a little at a time.
Meanwhile the filter started to become mushy, I kept stirring.


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## 4metals (May 19, 2022)

snoman701 said:


> Be careful, as I tried using one for gold. I loaded it up with silver chloride without realizing what I was doing. Now its pretty much shot since it dried in there.


Try sucking ammonia through the sintered plate as it will dissolve the Silver Chloride to clean it. 

They sound great in concept but do seem to plug up.


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## richoc (May 20, 2022)

dpgold said:


> I have a question, I am making a test and have dissolved some filtered gold from AP, together with the filter in AR, should the filter dissolve completely in AR? Also how long should I let it in, I have added nitric just a little at a time.
> Meanwhile the filter started to become mushy, I kept stirring.


Question why did you put a filter from AP, in the AR were the particles to small to come off the filter when dry.

Depending on the filters you used the answer is there should be fiber goo, I have no better name for it ......
I have herd there are filters that are designed to dissolve but have never used any of this kind.

Well if all the gold in in solution and the filter is goo.............Now you filter the whole mass again.
Once the solution has passed through this filter you need to rinse the goo of the filter until all the color/AR is washed through the filter. 

One issue I see is you added more nitric acid so that most likely will now have to be dealt with.

Now you can do your preferred gold drop method on this filtered AR.

Now is this 100% effective, I do not think so.
That is why you save this filter with the goo in it for later processing of all your filters.


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## dpgold (May 20, 2022)

richoc said:


> Question why did you put a filter from AP, in the AR were the particles to small to come off the filter when dry.
> 
> Depending on the filters you used the answer is there should be fiber goo, I have no better name for it ......
> I have herd there are filters that are designed to dissolve but have never used any of this kind.
> ...


Thanks, due to the specific type of small ribbons I had I went with AP when I probably should have process with AR from the beginning because it was very hard to wash the material afterwards and had clinging problems of the recipients I used for washing everything well. I used coffee filters. I will wash the filter goo as well. I am keeping everything for the stockpot. I have only added nitric bit by bit.


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## dpgold (May 21, 2022)

richoc said:


> Question why did you put a filter from AP, in the AR were the particles to small to come off the filter when dry.
> 
> Depending on the filters you used the answer is there should be fiber goo, I have no better name for it ......
> I have herd there are filters that are designed to dissolve but have never used any of this kind.
> ...


i did some decanting and tried to filter the remaining water and used a different type of coffee filter and discovered a lot of the very fine gold passes through. Of course I am not throwing anything away but this is something to consider. You trust a filter and it lets you down eventually. I am keeping even that filtrate test everything over and over


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## Ohiogoldfever (May 21, 2022)

I have found that storing and processing filters several times helps me. They catch what they catch and I’ll leach it out at a later date if it’s something I want. The filters do a great job of separating things so they can be sorted correctly. 

I use poor mans so the cost to re run some suspect filter media is very low. Never hurts to be certain before they get discarded.


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## dpgold (May 21, 2022)

richoc said:


> Question why did you put a filter from AP, in the AR were the particles to small to come off the filter when dry.
> 
> Depending on the filters you used the answer is there should be fiber goo, I have no better name for it ......
> I have herd there are filters that are designed to dissolve but have never used any of this kind.
> ...


I am not sure I have answered you first question, yes the gold was so fine and I could not get it off the sides of the containers and beakers I have used during first phase and second to filtration, they became very small some of the fine particles were floating, it was very difficult, I had to use filter paper to wipe and then water spray .... In this case I believe now that using directly AR would have been better due to the ribbons ends small size and the clinging problem as well as the washing difficulty being so many I had to wash everything several time in a bigger bucket so .. more gold clinging to the bucket......


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## dpgold (May 21, 2022)

Ohiogoldfever said:


> I have found that storing and processing filters several times helps me. They catch what they catch and I’ll leach it out at a later date if it’s something I want. The filters do a great job of separating things so they can be sorted correctly.
> 
> I use poor mans so the cost to re run some suspect filter media is very low. Never hurts to be certain before they get discarded.


what exactly do you use for filtering? What kind of poor man's filter?


