I’m pretty new to PM refining and just purchased a $80 vacuum pump for my Büchner funnel for obvious reason. The issue is that the thing has already seized up due to what I can only assume is corrosion after one full run extracting gold from GF material. Is there a way to keep this from happening. I know there’s lab anti corrosion vac pumps for big $, but don’t want to spend that.. TIA!
Help With Vacuum Pump
- Thread starter BRC1
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If you set up a Buchner with lye solution in then add the line from the vacuum into the Buchner which is sealed on the top with a rubber bung and a line out to your filter flask that should keep most of the corrosive fumes away from your pump, also do not set your pump up inside your hood as the fumes will still wreck it fairly fast .
Easiest is a plastic venturi pump.
If you don't have access to mainline water, just use a cheap waterpump to pump water from a keg/barrel/bucket in a way that eject the water back into the same reservoir.
No water use and nothing becomes fumed down.
And if there is a spillover either by accident or co drag, no problem it is all in the bucket.
If you don't have access to mainline water, just use a cheap waterpump to pump water from a keg/barrel/bucket in a way that eject the water back into the same reservoir.
No water use and nothing becomes fumed down.
And if there is a spillover either by accident or co drag, no problem it is all in the bucket.
i appreciate the reply! i already had a replacement sent to me from the manufacturer so if there's anyway to use this pump i would like to go that route. Does anyone know if a cold trap would work for HCL vapors? that's really what the issue is. When i separate the gold precipitate after using SMBS the fumes are awful. All the nitric is gone as i use just enough or denox with Sulfamic acid but the HCL vapors are insane when vacuuming.
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Most acid vapors (other than SO2) and mists are nearly eliminated by an alkali trap, even something mild like sodium carbonate solution has a great affinity for HCl. I set up a little bubbler in a mason jar, with the line from the flask going to the bottom of the jar so it bubbles up through the solution, and the line to the vacuum pump coming from the top of the jar (above the solution). I like mason jars for this because you can epoxy the tubing into the lid and still unscrew the jar to change the solution.
It's still good practice to drain and change the vacuum oil after pulling anything corrosive through.
The little manually operated piston pumps (like for bleeding brake lines) will also work on a Buchner, they're all plastic in the pressure path, although it will give your forearms a workout if you need to pull for more than a minute or two.
It's still good practice to drain and change the vacuum oil after pulling anything corrosive through.
The little manually operated piston pumps (like for bleeding brake lines) will also work on a Buchner, they're all plastic in the pressure path, although it will give your forearms a workout if you need to pull for more than a minute or two.
Thanks for the response! I just bought a vacuum chamber that I think I can I mod into something like what you refer to above. Do you happen to have a pic of your set up?
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I set up this scrubber jar several years ago, evidently I used 1/4" HDPE tubing and fabricated a thick HDPE jar lid for these small 16oz mason jars. The sealant appears to be hot glue (epoxy doesn't really work on HDPE, and I hadn't gotten comfortable with silicones yet). I have some recollection of needing a bit of petroleum jelly on the jar mouth to get an airtight seal on the fabricated lid, so perhaps the original canning jar lid would have been a better choice (assuming the metal lid doesn't corrode through before you're done using it!).
Hopefully the basic idea is clear: the inlet line (with the incoming arrow) runs to the bottom of the alkaline scrubber liquid and has small holes to bubble up your acid vapor / mist through the scrubber liquid; the outlet pulls the scrubbed gas from the airspace on top of the liquid off to your vacuum pump (which pulls the gas in at the inlet). The same exact setup can be filled with desiccant if you don't have an inline drier before your vacuum pump, since water picked up at the scrubber will slowly accumulate in the oil and corrode your vacuum pump too.
The glass jar seems to hold up fine with reasonably dilute sodium hydroxide scrubber liquid, although for HCl even plain water would likely remove most of the acid vapor. You could probably fill the jar with marbles to make the bubbles spend longer in contact with the liquid if the short path isn't getting rid of enough.
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Quiklearner
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Proper gas washing bottles (Drechsel bottles) are only around $30-$40 bucks on Amazon. I used 2 of them, in line, as scrubbers on the output of a Birkeland-Eyde reactor with great success.
Also, you may want to let your vacuum pump run for a few minutes after filtering to help clear out any acidic vapors.
Also, you may want to let your vacuum pump run for a few minutes after filtering to help clear out any acidic vapors.
Basic scrubber is needed when working with acidic vapors arising from AR and AP stuff. Chlorine, NOCl and NOx gases have very bad impact on the rubber and with time also on plastic. Metals are corroded very quickly by HCl vapors and practically any other vapors created in common recovery processes. If the vacuum pump is filled with oil - NOx and chlorine like to polymerize the oil inside - you will need to change it more often, because it is more quickly turned to jelly/grease.
Scrubbing acidic vapors like HCl is relatively easy, and very convenient trap is using solid scrubber - like granulated lime. It must be done properly to avoid clogging tho. We used lime and powdered slaked lime.
We also had scrubbers with aqueous hydroxide solution - on the inlet of the pump, gas bubble through relatively high column of the basic solution (at least 20-30 cm vertical). We conveniently used a fritted glass on the end of the submerged tubing to create very small bubbles=big surface area for adsorption.
One thing that prolong the lifespan of the pump is pressure regulator. Could be purchased for like 20-30 euros on aliexpress. Basically, it switch the pump on, when pressure is like 800mbar. Then shut the pump down, when it reach like 250 mbar. Then turn on only when pressure reach 800mbar again.
