# AP and zinc cementing issue



## kjavanb123 (Jun 14, 2011)

This is so frustrating, being able to complete the process from leaching to calcining and melting the PGMs for at least 10 times, I got stuck in the basic thing again. I don't know anymore, it's so annoying I can't even talk for hrs.

The AP solution as can be seen in picture from my other post "Acid combination" contains PGMs, so after decanting most of it from grinded catalytic converter, it comes to 500ml. WITHOUT heating or boiling it to rid of chlorine, or DILUTING it with some water, I just added zinc, stirred, and added more till the solution changed color from BROWN to DARK BLACK, I checked the dark black with stannous and no signs of PGMs in the solution, 

Here is the confusing part, did the solution turn black and wouldn't dissolve anymore zinc because of missing steps of NOT BOILING or NOT ADDING WATER?

For AR, do i have to steam bath and replace the nitric with hcl then dilute and do the zinc addition?
For AP, boil it once, then dilute with water, then zinc addition?

Also, now that I have this black liquid, that tested negative with stannous, just filter it and get the any remaining black powder that might have left at the bottom/? is there any other way to recover?!!

Geez this is soo annoying.
Thanks
Kev


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## qst42know (Jun 14, 2011)

Zinc is an alkaline metal. All your values were cemented long before you neutralized the acid with base metals. A small addition of zinc and a stannous test, repeat only if necessary.


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## kjavanb123 (Jun 14, 2011)

I know that qst, however why liquid turns dark? shouldn't be clear and see the mixed black powder on the bottom!?!


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## Lou (Jun 14, 2011)

The black is probably your colloidal values. Boil it and then see if it clarifies.


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## HAuCl4 (Jun 14, 2011)

Put a strong magnet below the beaker and discover the magic of paramagnetism. 8)


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## kjavanb123 (Jun 14, 2011)

Lou,

Thanks for the tip, I havent done that yet. I am gonna try to boil it then let cool to see if it clearifies. Should I have boiled it before any zinc addition? could that cause the problem?

Here is the picture show, if this allows me to upload.

Part of decanted solution from the powder cat.



After few zinc addition.



This is the state that stannous showed no PGMs in the solution, and it wouldn't react with more zinc addition. even after i poured 300ml of hcl to 
dissolve extra zinc.



At this stage, I don't know if I should go on with this, or crush another catalytic converter and this time use aqua regia since it will dissolve all 3 PMs. I just don't wanna give up yet, as these catalytic converters have been exported for last 2 yrs every week, so if they had no values in them or any profit, they would be discontinued. unless what I am doing only gets 0% of the metals in the cat. 

This feels like Edison and light bulb lol. 

Thanks for ur advise
Kj


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## samuel-a (Jun 14, 2011)

Kev

This is how cementing PGM looks like, you are ok.
you can reduce volume by boiling or stirr until some of the powder clump togather.

Since my vacume pump isn't so storng, at this point i usually let it sit for 24 to settle, decant and filter most of the barren solution, leaving the black powder in the flask to be filtered last, then wash the filter and powder cuple of times with water and allowed to dry completely.
You most make sure no powder is geeting through, it is very fine.

The left over filters from this process i keep seperatly, they hold PGM black still.


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## kjavanb123 (Jun 14, 2011)

sam,

I have done this many times before, but this is the first time dropping PGMs from aqua peroxide solution. this is from my previous experiences as you can see from the photos solution turns gray then clears. This solution i am dealing didn't do it like that.

Here is from a Pt solution i have added ammonium chloride, but it wasn't concentrated enough, so i added zinc to drop the Pt powder, so i can redissolve it in minimal AR and follow it.



After some zinc addition.



More zinc addition.



some more zinc addition.



And finally Pt in form of black powder is completely precipitated. As u note the solution is clear.



I am gonna try Lou's suggesion, if that failed, I am gonna start with a new cat and use AR this time.

Thanks
Kev


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## Joeforbes (Jun 14, 2011)

Kev,

Try taking a small amount of your solution that you have added zinc to and vacuum filtering it. You should find black PGM's on the filter. I've had this same problem dropping AP solution with zinc. After you have confirmed that you do have the PGMs, which I'm guessing you will, let it settle. 

