Sciencemadness Discussion Board

Easy, fast and cheap purification of Pool Acid.

10fingers2eyes - 26-6-2016 at 15:25

Hello, I'm new to the site but have been a fan for a long time. It's time to give some good information back to everyone on the forum! I know many have had trouble with contamination in the yellow muriatic acid (HCl) from hardware stores, but the various purification methods here or on Youtube are either a pain in the arse or change the concentration unacceptably. I can't seem to find the method I'm using posted anywhere yet, so excuse me if this is redundant, but it works like a charm.
Patent US 2695875 A on google patents uses a Type 1 strong base resin bead anionic filter to take out iron cations from HCl. Iron is the primary contaminant from what I can tell. Resin bead filtration is widely used in water softeners, but the type of beads in water softeners wont work. Lucky for us, you can get a resin bead filter from aquarium suppliers that are just the right type/size/cost ($20-25) for home chemistry and can process 500 gals of HCL. Make sure the filter contains at least some Type 1 STRONG BASE ANIONIC beads. I'm currently using a mixed bed filter where a portion is Type 1 Strong Base beads and it seems to work fine.
See my photo for my set up, I just wedged a plastic kitchen funnel onto a quick disconnect tube at the top and put a valve on the bottom, pour in yellow acid at top, open valve, get clear acid at bottom, one pass through you can see how clear it comes out in the beaker. I've not done any purity measurements at this point as I don't have too many facilities to do so, but visually, it's clearly working and it's fast and easy and you can do small portions as you need. Resin is rechargeable with hot distilled water wash or replaceable and changes color when it's saturated with contaminants but with a 500 gal capacity, you'll probably never need to.



HClpure.jpg - 99kB

Metacelsus - 26-6-2016 at 16:24

I would think that you'd want a cation exchange resin to remove Fe3+ (by exchange with H+). How would a positively charged anion exchange resin remove the Fe3+?
However, the patent's method appears to work, so maybe I'm wrong. Can you test for iron in your final acid?

[Edited on 6-27-2016 by Metacelsus]

10fingers2eyes - 26-6-2016 at 16:41

UPDATE: I failed to mention I was using the weaker Home Depot acid which is 15% and had run only a few 400 ml beakers full of acid through it. I decided to try the filter on some stronger pool acid I had (31.45%) and lo and behold, it made the acid MORE contaminated; a deep yellow color!!?? It took a lot of flushing of the filter with distilled to get it back to where it would work with the 15% again. The entire housing and valves are plastic so I doubt it's coming from there. I suspect this has something to do with the mixed bed resin that is in the filter and super low-pH. Resin types are very pH sensitive supposedly. I will try to get a package of resin beads that is pure type 1 strong base (Dowex) and see how it goes. Anyway, this method shows a lot of promise. I will continue to experiment.

Metacelsus - 26-6-2016 at 16:46

Maybe some iron from the previous (less concentrated) acid got released from the column into the more concentrated acid?

[Edited on 6-27-2016 by Metacelsus]

10fingers2eyes - 26-6-2016 at 16:51

Quote: Originally posted by Metacelsus  
I would think that you'd want a cation exchange resin to remove Fe3+ (by exchange with H+). How would a positively charged anion exchange resin remove the Fe3+?
However, the patent's method appears to work, so maybe I'm wrong. Can you test for iron in your final acid?

I thought exactly the same when I first read up on this, but apparently the Fe ions form "halo" groups of Cl around them and the anion resin beads grab onto that. I suspect my problems with the higher strength acid has something to do with the other type of beads that came mixed in with the filter. I'm currently trying to find what the other bead type is and try to make sense of it before I go spending more money on resin beads.

10fingers2eyes - 26-6-2016 at 16:55

Quote: Originally posted by Metacelsus  
Maybe some iron from the previous (less concentrated) acid got released from the column into the more concentrated acid?

[Edited on 6-27-2016 by Metacelsus]


Indeed I suspect that may be one possibility; I concentrated the contaminants of one into the other with the pH shift. I will conquer this!

10fingers2eyes - 5-7-2016 at 18:58

Update: I ordered a new ion exchange resin that is suitable for Iron removal in low pH solutions. 8lbs of Purolite A850 ion exchange resin. I cannot say it is "cheap" at $100 but 8lbs is enough to fill approx 10-12 1 liter filter cans so it's a lot of resin for the price. And...so far it works. I've run 1 liter of 31% HCl from the hardware store through it and it comes out nearly water-clear, hardly any yellow left in it. I will see how much I can run through before I have to attempt to regenerate the resin with H2O flush out. This is a promising method for purification of OTC HCl for sure.

careysub - 5-7-2016 at 20:38

Sounds like something that members might be interested in bulk ordering. What's your source?

(And I hope that your monicker remains appropriate throughout all your experimenting!)

[Edited on 6-7-2016 by careysub]

Texium - 6-7-2016 at 14:05

That's very interesting, I might be interested in buying enough for one filter, say $10 worth. If it works long term, then it could really be worth it rather than having to buy iron free HCl or go to the trouble of making it.

hyfalcon - 6-7-2016 at 18:28

I would be interested in getting in on a group buy of some of this resin myself. 10fingers2eyes, what's your source?

This looks like the particular resin needed: The strong base resin,
DOWEX MSA-1, has a high affinity
for iron in high concentrations of HCl
and has been used to remove the
contaminating iron.

[Edited on 7-7-2016 by hyfalcon]