# Packing material for scrubber columns



## madscientistatlarge (Sep 18, 2022)

I've been reading the scrubber posts and had a question. Would something like plastic pellets (the kind they sell for plastic injection molding) make good column packing? IIRC most are about 1/4" or less. Also, if used in layers would fiberglass be reasonable or would there be too much pressure drop in a tall enough to work column. I definitely don't want to harm my neighbors or draw attention. Thanks.


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## orvi (Sep 18, 2022)

You want to have surface area as large as you can together with blocking the air passage minimally. In industry, they use ceramic rings as a standard (like when you take tubing and cut it into small pieces). Pellets have insanely high dead-mass, so not much benefit of them. You will be OK with PE or PP plastic I think. Not the best, but it will certainly work - if the plastic won´t be too much hydrophobic. Glass or ceramic rings are the thing of choice, as they are nicely wetted by water and are corrosion resistant.

Wool will dampen and act as impermeable solid after very short time.

One thing that is also usable is PP or PE mesh used for windows to protect from the insects. You can take a roll of it, make very little spaces between layers, and put this "spiral" of mesh into the scrubber (I would conveniently use large diameter PVC sewer pipe). Nice thing about the mesh is inside the individual "windows", due to surface tension of water, you will not only wet the surface of it, but also fill these "windows" with water, enlarging the surface area even more.


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## madscientistatlarge (Sep 18, 2022)

Thank you! I was also thinking about aquarium size gravel, thou obviously it would dissolve slowly. Any recomended sources for the glass/ceramic rings in smallish quantities? Thanks. P.S. I've been a lab tech at a couple of places and I'm a total science geek, but unfortunately never worked with these types of chemistry (PMG). I was planning to use pvc pipe for the scrubber. PP and PE for extraction gear. If I build a bigger hood/scrubber I'll likely use used 55 Gallon drums, they are cheap/free if used.


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## orvi (Sep 18, 2022)

madscientistatlarge said:


> Thank you! I was also thinking about aquarium size gravel, thou obviously it would dissolve slowly. Any recomended sources for the glass/ceramic rings in smallish quantities? Thanks. P.S. I've been a lab tech at a couple of places and I'm a total science geek, but unfortunately never worked with these types of chemistry (PMG). I was planning to use pvc pipe for the scrubber. PP and PE for extraction gear. If I build a bigger hood/scrubber I'll likely use used 55 Gallon drums, they are cheap/free if used.


Try to find some manufacturers and ask about smaller quantity. Take it big and write everyone you find, most of them won´t even respond  but maybe you will be lucky. I doubt they will sell you less than a drum, but you will need about that quantity.

Everything you need is here on the forum, just search for it. Ask before commiting some wild half-baked plan to get rich quickly  many reputable members here can guide you, and it is always easier to stop something, than resolving mess created 

PE or PP reaction vessels came with their own troubles - biggest one, they are very tricky to heat. And you will need heating for sure. You need to figure out how you will do it, because hotplate won´t do anything nice  I advise you to stick with beakers for the start and practically use glass wherever possible.


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## madscientistatlarge (Sep 18, 2022)

Thank you again. I was planning on the plastic drums only for recovery. I was going to pump the solution and use misting nozzles with an inline heater (likely inductive heating to avoid corrosion issues) to minize the solution volume/maximize solution metal content. This would be for electronic gear, mostly whole circuit boards and later I'll worry about what's in the chips. I'm designing for 140 Deg F for a maximum temperature. I'll be using a borosilicate or titanium thermowell for temperature measurement on the recovery tank. For that part of it I'll be using magnetically coupled corrosion resistant pumps with coated magnets to circulate the solution.

That's exactly why I'm asking, I really don't want any unnecessary expenses or problems. I was planing on borosilicate for all the refining steps. 

O.K, I've found polyethylene mesh cheap on Aliexpress. What kind of mesh size would be optimalish? Thanks to all, I plan to thoroughly plan this so I'll be asking more questions as I obviously haven't done this before, and I'm smart enough to know there are hazards and have already learned the hazards of some of the metals that are very hazardous to recover. I'll also be trying all the steps in small quantity in the hood before I even start going at the volume recovery/purification. Expecting ounce quantities in the end, probably 1-2Oz.

