Sciencemadness Discussion Board

Lab-scale waste recycling

Texium - 12-8-2014 at 21:24

One thing that I've always (since before I started actually doing chemistry) thought would be neat, would be to have a lab that was able to recycle almost everything. Now that I've actually done a good bit of experimenting, I've long since realized how difficult it is to attempt that, and despite trying to produce as little hazardous waste as possible, I still find that I have a 2-gallon bucket with a couple inches of gray sludge and a gallon of green liquid in it that I'd prefer to not have in my septic tank.

Anyway though, today I started thinking that it may be easier to recycle some things than I'd previously thought. For example,
-Solvents can be redistilled in many cases, and kept as a lower grade version for cleaning and less sensitive experiments.
-Metals like copper and nickel can be precipitated and reused later.
Those are the only two practical examples that I can think of at the moment, but there's probably others. Sometimes, a recyclable waste product can be set aside and stored for a mini project another time, if time or willpower don't permit salvaging it immediately. It could even possibly be kind of fun sometimes... at least in theory anyway.

What I was wondering was what level of recycling is currently implemented by other members, so now this poll exists.

Edit: That's too bad, I thought it was possible to edit poll options if you created the poll. I might have wanted to add other categories at some point.

[Edited on 8-13-2014 by zts16]

prof_genius - 13-8-2014 at 03:56

I don't recycle much because I use small amounts of reagents and I don't want the hassle. If you use a solvents a lot, I would recommend distilling them.

UnintentionalChaos - 13-8-2014 at 04:29

I have a lot of little bottles of odd, poorly soluble salts from when I did inorganic chem regularly- my attempts at recycling. I probably wouldn't bother now given the hassle except for expensive catalysts (Pd).

Now that I am solely doing organic chem, I really only do solvent recycling, and that depends very much on the solvent. I recycle ether, chloroform, and benzene where possible because of cost and/or effort of manufacture. DCM, I can obtain in large quantities. Small amounts, I let evaporate, but generally I use it to extract and wash high-boiling organics which makes isolation/recycling trivial.

All of the above and more

Praxichys - 13-8-2014 at 08:45

Cheap metal salts of aluminum, calcium , sodium, magnesium, and potassium typically get disposed of as solutions.

Cu and Fe is often worth recovering but I am generally not too afraid to dump them if recovery is troublesome.

Ag gets precipitated and recovered as much as possible due to the high cost.

Hg, Pb, Cd, Ni, and Cr get precipitated and recovered because of environmental concerns. As long as they remain reasonably free of other metals, recovery and re-processing into reagents is usually possible and helps provide experience in preparative chemistry. Otherwise, they get precipitated and dried into oxide/hydroxide powders, mixed with cement, and the block is disposed of in a landfill.

Solvents like DCM, TCM, toluene, benzene, dioxane, Et2O get recovered as much as possible. Acetone, methanol, and ethanol are cheap and harmless enough to just dump outside and let evaporate. I often burn these solvents in a fire pit if they might contain nasty organics. Otherwise, simple evaporation is fine, and prevents flammable vapors from creating a dangerous environment in the sewers.

I am also a fan of re-purposing "waste" reagents. If a reaction gives off ammonia, instead of just letting it fly into the wind, I try to capture as much as possible. It helps keep the lab discreet, and I can then co-produce ammonium nitrate, sulfate, chloride, etc. with a simple acid gas wash.

EDIT: @ UC - I also have a bad habit of keeping reaction waste laying around waiting for metal recovery.

[Edited on 13-8-2014 by Praxichys]

subsecret - 13-8-2014 at 11:06

If I'm isolating an organic product dissolved in a solvent, I distill and keep the solvent. For smaller amounts (such as rinse solvents), I soak it into a piece of paper and burn it outside, provided it's non-chlorinated. Chlorinated solvents get their own waste container, and I've yet to figure out what to do with it once it gets full. :D

In the amateur setting, it's always advisable to recycle waste that can be purified efficiently. There is always a point when recycling loses its value, though.

[Edited on 14-8-2014 by Awesomeness]

Pyro - 14-8-2014 at 06:05

dump paint section with a clear label of what's in it. (those people are paid to know what to do with those things)

i only recycle expensive solvents (benzene, chloroform,...)

arkoma - 14-8-2014 at 09:16

Solvents--pretty much all of them. If nothing else keeps the smell and flammable vapors in check. When I get cheap 70% IPA, I distill off half and use the weak remnant as glassware rinse. My sister JUST asked me "Hey, whats this squirt bottle that says 'weak IPA' by my sink?". I also use a Sharpie for EVERYTHING--"to do" notes on my hand, label of whats in a particular flask at the moment etc, and that IPA takes it right off.

Texium - 14-8-2014 at 09:24

@arkoma: Have you seen the 95% version? That's what I normally buy. It saves a lot of trouble, and is only a few cents more expensive.

@Praxichys: Ah yes, using waste gases... knew I was forgetting another important one when setting up the poll. I should have put that as an option too.

Pyro - 14-8-2014 at 11:34

arkoma, i like the idea of labeling beakers and flasks with a sharpie!

arkoma - 14-8-2014 at 12:32

Quote: Originally posted by zts16  
@arkoma: Have you seen the 95% version? That's what I normally buy. It saves a lot of trouble, and is only a few cents more expensive.


The 91%? Yes, but I like distillations ;)

edit
Quote: Originally posted by Pyro  
arkoma, i like the idea of labeling beakers and flasks with a sharpie!


I keep a black sharpie in my pocket at ALL times LOL, and even dilute IPA takes the ink off pretty much anything

[Edited on 8-14-2014 by arkoma]

aga - 14-8-2014 at 12:38

hanging on to bottles of forgotten byproducts in the hope of doing something with them is crazy.
i hope to stop doing that soon.

arkoma - 14-8-2014 at 12:42

I've had to throw away more than one thing because I couldn't fekkin remember what it was *sigh*

Mailinmypocket - 14-8-2014 at 12:53

Quote: Originally posted by zts16  
@arkoma: Have you seen the 95% version? That's what I normally buy. It saves a lot of trouble, and is only a few cents more expensive.

@Praxichys: Ah yes, using waste gases... knew I was forgetting another important one when setting up the poll. I should have put that as an option too.


If you happen to have a Costco membership they sell 3x 99% IPA for something like $10 here, check that out :)