Sciencemadness Discussion Board

Activated Charcoal

CHRIS25 - 21-11-2014 at 13:05

Yesterday I made some charcoal in a sealed drum that had a couple of holes in the top; for a couple of uses, one of them being to make activated carbon. In effect no air was allowed in the container on completion.

Reading up about how to make carbon 'activated' at home I keep coming across the use of calcium chloride during the process, but I also read that phosphoric acid is the best. This is the first question, has anyone any experience at this?

Second question, I read the following:QUOTE: You could make activated carbon by placing
wood in a sealed container with only a very
tiny hole in it and heating it until the
wood is charred into activated carbon.

Ideally, a tube leading into the container
would be used to force water onto the wood to
create steam inside the container though this
is not essential. END QUOTE. (Source: http://www.peprimer.com/charcoal.html)
The above is not the first time I have read this, and I can not see how this can be so? This is not the way to increase that surface area in carbon? I know steam or chemicals are used in Industry, but this method above does not seem correct?


[Edited on 21-11-2014 by CHRIS25]

blogfast25 - 21-11-2014 at 13:29

Quote: Originally posted by CHRIS25  
Reading up about how to make carbon 'activated' at home I keep coming across the use of calcium chloride during the process, but I also read that phosphoric acid is the best. This is the first question, has anyone any experience at this?

Second question, I read the following:QUOTE: You could make activated carbon by placing
wood in a sealed container with only a very
tiny hole in it and heating it until the
wood is charred into activated carbon.



Activated charcoal or activated carbon? Not the same thing at ALL.

Charcoal is indeed obtained essentially from the controlled pyrolysis of dry wood. A small amount of it is sacrificed by burning it, the combustion enthalpy of which then drives the pyrolysis. (Wood) charcoal however is only impure carbon, as evidenced by the ashes that are left behind when you burn it completely. These ashes are really the remainder of the metabolism that was once part of the living being called a 'tree'. It contains K2CO3, CaCO3, silica and some other stuff (the name 'potassium' comes from 'potash', the lixiviate obtained by leaching wood ash with water). All these things are in your charcoal, besides carbon (graphite).

Much purer carbon is obtained from the pyrolysis of a purer form of carbon compound like cane sugar, i.e. white refined sugar, chemically known as 'sucrose'. That can be very pure carbon, if done properly.

[Edited on 21-11-2014 by blogfast25]

CHRIS25 - 21-11-2014 at 13:43

Yes, the sulphuric acid absorbs the water and leaves behind purest form of carbon as I understand it. The charcoal I have was heated inside a sealed container until all the gases had left, then the flames appeared and when these dies down to a bare flicker I placed a wet cloth over the holes. This prevented the air getting in. I understood this to be the second purest form of obtaining carbon? What you described is not the way I did this.

aga - 21-11-2014 at 13:56

Quote: Originally posted by blogfast25  
the lixiviate obtained by leaching wood ash with water). All these things are in your charcoal, besides carbon (graphite).

Now there is a strange word.

What on earth does 'ash' mean ?

blogfast25 - 21-11-2014 at 14:27

Quote: Originally posted by CHRIS25  
I understood this to be the second purest form of obtaining carbon? What you described is not the way I did this.


May be the 'second' purest (don't know, really) but it most obviously does not get rid of the non-carbon solids in the charcoal, as these are non-volatile. Your charcoal may however have been 'activated', whatever you may understand by that.

CHRIS25 - 21-11-2014 at 14:50

"Activated" as they say, in that the ability of the carbon to absorb hundreds of times its size in chemicals through "tunnels" "porous layers" created by either the steam or chemical treatment. Obviously have to find out what thee non-volatile solids might be. I don't understand the process yet.

Artemus Gordon - 21-11-2014 at 15:13

Quote: Originally posted by aga  
Quote: Originally posted by blogfast25  
the lixiviate obtained by leaching wood ash with water). All these things are in your charcoal, besides carbon (graphite).

Now there is a strange word.

What on earth does 'ash' mean ?


I'm not sure if you are asking for a definition of the word 'ash', but if you are, it is the residue left over after burning something. In the case of wood, it is usually a gray, fluffy, powder which, as Blogfast said, was collected in usually a large barrel or pot, and water was poured through it to leach out the water soluble 'potash' as a step in soap making.

blogfast25 - 22-11-2014 at 04:10

Quote: Originally posted by CHRIS25  
Obviously have to find out what thee non-volatile solids might be.


The non volatile matter is what comes to make up the ash when you burn the charcoal: potash, calcium carbonate, silica etc. No amount of steam treatment will remove these. Steaming charcoal presumably does activate it but it's less pure than activated carbon, which uses a different carbon precursor.

