# Will This Work? AR Fume Filtration.



## Johnnycat535 (Sep 20, 2012)

I'm designing a fume hood with a water filtration system for my AR. If I add charcoal or even ashes to the water until it becomes thick, but not to thick, would that filter out the toxins? I've researched it but haven't gotten a definite answer on this topic. Thank you for your input.


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## NobleMetalWorks (Sep 20, 2012)

Are you talking about neutralizing the acid in a wet fume scrubber? Maybe if you gave us a little more background information on what you are actually attempting to do.

Charcoal will only absorb a finite amount of material before it's saturated and either needs to be thrown out, or re-activated. I'm not sure what you are doing with the ashes however. Soda Ash?

If you are in fact attempting to neutralize water in a wet fume scrubber, you can use many different ways of doing so. If it is only acid you are neutralizing, you can do so with substrate in the water, like limestone broken up, or sodium hydroxide to adjust the PH level, or Urea, etc. To find out which method is best for your application you can search the forum, there is a lot of information about what you are attempting to do.

One thing I have found to be useful, in many different ways, is a PH/ORP meter. You can find them inexpensively on eBay. This will not only give you the ability to adjust your PH by instantly testing, but also tell you if there is any reduction potential in your wasted scrubbing solution.

Scott


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## Johnnycat535 (Sep 20, 2012)

Basically what I'm asking is yes will charcoal or ashes (Referring to burn pile ashes) neutralize the acids fumes in the water. To give a little more detail I've made a small home made fume hood and the fumes are transferred into a container of water in which I hope to add something to absorb the toxic chemicals. I got the idea from that a acid vapor respirator uses charcoal to capture the toxic fumes as well as I saw it mentioned in this forum somewhere. I've search and search for something similar to my design, but maybe that's because I didn't know what a scrubber was LOL. I'm considering maybe patenting my idea and selling the plans. So you'll have to forgive me if I don't give every aspect of how it works. Would perhaps baking soda work as well to neutralize the fumes? Also thank you for the quick response. I'm sure glad I found this forum.


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## butcher (Sep 20, 2012)

My opinion,

Wood ashes can neutralize acids if solution is concentrated enough, they do not work as well as sodium hydroxide (lye or caustic soda), create a dirty solution, and more waste.

I usually use wood ashes to treat my waste after I have neutralized the acid with sodium hydroxide precipitate the metal hydroxides decant salt water, the ashes are then added to the salty metal sludge, the ashes help to soak up water from the sludge, and to help dry the sludge, making drying go much faster and this also helps to insure the powders are not acidic.

Charcoal filter would be fairly ineffective with the acids we use, and nitric fume could create a fire hazard.

Charcoal and wood ashes are not the same thing, and do not serve the same purposes.

Baking soda neutralizes acids, but it is very reactive and foams like crazy.

Lime would also neutralize acids but also takes volumes to do so, it is good for treating waste (I use it also).

Out of these I would prefer to use sodium hydroxide, in a fume scrubber.

Think if you can use a product before calling it a waste, many of these reactions create byproducts we can reuse or convert into a useful product, example: if only scrubbing nitric the in a solution of sodium hydroxide, the sodium nitrate formed could be reused, also I reuse the many of the acidic fumes we generate, using these fumes where I can many time these acidic fumes can be bubbled into water and made into an acid to dissolve base metals in other reactions.


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## Johnnycat535 (Sep 20, 2012)

Just the answer I was looking for. Just to be sure I understand correctly (I'm new to this). I'll try and write this out step by step.

1: Mix Sodium Hydroxide with the water in the container. (How much do I add?)
2: Once waste is "Full"(How would I tell) I then decant the waste (Am I separating any solids or just moving to different container?)
3: Add wood ashes to solidify salty metal waste into powder (Whats a good way to dispose of this powder and if any solid waste from decanting waste?)

