Chemically regenerating my auto's catalytic converter?

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In summary: The effectiveness of oxalic acid and citric acid washing on the deactivation of a commercial three-way catalyst” (2008).In summary, this CA smog test involved checking the car's emissions and the engine code was P0420. The car's cat (a part that helps the engine run smoothly) may have gone bad and needs to be replaced, but there is also the possibility that the cat is just old and will eventually die. The researchers in Europe are trying to find a way to regenerate the cat without having to replace it.
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BadCatP0420
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Researchers successfully regenerated chemically poisoned catalytic converter substrates in laboratory; I want to do it to my car's 'cat', but first some basic chemistry ?'s. Pls help; thanx!
Greetings folks! Total noob (and total chemistry layman) here, so apologies in advance for anything I screw up, and also for my lack of brevity, but this will unfortunately take a bit.

I live in CA & drive an "older" vehicle (technically a 'classic'). CA has strict emissions requirements, which (on older vehicles) are tested bi-annually (& MUST be passed) prior to registration renewal. Smog test was due in March and it passed, but with the lowest possible score on one of the tests. In the months immediately preceding my smog test, my car's dreaded Check Engine Light (CEL) came on a few times intermittently; it has never otherwise come during the whole time I've owned this car. It has also re-illuminated a few times since the test. It ain't going away and it ain't going to fix itself.

So this is war! I’ve always wanted to better understand the auto emissions processes because knowledge is power and before some mechanic says, "Bro, you need new cat; 2 G’s My Friend," I want a second opinion, to understand the process, and what my options are going to be. Since the D-minus-minus smog score, I’ve set about to learning everything I can about emissions, how my car makes them, why it’s making them at the levels it’s currently making them @, catalytic converters, what causes them to fail, what can be done to improve my car’s emission output, how can I make it burn its fuel and air more efficiently, what are the ways a cat can go bad, and what can be done with a “BadCat” throwing a P0420 code.

If you don’t know, generally speaking, when your car’s engine experiences a problem, mishap et. al., its engine management computer (usually ECM) will signal a “code” which pertains to that specific mishap and thus illuminate the dreaded CEL. Plugging a scanner into your vehicle’s OBDII port, will tell the scanner what code (or problem) the engine is having. In my case, the code is P0420 which, when you look that up, means that my engine’s "Catalyst Is Operating Below It’s Intended Efficiency Threshold."

When you Google how to fix this, you get the phonebook. Could be a bad O2 sensor; could be a bad cat; could be a vacuum leak; could be a bad MAF sensor; could be a dirty throttle body; running too lean; too rich; clogged fuel injectors, leaky fuel injectors, & on & on & on… (If one is not careful, a situation such as this can easily become what some “car guys” call a 'parts cannon': one just keeps throwing replacement parts at a problem until something fixes it, without ever having correctly determined where the real problem(s) is/are.) So I give my trusty neighborhood mechanic 2 G’s to replace my dead cat, but whatever killed it may still be out there. Treating the symptom may alleviate the condition temporarily, but underlying problem(s) may in fact still be present, and my hypothetical new cat (& my 2 G’s) would then be next up on the proverbial chopping block.

It could just be that my car’s cat is 25 years old and things simply wear out after while, or it could be mechanically dead, (substrate has melted or broken apart) in which case I will have to pony up the 2 G’s, or it could simply be “chemically dead”, in which case (as you will shortly find out if you’re patient enough to continue reading) it may be able to be “chemically regenerated”.

In my quest to gain as much knowledge about the subject as I can, (it’s ongoing) I discovered research being conducted by some chemistry professors in Europe (1 in Sweden, 2 in Cyprus & 1 in Spain, although the Spaniard has recently passed away) with regard to chemically treating “heavily used” catalytic converter substrates (their internal ‘active ingredient’) in order to regenerate the catalyzing performance: essentially de-poisoning a chemically poisoned (i.e.: non-functioning, but otherwise intact) converter. And this research (though conducted scientifically in lab conditions (per the papers I read)) was ultimately geared toward performing this chemical regeneration in situ: that is, on actual practical catalytic converters that are presently part of an operational vehicle’s exhaust system. Wow! Fascinating! You have my complete attention!