[Edited on 22-11-2014 by blogfast25]

blogfast25 - 22-11-2014 at 04:12

Quote: Originally posted by Artemus Gordon  

I'm not sure if you are asking for a definition of the word 'ash', but if you are, it is the residue left over after burning something.


For 'strange word' he meant of course 'lixiviate'. He's been hitting the Fortified Mandrake Wine again! ;) He ends up muttering unintelligibly after a few of that. I've told his long suffering mom about it but she can't control him anymore!

[Edited on 22-11-2014 by blogfast25]

CHRIS25 - 22-11-2014 at 06:42

Several reliable sources clearly state that there is no difference between activated charcoal and activated carbon. One source states that there is only minor difference in the porous surface area being greater in activated carbon than charcoal, so that is fine.
http://generalcarbon.com/facts-about-activated-carbon/activa...
http://en.wikipedia.org/wiki/Activated_carbon

The website that claimed that my superheated charcoal even though deprived of oxygen in the making is 'activated' - is NOT activated, so that is an error.

So far so good, now on to the phosphoric acid.

Several papers from research sites treated the raw material with unspecified concentration of H3PO4 before the pyrolysis; however others suggest treating with H3PO4after the pyrolysis of the material. I have no means of testing any resulting material, therefore experimentation at this particular juncture is not possible, surely someone possibly has a little more knowledge at this point? I have ruled out using zinc chloride and any hydroxides, too dangerous and apparently the increased surface area is not as great with calcium chloride as with H3PO4, though I do appreciate from the little that I have read that the subject is far more intricate than what chemical one uses, but this is a home situation and not a lab, so I can only take it so far.

[Edited on 22-11-2014 by CHRIS25]

blogfast25 - 22-11-2014 at 08:00

Quote: Originally posted by CHRIS25  
Several reliable sources clearly state that there is no difference between activated charcoal and activated carbon.


In terms of microporosity that is probably wholly true.

But no matter how you slice it, activated carbon made from very pure carbon contains almost no impurities (> 99.9 % C), whereas activated charcoal contains the impurities mentioned. Surely for some applications that matters.

CHRIS25 - 22-11-2014 at 08:17

Yes, obviously for some areas pure is needed (I suppose medical), and it seems to be between 5 and 15% non volatile components left in the method that I did, an inert atmosphere with pressurized steam and so on is out of my reach.

S.C. Wack - 22-11-2014 at 09:58

Quote: Originally posted by CHRIS25  
I have ruled out using zinc chloride and any hydroxides, too dangerous


I never felt any danger using pistachio shells/ZnCl2...that experiment was to see if sand can substitute for inert atmosphere...answer: sort of...

What you need is to figure out what exactly you need the C for, and how to test your carbon products for fitness for that.

The carbons are washed with water after heating, so don't count your etc. inorganics before you've tested for their presence. And if what remains isn't washed out or react in some way, well, it isn't going to be washed out or react in some way is it?

CHRIS25 - 22-11-2014 at 10:24

Initially I want to make a water filter. So far discovered the following with ambiguity:
Procedure:

Soak charcoal in unknown percentage Phosphoric acid (charcoal made in sealed container all oxygen driven away, non volatile ingredients are about 15% or less); science papers/research docs used 70%- 90% phosphoric acid, 25% concentration suggested for strong alkali salts such as calcium chloride.

Leave 24 hours, some papers suggested heat at 120c for 24 hours to enhance the erosion of carbon, some papers suggest soak rinse and then re-heat after acid is washed away.

Drain and wash thoroughly.

Place in oven at 220c for 2-3 hours.

Crush and enjoy with a glass of water.

As you can see, I am just looking for a little clarity. Since this is all about the size of the pores in the carbon and increasing surface area, I have no way of really testing this, I don't think the quality of the water will be an indicator since I can not test that either. Posting this here with the hope that someone might have done this at home. I am not too sure about heating charcoal soaked with phosphoric acid in the cooking oven to be honest, this is more of a practical side task using emptied brita filters. They are scandalously priced.

S.C. Wack - 22-11-2014 at 11:50

Quote: Originally posted by CHRIS25  
brita filters. They are scandalously priced.


BRITA products include water jugs, kettles and tap attachments, all of which use silver-impregnated activated carbon and ion-exchange resin disposable filters as their primary filtering mechanism.

For water testing you've got ppm/ec/tds meters, these are not expensive.

If you can't reproduce patents in your oven and your oven products don't perform, you need to move towards trying to reproduce the patents. You realize that CO etc. is produced yes?

There are books named Activated Carbon, and these have a lot of references to making them.

CHRIS25 - 22-11-2014 at 13:01

QUOTE: BRITA products include water jugs, kettles and tap attachments, all of which use silver-impregnated activated carbon and ion-exchange resin disposable filters as their primary filtering mechanism.