I hope I read everything correctly and am on the right track. Thank you for your detailed response. I look forward to learning something new every day here.


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## butcher (Sep 20, 2012)

Johnnycat535, Read dealing with waste in the safety section (it is explained there better than I can explain it), also there are excellent threads on building and maintaining fume scrubbers and fume hoods.

For waste treatment I bring the PH to about 9 then back to neutral.
For a scrubber I would saturate solution with the base then monitor pH.
The values are cemented from solution on copper, these go back to be recovered, copper is cemented out of solution with iron (this copper I use to collect missed values from the next batch of waste solution), the iron solution is neutralized form metal hydroxide powders which are removed from solution and dried safe to throw in the dump.


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## Johnnycat535 (Sep 21, 2012)

Hey Butcher,
I've read the whole thread and found it very educational. I'm sure I'll read it a few more time's again as I do most threads I find intriguing lol. The only thing that I didn't take from it was if it applied to my purpose. I'll basically have a container full of water, sodium hydroxide, and toxins (Maybe ashes). That thread seemed to apply to just the remaining acid from my beaker and not from the fumes. My only question is that there would be sodium hydroxide in this solution (maybe ashes as well) and I didn't know if it would affect the process. I sure do like the idea of getting back all those PM's you'd may other wise loose though. I'll just have to research how to get the PM's into a sellable (solid)state without breaking the bank. That seems like it'll be the hardest part without breaking the bank. I'll just have to dig deeper and do more research research research. Thanks again for the help. I sure do appreciate it.


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## Johnnycat535 (Sep 21, 2012)

Me again! So I've decided what I'm going to do. I'm going to pick up a 55 gallon plastic drum tomorrow for my scrubber. I plan to put 2lbs of sodium hydroxide and water in it. Not sure of the ratio yet but I do plan to use all of the sodium hydroxide so any suggestions on how much water would be great. I'm using a vacuum cleaner hose to transfer the fumes into the scrubber, which I'm having some concerns about. I've seen everyone say use PVC piping and I read that lesser tubing may catch fire or explode. This will be my second prototype and once this is complete I intend to release the design and with everyone's help hopefully come up with a cheap scrubber and fume hood design we can all benefit from. I want to focus the design to where most of the parts can be obtained free or at a garage sale or thrift store. So far I've spent $0.00 so it shouldn't be to hard. Let me know if you have any input on the water to sodium hydroxide ratio as well as the ventilation tubing.


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## butcher (Sep 21, 2012)

Solubility of (caustic soda), sodium hydroxide solubility about 111g/100ml H2O @ 20deg.

I would try the scrubber without wood ash as it could make treating the scrubber waste more difficult, save them for the more solid powered metal waste.

Most metals are not volatile in solution unless you boil, or get the temperatures too high, and then they can be carried over in the steam fumes, so the scrubber solution could contain some metals depending on how you work, if these metals were in the solution these would precipitate at a PH of around 9, if the solution became acidic they would dissolve, some metals also dissolve in highly caustic base solutions, so here treating your scrubber solution as you do other waste would work.

If you kept the scrubber solution on the caustic side of the pH scale you could use this to treat your other waste,
I often treat my acidic waste with my caustic waste to save on chemicals used.

Most of what you will be scrubbing is fumes of acids, and these fumes in the caustic solution of the scrubber would form salts of these acids, HCl would form chlorides,

HCl + NaOH --> NaCl + H2O 
Notice here if we only had hydrochloric acid and sodium hydroxide and adjusted the to 7 pH we would just make table salt dissolved in water,

Sulfuric acid would form sulfate salts (NaSO4), nitric fumes form nitrate salts (NaNO3).


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## NobleMetalWorks (Sep 21, 2012)

You might also think about using a condenser between your reaction and fume scrubber. It should be placed so that any fumes condensed into liquid will flow/fall/drip back into the solution that is reacting. This allows you to recover some of the Nitric Acid back into your solution, it will also reduce the amount of Nitric Acid made in your scrubbing solution. They are not very expensive, and you can find many on eBay.

