Ir recycling step 5

This is a note of contention as to whether or not this step is necessary. Professor Heller suggested that the black Ir/ash was good enough to carry on, while I thought this step would yield better results. As such, I'll do some of the batch both ways and see if the result is the same.

I've used a glassblowing torch in order mix some O2 in with the natural gas. This increases the temperature of the flame considerably, enough so that the bottom of the crucible glows like a light bulb. After a fews tens of minutes of heating, the black Ir/ash has melted into a glowing red lava-like goo. There were two separate layers evident, what I can only guess is metalic iridium made up the glowing red material in the bottom of the crucible, covered by a clearish liquid layer which I'm guessing is molten salts. This step gave off some pretty intense radiant heat, making me wonder if the fire extinguishers in the top of the hood would be triggered, happily this did not occur.


Several attempts were made to get this process to work correctly. I was successful once, shown in the picture, but subsequent attempts led to the crucibles breaking due to thermal shock and uneven heating. I tried to remedy this by using a Meker burner on full blast for hours, but the temperatures achieved was not enough to convert the ash to salts and the (presumably) iridium oxides to metallic iridium. I tried to spread the flame of the glass blowing torch out by loosely affixing the Meker burner grating to the top of the torch, but the O2 content was too high in the cavity in between, leading to a lot of backfiring and me almost crapping my pants. Clearly, a safe, more controlled heating method is needed, either by furnace or adapting the current setup to prevent thermal shock to the crucible and promote even heating. More on this soon....

Ir recycling step 4

The crucible of concentrated nastiness has removed most of the volatiles, which will prevent a huge flame ball from forming in this step. Here, we are simply heating off any of the volatile salts and burning solid organics down to ash. The iridium/ash may be good enough to carry on, however, the recycling will be much easier after heating to higher temperatures. The setup is shown below: a crucible with the iridium residues being fired by a Meker burner with the air mixer on low, gas on low. Lots of smoke (fairly toxic) is given off in this step. Although the picture is taken with the sash up, it was down for the duration of the burn-off, save for the picture.

Ir recycling step 3

Many of the higher boiling solvents and other nasties (mineral acids, oils, phospines, etc.) are still present and the waste residue currently has the consistency of chunky fondue. Unfortunately the smell doesn't resemble fondue in the least. Many of the bad smelling, high boiling residues left are removed by extensive heating in a crucible to 300 - 350 C using a heating mantle and sand bath. This was also a good time to throw in the tissue papers I used to clean up a few spills. No worries, as all of the organics are being decomposed in the hot acid and will be fired off in the next step.

Ir recycling step 2

The next step is to strip all of the volatile materials from the waste, employing a Rotovap. This is merely a contraption which heats the solvent in one pot while cooling the vapors so that they drip into another pot (the solvent trap.) This step happened mostly without incident, save but one batch of waste which was not properly neutralized. Of course, if you take dilute acid and strip the solvents off, what you end up with is concentrated acid. This hazard is inherent, since most of the volatiles are benign, anything which is particularly nasty is going to be concentrated and become nastier. As my labmate says, usually to make himself feel better while pouring waste down the drain with the water on, "The solution to pollution is dilution!" I have discovered the opposite is also true "If you want to make nasty waste even worse, concentrate it!" Its not as catchy, but equally relevant to the task at hand.

This nastiness will all be remedied in the next step.

Ir recycling step 1

The first thing to do is collect the waste. As you can see in the photo, there is a good bit of it from the various labs in the department. Some of it has been evaporated already, so its pretty dense. Most of it, however, is a lot of solvent for not a lot of metal. This picture shows the bulk of what I collected initially. In the present form of whatever it was collected in I would estimate the volume to be 4 to 5 liters.