A good scrubber is a big part of staying safe. I will also be using respirator with appropriate cartridges for what can be filtered, Caution with the HN03 fumes and other nitrous oxides as I've seen here that they don't filter out in respirator cartridges, I figured they probably wouldn't given the reactivity of nitric acid, anything that would work would likely generate a lot of heat/fire. Will absolutely be using a fume hood for all the refining and forced ventilation for the recovery step (with minimal venting and slow addtion of chemicals while watching the temperature) with close monitoring (and scrubbing of the vent gasses during recovery).


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## orvi (Sep 18, 2022)

madscientistatlarge said:


> Thank you again. I was planning on the plastic drums only for recovery. I was going to pump the solution and use misting nozzles with an inline heater (likely inductive heating to avoid corrosion issues) to minize the solution volume/maximize solution metal content. This would be for electronic gear, mostly whole circuit boards and later I'll worry about what's in the chips. I'm designing for 140 Deg F for a maximum temperature. I'll be using a borosilicate or titanium thermowell for temperature measurement on the recovery tank. For that part of it I'll be using magnetically coupled corrosion resistant pumps with coated magnets to circulate the solution.
> 
> That's exactly why I'm asking, I really don't want any unnecessary expenses or problems. I was planing on borosilicate for all the refining steps.
> 
> ...


I would rather than building production-scale equipment, invested time into getting familiar with the recovery process on the material you intend to process. In addition, in bulk quantity, hydrometallurgy become very tedious and overwhelming. Processing boards with acids is generally a very bad idea since leaching in nowhere efficient, recementation is real and so is ammount of liquid waste.

Any bigger company doing whole boards is going pyrometallurgy. Incinerate, smelt down, pyrometallurgically refine the melt and then electrowinning of copper. Precious metals will stay in slimes.

Respirators aren´t of a great help with NOx fumes. Do not rely on a respirator please


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## madscientistatlarge (Sep 18, 2022)

orvi said:


> I would rather than building production-scale equipment, invested time into getting familiar with the recovery process on the material you intend to process. In addition, in bulk quantity, hydrometallurgy become very tedious and overwhelming. Processing boards with acids is generally a very bad idea since leaching in nowhere efficient, recementation is real and so is ammount of liquid waste.
> 
> Any bigger company doing whole boards is going pyrometallurgy. Incinerate, smelt down, pyrometallurgically refine the melt and then electrowinning of copper. Precious metals will stay in slimes.
> 
> Respirators aren´t of a great help with NOx fumes. Do not rely on a respirator please


I definitely won't rely on a respirator alone, just as protection from some of the less nasty stuff during recovery (and with excellent ventilation) and supplemental protection on the refining side.

I've already researched the process I plan to use for recovery, it's sound. I'll be using a sodium hydroxide plus slowly added H2O2, while monitoring the Redox potential. Yes, this is a piranha solution and eats flesh very quickly. I know of a plumber who removed a P-trap after someone was kind enough to use 3 bottles of drain opener on a clogged sink, the kind that's hydroxide plus bleach. It immediately removed all the flesh down to the bone. I'll be adding the H2O2 slowly, and after base metal recovery I'll deactivate it with some Manganese oxide which rapidly catalyses H2O2 to water and oxygen (else on drying you can have sodium peroxide, very nasty stuff). Yes, everything involved in any extractive metallurgy is hazardous. I don't want to use the pyro technique as it's terribly polluting, produces carcinogens, and it's hard to clean up the gasses generated. I am aware that people use fire for this often and on a very large scale it is practical.

Scale wise I'm not going too big, and I will test before I build equipment to verify. Random ideas get expensive very quickly. Fortunately I'm fairly good at doing library and internet research which eliminates many ideas quickly. Still, I will test all reactions in a small beaker first. I will have a pH and Redox probe and will test samples often, especially at first


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## 4metals (Sep 18, 2022)

The benefit of pyrometallurgy before a copper cell is the low quantities of chemicals used versus through put. What you seem to be working towards will generate a lot of waste liquors if you scale it up.


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## orvi (Sep 18, 2022)

4metals said:


> The benefit of pyrometallurgy before a copper cell is the low quantities of chemicals used versus through put. What you seem to be working towards will generate a lot of waste liquors if you scale it up.