One thing I've noticed is that after I siphon AP it weighs so much in the siphon container. Much more than AR does when I siphon that off. I'm guessing (even though I have no actual idea) that the AP solutions are a lot denser, so it takes a lot longer for the contents to settle.

I'll post a picture of my siphon for you once I get to my lab today. They are cheap and easy to make. Even easier to use!


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## samuel-a (Jun 14, 2011)

Kev

What difference does it make?

just filter and process whatever cought on it.
You can always throw the entire filter in the AR and boil so you won't have any metal loss.

Each batch can be different from other, there are dozens of variables. If AP doesn't act well, try AR.
The important thing in my mind, is that you are able to recover it all at the end.


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## Joeforbes (Jun 14, 2011)

Joeforbes said:


> Kev,
> 
> Try taking a small amount of your solution that you have added zinc to and vacuum filtering it. You should find black PGM's on the filter. I've had this same problem dropping AP solution with zinc. After you have confirmed that you do have the PGMs, which I'm guessing you will, let it settle.
> 
> ...




Didn't make it to my lab today. I'll post pictures for you tomorrow.


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## kjavanb123 (Jun 20, 2011)

All,

Thanks for your help on this. I have taken a sample from my AP solution this morning, boiled it, then added zinc, and it worked fine, solution became clear and black powder precipitated. Lesson #`22322 learned, boil the AP solution before cementing.

Also I tried the gsp wick filtering with piece of cloth got only part of the clear solution into the empty bucket, I tried decanting, I am gonna try charming plug method and let u all know.






This is my trial wick filter, 





Thanks
Kev


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## Joeforbes (Jun 21, 2011)

You will probably want to move the receiving container directly under the spot where the wick comes out of the container with the unfiltered solution. For two reasons - 

1. It may drip from the wick before it gets to the receiving container, causing you to lose values and get acid on something that shouldn't have acid on it.

2. The more vertical the wick is the faster it will do its job. 

Just a couple of tips for you.


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## kjavanb123 (Jun 21, 2011)

Joeforbes said:


> You will probably want to move the receiving container directly under the spot where the wick comes out of the container with the unfiltered solution. For two reasons -
> 
> 1. It may drip from the wick before it gets to the receiving container, causing you to lose values and get acid on something that shouldn't have acid on it.
> 
> ...



Thanks Joe for the tips. I changed the receiving container positions, but the tilting container which holds the sludg still had some solution, so do i tilt it more? I thought the wick would somehow pull the liquid out off?

Regards,
Kev


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## Joeforbes (Jun 21, 2011)

It will. The cloth will absorb and attempt to diffuse the liquid. Once it gets to the point in the wick where it drops vertically, gravity will do the rest. 

You may be left with a slight amount of solution in the sludge, but it's impossible to get 100% in anything.


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## kjavanb123 (Jun 21, 2011)

Joeforbes said:


> It will. The cloth will absorb and attempt to diffuse the liquid. Once it gets to the point in the wick where it drops vertically, gravity will do the rest.
> 
> You may be left with a slight amount of solution in the sludge, but it's impossible to get 100% in anything.



Thank u all for ur uncompromised help here. I owe you all one.

Regards,
Kev


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## Harold_V (Jun 22, 2011)

Joeforbes said:


> You may be left with a slight amount of solution in the sludge, but it's impossible to get 100% in anything.


That's what gasketed filter presses are for. The remaining solids would be taken up with a substantial amount of water, then run through a filter press that is capable of handling solutions without exposing the fluid to base metals. By this method, you can wring out virtually all of the values, even from materials that aren't easily filtered. Filter presses present a huge amount of surface area to the solution, and can be equipped with fabrics made of plastic that resist corrosion. 

Harold


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## Joeforbes (Jun 22, 2011)

Harold_V said:


> Joeforbes said:
> 
> 
> > You may be left with a slight amount of solution in the sludge, but it's impossible to get 100% in anything.
> ...



Yeah, you've got me there Harold.  Thank you for the correction.

Also, are there any smaller scale vacuum presses that you might know of or, better yet, you would recommend?


Thanks in advance.


