Wow, when I first read the topic, I thought it was about beer!

This is how you dispose of "used" IPA (beer)

Ive had the "jello" in a Zip-Lock plastic bag outside for about 4 days now, and it still hasn't hardened.  It's like a very thick rubber.  It got about 4 hours of sun a day, which should have hardened it, but I guess the concentration of alcohol in it is keeping it from hardening completely.

I'll give it another couple of days, but if it doesn't cure completely, I'll just throw it away as it is.

I wonder would a simple solar still work with IPA??

Place a clean can in the middle of the tub . Weight  it down. The can height must be lower than the top of the tub. then place plastic over the tub leave a bit loose . tape the edge of the plastic to the outside of the tub then place a weight rock marble whatever on the plastic over the can the idea is the  IPA evaporates    then condenses on the plastic then drips into the can .
The plastic should not touch the collection can . 
If it works you should be able to recover and reuse a good bit of the IPA rather than it just become part of the local air pollution.

Solvents are commonly recycled in industry . the problem is the commercial equipment is expensive. And Home built stills may be a bit taboo .

Another option would be put the IPA in a sealed glass jar and leave in the sun then filter it after the sun cures the resin.

Tin

Neat idea, but making 'shine in your bathtub is still against the law ! 

'sides, I'm not sure it would taste that great.

Place a clean can in the middle of the tub . Weight  it down. The can height must be lower than the top of the tub. then place plastic over the tub leave a bit loose . tape the edge of the plastic to the outside of the tub then place a weight rock marble whatever on the plastic over the can the idea is the  IPA evaporates    then condenses on the plastic then drips into the can .
The plastic should not touch the collection can . 
If it works you should be able to recover and reuse a good bit of the IPA rather than it just become part of the local air pollution.

Solvents are commonly recycled in industry . the problem is the commercial equipment is expensive. And Home built stills may be a bit taboo .

Another option would be put the IPA in a sealed glass jar and leave in the sun then filter it after the sun cures the resin.

Tin

For those that are not familiar with SLA printers, one of the steps in finishing a model is to clean it in isopropyl alcohol (IPA).  IPA dissolves uncured resin, which the model is covered in as it's extracted out of the resin tank during build.  After a lot of prints, the IPA gets contaminated with uncured resin, and becomes "oily", and ineffective.  At this time it's time to replace it with new "clean" IPA.

Some people have go to great extents to "save" the IPA, by filtering the resin particles out of it, but ultimately, the "liquid" IPA is still dirty.  FormLabs suggest disposing of it in accordance to "proper hazmat disposal rules governing your local area".  Bu that can be cumbersome, inconvenient and costly.

I for one used a different tactic. 

I took the entire tub and put it out in the sun for a day.  The IPA turned into a thick jello, which I scooped up and put into a large ziplock bag,  which I left outside to cure further.  Depending on how many hours of sun it gets, and what the ratio of IPA to resin the concoction is, it might take as long as a week to cure, but in the end, you'll have a solid piece of plastic that can be simply disposed of in the trash.

Hope this helps those of you that are using SLA printers