As not always easy and straightforward, apparent push was always towards pyro due to reduction of volume, that is for sure. As an old saying, look what big guys are doing, and it is probably the state of the art and most economic way currently developed 



madscientistatlarge said:


> I definitely won't rely on a respirator alone, just as protection from some of the less nasty stuff during recovery (and with excellent ventilation) and supplemental protection on the refining side.
> 
> I've already researched the process I plan to use for recovery, it's sound. I'll be using a sodium hydroxide plus slowly added H2O2, while monitoring the Redox potential. Yes, this is a piranha solution and eats flesh very quickly. I know of a plumber who removed a P-trap after someone was kind enough to use 3 bottles of drain opener on a clogged sink, the kind that's hydroxide plus bleach. It immediately removed all the flesh down to the bone. I'll be adding the H2O2 slowly, and after base metal recovery I'll deactivate it with some Manganese oxide which rapidly catalyses H2O2 to water and oxygen (else on drying you can have sodium peroxide, very nasty stuff). Yes, everything involved in any extractive metallurgy is hazardous. I don't want to use the pyro technique as it's terribly polluting, produces carcinogens, and it's hard to clean up the gasses generated. I am aware that people use fire for this often and on a very large scale it is practical.
> 
> Scale wise I'm not going too big, and I will test before I build equipment to verify. Random ideas get expensive very quickly. Fortunately I'm fairly good at doing library and internet research which eliminates many ideas quickly. Still, I will test all reactions in a small beaker first. I will have a pH and Redox probe and will test samples often, especially at first


I quite cannot relate to the statement that pyrometallurgy is terribly polluting and creating carcinogenic waste more than hydrometallurgy. I am in this "business" for quite a few years, two or three in bigger scale for most of the time. Pyro is much easier to handle, if done right no toxic outgas is produced (and overwhelmigly less ammount of outgas to scrubb as with hydro) and if toxic waste as some metal slags is produced, it is fraction of the volume which is created by hydro treatment.

Rule of thumb is you need 4L of HCL and 1L of HNO3 to dissolve 1kg of base metal such as copper/nickel/tin alloys usually found in e-scrap. Say you want to process e-stuff that is net weight of 15kg in BM + precious metals. You will need to apply at least 75 L of acids, creating some 75L of acidic heavy metal waste. Which you then need to either cement or basify with unhealthy ammount of hydroxide, creating hydroxide or cement metal slime, which you either dispose or give/sell to large smelters. And I will say you, you better have few tons of it, because in smaller lots, *they don´t even respond to your request to take the metals FOR FREE.*

On the other hand, you can pyrolyze/incinerate the lot of e-stuff down to metallic ingot containing every metal imaginable in one puddle. Then you apply pyrometallurgy magic, for example you oxidize reactive base metals like remains of iron (which should be avoided as much as possible in the feed), tin and lead by oxygen sparging of the melt (cost of the oxidant = 0 USD, in comparison with nitric acid around 1-2 USD/L tech grade bulk). You obtain relatively usable copper ingots with PM contained, which you then DOES NOT DISSOLVE, but electrowin to get payable copper and PM slimes. *These 15kg of BM would represent around 2 L of the molten metal. 35x fold difference against hydrometallurgy.* And your tin and lead are nicely contained in the slag with volume equivalent to few bricks. Plus sellable copper benefit, not bleeding with hard to filter awful hydroxide cakes which nobody wants.

I am going pyro anytime I possibly can for the sake of my mental health and cost + time saving. Of course it need bigger starting capital, like building your own gas-furnance of suitable proportion, or even better - purchasing larger induction furnance. We have 35 kW one, and surprisingly you can get one under 5000USD, brand new from China. Electricity is much cheaper and effective than gas nowdays. Crucibles of these proportions are nowhere cheap, but if you are clever enough, you purchase dead-burnt magnesia for few bucks, and from mix of portland cement and magnesia press your own crucibles or scorifying/cupelling boats/trays. Or line the fine purchased SiC/graphite/clay crucibles with magnesia from inside to protect the crucible and greatly prolong it´s life.


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## 4metals (Sep 18, 2022)

And the base metal containing slags are relatively compact. They are also encased in glass slag so, for the most part, insoluble. Here in the US they pass the TCLP (toxic leach process) so they are considered non hazardous. 

However if high in tin, some consideration should be made about recovery or sale as a concentrate.