I am not sure how to post / append .pdf files – if someone knows how to, please lmk. I had to jump through some gate-keeping hoops in order to download and read the full papers, but I have 3 of them locally on my own computer.

If interested, you can search for “Reactivation of an Aged Commercial Three-Way Catalyst by Oxalic and Citric Acid Washing” (2006), “Reactivation of severely aged commercial three-way catalysts by washing with weak EDTA and oxalic acid solutions” (2007), and “Regeneration of Aged Commercial Three-Way Catalysts Using CI-Containing Reagents” (2013). But I think all you will be able to read without first signing up are the abstracts / teasers from each.

I will try to link the papers I read here:
(2006): https://pubs.acs.org/doi/10.1021/es052310t
(2007): https://www.sciencedirect.com/science/article/abs/pii/S0926337306003936
(2013): https://www.academia.edu/33689322/R...ee_Way_Catalysts_Using_CI_Containing_Reagents

So what did these professors / researchers do and how did they do it? As mentioned, they did their work in labs, not in auto repair shops, so there’s going to be significant differences between the researcher’s applications and my own, and therein will be the chemistry questions I will ultimately come to in this post. But the results of their experiments are undeniable and astounding!

To paraphrase, they opened up severely used cats and removed the substrates. From the substrates, they cut out cubes of about 2 cm x 2cm x 2cm – sample pieces. They placed each of these “cubes” into a kind of laboratory “flow tube” enabling a solution to pass into the tube, over and thru the substrate cube and then back out of the tube. This was plumbed into a system consisting of a peristaltic (roller) pump, a heater, a supply vessel containing a 0.1 molar acid wash of (in the first case) EDTA (Ethylenediaminetetraacetic) acid solution, and (in the second case) a 0.1 molar Oxalic acid solution.

Their most dramatic results involved heating EDTA solution to 50º C and then flowing it at a rate of 600 ml / minute for 60 minutes. After which, the cubes were washed with water for 30 minutes at 600 ml / minute and then the second solution (also heated to 50º C) was flowed, again for 60 more minutes at 600 ml / minute. After the second solution flow completed, the cubes were again washed with water for 30 minutes at 600ml / minute and then thoroughly dried. It should be noted that the researchers flowed their solutions over the substrate cubes in the opposite direction of the normal flow of exhaust; but none of the papers I read explained why.

Before and after testing with real world exhaust gasses revealed astounding reductions in the amount of elements and compounds that had been “chemically poisoning” (& thus rendering inactive) the substrate cubes, the presence of which (prior to the acid washes) had rendered the Platinum, Palladium & Rhodium coatings of the substrates ineffective at both conversion and oxygen retention. These ‘poison’ reductions vis-a-vie the acid backwashes reactivated the catalyzing effect on the exhaust gasses significantly, in some cases 60%, 70%, 80%, 90% restoration (if I read correctly)!

As I understand it, a car’s exhaust gas is primarily composed of Hydro Carbons (HC) – unburned fuel, Carbon Monxide (CO) – the silent killer, & Nitrogen Oxides (NOx) – byproducts of lean fuel / air mixes, hot combustion temps, and are also smog forming particles. The way a properly functioning cat works is that its honeycomb substrate is coated with thin layers of the precious metals Pt, Pd & Rh, and when hot exhaust gasses pass in close proximity to these heated metals, the hot metals cause the hot HC, CO & NOx to transform into less harmful CO2, H2O, O2 & N2 where after most are free to exit the tailpipe. The O2 is temporarily retained within the substrate so it can be released during the formation of soon to be released (i.e.: the next batch of) CO2 & H2O.