Also, if you are only using this for AR, and making weak Nitric Acid in your fume scrubber, this could be used for other parts of your process. 

Scott


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## Johnnycat535 (Sep 22, 2012)

Check out what I've posted on this thread http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=15371 I've include details of to how I plan to build the scrubber and fume hood. May help better understand what it is I'm doing.

Butcher: Thanks you for that answer I've been searching everywhere for it. So *IF* my math is correct that comes out be for every 1 gallon of water 9.26lbs of sodium hydroxide. To fill up 20 gallons worth of water at an average of say $1 a lbs of sodium hydroxide that be $185.20. Kinda of expensive for my budget, but would I have to go by that ratio for it to be affective? Basically I'm new and trying to stay on a budget. Also thank you for the explanation of what is happening chemically inside the scrubber. It really shed some light on what to expect. You also had mentioned you sometime treat your acidic waste with your caustic waste. Do you mean you dump say your used up AR solution into the scrubber? Sorry I'm learning everyday but not as fast as I'd like. I think I'm confused is all.

SBrown: Budget doesn't call for a condenser yet but I do hope to build one down the road. Seems like a good investment to save on chemicals. I'd like to have it actually drip into a storage container so I can later use it to process my BM's. Therefore being able to process more gold with less chemicals. Little more time but I've got nothing but it. Thanks for your input as well.


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## butcher (Sep 22, 2012)

Excess undissolved NaOH powder in the bottom of the scrubber would do no harm It would eventually dissolve as the acidic fumes condensed.


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## Johnnycat535 (Sep 22, 2012)

So you wouldn't dump you excess chemical into your solution?


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## butcher (Sep 22, 2012)

I would probably want some excess NaOH added in the beginning, that way the scrubber could scrub fumes longer without having to add more caustic or replace solution.


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## Johnnycat535 (Sep 22, 2012)

So your beaker full of used up AR you would or wouldn't dump into the solution?


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## butcher (Sep 22, 2012)

I am getting lost on what the question is.


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## Johnnycat535 (Sep 22, 2012)

What did you mean by this? I often treat my acidic waste with my caustic waste to save on chemicals used.


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## butcher (Sep 22, 2012)

Say I have an acidic waste I need to neutralize to precipitate metals from solution, I will use my caustic waste and mix these together, this brings down the pH of my caustic waste, and raises the pH of my acidic waste, in the right combination all I would use is waste to treat waste (although I do generate more acidic waste and still some addition of base to neutralize.

I will also use a highly acid waste to remove base metals.

It is hard to explain but you can move waste from one bucket to another and dissolve powders you wish to remove, say I have a bucket of copper and Iron powder that may be somewhat caustic, I can use a batch of fresh acidic waste to dissolve some iron from these powders, the caustic powders will raise the pH of this acidic waste, saving me on caustic soda later, I can also use electrolysis or cementing with a metal like iron to remove the copper from solution, leaving an iron waste solution and copper powder for cementing values from a solution.

Say I make nitric acid with a nitrate salt and sulfuric acid, I have no waste (nitric acid is used),the salts of sodium or potassium bi sulfate is used for other processes like making ferrous sulfate to test and precipitate gold.

Say I dissolve silver chloride in an ammonia solution and the precipitate it with HCl, no waste silver chloride is used, and the ammonium chloride solution is made into crystals for a reagent.

Say I have to evaporate an aqua regia solution the gas can be bubbled into another solution I wish to dissolve metals from.

Say I have some copper chloride solution that I have used to dissolve iron, now I have copper I chloride powders and an iron chloride solution, this iron chloride I may evaporate down, add some H2SO4, drive off HCl gas (recovered bubbling into water to form acid), then the ferrous sulfate is evaporated to crystallize, dissolved and re-crystallized for purity and bottled for use.