If you can't reproduce patents in your oven and your oven products don't perform, you need to move towards trying to reproduce the patents. You realize that CO etc. is produced yes?.[/rquote]QUOTE

Punch a big hole at the top of the brita filter and fill it with the carbon, stopper it back up again with a cork or rubber stopper, simple.

But I really do not understand your remark about "reproducing patents in the oven"? I am not doing that, if this is what you meant.

Just had a quick look a two e-books from that site. Horrendously complex analysis of everything you need to know about the carbon, but nothing about methods of creation, bit of information overload just to find a answers to the above questions. But thanks for the link, it may come in useful in the future for something that i might want to study in-depth.

[Edited on 22-11-2014 by CHRIS25]

S.C. Wack - 22-11-2014 at 14:45

Quote: Originally posted by CHRIS25  
nothing about methods of creation


Those two were specifically recommended for the details and references, in the newer one the phosphoric acid method is rather detailed. I knew it would be a mistake to post in this thread.

aga - 22-11-2014 at 15:42

Your view is appreciated in whichever thread you post in SCW.

In this one, regard it as casting pearls before swine.

Some of us pigs will gobble them up greedily.

Edit

Be aware that we may burp and fart a lot afterwards, possibly grunt a bit too before seeing the Light.

[Edited on 22-11-2014 by aga]

subsecret - 22-11-2014 at 21:40

Quote: Originally posted by CHRIS25  
Initially I want to make a water filter. So far discovered the following with ambiguity:
Procedure:

Soak charcoal in unknown percentage Phosphoric acid (charcoal made in sealed container all oxygen driven away, non volatile ingredients are about 15% or less); science papers/research docs used 70%- 90% phosphoric acid, 25% concentration suggested for strong alkali salts such as calcium chloride.

Leave 24 hours, some papers suggested heat at 120c for 24 hours to enhance the erosion of carbon, some papers suggest soak rinse and then re-heat after acid is washed away.

Drain and wash thoroughly.

Place in oven at 220c for 2-3 hours.

Crush and enjoy with a glass of water.

As you can see, I am just looking for a little clarity. Since this is all about the size of the pores in the carbon and increasing surface area, I have no way of really testing this, I don't think the quality of the water will be an indicator since I can not test that either. Posting this here with the hope that someone might have done this at home. I am not too sure about heating charcoal soaked with phosphoric acid in the cooking oven to be honest, this is more of a practical side task using emptied brita filters. They are scandalously priced.


What's the advantage of using phosphoric acid? Wouldn't you want to use an acid that has fewer insoluble salts? Is phosphoric acid used to remove most of the silica from the slurry?

CHRIS25 - 23-11-2014 at 03:00

Phosphoric acid is recommended overall and using any other acid is advised against, the reasons I have not yet found out, but the fact that phosphoric is a weak acid has been stated. I am at the beginning of this project so much to learn, but for the moment I just am going to start with what I already know and see what happens - again, by tasting, I seem to do a lot of that recently.

@ScWack - your references I have kept, I find that I come back to things even after a year. But for the moment, yes not what I need. But thankyou.

@ - Aga - they were not pearls he threw - more like the oysters containing the pearls, I have no tools to open them at the moment.

blogfast25 - 23-11-2014 at 06:47

Quote: Originally posted by CHRIS25  
Phosphoric acid is recommended overall and using any other acid is advised against, the reasons I have not yet found out, but the fact that phosphoric is a weak acid has been stated.


Phosphoric is generally regarded as a strong acid (although weaker than sulphuric or hydrochloric acid), with a pKa1 = 2.15. A 1 M (mol/L) phosphoric acid solution is about 90 % dissociated acc.:

H3PO4 + H2O === > H2PO4(-) + H3O+

http://en.wikipedia.org/wiki/Phosphoric_acid#Aqueous_solutio...

That's the hallmark of a fairly strong acid.

But I'm not sure how acid strength relates to the process you describe anyway.

Any acid would leach out part of the inorganics in charcoal, like K2CO3, but not everything either.

Re. Brita filters. Does Brita ever produce any scientifically verifiable date on the water improvement that is allegedly achieved by use of their filters? At best, I think good quality activated carbon may remove chlorine and perhaps any other odorous gases that might be part of, for instance, well water.

Filtering decent tap water with Brita filters seems an expensive waste of money to me. If the water quality in your area is poor than you should take that up with your local water board, if you haven't already.


[Edited on 23-11-2014 by blogfast25]

S.C. Wack - 23-11-2014 at 07:11

I'd imagine that Brita's combination of carbon and ion-exchange resin has some effectiveness, since these are in RO systems. I doubt one could do better for water treatment carbon than just buying a bag of Calgon et al. product sold for industrial RO.