However in a “chemically poisoned” cat, the Pt, Pd & Rh are “clogged” by layers of accumulated elements such as Ca, Cu, Fe, Pb, Mg, Ni, P, S, & Zn and are thus unable to effectively catalyze the exhaust gasses passing by them. This clogging also severely limits the ability of the substrate to temporarily “store” the O2 needed to form less harmful exhaust. How all these trace elements and the compounds composed of them accumulate in the cat and clog its substrate is a mildly interesting aside, but (in the name of one of the only bits of brevity I can afford here) not technically germane.

If I have understood correctly, the 0.1 m EDTA solution chemically removes significant quantities of the Ca, Cu, Fe, Pb, Mg, Ni, S & Zn contaminants embedded in the substrate. And the 0.1 m Oxalic solution chemically removes the P, as well as restoring the O2 retention capacity of the substrate.

I have been thinking through the "how-to" of performing these procedures, and have also been making notes because I want to attempt to backwash my own vehicle's catalytic converter in situ. And this layperson's thinking-through of a real-world application of these highly controlled laboratory procedures has prompted some basic questions. Following are notes I've made on the broad strokes of applying these procedures to a piece of exhaust pipe with a non-functioning (but likely intact) catalytic converter in the middle of it. Following those notes shall finally be my questions and the end of this post…

Catalytic Converter Two Acid Wash:
Remove cat portion of exhaust pipe then remove O2 sensors. Borescope both visible ends of cat looking for fragmentation & / or melting of substrate matrix. If any, cat is dead & this procedure will not help. However, assuming cat is structurally “intact”…

Prepare a 0.1 Molar solution of EDTA (Ethylenediaminetetraacetic acid) heated to 50º C and maintain temp while backwashing thru cat for 1 hour @ 600ml / minute. This flows a bit more than 9.5 US gallons of solution upstream thru the cat. If I have understood correctly, this procedure is supposed to chemically remove significant quantities of the Calcium, Copper, Iron, Lead, Magnesium, Nickel, Sulfur, and Zinc contaminants embedded in the substrate.

Rinse for 30 minutes @ 600 ml / minute. This will flow about 4.75 gallons of pure water over the surfaces to remove residues.

Prepare a 0.1 Molar solution of Oxalic acid heated to 50º C and maintain temp while backwashing thru cat for 1 hour @ 600 ml / minute. This also flows a bit more than 9.5 US gallons of solution upstream thru the cat. If I have understood correctly, this procedure is supposed to chemically remove significant quantities of Phosphorus contaminants embedded on the substrate as well as greatly improving the Oxygen Storage Capacities of the re-exposed, decontaminated noble metal catalysts (Palladium, Platinum, & Rhodium) embedded on the substrate’s surfaces.

Rinse for 30 minutes @ 600 ml / minute. This will flow about 4.75 gallons of pure water over the surfaces to remove residues.

Dry cat @ 120º C overnight, then an additional 2 hours @ 200º C. Install O2 sensors & reinstall assembly into exhaust system.

To do this I will need:
o New pre- & post-cat O2 sensors, studs, nuts, gaskets, exhaust pipe gaskets, penetrating oil, & appropriate tools.
o 30 Gallons of distilled water.
o Enough EDTA to make about 4.75 gallons of a 0.1 Molar solution.
o Enough Oxalic Acid to make about 4.75 gallons of a 0.1 Molar solution.
o 5-Gallon buckets that won’t melt while full of acid and while sitting on a heating plate @ 50º C for an hour.
o A heating plate able to heat and maintain a 5-gallon bucket full of acid sitting on it for an hour at 50º C.
o Bore-scope, thermometer & stir sticks.
o A peristaltic (roller) pump able to deliver a 600 ml / minute flow rate for 3 hours.
o Enough acid-resistant, pump-compatible flexible tubing to get from solution reservoir to pump, thru exhaust pipe, to cat.
o Miscellaneous rigging items to keep cat-portion of my exhaust assembly suspended in a 5-gallon bucket.
o White Vinegar (as neutralizing agent for after procedure and maybe as part of solution disposal).

