Sciencemadness Discussion Board - Cleaning up primer residue at a gun range

Cleaning up primer residue at a gun range

Fusionfire - 4-4-2012 at 03:25

Hello all,

Suppose I am interested in periodically cleaning the residue at the firing end of the range, particularly of heavy metal contamination (from the primers).

My questions are:
1) What are the likely heavy metal compounds to be found at the firing end of the range?

2) What is the best way to reduce their toxicity to humans?
- Either make them totally insoluble (e.g. lead (II) sulphate) so they are not bioavailable
- Or make them soluble (e.g. clean with acetic acid to get soluble lead (II) acetate and wipe/wash it away). Depends on the starting point; obviously lead (II) carbonate would react with acetic acid to get a soluble product but not lead (II) sulphate.

Thanks & have a great day!

watson.fawkes - 4-4-2012 at 04:17

Quote: Originally posted by Fusionfire

Suppose I am interested in periodically cleaning the residue at the firing end of the range, particularly of heavy metal contamination (from the primers).

The standard mechanism for chemical isolation in firing ranges is ventilation. There's a one-way air flow away from the firing line toward the backstop. It's like shooting within a fume hood. Any gas or particle contaminants get swept out, and although it's at a slower velocity, there's less contamination to remove.

If you want chemical cleaning for lead, though, I'd worry first about testing for lead, so that you know (1) if you need to clean and (2) whether your mitigation measures are working.

Fusionfire - 4-4-2012 at 05:32

Thanks for the info.

The firing range is underground and the firing points are fairly grimy. Ventilation is poor, and there is no exposure to rain to wash anything away. Running your finger over smooth surfaces results in a fine black residue on them.

A clean up of the firing points was brought up, but the range owner said if we're going to clean it up we might as well do it properly, and also remove any heavy metal contamination.

Some shooters bring old muskets (one guy has a musket revolver that uses lead shot and is sealed with grease) so heavy metals can come not only from the primers but from any bits worn out by the lead in the barrel. We are not talking about the obvious contamination downrange, of course.

The firing points have been swept and brushed up with a coarse brush but never given a proper cleaning. I understand the range has been operating before WW2 so it is probably safe to assume there is heavy metal contamination at the firing points.

What is the standard test for lead contamination at concentrations you'd expect at gun range firing points?

AJKOER - 4-4-2012 at 09:21

OK, checking the solubility table for Lead, only soluble candidates (in declining order of solubility) are Lead(II) perchlorate, Lead(II) fluorosilicate, Lead (II) chlorate, Lead (II) nitrate and Lead (II) Acetate.

So my idea react a small amount of vinegar with an excess amount of Bleach (NaClO). Heat to 70 C for about an hour. You now have an inexpensive cleaning solution consisting of the active ingredients of Sodium acetate and a small amount of Sodium chlorate.

Some chemistry, reaction of Acetic acid (HAc) and NaClO forms Sodium acetate and Hypochlorous acid (cannot be stored due to decomposition into HCl and Oxygen gas):

HAc + NaClO --> NaAc + HOCl

Reaction of HOCl with the excess NaClO and mild heat 70 C (no boiling necessary or even productive):

HOCl + NaClO --> HCl + NaClO2

HOCl + NaClO2 --> HCl + NaClO3

This is the disproportionation of Sodium hypochlorite into Sodium chlorate. A common industrial route to this reaction is to treat aqueous NaClO with Cl2 (as the resulting chlorine water is HCl and HOCl). Reference on the disproportionation: "Handbook of Detergents: Production Volume 142", pages 445 to 446 by Uri Zoller and Paul Sosis. Note, this is a Google online book and these pages may not be currently available as part of a free preview..

LINK:
http://books.google.com/books?id=dXn3aB1DKk4C&pg=PA247&a...

Please take precautions as soluble Lead salts permit skin absorption of toxic Lead.

[Edited on 4-4-2012 by AJKOER]

phlogiston - 4-4-2012 at 10:54

I think that is not the best solution for several reasons, including:

1. Even if the lead dissolves, it will precipitate again as poorly soluble lead chloride.
2. If the surfaces are made of wood (and being pre-WO II, I suspect they are), you certainly do not want to impregnate them with chlorate. A very flammable combination.
3. You risk poisoning yourself with chlorine gas (acid + bleach in a poorly ventilated underground space... bad idea)
3. The formation of chlorate will take some time in reality.
4. Possibly, the acetate ion will be oxidised by the strong oxidizers in this solution, destroying the oxidiser (why the acetic acid rather than e.g. hydrochloric acid?).

etc.