CHRIS25 - 23-11-2014 at 07:39

Take it up with the water board? They deliver minimal quality and get away with the rest. The brita filters filter out huge amounts of chlorine plus the taste is awful without them. But that is not the concern of Irish water so long as they are not poisoning anybody, which happens. Filtering out the chlorine and maintaing the decent taste is sufficient for us. There are no costs at all in making this stuff, everything is freely obtainable. So it seems daft not to try it. Plus it is an education and I like that. If the phosphoric acid (or calcium chloride should I use that) is thoroughly washed away after soaking, then there should be no dangers in putting it in a conventional oven, but again, I am not 100% on that, so SCwack mentioned carbon monoxide with regards the acid, but I can not see how that could occur after thoroughly washing away very festidiously the residue?

@Blogfast - My source for believing that it was a weak acid came from here: http://dwb4.unl.edu/Chem/CHEM869R/CHEM869RLinks/scifun.chem....

What have I wrongly interpreted? (for future understanding of this sort of thing)

[Edited on 23-11-2014 by CHRIS25]

blogfast25 - 23-11-2014 at 09:16

Quote: Originally posted by CHRIS25  
Take it up with the water board? They deliver minimal quality and get away with the rest. The brita filters filter out huge amounts of chlorine plus the taste is awful without them. But that is not the concern of Irish water so long as they are not poisoning anybody, which happens.


Fairly strong accusations there, Chris, I'd be careful with that. Do you have any actual data on Cl2/hypochlorite content of your water? Or that they've actually poisoned anyone? I hear similar stories about some British water but have never seen a single credible corroboration so far.

Non-chemist have the tendency to express concerns over chlorine in tap water in terms like 'huge amounts of chlorine' but in reality the amounts are very, very small. Typical levels in Britain are less than 0.5 mg/L of free or combined chlorine. It's an incredibly effective way of 'sterilising' water and trust me: without sterilisation centralised water distribution would be equal to centralised infectious disease distribution.

Personally I think you're buying into Brita's marketing fairy tale. Don't take that the wrong way, please.
Quote: Originally posted by CHRIS25  
@Blogfast - My source for believing that it was a weak acid came from here: http://dwb4.unl.edu/Chem/CHEM869R/CHEM869RLinks/scifun.chem....

What have I wrongly interpreted? (for future understanding of this sort of thing)




Nothing really. They mention "It is a stronger acid than acetic acid" but as the Wiki page shows the first dissociation of H3PO4 is nearly complete (about 90 %), whereas the dissociation of 1 M acetic acid is less than 1 %, off the top of my head. Big difference. These small negative exponents are deceptive.

So you can call H3PO4 'medium' if you like, it's a kind of "how long is a piece of string" question really.

[Edited on 23-11-2014 by blogfast25]

blogfast25 - 23-11-2014 at 09:24

Quote: Originally posted by S.C. Wack  
I'd imagine that Brita's combination of carbon and ion-exchange resin has some effectiveness, since these are in RO systems. I doubt one could do better for water treatment carbon than just buying a bag of Calgon et al. product sold for industrial RO.


Not sure what you mean by 'RO systems'. Ion exchangers can eliminate 99 % (and more, of course) of all ions, thus reducing water hardness to zero, thus reducing scaling enormously.

But eliminating ions from drinking water is folly. They don't harm, yet tend to affect taste positively. Deionised water is very bland.


[Edited on 23-11-2014 by blogfast25]

CHRIS25 - 23-11-2014 at 10:55

@Blogfast. I should not deviate from topic.....I know, though running the cold water tap fast smells exactly the same as opening up a bottle of bleach, that I will say.
Good News: I have found these excellent references on measuring the carbon pores, well within my reach to work on, I only put them here in case others might be reading: I can't obviously employ the nitrogen gas, but the iodine capacity number looks interesting.

http://www.cefic.org/Documents/Other/Test-method-for-Activat...
http://www.filtrextechnologies.com/acproperties.htm

blogfast25 - 23-11-2014 at 11:15

Chris:

Why not turn it into small project, those chlorine concerns?

Look at this kit:

http://www.ebay.co.uk/itm/Watersafe-Drinking-Water-All-in-On...

Although I cannot vouch for the validity of obtained results, I feel it would be good enough to compare raw tap water, post-Brita tap water, a good quality bottled water and a good quality deionised water, for some decent, relative data.

Total solids meters (conductivity meters, pen type) are also cheaply available from loads of eBay sellers.

Peace of mind plus scientific corroboration of your concerns, what's not to like? :)


Activated carbon was once available from pharmacies, brand name 'Norit', if I recall well. Dirt cheap too...

CHRIS25 - 23-11-2014 at 11:37

It's no concern I have. Just the chemistry and the possibility that I can create something to replace buying it..and thankyou for the link

[Edited on 23-11-2014 by CHRIS25]