Questions:
Should I pre-wash or pre-soak cat to soften or remove any soot, grease, oils or other “dirt” prior to performing the chemical un-poisoning procedures? If yes, any advice? In the absence of advice, I would likely default to using a warm overnight bath (or perhaps backflow) of soapy dishwashing (Dawn) water or degreaser (Simple Green), followed by a thorough post-wash rinse.

Per the papers, the researchers experimented on portions of cat substrates of approximately 2 cm3 in enclosed tubes for their tests, and they were flowing 600 ml / minute solutions over relatively small 2 cm3 pieces of substrate placed inside lab flow tubes. So, do I need to seriously upscale my flow volume since I’m decontaminating the whole cat in situ, versus just little pieces of extracted substrate placed in lab flow tubes? I don’t know how to even derive the answer, but if it’s yes, I’m definitely going to require learned help to up-scale my flow conversions.

Are 5-gallon buckets made of HDPE (High Density Polyethylene) okay for mixing, heating & as catch basins for these solutions?

Is it acceptable to recycle these solutions back thru cat during these processes? Or should only “fresh” solution back-flow over cat?

The research papers list silicon as one of the contaminants these washes remove from the cat. It was surmised that the silicon got into the cat due to some silicone engine seal & gasket materials slowly degrading then making their ways thru combustion & out the exhaust stream. Peristaltic pumps are often plumbed with silicone hoses because of their flexibility and pliability. Is it OK to “plumb” my acid wash flow system with the silicone tubing used by this kind of pump? Or will the acid degrade the silicone tubing? If the answer is yes, what then would be a more appropriate tubing for pumping acid thru a ‘roller’ pump? Which acid solution removes the cat’s silicon contaminants?

Why were these washes flowed backwards thru the substrate, as opposed to the direction the exhaust would normally flow?

Since these procedures will be performed in situ, what can I expect regarding the solutions contacting the interior surface of my exhaust pipe?

Is white vinegar an acceptable neutralizer? If so, how much should I keep on hand? If not, what is an acceptable neutralizer (and how much of that should I have)?

And finally, please characterize 0.1 Molar solutions of EDTA & Oxalic acids so as to give a layperson perspective of their relative corrosive strengths and better understand the dangers of what they’re dealing with.

Thank you all so very kindly for your time reading this post all the way thru, and also in advance for any additional outlay you may choose to spend responding – please be gentle with me; I’m neither a chemist nor an auto mechanic, but I love my old 4Runner and if I can successfully regenerate its cat instead of just buying a new one, it’ll make for one helluva good story, not to mention some immense personal satisfaction!!
 
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  • #2
Definitely not an expert in this field, that said here is my take on three of your simpler concerns.
BadCatP0420 said:
Why were these washes flowed backwards thru the substrate, as opposed to the direction the exhaust would normally flow?
If you have a live cat (a feline), try petting it back to front. You will find the hair is sticking up! (and that the cat doesn't like it much).
The backflow flushing works the same way, it gets underneath the edge of surface contaminants and lifts them off. Contaminants with their other edge loose (raised) have largely already been removed by the normal flow thru the catalytic converter.

BadCatP0420 said:
Is white vinegar an acceptable neutralizer? If so, how much should I keep on hand? If not, what is an acceptable neutralizer (and how much of that should I have)?
Since your cleaners are acids, using another acid (vinegar) to 'neutralize' them is in-effective, and you then have to flush the vinegar out.

Keep with the clear water flush. Any 'neutralizing' you try to do will just create further compounds that are a combination of your starting chemicals and the neutralizer.

