[azmanam]

Just wondering a) if the lab you work in or b) if you've heard of or seen a lab which recycles uncontaminated ethyl acetate/hexanes by distillation. (You can vote in the poll above)

[Dan]

a) I've worked in 4 labs (3 in the UK, 1 in Iceland), never seen any solvent recycled except solvent for cryogenic baths.

b) I have heard of groups recycling solvent, but I think this was distilling acetone waste for use as wash solvent - but I'm not sure, it was second hand info.

Presumably if you recycled EA/Hex you'd be looking to column with it. In that case it must be a bit of a hassle to run test TLCs for every single column/batch due to variance between batches? Still cheaper than fresh solvent though I suppose.

[the.khemist.ds]

When I first started my PhD the department I worked at bought drum grade petroleum ether and distilled it. However, this practice was soon discontinued.

I believe that there were several issues, amongst them were:

1. the cost savings were actually not that great when the fact that a technician had to spend an afternoon a week distilling the solvent for the department was factored in.

2. The risk associated with distilling solvent on the scale of 10s of litres is significant (and more importantly the consequences of any accident that might occur). Nowadays, I've seen departments where it is difficult to even get approval for a small scale THF still.

3. The distillation apparatus takes up lab space that could be used for something else.

[enahs]

If it is going to be fairly clean stuff, we sometimes keep a little used solvent for cleaning purposes. For those round bottom flasks that you need to first use a whole bunch of organic on to just get the chunks out; then wash it again with soap and water and then good fresh acetone or whatnot.


But our organic waste goes to a company that reclaims it for alternative fuel resources (it gets burned in cement kilns once, so it is not a total waste).

[BluePill]

Saw that in our lab. Not my experiment through. She collected the solvents using rotavap and used it again for soxhlet extraction. Bad idea though.

[azmanam]

When I was in grad school, we'd submit uncontaminated EtOAc/hex from the clean fractions off of columns and we had a big ol' permanent distillation apparatus to recycle the mixture.  This was someone's lab job (along with distilling uncontaminated acetone).  We used the acetone for washing glassware and the EtOAc/hex for columns.  Yes the batches were different each time.  We collected the distillate in recycled 20-L drums.  The person would NMR the batch and calculate the %EtOAc for the drum. 

If you needed a different polarity solvent, though, you had to add EtOAc or hex, naturally.  So I made an excel sheet to figure out the right proportions of mixture:pure I needed for my column.  If this was commonplace, I was going to blog a javascript version of the calculator.  If we were the only wierdo lab to do this, then perhaps I won't

[azmanam]

So I'm seeing a lot of no votes.  Would a calculator like this be of use to anyone?  Or should I shelve it?

You can see a mockup of the calculator here:
http://www.chemistry-blog.com/?p=5381&preview=true

[OC pro]

Have never been a fan of this. Energy consumption of the distill is more than a can ethyl acetate or hexane costs (especially the big ones with 250 L).