# Processing Cats with HCL/Bleach



## kkmonte (May 24, 2013)

If I don't care about measuring yields, etc. Can I use the same Acid and process multiple cats before I precipitate with zinc? If I have 1 gal. of solution in a 2 gal bucket, and I place 2 honeycombs in the acid, add bleach every other day for 2 weeks for each set of honey combs, then pull the honeycombs and rinse, and put in two new honeycombs (or even a second pass on other ones), can I keep that going for a while? 

If I only add a cap full of bleach every two days, over the course of lots of cap fulls of bleach, will the PH eventually get too high and not dissolve any more PGM's?

Also once I filter out my PGM's using a charmin plug, i'm assuming the solution I'll have is zinc chloride. Now can I cement out the zinc using aluminum and then will have aluminum chloride? Then process this aluminum chloride as regular waste by raising PH to 9, drop out aluminum, bring PH back to 7 and dispose? Can I reuse the zinc powder and aluminum powder in the future for precipitating PGM's and Zinc ?

Thanks as always.
Ken


----------



## lazersteve (May 24, 2013)

Yes, you can use your extraction acids on as many cats as you like. There will come a point when the solution will not be able to extract any more metals and will either need to be refreshed with more Clorox and/or acid, or precipitated.

Steve


----------



## kurt (May 25, 2013)

kkmonte said:


> Also once I filter out my PGM's using a charmin plug, i'm assuming the solution I'll have is zinc chloride. Now can I cement out the zinc using aluminum and then will have aluminum chloride? Then process this aluminum chloride as regular waste by raising PH to 9, drop out aluminum, bring PH back to 7 and dispose? Can I reuse the zinc powder and aluminum powder in the future for precipitating PGM's and Zinc ?
> 
> Thanks as always.
> Ken



Yes you can cement the zinc out with aluminum - however it does not work well as it is difficult to filter & wash out the AlCl - also the Aluminum is lost - its lost because you are using PH adjustment to drop it & therefore ending up with aluminum hydroxide - not aluminum metal (therefore it is costing you the value of aluminum as scrap to recover the zinc in this way & you actually increase the amount of waste when filtering & washing the AlCl out of the zinc powders

Aluminum hydroxide is very voluminous & very difficult to filter & although the liquid part of your waste should be safe to dump after PH adjustment (depending on other metals that "may" be in solution & at what Ph they drop at) you still have the aluminum hydroxide (& a large volume of it at that) as a waste product

I would look into setting up an electrolytic winning cell to win the zinc back out of solution --- with a winning cell not only should you be able to recover most of your zinc but also recover your acid for re-use

I haven't actually tried this myself yet - but have discussed it with another member on the forum --- I am waiting for the power supply I ordered to arrive & I still need to order the carbon for the anodes to set up a winning cell & give it a try

The only thing I am not sure of is what to use as a cathode (not sure if it should be zinc - like a copper cathode in a copper winning cell - or something like stainless steal or maybe titanium)

Kurt


----------



## kkmonte (May 25, 2013)

lazersteve said:


> Yes, you can use your extraction acids on as many cats as you like. There will come a point when the solution will not be able to extract any more metals and will either need to be refreshed with more Clorox and/or acid, or precipitated.
> 
> Steve



So from what I've read the PH of 32% HCl is -1 and the PH of bleach is 12ish. Does each bleach addition raise the PH ever so slightly? If I add 20ML of bleach every two days for a total of 7 bleach additions per honeycomb (140ML total bleach added over 2 weeks) to about 2000ML of HCl (either 32% of maybe dilute is 50/50 with water), i'm guessing the PH will still be relatively low. If I keep processing honeycombs this way, maybe after I do 4-5 honeycombs, do you think the PH will be getting too high to not dissolve the PGM's? I know it's the chlorine gas that is actually dissolving the PGM's, how much bleach would be too much before I need to add more acid do you think?


I also had an idea to try and improve the bucket in a rubbermaid adding bleach while holding your breath trick. Do you guys think this would work? The idea would be when a bleach addition is needed, I unhook the quick connect outside of the bucket, put a small funnel in the pipe, dump the bleach in, attach the pipe back up and turn on the bubbler/aerator to push the bleach down into the bucket and out the holes directly underneath the honeycomb. I then either leave the bubbler going if it would help the process along or shut it off after I let it run for a bit to push the bleach through the pipe. I was thinking of putting a small trap in the 1/2" PVC pipe to maybe block some of the fumes from escaping, realizing the bleach will sit in the trap while I add it, giving me plenty of time to attach the air to it before I need to take a whiff of the gas. 

What does everyone think? Here is a sketch I drew up in autocad. Thanks
-Ken


----------



## Marcel (May 26, 2013)

You could drop in a chlorine tablette (used for swimming pools) instead. That will release fumes slower.


----------