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## madscientistatlarge (Sep 25, 2022)

Orvi, I respect what you are saying, but that is no where near the process I posted above. And yes there will be a lot of tin, and also palladium. 5K for a furnace alone (though I can build an inductive furnace) is way, way out of any budget. Labor not an issue for me. Also, electricity sure isn't cheaper than natural gas here in the U.S. I plan to recover ALL the metals to the extent possible, including also the copper. I've actually read about the very method you suggest, noting also that if there isn't sulfur the boards are burned as well, otherwise just cooked in a gas heated vacuum. It requires rather large vacuum pumps and bag houses. If the gas isn't moved out of the hot zone quickly enough you get all kinds of nasty organic fragments/radicals. I also don't need that production rate to make it well worth my time etc. By the way, I'm nearly 60 years old and have built electronic and other lab gear involving multiple disciplines. As I said, before I build gear I'll try it in beaker quantities, in a proper acid/other fume hood. On smaller scales most industrial processes are completely unworkable or proportionally very expensive to set up compared with the production rate. Different process work best at different scales. It is notoriously hard to scale from bench scale to industrial scale for many processes that would be great otherwise. Also, not renting a large commercial space. Not having so high a process rate, but reasonable for every consideration involved. Yes, using aqua regia to disslove base metals would be foolery, not to mention the heat generation. Not what I'm planning. And frankly there are pollution problems in pyro metallurgy that do, in general, make it a dirtier process than hydrometallurgy per many sources, hence the move in the metals extraction business away from pyro and to hydro. Or do you think such industrialist to be fools?


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## eaglekeeper (Sep 25, 2022)

madscientistatlarge said:


> I've been reading the scrubber posts and had a question. Would something like plastic pellets (the kind they sell for plastic injection molding) make good column packing? IIRC most are about 1/4" or less. Also, if used in layers would fiberglass be reasonable or would there be too much pressure drop in a tall enough to work column. I definitely don't want to harm my neighbors or draw attention. Thanks.



I'm not sure how big of a scrubber you are looking to build. If it's small enough you could use glass marbles as packing material.... If you are in the US you can probably pick up a ton of them at the Dollar Store.... Correction, with inflation it's now the $1.25 Store.


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## madscientistatlarge (Sep 26, 2022)

Actually I'll try the polyethylene insect mesh. Very cheap on aliexpress for a large volume. Now I have to figure out which solutions will wet the poly and which won't and what I can use as a degergent or other wetting agent. Planing to use the counterflow design, especially for a small hood. To reduce the air flow into the hood I was thinking about a segmented plastic window in strips magnetically secured to the front of the hood. That way I can open just one horizontal section to reach what I need to reach. I did think of gloves (as in glove box) but they are definitely a major hassle. Of course I'll have to wear chemical safety gloves. Everything involved is toxic, carcinogenic, or corrosive if not all three. Not surprising, we are talking about recovering/refining heavy metals, and obviously the reason gold is simple to extract is that all the other metals are soluble in solutions less oxidizing than aqua regia. In any case, that's a couple of months away, next month I do beaker scale trials. I don't have money to waste being stupid, and I usually plan things out fairly well including trying what I can't find a reference for as well as the straight forward things.


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## orvi (Sep 26, 2022)

madscientistatlarge said:


> Orvi, I respect what you are saying, but that is no where near the process I posted above. And yes there will be a lot of tin, and also palladium. 5K for a furnace alone (though I can build an inductive furnace) is way, way out of any budget. Labor not an issue for me. Also, electricity sure isn't cheaper than natural gas here in the U.S. I plan to recover ALL the metals to the extent possible, including also the copper. I've actually read about the very method you suggest, noting also that if there isn't sulfur the boards are burned as well, otherwise just cooked in a gas heated vacuum. It requires rather large vacuum pumps and bag houses. If the gas isn't moved out of the hot zone quickly enough you get all kinds of nasty organic fragments/radicals. I also don't need that production rate to make it well worth my time etc. By the way, I'm nearly 60 years old and have built electronic and other lab gear involving multiple disciplines. As I said, before I build gear I'll try it in beaker quantities, in a proper acid/other fume hood. On smaller scales most industrial processes are completely unworkable or proportionally very expensive to set up compared with the production rate. Different process work best at different scales. It is notoriously hard to scale from bench scale to industrial scale for many processes that would be great otherwise. Also, not renting a large commercial space. Not having so high a process rate, but reasonable for every consideration involved. Yes, using aqua regia to disslove base metals would be foolery, not to mention the heat generation. Not what I'm planning. And frankly there are pollution problems in pyro metallurgy that do, in general, make it a dirtier process than hydrometallurgy per many sources, hence the move in the metals extraction business away from pyro and to hydro. Or do you think such industrialist to be fools?