BadCatP0420 said:
So, do I need to seriously upscale my flow volume since I’m decontaminating the whole cat in situ, versus just little pieces of extracted substrate placed in lab flow tubes?
Afraid so. :cry: The pieces the researches used were each 8cc (cubic centimeters), or 1/2cu.in. in volume. You don't state the dimensions of yours, but 300cu.in. seems reasonable for a small to mid sized car. I expect that flow rate is important to scrub off the surface contamination, so scale up flow rate proportional to cross section area.

Then there is the question of was the cleaning solution re-circulated or was in a one-time-thru-and-discard operation.

When looking for physical sizes of converters, I did stumble across a sight for cleaning them. As I didn't read it through, I have no idea how practical/useful it may be.
https://vehq.com/cleaning-catalytic-converter/

Good Luck! and please keep us posted on progress and what you find.

Cheers,
Tom
 
  • #3
Thanx so much for responding, Tom! Means the world!

Makes sense on the backwashing; I get it now. As far as the vinegar goes, sorry, I thought it was the opposite of an acid (a base or alkaline: the other way on the ph scale). But that's why I'm asking chemists BEFORE I jump into this project. I'll figure out something that is and keep some of that handy. I was NOT intending to run vinegar thru the cat, just to keep a neutralizer handy in case I accidentally spill the acid, and to render it non-corrosive before disposal.

As a humorous side note, there are lots of people on youtube who make all kinds of cat cleaning videos; if you can think of a product, there are fools with cameras out there dumping that into their cats or gas tanks in an attempt to pass a smog test. There was however one man who cited the same papers I did and attempted his own version of the procedures with (what appeared to be) a fair degree of success. However, without pre-procedural and post-procedural 5 gas analysis to compare, we will never know, but at the end of his video, his cat's substrate did appear dramatically cleaner than it did at the start of his video!

As far as a little bottle of magic liquid that one dumps into their gas tank and hocus pocus everything's fine, imo, most of that stuff appears to be snake oil. Before it can get to the cat, it first has to survive combustion and few things do. I pulled the data sheet for the most well known of the over the counter magic liquids, and though I cannot recall @ the moment which ingredients it contained, the major percentages of its make-up were some of the liquids the aforementioned "fools" had been dumping in their tanks.

Dunno the dims of my cat, will get under there and measure the exterior to ballpark it. I appreciate the hints on the scale-up! Thanx again!!!

P.S.: here's the link for the man who tried his own version of what I want to attempt:
 
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  • #4
I would try the following (which is similar to what is found in @Tom.G 's link). It seems a lot simpler than what you are trying to do.

 
  • #5
I do appreciate you're having cared enough to read and respond - truly, and thank you for that! However:

Method A from everything I've seen (& I've watched lots of YT vids (including this one)) is ineffective at best.
Method B is also not very effective (it may remove some grease or soot, but not 'embedded' elements).
Method C is illegal in California, an automatic test failure, immediately citable, the car still runs less-than-optimally (& it still pollutes).

No; after really focusing on this issue since March and absorbing as much as I can on the subject, my sense is that the only thing that will work here is applying 'science' (or just buying a new cat, so it's worth experimenting either way). Unfortunately, some things in life just have to be done the hard way, b/c sometimes that's the only way. And in truth, I don't think it'll be all that difficult once I get the chemistry variables nailed down by you good folks! I'm actually looking forward to trying this out; imagine how cool if it's successful!

Thank you!
 
  • #6
BadCatP0420 said:
I live in CA & drive an "older" vehicle (technically a 'classic'). CA has strict emissions requirements, which (on older vehicles) are tested bi-annually (& MUST be passed) prior to registration renewal. Smog test was due in March and it passed, but with the lowest possible score on one of the tests. In the months immediately preceding my smog test, my car's dreaded Check Engine Light (CEL) came on a few times intermittently; it has never otherwise come during the whole time I've owned this car. It has also re-illuminated a few times since the test. It ain't going away and it ain't going to fix itself.
How many miles did you drive with the Check Engine light out before the smog test? I recently had an intermittent Check Engine light issue in my 2001 Jeep Grand Cherokee that had me in the shop a few times trying to correct it (emissions system related false failure), and when I got close to the deadline for my smog test after the latest fix attempt, the shop let me know that I had to put several hundred miles on the vehicle with the Check Engine light out or it would be an automatic fail when the smog test station read out the car computer log. I was able to do that, but I'm wondering if you were able to put in those miles as well.