With this regulation, runtime is lowered to the minimum=less possible corrosion from evolved gasses. Also, when vacuum is quite deep (less than 100 mbar), it tend to suck out more of the HCl gas from the liquid. Because of this, regulator is strongly advised to minimize the unnecessary evaporation of the acidic gases to the pump. Because of this, it is also very good to make the apparatus tight = less time for the pump to reach proper level of vacuum = less gasses pulled through.
On the cheap and safe side -as suggested by Yggdrasil - there is aspirator vacuum pump, recycling water inside big barrel of water with small pressure pump. This setup is very cheap, highly resistent to acidic vapors, and simultaneously scrubb the gasses to the water in the barrel.
I used it extensively - 12V 80W membrane pressure pump from aliexpress (5,5 L/min flowrate but 1,5 MPa max pressure) connected to the classic glass aspirator pump, recycling water inside the 50 or 120 L barrel. Only drawback is the runtime, as these cheap pumps overheat very quickly. Submersible types are better in the means of runtime as they cool themselves in the liquid - but on the other hand, seals and metallic parts in the pump are wrecked more quickly than on the membrane pumps.
Also, you need a good bit of water (said 50-100 L), because it heat up quite a bit from running the pump.
Sadly, this type is not compatible with pressure regulators - stopping the pump with evacuated apparatus will quickly flood your tubing and apparatus because of negative pressure inside suck the water in.
Scrubbing acidic vapors like HCl is relatively easy, and very convenient trap is using solid scrubber - like granulated lime. It must be done properly to avoid clogging tho. We used lime and powdered slaked lime.
We also had scrubbers with aqueous hydroxide solution - on the inlet of the pump, gas bubble through relatively high column of the basic solution (at least 20-30 cm vertical). We conveniently used a fritted glass on the end of the submerged tubing to create very small bubbles=big surface area for adsorption.
One thing that prolong the lifespan of the pump is pressure regulator. Could be purchased for like 20-30 euros on aliexpress. Basically, it switch the pump on, when pressure is like 800mbar. Then shut the pump down, when it reach like 250 mbar. Then turn on only when pressure reach 800mbar again.
With this regulation, runtime is lowered to the minimum=less possible corrosion from evolved gasses. Also, when vacuum is quite deep (less than 100 mbar), it tend to suck out more of the HCl gas from the liquid. Because of this, regulator is strongly advised to minimize the unnecessary evaporation of the acidic gases to the pump. Because of this, it is also very good to make the apparatus tight = less time for the pump to reach proper level of vacuum = less gasses pulled through.
On the cheap and safe side -as suggested by Yggdrasil - there is aspirator vacuum pump, recycling water inside big barrel of water with small pressure pump. This setup is very cheap, highly resistent to acidic vapors, and simultaneously scrubb the gasses to the water in the barrel.
I used it extensively - 12V 80W membrane pressure pump from aliexpress (5,5 L/min flowrate but 1,5 MPa max pressure) connected to the classic glass aspirator pump, recycling water inside the 50 or 120 L barrel. Only drawback is the runtime, as these cheap pumps overheat very quickly. Submersible types are better in the means of runtime as they cool themselves in the liquid - but on the other hand, seals and metallic parts in the pump are wrecked more quickly than on the membrane pumps.
Also, you need a good bit of water (said 50-100 L), because it heat up quite a bit from running the pump.
Sadly, this type is not compatible with pressure regulators - stopping the pump with evacuated apparatus will quickly flood your tubing and apparatus because of negative pressure inside suck the water in.
I refine at a hobby level only... So if you're going to constantly do large amounts of material this probably won't last long.
Go to Amazon type in "12 volt vacuum pump", I've used this for a long time now. They have a plastic housing with a silicone diaphragm and check reeds. Initially I thought about putting in a gas wash bottle with a dispersion tube to catch the acidic gases... but I got lazy. I have never used a fume scrubber, So once a year or if I accidently draw in acid I clean the diaphragm/reeds. I usually don't run it for more than five minutes at a time so I can't comment on how long before it over heats. I tested it when I first got it and if I remember right I was getting -10/ -15 psi (-20/-30 inHg). To power my pump I use an old computer power supply with an in-line fuse. I have everything mounted under my work bench with plumbing ran to my fume hood and the outlet tube vented outside.
Two draw backs: It doesn't pull a lot of volume, so if there is any leaks in your set up, it may take a minute to reach vacuum. Second, It is slightly loud when it's running.
Go to Amazon type in "12 volt vacuum pump", I've used this for a long time now. They have a plastic housing with a silicone diaphragm and check reeds. Initially I thought about putting in a gas wash bottle with a dispersion tube to catch the acidic gases... but I got lazy. I have never used a fume scrubber, So once a year or if I accidently draw in acid I clean the diaphragm/reeds. I usually don't run it for more than five minutes at a time so I can't comment on how long before it over heats. I tested it when I first got it and if I remember right I was getting -10/ -15 psi (-20/-30 inHg). To power my pump I use an old computer power supply with an in-line fuse. I have everything mounted under my work bench with plumbing ran to my fume hood and the outlet tube vented outside.
Two draw backs: It doesn't pull a lot of volume, so if there is any leaks in your set up, it may take a minute to reach vacuum. Second, It is slightly loud when it's running.