If you want to find yourself eventually making some profit for yourself and not just spending your time for few dimes revenue, you need to have equipment to do so. Efficiently.
If your material are whole boards, you find hydrometallurgy processes very tiring and resource intensive. And waste producing at an enourmous rate. Even with cleaned components like RAM IC chips, of some other material like fingers (which are easily done with AP = hydro), I would make a calculation when intended to process like a ton of this material - if it is worth investigating pyro possibilities, even fingers are probably the best material for hydro.
If you are afraid of nasty organics and "radicals", just add air  and burn it properly. Properly burning gas furnance can be build very cheaply, that´s right. And no nasty radicals would be ever produced outside of it. Just CO2, N2 and water. Like nicely functioning big scale waste incinerator, more than 800°C inside, little excess of air. Your material adds enormous portion of energy needed to properly burn it. If you work it up still hot (600-800°C after incineration) and directly smelt it, you save a ton of energy. More healthy outgas than your campfire, sadly. Saying as an organic chemist.

Now I am interested. Name some of the pollution problems with pyrometallurgy, which are harder and more expensive to fix than with hydro. What exactly is shifting to hydrometallurgy ? Aside of Li-Ion recycling due to reasons folks also want to extract Li from the feed now ? And which of that is real thing and is making money, or it is just R&D or PR move of the big guys which just look nice - no CO2 in the promo video


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## madscientistatlarge (Sep 26, 2022)

I'll only be reocvering from 200+ pounds, already on hand and I can get more. I'll probably do a small extraction every 2-3 months.

Re: pyrometalurgy Vs hydrometalaurgy, Let me check my books, sadly my ebooks aren't organized yet.


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## olawlor (Sep 26, 2022)

eaglekeeper said:


> I'm not sure how big of a scrubber you are looking to build. If it's small enough you could use glass marbles as packing material...


I was impressed how well just 10cm of wet marbles scrubbed red-brown NOx fumes, which I was getting from dissolving multi-ounce batches of silver in nitric. I just used a wide-mouth funnel filled with a few handfuls of marbles, sitting on top of the beaker so the fumes rise up into them, and kept the marbles moist with distilled water occasionally dribbled down from on top. 

I was mostly doing it to recycle my homemade nitric, but the former angry red fumes were also made completely invisible. (Of course, this still needs a good fume hood, NOx is a silent killer.) 

This was well below a liter, scaled up to bucket size the weight of the marbles would start to become an issue, and rings or mesh would be lighter to move around.


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## madscientistatlarge (Sep 26, 2022)

A small one for flask in the hood, and a larger but less critical one for the hood. I'll probably shoot for 200-400 CFM for the hood. Hood will not be completely open during reactions/reagent addition, just for cleaning and stocking.


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## madscientistatlarge (Sep 30, 2022)

After visiting web sites I see that "structured" packing is usually more efficient. I"m thinking of single wall corrugated polyethylene sheeting. It comes on huge rolls. It's cheap. It can easily be rolled up and stuffed into any round vessel. It's polyethylene so its chemically resistant. I'd use a plastic rod to fill the center as you can't roll it tightly around it's center. The openings are about 4mm, should work great for anything other than lime, but should work great with sodium hydroxide solution.


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## Skeeter8154 (Nov 19, 2022)

madscientistatlarge said:


> Thank you! I was also thinking about aquarium size gravel, thou obviously it would dissolve slowly. Any recomended sources for the glass/ceramic rings in smallish quantities? Thanks. P.S. I've been a lab tech at a couple of places and I'm a total science geek, but unfortunately never worked with these types of chemistry (PMG). I was planning to use pvc pipe for the scrubber. PP and PE for extraction gear. If I build a bigger hood/scrubber I'll likely use used 55 Gallon drums, they are cheap/free if used.


I’m using 1” diameter glass gems from a craft store


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