francis - 31-3-2012 at 18:49
Hi,
We were given a sample of paint waste to analyse, so that the company who produced it had a disposal plan in accordance with our local government
guidelines.
The sample was a sludge, thick and green with floating particulate matter. It smelt of turpentine.
Addition of polar organic solvents simply diluted it.
Addition of n-heptane dissolved the solvent layer: it produced a white, cloudy layer, and a very viscious, thick resin which lined the bottm of the
container.
MgSO4 was added to the n-heptane, which was filtered by gravity. By this method, the moisture content was quantified (weighing the hydrous MgSO4 and
measuring the difference between the hydrous and the anhydrous).
The dried n-heptane was clear (no longer was it cloudy).
We examined the n-heptane solute by GC-MS:
the chromatogram showed only aromatic hydrocarbons (lowest was cumene, BP 152 deg C, highest was 1-methylnapthalene, BP ~240 eg C). The solvent for
the paint waste was determined to be a high BP aromatic naptha. We determined the solvent was Aromatic 150.
By the distillation method it is possible to recycle the Aromatic 150, which the company can do on a large scale.
My question is:
How can the resin, which is heptane and hexane insoluble, be analysed for residual hydrocarbons? It has the consistency of chewing gum, but
presumably, still has some aromatic hydrocarbons on it or in it, which means it can't be disposed of by landfill.
Perhaps we could do numerous heptane extractions, analysing each extraction until no further hydrocarbons are dissolved? (Which we'd check by running
the heptane on the GCMS)
What about n-heptane insoluble hydrocarbons which remain? More polar solvents dilute the resin, essentially turning it back into paint..which makes it
difficult to analyse.
[Edited on 1-4-2012 by francis]