Are you sure it's the cat that's the problem? Have you had a shop diagnose the issue? (Apologies if you mentioned that in your Original Post [OP], but it was kind of long so I may have missed it) :wink:

Edit/Add: my trusted local shop does not do smog tests, so there was no conflict of interest in their diagnoses and work. And we finally did get it fixed on the 3rd try (I forget which component in the smog system was the root cause -- maybe a valve or something).
 
  • #7
Since I'm a noob here, I don't want to get under anyone's skin by turning this into a car post. Sorry in advance!

That being said, what you are asking about is something commonly referred to as 'Drive Cycle'. Once a CEL is de-luminated, the drive cycle resets. It's not about a particular number of miles, but rather cycling your car thru a number of different driving conditions. Each make, model, engine computer, firmware v, and vehicle options (2WD, 4WD, Stick, Auto, etc.) will affect the specifics of the individual vehicle's unique drive cycle. So many miles, at such-and-such speed, with X% engine load, Y# of RPM's, for Z minutes, how many stops, starts, reverses, & so on... You get the idea. Check the forums for your specific vehicle; someone will know your Jeep's DC. Also check youtube; apparently people love to post videos of hacking & / or correctly satisfying drive cycles.

1st time my CEL came on, I got where I was going & yanked my EFI fuse for 60 seconds to reset the ECM (thanx youtube)! I don't know if that will extinguish your CEL, but that's the hack for de-luminating a CEL on a '98 4Runner with Toyota's 3.4L V6. Problem NOT solved, but @ least the light's off. That was late Oct '22; smog was March '23. At the time, I didn't know about drive cycles, I also didn't drive a particularly great deal, but apparently it was enough.

From Amazon, (& many other places as well) you can get an OBDII port reader with bluetooth; they're cheap: $10 -$30. On Android phones and tablets, an app called Torque-Pro is about $5 (no Torque for Apple, but there must be something available). Torque connects to the OBDII Port Reader via bt and once correctly configured for your car, you get access to damn near every sensor, readout, fault code, real-time data, the ability to clear faults, look up the codes, drive cycle status, vacuum, emissions status, graphing, export functions, etc. etc., etc. Bit of a learning curve to get familiar with the software but well and truly worth $20 all in!

In a healthy cat, the upstream sensor's voltage should fluctuate rapidly as the ECU adjusts between lean & rich air/fuel mixtures, but the downstream sensor should remain dramatically less dynamic - i.e.: it's graph should be flatter - indicating that the cat between the 2 sensors is doing its job correctly. One tell tale sign pointing to a BadCat is when the downstream O2 sensor's voltage fluctuations mirror the upstream sensor's voltage fluctuations; that's what mine are doing. In some cases (according to Torque's graphs) my downstream voltage fluctuations are slightly more dynamic than the upstream.

However, one of my problems could also be dirty or lazy O2 sensors. I've read that O2 sensors (@ least in my 4Runner) ought be cleaned every 90K & replaced @ 270K; I'm @ 261K and as far as I know, my O2 sensors have never been touched. So once I finally do pull the cat to backwash it with these acids, I'm going to install 2 new OEM O2 sensors also - I'm gonna have to pull 'em anyway to get a borescope in there to actually view the cat's substrate in order to see if this project is even applicable to my situation (though I suspect it is).