Also, dissolving the lead may not be the best solution anyway if the contaminated surfaces are porous (wood). The lead solution will then be absorbed by the wood and become impossible to remove for good. Also, the soluble salts of lead are -far- more dangerous than metallic lead or insoluble compounds.

I would start by cleaning with good old soap and water, and, assuming the surfaces are wood, proceed by sanding them with a sanding machine that has a professional dust catching system. Obviously wear adequate protective gear.

[Edited on 4-4-2012 by phlogiston]

AJKOER - 4-4-2012 at 11:55

Phlogiston:
1. I do not agree, but if it first dissolves the contaminant and then breaks down into an insoluble form on disposal, this is a good thing!

2. I agree that soaking is probably not advisable. Wiping yes. See point 4.

3. Vinegar is too weak an acid to create Chlorine. The smell is one of HOCl, a noted strong disinfectant/bleach (possibly also a good idea!). But, nevertheless, avoid inhaling fumes and use adequate ventilation.

4. We are not actually forming Chlorates, just an ionic solution capable of dissolving, at least partially, the otherwise insoluble Lead salt.

5. The acetic salt formed (Sodium acetate) is stable. HCl can NOT be formed from a weak acid like Acetic, otherwise, there would be extensive Cl2 formation. For example, with a strong acid like HCl:

HCl + NaOCl --> HOCl + NaCl
HCl + HOCl <---> H2O + Cl2 (g)
-----------
On net:
2 HCl + NaOCl --> NaCl + H2O + Cl2 (g)

Fusionfire - 4-4-2012 at 12:19

Are there any compounds of lead that are so insoluble in water as to render them effectively non-toxic? Sort of like a barium sulphate radiocontrast agent.

Is it worth trying to chemically treat the area to get those compounds?

I am inclined to suggest good ol soap and water too.

AJKOER - 4-4-2012 at 13:58

Lead(II) hydrogen phosphate is pretty insoluble (as a lot of Pb salts are).

Perhaps using Sodium tri-Phosphate (STP is sold in Lowe's) as a cleaner (it is after all good old soap) is a good idea.

[Edited on 4-4-2012 by AJKOER]

phlogiston - 4-4-2012 at 14:33

Lead sulphate, lead phosphate and lead sulphide are extremely insoluble, but still toxic as far as I can tell from the scarce literature I am able to find (albeit much less so than more soluble lead compounds). I could not find much data though on oral toxicity. This articles talks about intravenous injection: http://jpet.aspetjournals.org/content/34/1/85
The MAC values in my country are 0.15 mg Pb/m3 for any lead compound (soluble or not) I have data on (or at least they were in 2001)
My book on hazardous substances advices the following for cleaning up spills of lead metal: 'remove as much material as possible by suction. Remove remaining traces with water or slightly acidic aqueous solution'.

To be able to convert the lead to one of these insoluble salts does require you to dissolve it first (then you just add some soluble sodium sulphate solution for instance to precipitate lead sulphate). It is very difficult, however, to dissolve the lead first unless you know what form it is in currently. I would say it is not unlikely that some of it is already in the form of sulfides and sulphates, given the gasses resulting from black powder shooting. Then it will not dissolve easily even in strongly acidic or oxidising solutions.

@AJKOER:
1) poorly soluble is not the same as insoluble. Lead(II)chloride is sufficiently soluble to be very, very toxic.
3) The strength of the acid is irrelevant. Cl2 is formed in acidic HOCl solutions by the equilibrium:
HClO + H+ Cl- <------> Cl2 + H2O
The smell is certainly not HClO, since it only exists in solution.
5) There is no 'sodium acetate', because we have only a solution containing Na+ and acetate ions. I agree that acetate is certainly not easily oxidised ("stable" is a very nondescript term), but this is a very strongly oxidising environment.

'HCl can NOT be formed from a weak acid'. ????? You should perhaps look up what the terms 'weak' and 'strong' mean exactly in the context of acids. Essentially, there is no HCl in solution, HCl is completely ionized into H+ and Cl- and these ions are certainly there. A bit of HCl gas most definately will form and escape the solution, but this is irrelevant for the evolution of Cl2 or not.

