Nanoparticles and Magnets Offer New, Efficient Method of Removing Oil from Water | Hacker News Reader

Nanoparticles and Magnets Offer New, Efficient Method of Removing Oil from Water

news.utexas.edu

30 pointssr28 comments

“This new technique is really aimed at removing that little bit of oil in that water that needs to be removed before you can consider it treated.”

This is for the tail end of oil/water separation, after existing processes have done most of the work. Here's an overview of oil/water separation.[1] Note the line "Very small particles, such as those of 10 microns (micrometers) and less in diameter, do not rise according to Stokes’ Law (or hardly at all) because the random motion of the molecules of the water is sufficient to overcome the force of gravity and therefore they move in random directions." This is a way to apply magnetic forces to those tiny droplets.

The lines at the end of the article, about this being useful in oil fields, probably were added by some PR person.

[1] http://www.hydroflotech.com/oil-water-separator-theory-of-op...

This work was done years ago at MIT, and MIT holds the patent. Look up Zahn and Hatton.

https://news.mit.edu/2012/how-to-clean-up-oil-spills-0912

They don't even seem to cite that work: https://link.springer.com/article/10.1007/s11051-017-3826-6

They mention at the end of the article they are working on larger scale water processing systems which would recover and reuse the particles. I think this is critical not only for efficiency but also health and safety. I'd rather not end up drinking unknown nanoparticles... I hope the musings in the article that it might also work for lead removal turn out true. Good luck!

By "recover", they mean recovering them out of the removed oil. The nanoparticles are fully recovered from the water by the magnetic force (it wouldn't really be a useful invention otherwise) but much of them are trapped in the oil they bring with them (that being rather the point) and this means that it's hard to "clean" the now-dirty nanoparticles in order to make them useful for extracting more oil.

(Though, I'm not too clear on why this is a hard problem—couldn't they just, say, throw them into some nitric acid to destroy any organics, like you'd do with chem-lab glassware?)

I'm super unclear on exactly what these nano-particles are made of, or the nature of the charged polymer coating that is required for binding.

There was an oil spill on the East River in NYC a month ago, about 5000 gallons of oil[0]. Since each nanoparticle binds to some small amount of point, then would we need some close fraction of 5000 gallons worth of charged-polymer coated nanoparticles to extract it all?

If the production of this awesome substance is even close to as straining on the environment (aren't most polymers oil-based?) then I don't see it as a magic bullet for solving all of our water-contamination problems.

Still super freaking cool though.

[0] http://www.amny.com/news/east-river-oil-spill-thousands-of-g...

This isn't for cleaning up large spills, it's for polishing water with O(0.1%) oil dispersed, to the point that it's clean enough to release into the environment.

> Though, I'm not too clear on why this is a hard problem—couldn't they just, say, throw them into some nitric acid to destroy any organics, like you'd do with chem-lab glassware?

The expensive and tricky part of these (like any) magnetic nanofluid particles is the surface covering that makes them soluble in water but also attracted to oil droplets. Any harsh chemicals would destroy that, and you're left with just fancy rust.

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