Take a small permanent magnet and pour iron filings over and around it, the way children sometimes play. The question is, is there an efficient way to remove the particles, leaving the magnet clean again?
Sticky tape. Or Blue tack.
But then the iron filings are stuck to the tape. I’d start by just brushing the filings off the magnet. Or get a more powerful electromagnet, use it to draw the filings away from the permanent magnet and then turn off the electromagnet. The filings should fall right off.
Probably a bad idea. You could end up demagnetizing your original magnet if you’re not really careful.
Are the filings already stuck on the magnet or is this going to happen in the future. IOW, can you just cover the magnet with something that can be peeled off or is it already done.
Also, depending on exactly what you’re doing, they do make non-electromagnetic magnets with an ‘on/off’ switch. I assume the switch just moves a magnet away from the surface, but it may work in your application and be easier than pulling tape off a magnet or putting the magnet in a bag each time.
Going forward, prevention is probably best, but if it’s a one and done, you’re probably going to have to brush them off one way or another. Maybe with a dry cloth or even putting on a glove and wiping them off by hand.
Who cares? The parameters of the problem didn’t require us to preserve the magnet.
FWIW careful brushing+wiping gets most of them off, and then a bit of sticky tape takes care of the remaining dust.
Soak the magnet in water. The iron filings will turn into non-magnetic hematite and fall off.
Maybe jam some Silly Putty or similar substance over the filings?
I’d pull off as much as I could by hand, and then get a second magnet. Put a layer of something thin (paper or whatever) over the second magnet, and put it up against the original magnet. When you pull them back apart, each should have about half of the filings. Remove the paper from the second magnet, and drop the filings into whatever container you’re storing them in, then put the paper back on and repeat. Each cycle, you’ll remove half of the filings, until the amount left is small enough to not worry about.
Yeah, but the variant I’d use is to scrape them off with a paint scraper or similar utensil while holding the magnet over a sheet of paper.
Joey P. had it right – prevent it from happening.
Usually, this is done to show children/students how magnetic force works. It’s easy to do that by putting the magnet underneath a sheet of white paper or a clear plastic page protector – then the filings move around on the sheet, but don’t stick to the magnet. And it’s usually easier to see the movement on a sheet like that.
I just wipe the magnets off with a shop rag, if i need to, hit it with some compressed air.
Works for what i need
This! Just remember to wear safety glasses. You do not want iron filings in your peepers. Trust me on this.
I do wonder though, how hot would one have to get the magnet for it to loose it’s effectiveness?
Big crane mounted electromagnets will get hot & quit picking up steel parts. What if you boiled a permanent magnet in oil? Could you then just remove the magnet from the kettle while it was hot? Oil would be used so that the iron filing will not rust.
The next rainy day when i have my grand kids, I think that we may try this.
If the magnet is of large enough size, use a plastic putty knife, if it isn’t too powerful, try a metal putty knife, or razor/scraper (the dollar store ones used to take off old City Stickers). This is of course if you are trying to preserve the filings.
Hot. Seriously hot. 1000K plus.
Propane torch will do it. Medium red is where you need to get it.
Right, but why cook a perfectly good magnet? 
The OP did not say that he wanted to preserve the iron filings.