[Edited on 4-4-2012 by phlogiston]

AJKOER - 4-4-2012 at 16:12

Quote: Originally posted by phlogiston

@AJKOER:
1) poorly soluble is not the same as insoluble. Lead(II)chloride is sufficiently soluble to be very, very toxic.
3) The strength of the acid is irrelevant. Cl2 is formed in acidic HOCl solutions by the equilibrium:
HClO + H+ Cl- <------> Cl2 + H2O
The smell is certainly not HClO, since it only exists in solution.
5) There is no 'sodium acetate', because we have only a solution containing Na+ and acetate ions. I agree that acetate is certainly not easily oxidised ("stable" is a very nondescript term), but this is a very strongly oxidising environment.

'HCl can NOT be formed from a weak acid'. ????? You should perhaps look up what the terms 'weak' and 'strong' mean exactly in the context of acids. Essentially, there is no HCl in solution, HCl is completely ionized into H+ and Cl- and these ions are certainly there. A bit of HCl gas most definately will form and escape the solution, but this is irrelevant for the evolution of Cl2 or not.

phlogiston:

I will let you correct/self-educate yourself.

Add an excess of vinegar to 50 ml of Bleach (NaClO/NaCl/NaOH).
In another flask, add an excess of NaHSO4 to 50 ml of the same Bleach.

Now, report back on the major differences in these reactions in term of gas volume, heat generation, smell and colors (you obviously have never performed these reactions).

Please note, we are talking about aqueous NaClO/NaCl solution and not dry Bleaching Powder (Ca(ClO)2/CaCl2.xH2O/Ca(OH)2).

By the way, HOCl is such a weak acid, even H2CO3 will (with time) form HOCl upon acting on NaClO:

2 NaOCl + H2CO3 --> Na2CO3 + HOCl

Have fun.

watson.fawkes - 4-4-2012 at 18:35

Quote: Originally posted by Fusionfire

Is it worth trying to chemically treat the area to get those compounds?

I am inclined to suggest good ol soap and water too.

Honestly, the best way to deal with the contamination you describe may well be by using the landfill. Rebuild the shooting stations; scrap the old ones. Quite possibly cheaper than the labor and material for adequate clean up. It sounds positively encrusted.

If there's inadequate ventilation, I personally would look for another place to shoot. YMMV.

Fusionfire - 4-4-2012 at 22:48

Quote: Originally posted by watson.fawkes

Quote: Originally posted by Fusionfire

Is it worth trying to chemically treat the area to get those compounds?

I am inclined to suggest good ol soap and water too.

It is not easy to find ranges that will allow you to test "non-standard" firearms. My gun club does a lot of shooting at Ministry of Defence ranges but they only allow certain muzzle energies for civilians there. Effectively civilians are limited to .223 caliber in those MoD ranges...although the military obviously can and does use more powerful rounds at their own range.

That underground range is privately owned and the owner gives lattitude to more powerful/unusual guns.

Gun control laws here are fairly excessive: no private ownership of pistols under any circumstances (unless you're a criminal). Our Olympics pistol teams have to go to mainland Europe to train - this is how ridiculous things are. Muskets are excepted.

If anyone finds a low tax (for smaller startup businesses), non-chemophobic and non-gunphobic country let me know

phlogiston - 5-4-2012 at 02:04

Quote:

Add an excess of vinegar to 50 ml of Bleach (NaClO/NaCl/NaOH).
In another flask, add an excess of NaHSO4 to 50 ml of the same Bleach.

Now, report back on the major differences in these reactions in term of gas volume, heat generation, smell and colors (you obviously have never performed these reactions).

We agree on the expected results, but all that would demonstrate is that your vinegar is apparently not very concentrated while your NaHSO4 is, and you failed to specify concentrations. The more acid you add, the more Cl2 evolves according to le Chatelier's principle which I am sure we both agree on.

Perhpas you should try your own little experiment with concentrated acetic acid, and dilute NaHSO4 and learn a little lesson on the differences between strong and weak acids.

Quote:

By the way, HOCl is such a weak acid, even H2CO3 will (with time) form HOCl upon acting on NaClO:

2 NaOCl + H2CO3 --> Na2CO3 + HOCl

Again, this demonstrates a lack of understanding regarding the difference between strong and weak acids.

Consider the following equation:

ClO- + H+ <-----> HClO

-Any- acid will result in HClO if added to a solution containing hypochlorite ions. Neither sodium nor carbonate play any role here.

AJKOER - 5-4-2012 at 04:31

Phlogiston:

Do yourself a favor and perform the experiments.