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## kjavanb123 (Jun 22, 2011)

Some tips from my today experiences with AP cementing uzing zinc powder;

1. If the volume of AP is small, like 20ml, once the cementing is completed, the solution is clear and black powder is clinged together like tea. Yet when decant it and put it under the sun to dry it naturally, they become so small as you can see in following pictures.

Cementing completed for 20ml sample AP.



decanted and dried



I think sticking to AR method is far better than peroxide method in leaching. 

I will search the gasket filter press. Thanks 

Kev


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## Harold_V (Jun 23, 2011)

Joeforbes said:


> Harold_V said:
> 
> 
> > Joeforbes said:
> ...


It's not as rosy as I made it sound---there's always going to be some lost--but you can either keep rinsing (water) or put the solids back in slurry and re-filter. I used to do just that when I'd process ores and some of my waste materials with cyanide. The filter press I built was worth its weight in gold.



> Also, are there any smaller scale vacuum presses that you might know of or, better yet, you would recommend?


Frankly, I'm not convinced vacuum would be the answer, but then I have no experience with such a press. I can visualize one working much the same way as does a filter press, relying on vacuum instead of applied pressure. The one real negative is likely to be the limitations of the vacuum. You can apply some serious pressure with the air driven pumps. Much greater than atmospheric. 

Harold


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## Joeforbes (Jun 23, 2011)

> > Also, are there any smaller scale vacuum presses that you might know of or, better yet, you would recommend?
> 
> 
> Frankly, I'm not convinced vacuum would be the answer, but then I have no experience with such a press. I can visualize one working much the same way as does a filter press, relying on vacuum instead of applied pressure. The one real negative is likely to be the limitations of the vacuum. You can apply some serious pressure with the air driven pumps. Much greater than atmospheric.
> ...



Right, I meant to say filter press. I apologize. I was thinking of constructing one, but I'm afraid it would be outside of my current ability and know-how.


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## kjavanb123 (Jun 23, 2011)

Is this filter press for sale? or the design for sale? please advise.

Also, is there any faster method of drying the mixed black powder, has anyone tried to put them in microwave?


Regards,
Kev


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## Harold_V (Jun 25, 2011)

kjavanb123 said:


> Is this filter press for sale? or the design for sale? please advise.


There's a remote possibility that the press could be purchased, yes. I know it sits idle, considering the individual that purchased the refining business was akin to a moron and killed the business in short order. 

As for the design, I didn't keep records, but in all honesty, it would not lend itself to use for acidic solutions. It was designed for use with cyanide, where contact with base metals isn't an issue. It could be modified with a little effort, so acidic solutions do not contact metallic surfaces, however. That would require machining skills, plus the replacement of several metallic fasteners, which may have to be made (titanium may be an option). In any case, understand that a fully gasketed filter press would be required---a standard filter press would not be advised because you have little control over the discharge. 

As to building a filter press, trust me, that's not for those without at least some experience on machine tools. There are some tricky features that are a requirement for the press to function properly, without collapsing the plates. The builder would be required to understand close tolerance work. While I built the press, do keep in mind, I did so as a seasoned machinist. I had worked in the machine shop for 26 years, with many of them working as a tool maker. 



> Also, is there any faster method of drying the mixed black powder, has anyone tried to put them in microwave?


Have you given any thought to filtering by vacuum assist, then heating in an evaporating dish or beaker? Works just fine, and is fast. You can heat to the point of driving off residual acids that way. I'm not convinced the use of a microwave is a good idea. 

Harold


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## ashir (Mar 13, 2021)

Harold_V said:


> Joeforbes said:
> 
> 
> > Harold_V said:
> ...


Harold....... nice filter press. Can i have some words on plates material for acidS


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## Yggdrasil (Mar 13, 2021)

Ashir:
This thread is 10 years old and I'm not sure Harold is in this forum much anymore.
Someone may or may not point you in the right direction.


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## ashir (May 11, 2021)

Yggdrasil said:


> Ashir:
> This thread is 10 years old and I'm not sure Harold is in this forum much anymore.
> Someone may or may not point you in the right direction.



Thanks man. I totaly ignore the dates. I have filter press but of stainless steel frame and plates that i think will not stand with br+cl at ph 3.


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