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## Ohiogoldfever (May 21, 2022)

I just use a few different sized coffee filters depending on the amount o be filtered. 

As for the super fine stuff I try and get it all but there is a point where your chasing 10 cents in gold.


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## eaglekeeper (May 21, 2022)

Does anyone here use celite for extremely fine particle filtering, I seen Nilered use it, but I don't know if it would hold up under extremely high/low Ph solutions. Can it be cleaned and reused?, if not then it's probably not cost effective to use it.


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## Shark (May 26, 2022)

eaglekeeper said:


> Does anyone here use celite for extremely fine particle filtering, I seen Nilered use it, but I don't know if it would hold up under extremely high/low Ph solutions. Can it be cleaned and reused?, if not then it's probably not cost effective to use it.


I have not used it but do something similar with broken paper fiber. After watching a few videos on it it has me curious to see how fine particulate size it can remove.


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## Yggdrasil (May 26, 2022)

Shark said:


> I have not used it but do something similar with broken paper fiber. After watching a few videos on it it has me curious to see how fine particulate size it can remove.


Is it some kind of “molecular sieve” like Zeolite?


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## Shark (May 26, 2022)

I am not sure what it is called. It is made from diatomaceous earth. It’s most common use is as a secondary filtering aid in that iit reduces pore size of the filter. Usually it will be from 2 to 200um. The more you use the finer particulate it can catch. As with anything that can plug up a filter it will cause slow filtration. My concern is the potential problems in the waste stream. I really need to know more before trying it.


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## Yggdrasil (May 26, 2022)

Shark said:


> I am not sure what it is called. It is made from diatomaceous earth. It’s most common use is as a secondary filtering aid in that iit reduces pore size of the filter. Usually it will be from 2 to 200um. The more you use the finer particulate it can catch. As with anything that can plug up a filter it will cause slow filtration. My concern is the potential problems in the waste stream. I really need to know more before trying it.


Ok, I see


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## 4metals (May 26, 2022)

Years ago I used a filter which we always called a super filter. It was simply a deep bed of diatomaceous earth, 3-4" over a sheet of filter paper on a large 120 cm table top Buchner funnel. It was used on gold that was dropped "dirty" and filtered very slow. The benefit was it could be raked with a glass rod to break up the surface and expose new clean DE. Then when I filtered all the liquid out what I really needed were values in the filter. The DE was mixed with a few other flux ingredients (after all it is mostly clean silica to start) and it would melt into glass. Pour it into a cone mold and the glass is on top and all the values are below. 

The process involved dissolving thick film e-scrap metallics in aqua regia, in a 500 gallon vessel until the reaction was spent. Then we added scrap metal and essentially cemented out the gold on to all of the other materials that didn't dissolve. By the next morning the acid was spent and the solution tested negative for values. We siphoned off the supernatant liquid as close as possible to the nasty slimy bottom mud (and all of the gold) which saved a lot of time filtering. Then the nasty bottoms went into a super filter. What remained on the filter was melted with the diatomaceous earth "filter" layer and the metallic cone was de-slagged and melted into shot for digestion in a much more manageable quantity of aqua regia. 

The trick to the process was the filtration.


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## Shark (May 26, 2022)

Very interesting. This could be a good way of filtering sludge from various cells. A lot to think about.


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## eaglekeeper (May 26, 2022)

Shark said:


> I am not sure what it is called. It is made from diatomaceous earth. It’s most common use is as a secondary filtering aid in that iit reduces pore size of the filter. Usually it will be from 2 to 200um. The more you use the finer particulate it can catch. As with anything that can plug up a filter it will cause slow filtration. My concern is the potential problems in the waste stream. I really need to know more before trying it.


Good point..... I didn't think about dealing with it as a waste stream. I'm not sure if it would absorb metal salts but it would have to be dealt with one way or another.


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