Say I have those red brown fumes from dissolving silver in nitric acid, bubbling those NO2 fumes into water with a few drops of peroxide will make nitric acid which can be concentrated with careful evaporation, why scrub a perfectly useful gas?

get the idea?

Basically do not look at your waste as waste until it is actually not useful to you, but look to see if there is a useful byproduct in the reaction.


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## Johnnycat535 (Sep 22, 2012)

Being a noob I kind of understand. Little over my head at this stage of course. I've only got about 2 months worth of research, and less then a week of hands on experiments (which I haven't experimented much at this point really). Once I have the fume hood and scrubber down pat then I'll begin to add other things to safe chemicals. I'll do further research before building that assembly. Thanks for the pointers.


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## jonn (Dec 14, 2012)

butcher said:


> Say I have an acidic waste I need to neutralize to precipitate metals from solution, I will use my caustic waste and mix these together, this brings down the pH of my caustic waste, and raises the pH of my acidic waste, in the right combination all I would use is waste to treat waste (although I do generate more acidic waste and still some addition of base to neutralize.
> 
> I will also use a highly acid waste to remove base metals.
> 
> ...


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## jonn (Dec 14, 2012)

Thank you Butcher, let's post this somewhere in the tutorial


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## UncleBenBen (Sep 10, 2015)

This may be a little off topic, but I saw the mention of ashes and water and had to speak up. Brought back some painful memories from a deer hide I tanned with it when I was about 10 years old. I didn't know it until my knuckles started to split open, that hardwood ashes in water will make lye. It's the first step in an old process for making lye soap. So if anyone is going to mix ashes and water for any reason, please wear gloves! Eye protection wouldn't be a bad idea either! Y'all be safe!


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## butcher (Sep 10, 2015)

The hardwood ashes will not tan the deer hide, we use the hardwood ash to remove the hair from the hide before tanning, basically to make raw hide, the ashes in rain water makes a caustic solution (lye or caustic soda) the caustic soda water takes the oils from the hide making soap, the swelling hide can then be DE-haired with simple scraping (to make raw hide before tanning the leather... (if the hide is left too long in the caustic solution and warmer temperature where the reactions are intinsified, the hide itself can dissolve in the caustic solution) a hide left too long in the caustic bath can become holy raw hides. :lol: 
Gloves are a good idea. 
Glasses or a face shield are a must, caustic soda in your eyes is one way to easily go blind, as your eye ball dissolves. Even washing your eyes with water is not much help if you get caustic soda in them, it takes tons of water to neutralize a drop of caustic, and who in their right mind would want to pour acid in your eyes to neutralize the caustic in their eyes while the caustic is dissolving their eyeballs?


I never personally wear gloves when De-hairing or tanning hides, but my hands have always been so callused, the caustic solution just made my hands cleaner and a bit more softer by removing the harder callused skin.

The hydroxide or caustic solution will make soap from the oils in your skin, if left long enough in solution it can dissolve all of the meat from your bones.

Back in the olden days when men sailed in ships on long voyages, when someone died on the ship they had two choices of dealing with the body, to dump it overboard burial at sea, or sometimes they may have wished to store the body to be buried on land, which may take months to reach land. without refrigeration or a way to safely store the body (and not creating disease on ship) they would pack the body in wooden barrels of caustic soda (fresh water and wood ash), the caustic solution would eat all the flesh from the bones, they could then dump this soap overboard, and dry the bleached bones and haul them with them until they reached land for burial.


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## UncleBenBen (Sep 11, 2015)

Very true sir. Butcher you are a wealth of information. I am thoroughly enjoying your posts! I should have mentioned it as the first step in tanning that hide. First one I successfully completed, and made myself a nice pair of knee high moccs with it after waiting a few weeks for my young soft hands to heal up! By the way, a mix of the brain and liver on rubbed into the raw side and the hair will just wipe off after about a day if you keep it warm!


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