Destroying carbon monoxide in a gas stream

A material called hopcalite (try Google) is/was used in gas masks to remove CO. It comprises a mixture of oxides which catalyse the oxidation of CO to CO2.

Hopcalite: Manganese dioxide (50%), copper oxide (30%), cobaltic oxide (15%) and silver oxide (5%). Works at room temperature. It may be possible to obtain an appropriate gas filter from a "safety supplies" shop that sells respirators.

Many metal oxides when heated are reduced to metals by CO, with the CO oxidised to CO2.

In the "old style" gas analysers, an ammoniacal or HCl solution of cuprous chloride was often used to quantitatively absorb CO.

For truly OTC and if you are really desperate, you could bubble the gasses through a solution of blood. Haemoglobin combines with CO to form cherry-red carbonyl haemoglobin ....

I have plenty of knowledge of the application. Here's your formula:

I need to have a CO2 stream of 5 liters per day at standard pressure, and it can have any contaminant as long as it is not toxic to aquatic life, and the CO2 is over 10% by volume. How might I do this?

The cost of the setup is probably the most important factor right now. It has to be able to run continuously for a long time with minimal maintenance. Preferably it could be controlled by a timer or controller although this is not critical.

Obviously a canister is ideal for this. And I might end up going that route, but I would much rather avoid it. And maybe have fun building something while I'm at it.

Yeast is an option that I have tried, and it does work although it is much harder to control, inconsistent and high maintenance. It is fairly cheap though.

Reaction of an acid with a carbonate is possible if the acid can be found cheap enough. This might be viable, although will need more maintenance than I'd like. A 20 dollar 5 gallon container of battery acid would give me 200 liters of CO2. 15 bucks a month plus the carbonate is pretty spendy. And thats not including the required pumps, etc.

The only other viable thing I can think of off hand is combustion. The cost of running it would be amazingly cheap, 110 grams (50-25 cents) of propane would be equivalent to that 25 dollars worth of H2SO4/carbonate. One problem is the CO2 will only be 10-14% and a little more will have to be made to compensate. For my applications that will not be of much consequence. The main problem with this comes from the more challenging apparatus construction, the possibilities of CO production, propane leaks and things (my house ) catching fire. I think the construction issues could be resolved with some ingenuity. The cost of the apparatus would be minimal too, simply a screw on propane valve, an aquarium pump, and some tubing and glass. I'll attach my design when I can.

Maybe there's something I'm forgetting? What do you think?

@ 497

What is the point of people replying to posts if they are obviously never read...

I suggested and described "Hopcalite" 6 posts from the start of this thread.....!

I used to be an aquariophile myself, and tried a few application for supplying CO2 to the aquarium. Like you, i started off with yeast

Very cheap indeed, but messy and hard to control to flow. The bottle was depleted in a couple days... On the second hand, i was advised to not supply a continous flow of CO2, but rather alterning periods (1day on, 2days off, etc etc).
I tried the CaCO3 + dilute H2SO4, both very cheap, and gives off a rather consatnt flow if controlled well enough. I just had to empty the sludge evry now and then. Not having much chemsitry equipment back then, I did have a addition funnel So iused on of those little tap for the air pumps. i used two bottles, on with the acid on top, a hole in the bottom where a little aquarium tubing was sealed in, the tap, and more tubing attached to the lid of the second bottle, with a wide neck. In the lid there was attached a piece of tubing going half way down the bottle, to which the air pump was attached, and a third hole with the tubing going to the aquarium. I used a little in-line activated carbon on that tubing, although it might not have been very necessary.

The whole system worked pretty well, but after a while the connection started to leak a bit (acid!), and the whole thing started to be a pain to maintain, so I finished by buying a CO2 cartridge at the aquarium shop, with on of those cool adsorption sytems where CO2 bubbles stay in contact with the water for a long time. The initial cost was relatively high although I don't remember the exact price, and I latter discovered CO2 gas was much cheaper at the ice-factory, so got a rechargeable bottle from them. I needed to swap the detender (?), the new one was less precise and it was tricky to get a good setting.

If you are ready to put alittle money in it, I would sugest this kind of system, but DIY would come out much cheaper than what the aquarium people try to sell it. And get a rechargeable cartridge