With a little field work, you will understand that pH is a log scale (order of magnitude in powers of 10) and what this implies in practical terms with respect to so called weak and strong acids.

When working with HOCl, never consider writing ClO- + H+ <-----> HClO to understand practical paths. For example, Chlorine water:

Cl2 + H2O <------> HOCl + H(+) + Cl(-)

and preparatory routes to HOCl are based on adding metal oxides and carbonates to the Chlorine water to remove the ionic HCl followed by distillation to isolate the volatile HOCl/Cl2O.

As an example, please see "Modern inorganic chemistry", by Joseph William Mellor, page 271:

"R. Chenevix notes the ready solubility of cupric oxide in chlorine water, and P. Grouvelle found that the soln. obtained by passing chlorine into water with cupric oxide in suspension possessed bleaching properties, and these were retained even after the soln. had been boiled for a quarter of an hour. A. J. Balard found that the distillation of P. Grouvelle's liquor furnished some hypochlorous acid and a green oxychloride, 3CuO.CuCl2.4H20, was formed in the retort."

LINK:
http://books.google.com/books?id=pNNIAAAAIAAJ&q=hypochlo...

[Edited on 5-4-2012 by AJKOER]

phlogiston - 5-4-2012 at 12:59

I would do the experiment if it wasn't a waste of time. We agree on the outcome and I would rather do fun and meaningful things.

The equation you write is exactly the point.
Add any acid and what will happen? The equilibrium will shift to the left, and Cl2 will form. You may deny it, but it won't help. If you take dilute acetic acid, it will not be a huge amount, and most if it may even stay in solution, but that is what we started this disscussion about. Adding amphoteric or basic oxides will indeed remove H+ and shift the equilibrium to the right. No surprises I would say.

This graph (borrowed from the kirk-othmer encyclopedia of chemical technology) perhaps conveys the point more clearly:

Household vinegar is typically in the range of 1M acetic acid and around pH 2.4. Therefore, in your experiment (put a bit of bleach in an excess of vinegar) most of the chlorine will be in form of Cl2, most of it remaining dissolved I suspect.

If you believe otherwise, I suggest we agree to disagree and move on to more interesting things. Although this discussion adds a little chemistry to the thread, it is not going to help answer the original question (how to remove the lead) and our discussion is also probably not going to lead to an exiting new insight soon.

AJKOER - 5-4-2012 at 17:25

pH of white vinegar 2.9 (2.4 to 3.4) and the pH of Bleach solution about 12. Assuming equal portions of each solution are mixed, we (per your nice graph) are about 100% HOCl (thanks).
------------------------

But back on topic, I do not support burying or burning or blowing it up. The Firing Range pollution just spreads.

I would start with a vacuum and remove all dust/dirt (needless to say, be sure appropriate breathing apparatus is employed). Let dust in air settle, then wash all areas with STP soap (again wear gloves/clothes to avoid any skin contact). Install a high quality air filter to remove dust.

chemicalmixer - 5-4-2012 at 18:30

AJKOER seems to have a real thing for mixing bleach and vinegar, lol.

Instead of messing with hypochlorous acid, why not use a 50/50 vinegar/peroxide mixture? AFAIK, this mixture has been used by some as a homemade gun cleaning remedy.

I would first clean up the firing line and/or shooting booths as best as possible, and then coat everything - especially wood and concrete - with a good quality, durable, epoxy-based paint, then allow it to cure. Maybe using an unwaxed shellac or Killz paint underneath on any bare wood first, before going over it with the paint (as long as both coatings are compatible when used in succession). This way, you won't have to worry about lead and other toxic heavy metals soaking into any porous materials where they might accumulate in the future.

Once the firing line is nicely painted, you can perform periodic cleaning with the vinegar/peroxide mixture. Make sure to wear thick rubber gloves, and then wipe down the surfaces with a rag dampened with the solution, wringing out the dirty rag into a separate bucket. Once everything's cleaned, you might be able to precipitate the lead acetate from the dirt solution in the form of lead sulfate, by adding epsom salt to the mixture. Then filter and/or evaporate the lead solution (in a safe manner so as not to expose humans are animals to it), and then dispose of the lead sulfate precipitate properly and legally.

AJKOER - 6-4-2012 at 18:03

Chemicalmixer:

I think the paint suggestions are good.

FYI, after some thought, I am not too keen on possibly converting nearly insoluble lead sulfide into soluble Lead Acetate (more easily absorbed). Remember one of my earlier suggestions was acetate/chlorate mix to dissolve also.