If you spread magnetic iron oxide on crude oil will a magnet pick up the oil?

Answer 1

It's possible that this will work, but the idea is highly inefficient at its best. Black sand is a general term, but there is black sand which has some iron oxide in it. This kind of iron oxide (there's more than one kind) is ferromagnetic, and it can be attracted by a magnet, as you'd expect. But there are problems. Should black sand be applied in a manner that distributes it widely, it can then "collect" oil on the surface of the particles and be attracted to a magnet bringing the oil with it (if the magnet is strong enough, close enough, etc.). But though the collection of the oil clinging to the black sand particles could be accomplished via a magnet, it would be easier to simply use absorbent materials to gather the oil. Also, there are a lot more bales of hay (or straw) around than bags of black sand.

If the oil is concentrated enough for the black sand/magnet approach to be effective, absorbent pads would work a lot better to collect the oil. Particles of black sand can only collect material sticking to their very limited surface area (in spite of the large number of particles. Absorbent fibers trap far more oil through capillary action and "stiction" to and between the fibers than sand particles. Ask yourself this question: "Which will collect oil more efficiently, a hair (a fiber) or a particle of sand?" The hair has far, far more surface area than the sand particle, and hair fibers or some kind of fibers are at the heart of absorbent pads. Cat litter would work far better to collect oil (though it cannot be attracted by a magnet) than black sand. In addition to greater effectiveness, fibers are light, cheap and readily available. And they will float easily.

Certainly if you had enough black sand, you could build a berm in shallow water outside a sensitive marsh and protect it that way. (Sand is being strategically deposited to perform this function as this answer is being written, by the way.) The black sand/magnet idea is a good one, but it is far too inefficient to work well. The physics is pretty clear, and thinking it through will reveal the truth.