I expect that I'm going to need 2 new O2 sensors and a new cat. [I don't actually believe my O2 sensors are bad per se, but if I'm gonna pull 'em, I'm gonna change 'em (@ 260+K).] If my substrate's okay, first gonna try this 2 acid backwash procedure. If the procedure doesn't work, it doesn't matter, I'll still have to buy a cat. (What am I gonna do? Break something that already doesn't work?) But if it does work: hubba hubba! I'll have ultimate bragging rights for sciencing the sh*t outta something (that no one else has been able to).

Since we're on the chemistry forum, I have to ask: do you know anything about 0.1 molar solutions of either EDTA or Oxalic acids, or if Hi-Density Polyethylene 5-gallon 'paint' buckets are safe to mix them in?
 
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  • #8
BadCatP0420 said:
Since we're on the chemistry forum, I have to ask: do you know anything about 0.1 molar solutions of either EDTA or Oxalic acids, or if Hi-Density Polyethylene 5-gallon 'paint' buckets are safe to mix them in?

Oxalic acid solution is corrosive, polyethylene should easily survive though. EDTA is mostly inert in the context.
 
  • #9
If I read you correctly, 5 gallon "painter's" buckets made of HDPE are okay for mixing and heating (to 50º C) 0.1 molar solutions of both EDTA & Oxalic acids? Yes?

Thank you!!!!
 
  • #10
BadCatP0420 said:
If I read you correctly, 5 gallon "painter's" buckets made of HDPE are okay for mixing and heating (to 50º C) 0.1 molar solutions of both EDTA & Oxalic acids? Yes?

Thank you!!!!
Chemistry is definitely on your side. The heating part can be a bit problematic, as you don't want to put them on the oven - but 50º C is definitely in the range HDPE will easily withstand. Some kind of immersion heater should be OK.
 
  • #11
My first heater thought (as a non-scientist) was to use a heating plate like what is commonly used in buffets. I found a round one that gets up to 68º C and is a little larger in diameter that the bottom of a 5 gallon bucket. I had thought to place a several ply layer of fabric on the heating plate and place the bucket on top of that so the HDPE was not directly sitting on the heating surface. Never heard of an immersion heater before, but based on the name, it must have an element of some shape / type which can be inserted into the solution to warm it. I will be learning about immersion heaters - today!

Thank you very for your time and the tips!!!

P.S.: Is the flexible silicon tubing commonly used with a peristaltic (roller) pump also safe for these acids?
 
  • #12
BadCatP0420 said:
P.S.: Is the flexible silicon tubing commonly used with a peristaltic (roller) pump also safe for these acids?

Most likely - yes. Oxalic acid is not THAT strong, it is also not an oxidizing acid, these always can produce problems. But the simplest thing to do is to soak piece of tubing in the solution of oxalic acid and see if it visibly changes in any way.
 
  • #13
The pre-soak is a GREAT idea! Thank you again, Borek!!!!!
 
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  • #14
BadCatP0420 said:
in case I accidentally spill the acid, and to render it non-corrosive before disposal.
Baking soda for neutralizing and cat litter (clay based with no additives) for larger spills to contain them while neutralizing.

BoB
 
  • #15
Thank you for replying! How much baking soda would be required to neutralize 1 liter of 0.1 molar solution of either of these acids (EDTA & Oxalic)?
 
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  • #16
You need to follow the stoichiometry - and giving an answer (while technically trivial) is difficult, as per forum rules we don't give solutions.

In general - oxalic acid has two protons that can react, so one mole of it will react with two moles of baking soda, and n=CV. Converting moles to mass is trivial.

As a first approximation you can assume EDTA to be diprotic as well (it is actually tetraprotic, but later dissociations steps can be ignored in this case).
 
  • #17
You won’t be able to make a .1M solution of EDTA. It isn’t soluble in water at that concentration. Perhaps either disodium EDTA or tetrasodium EDTA would work. Sometimes these are referred to as “EDTA” but actually aren’t. The # of sodiums affect the molar mass so it is something you need to know.
 
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